1<!-- 2 $Id: ncurses-intro.html,v 1.53 2019/07/28 16:53:26 tom Exp $ 3 **************************************************************************** 4 * Copyright (c) 1998-2017,2019 Free Software Foundation, Inc. * 5 * * 6 * Permission is hereby granted, free of charge, to any person obtaining a * 7 * copy of this software and associated documentation files (the * 8 * "Software"), to deal in the Software without restriction, including * 9 * without limitation the rights to use, copy, modify, merge, publish, * 10 * distribute, distribute with modifications, sublicense, and/or sell * 11 * copies of the Software, and to permit persons to whom the Software is * 12 * furnished to do so, subject to the following conditions: * 13 * * 14 * The above copyright notice and this permission notice shall be included * 15 * in all copies or substantial portions of the Software. * 16 * * 17 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS * 18 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF * 19 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. * 20 * IN NO EVENT SHALL THE ABOVE COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, * 21 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR * 22 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR * 23 * THE USE OR OTHER DEALINGS IN THE SOFTWARE. * 24 * * 25 * Except as contained in this notice, the name(s) of the above copyright * 26 * holders shall not be used in advertising or otherwise to promote the * 27 * sale, use or other dealings in this Software without prior written * 28 * authorization. * 29 **************************************************************************** 30--> 31<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN"> 32 33<html> 34<head> 35 <meta name="generator" content= 36 "HTML Tidy for HTML5 for Linux version 5.2.0"> 37 38 <title>Writing Programs with NCURSES</title> 39 <link rel="author" href="mailto:bugs-ncurses@gnu.org"> 40 <meta http-equiv="Content-Type" content= 41 "text/html; charset=us-ascii"> 42</head> 43 44<body> 45 <h1>Writing Programs with NCURSES</h1> 46 47 <blockquote> 48 by Eric S. Raymond and Zeyd M. Ben-Halim<br> 49 updates since release 1.9.9e by Thomas Dickey 50 </blockquote> 51 52 <h1>Contents</h1> 53 54 <ul> 55 <li> 56 <a href="#introduction">Introduction</a> 57 58 <ul> 59 <li><a href="#history">A Brief History of Curses</a></li> 60 61 <li><a href="#scope">Scope of This Document</a></li> 62 63 <li><a href="#terminology">Terminology</a></li> 64 </ul> 65 </li> 66 67 <li> 68 <a href="#curses">The Curses Library</a> 69 70 <ul> 71 <li> 72 <a href="#overview">An Overview of Curses</a> 73 74 <ul> 75 <li><a href="#compiling">Compiling Programs using 76 Curses</a></li> 77 78 <li><a href="#updating">Updating the Screen</a></li> 79 80 <li><a href="#stdscr">Standard Windows and Function 81 Naming Conventions</a></li> 82 83 <li><a href="#variables">Variables</a></li> 84 </ul> 85 </li> 86 87 <li> 88 <a href="#using">Using the Library</a> 89 90 <ul> 91 <li><a href="#starting">Starting up</a></li> 92 93 <li><a href="#output">Output</a></li> 94 95 <li><a href="#input">Input</a></li> 96 97 <li><a href="#formschars">Using Forms Characters</a></li> 98 99 <li><a href="#attributes">Character Attributes and 100 Color</a></li> 101 102 <li><a href="#mouse">Mouse Interfacing</a></li> 103 104 <li><a href="#finishing">Finishing Up</a></li> 105 </ul> 106 </li> 107 108 <li> 109 <a href="#functions">Function Descriptions</a> 110 111 <ul> 112 <li><a href="#init">Initialization and Wrapup</a></li> 113 114 <li><a href="#flush">Causing Output to the Terminal</a></li> 115 116 <li><a href="#lowlevel">Low-Level Capability Access</a></li> 117 118 <li><a href="#debugging">Debugging</a></li> 119 </ul> 120 </li> 121 122 <li> 123 <a href="#hints">Hints, Tips, and Tricks</a> 124 125 <ul> 126 <li><a href="#caution">Some Notes of Caution</a></li> 127 128 <li><a href="#leaving">Temporarily Leaving ncurses 129 Mode</a></li> 130 131 <li><a href="#xterm">Using <code>ncurses</code> under 132 <code>xterm</code></a></li> 133 134 <li><a href="#screens">Handling Multiple Terminal 135 Screens</a></li> 136 137 <li><a href="#testing">Testing for Terminal 138 Capabilities</a></li> 139 140 <li><a href="#tuning">Tuning for Speed</a></li> 141 142 <li><a href="#special">Special Features of 143 <code>ncurses</code></a></li> 144 </ul> 145 </li> 146 147 <li> 148 <a href="#compat">Compatibility with Older Versions</a> 149 150 <ul> 151 <li><a href="#refbug">Refresh of Overlapping 152 Windows</a></li> 153 154 <li><a href="#backbug">Background Erase</a></li> 155 </ul> 156 </li> 157 158 <li><a href="#xsifuncs">XSI Curses Conformance</a></li> 159 </ul> 160 </li> 161 162 <li> 163 <a href="#panels">The Panels Library</a> 164 165 <ul> 166 <li><a href="#pcompile">Compiling With the Panels 167 Library</a></li> 168 169 <li><a href="#poverview">Overview of Panels</a></li> 170 171 <li><a href="#pstdscr">Panels, Input, and the Standard 172 Screen</a></li> 173 174 <li><a href="#hiding">Hiding Panels</a></li> 175 176 <li><a href="#pmisc">Miscellaneous Other Facilities</a></li> 177 </ul> 178 </li> 179 180 <li> 181 <a href="#menu">The Menu Library</a> 182 183 <ul> 184 <li><a href="#mcompile">Compiling with the menu Library</a></li> 185 186 <li><a href="#moverview">Overview of Menus</a></li> 187 188 <li><a href="#mselect">Selecting items</a></li> 189 190 <li><a href="#mdisplay">Menu Display</a></li> 191 192 <li><a href="#mwindows">Menu Windows</a></li> 193 194 <li><a href="#minput">Processing Menu Input</a></li> 195 196 <li><a href="#mmisc">Miscellaneous Other Features</a></li> 197 </ul> 198 </li> 199 200 <li> 201 <a href="#form">The Forms Library</a> 202 203 <ul> 204 <li><a href="#fcompile">Compiling with the forms 205 Library</a></li> 206 207 <li><a href="#foverview">Overview of Forms</a></li> 208 209 <li><a href="#fcreate">Creating and Freeing Fields and 210 Forms</a></li> 211 212 <li> 213 <a href="#fattributes">Fetching and Changing Field 214 Attributes</a> 215 216 <ul> 217 <li><a href="#fsizes">Fetching Size and Location 218 Data</a></li> 219 220 <li><a href="#flocation">Changing the Field 221 Location</a></li> 222 223 <li><a href="#fjust">The Justification Attribute</a></li> 224 225 <li><a href="#fdispatts">Field Display Attributes</a></li> 226 227 <li><a href="#foptions">Field Option Bits</a></li> 228 229 <li><a href="#fstatus">Field Status</a></li> 230 231 <li><a href="#fuser">Field User Pointer</a></li> 232 </ul> 233 </li> 234 235 <li><a href="#fdynamic">Variable-Sized Fields</a></li> 236 237 <li> 238 <a href="#fvalidation">Field Validation</a> 239 240 <ul> 241 <li><a href="#ftype_alpha">TYPE_ALPHA</a></li> 242 243 <li><a href="#ftype_alnum">TYPE_ALNUM</a></li> 244 245 <li><a href="#ftype_enum">TYPE_ENUM</a></li> 246 247 <li><a href="#ftype_integer">TYPE_INTEGER</a></li> 248 249 <li><a href="#ftype_numeric">TYPE_NUMERIC</a></li> 250 251 <li><a href="#ftype_regexp">TYPE_REGEXP</a></li> 252 </ul> 253 </li> 254 255 <li><a href="#fbuffer">Direct Field Buffer Manipulation</a></li> 256 257 <li><a href="#formattrs">Attributes of Forms</a></li> 258 259 <li><a href="#fdisplay">Control of Form Display</a></li> 260 261 <li> 262 <a href="#fdriver">Input Processing in the Forms 263 Driver</a> 264 265 <ul> 266 <li><a href="#fpage">Page Navigation Requests</a></li> 267 268 <li><a href="#ffield">Inter-Field Navigation 269 Requests</a></li> 270 271 <li><a href="#fifield">Intra-Field Navigation 272 Requests</a></li> 273 274 <li><a href="#fscroll">Scrolling Requests</a></li> 275 276 <li><a href="#fedit">Field Editing Requests</a></li> 277 278 <li><a href="#forder">Order Requests</a></li> 279 280 <li><a href="#fappcmds">Application Commands</a></li> 281 </ul> 282 </li> 283 284 <li><a href="#fhooks">Field Change Hooks</a></li> 285 286 <li><a href="#ffocus">Field Change Commands</a></li> 287 288 <li><a href="#frmoptions">Form Options</a></li> 289 290 <li> 291 <a href="#fcustom">Custom Validation Types</a> 292 293 <ul> 294 <li><a href="#flinktypes">Union Types</a></li> 295 296 <li><a href="#fnewtypes">New Field Types</a></li> 297 298 <li><a href="#fcheckargs">Validation Function 299 Arguments</a></li> 300 301 <li><a href="#fcustorder">Order Functions For Custom 302 Types</a></li> 303 304 <li><a href="#fcustprobs">Avoiding Problems</a></li> 305 </ul> 306 </li> 307 </ul> 308 </li> 309 </ul> 310 311 <hr> 312 313 <h1><a name="introduction" id="introduction">Introduction</a></h1> 314 315 <p>This document is an introduction to programming with 316 <code>curses</code>. It is not an exhaustive reference for the 317 curses Application Programming Interface (API); that role is 318 filled by the <code>curses</code> manual pages. Rather, it is 319 intended to help C programmers ease into using the package.</p> 320 321 <p>This document is aimed at C applications programmers not yet 322 specifically familiar with ncurses. If you are already an 323 experienced <code>curses</code> programmer, you should 324 nevertheless read the sections on <a href="#mouse">Mouse 325 Interfacing</a>, <a href="#debugging">Debugging</a>, <a href= 326 "#compat">Compatibility with Older Versions</a>, and <a href= 327 "#hints">Hints, Tips, and Tricks</a>. These will bring you up to 328 speed on the special features and quirks of the 329 <code>ncurses</code> implementation. If you are not so 330 experienced, keep reading.</p> 331 332 <p>The <code>curses</code> package is a subroutine library for 333 terminal-independent screen-painting and input-event handling 334 which presents a high level screen model to the programmer, 335 hiding differences between terminal types and doing automatic 336 optimization of output to change one screen full of text into 337 another. <code>Curses</code> uses terminfo, which is a database 338 format that can describe the capabilities of thousands of 339 different terminals.</p> 340 341 <p>The <code>curses</code> API may seem something of an archaism 342 on UNIX desktops increasingly dominated by X, Motif, and Tcl/Tk. 343 Nevertheless, UNIX still supports tty lines and X supports 344 <em>xterm(1)</em>; the <code>curses</code> API has the advantage 345 of (a) back-portability to character-cell terminals, and (b) 346 simplicity. For an application that does not require bit-mapped 347 graphics and multiple fonts, an interface implementation using 348 <code>curses</code> will typically be a great deal simpler and 349 less expensive than one using an X toolkit.</p> 350 351 <h2><a name="history" id="history">A Brief History of Curses</a></h2> 352 353 <p>Historically, the first ancestor of <code>curses</code> was 354 the routines written to provide screen-handling for the 355 <code>vi</code> editor; these used the <code>termcap</code> 356 database facility (both released in 3BSD) for describing terminal 357 capabilities. These routines were abstracted into a documented 358 library and first released with the early BSD UNIX versions. All 359 of this work was done by students at the University of California 360 (Berkeley campus). The curses library was first published in 361 4.0BSD, a year after 3BSD (i.e., late 1980).</p> 362 363 <p>After graduation, one of those students went to work at 364 AT&T Bell Labs, and made an improved <code>termcap</code> 365 library called <code>terminfo</code> (i.e., 366 “libterm”), and adapted the curses library to use 367 this. That was subsequently released in System V Release 2 (early 368 1984). Thereafter, other developers added to the curses and 369 terminfo libraries. For instance, a student at Cornell University 370 wrote an improved terminfo library as well as a tool 371 (<code>tic</code>) to compile the terminal descriptions. As a 372 general rule, AT&T did not identify the developers in the 373 source-code or documentation; the <code>tic</code> and 374 <code>infocmp</code> programs are the exceptions.</p> 375 376 <p>System V Release 3 (System III UNIX) from Bell Labs featured a 377 rewritten and much-improved <code>curses</code> library, along 378 with the <code>tic</code> program (late 1986).</p> 379 380 <p>To recap, terminfo is based on Berkeley's termcap database, 381 but contains a number of improvements and extensions. 382 Parameterized capabilities strings were introduced, making it 383 possible to describe multiple video attributes, and colors and to 384 handle far more unusual terminals than possible with termcap. In 385 the later AT&T System V releases, <code>curses</code> evolved 386 to use more facilities and offer more capabilities, going far 387 beyond BSD curses in power and flexibility.</p> 388 389 <h2><a name="scope" id="scope">Scope of This Document</a></h2> 390 391 <p>This document describes <code>ncurses</code>, a free 392 implementation of the System V <code>curses</code> API with some 393 clearly marked extensions. It includes the following System V 394 curses features:</p> 395 396 <ul> 397 <li>Support for multiple screen highlights (BSD curses could 398 only handle one “standout” highlight, usually 399 reverse-video).</li> 400 401 <li>Support for line- and box-drawing using forms 402 characters.</li> 403 404 <li>Recognition of function keys on input.</li> 405 406 <li>Color support.</li> 407 408 <li>Support for pads (windows of larger than screen size on 409 which the screen or a subwindow defines a viewport).</li> 410 </ul> 411 412 <p>Also, this package makes use of the insert and delete line and 413 character features of terminals so equipped, and determines how 414 to optimally use these features with no help from the programmer. 415 It allows arbitrary combinations of video attributes to be 416 displayed, even on terminals that leave “magic 417 cookies” on the screen to mark changes in attributes.</p> 418 419 <p>The <code>ncurses</code> package can also capture and use 420 event reports from a mouse in some environments (notably, xterm 421 under the X window system). This document includes tips for using 422 the mouse.</p> 423 424 <p>The <code>ncurses</code> package was originated by Pavel 425 Curtis. The original maintainer of this package is <a href= 426 "mailto:zmbenhal@netcom.com">Zeyd Ben-Halim</a> 427 <zmbenhal@netcom.com>. <a href= 428 "mailto:esr@snark.thyrsus.com">Eric S. Raymond</a> 429 <esr@snark.thyrsus.com> wrote many of the new features in 430 versions after 1.8.1 and wrote most of this introduction. 431 Jürgen Pfeifer wrote all of the menu and forms code as well 432 as the <a href="http://www.adahome.com">Ada95</a> binding. 433 Ongoing work is being done by <a href= 434 "mailto:dickey@invisible-island.net">Thomas Dickey</a> 435 (maintainer). Contact the current maintainers at <a href= 436 "mailto:bug-ncurses@gnu.org">bug-ncurses@gnu.org</a>.</p> 437 438 <p>This document also describes the <a href="#panels">panels</a> 439 extension library, similarly modeled on the SVr4 panels facility. 440 This library allows you to associate backing store with each of a 441 stack or deck of overlapping windows, and provides operations for 442 moving windows around in the stack that change their visibility 443 in the natural way (handling window overlaps).</p> 444 445 <p>Finally, this document describes in detail the <a href= 446 "#menu">menus</a> and <a href="#form">forms</a> extension 447 libraries, also cloned from System V, which support easy 448 construction and sequences of menus and fill-in forms.</p> 449 450 <h2><a name="terminology" id="terminology">Terminology</a></h2> 451 452 <p>In this document, the following terminology is used with 453 reasonable consistency:</p> 454 455 <dl> 456 <dt>window</dt> 457 458 <dd>A data structure describing a sub-rectangle of the screen 459 (possibly the entire screen). You can write to a window as 460 though it were a miniature screen, scrolling independently of 461 other windows on the physical screen.</dd> 462 463 <dt>screens</dt> 464 465 <dd>A subset of windows which are as large as the terminal 466 screen, i.e., they start at the upper left hand corner and 467 encompass the lower right hand corner. One of these, 468 <code>stdscr</code>, is automatically provided for the 469 programmer.</dd> 470 471 <dt>terminal screen</dt> 472 473 <dd>The package's idea of what the terminal display currently 474 looks like, i.e., what the user sees now. This is a special 475 screen.</dd> 476 </dl> 477 478 <h1><a name="curses" id="curses">The Curses Library</a></h1> 479 480 <h2><a name="overview" id="overview">An Overview of Curses</a></h2> 481 482 <h3><a name="compiling" id="compiling">Compiling Programs using 483 Curses</a></h3> 484 485 <p>In order to use the library, it is necessary to have certain 486 types and variables defined. Therefore, the programmer must have 487 a line:</p> 488 489 <pre> 490 #include <curses.h> 491</pre> 492 493 <p>at the top of the program source. The screen package uses the 494 Standard I/O library, so <code><curses.h></code> includes 495 <code><stdio.h></code>. <code><curses.h></code> also 496 includes <code><termios.h></code>, 497 <code><termio.h></code>, or <code><sgtty.h></code> 498 depending on your system. It is redundant (but harmless) for the 499 programmer to do these includes, too. In linking with 500 <code>curses</code> you need to have <code>-lncurses</code> in 501 your LDFLAGS or on the command line. There is no need for any 502 other libraries.</p> 503 504 <h3><a name="updating" id="updating">Updating the Screen</a></h3> 505 506 <p>In order to update the screen optimally, it is necessary for 507 the routines to know what the screen currently looks like and 508 what the programmer wants it to look like next. For this purpose, 509 a data type (structure) named WINDOW is defined which describes a 510 window image to the routines, including its starting position on 511 the screen (the (y, x) coordinates of the upper left hand corner) 512 and its size. One of these (called <code>curscr</code>, for 513 current screen) is a screen image of what the terminal currently 514 looks like. Another screen (called <code>stdscr</code>, for 515 standard screen) is provided by default to make changes on.</p> 516 517 <p>A window is a purely internal representation. It is used to 518 build and store a potential image of a portion of the terminal. 519 It does not bear any necessary relation to what is really on the 520 terminal screen; it is more like a scratchpad or write 521 buffer.</p> 522 523 <p>To make the section of physical screen corresponding to a 524 window reflect the contents of the window structure, the routine 525 <code>refresh()</code> (or <code>wrefresh()</code> if the window 526 is not <code>stdscr</code>) is called.</p> 527 528 <p>A given physical screen section may be within the scope of any 529 number of overlapping windows. Also, changes can be made to 530 windows in any order, without regard to motion efficiency. Then, 531 at will, the programmer can effectively say “make it look 532 like this,” and let the package implementation determine 533 the most efficient way to repaint the screen.</p> 534 535 <h3><a name="stdscr" id="stdscr">Standard Windows and Function 536 Naming Conventions</a></h3> 537 538 <p>As hinted above, the routines can use several windows, but two 539 are automatically given: <code>curscr</code>, which knows what 540 the terminal looks like, and <code>stdscr</code>, which is what 541 the programmer wants the terminal to look like next. The user 542 should never actually access <code>curscr</code> directly. 543 Changes should be made to through the API, and then the routine 544 <code>refresh()</code> (or <code>wrefresh()</code>) called.</p> 545 546 <p>Many functions are defined to use <code>stdscr</code> as a 547 default screen. For example, to add a character to 548 <code>stdscr</code>, one calls <code>addch()</code> with the 549 desired character as argument. To write to a different window. 550 use the routine <code>waddch()</code> (for 551 <strong>w</strong>indow-specific addch()) is provided. This 552 convention of prepending function names with a “w” 553 when they are to be applied to specific windows is consistent. 554 The only routines which do not follow it are those for which a 555 window must always be specified.</p> 556 557 <p>In order to move the current (y, x) coordinates from one point 558 to another, the routines <code>move()</code> and 559 <code>wmove()</code> are provided. However, it is often desirable 560 to first move and then perform some I/O operation. In order to 561 avoid clumsiness, most I/O routines can be preceded by the prefix 562 “mv” and the desired (y, x) coordinates prepended to 563 the arguments to the function. For example, the calls</p> 564 565 <pre> 566 move(y, x); 567 addch(ch); 568</pre> 569 570 <p>can be replaced by</p> 571 572 <pre> 573 mvaddch(y, x, ch); 574</pre> 575 576 <p>and</p> 577 578 <pre> 579 wmove(win, y, x); 580 waddch(win, ch); 581</pre> 582 583 <p>can be replaced by</p> 584 585 <pre> 586 mvwaddch(win, y, x, ch); 587</pre> 588 589 <p>Note that the window description pointer (win) comes before 590 the added (y, x) coordinates. If a function requires a window 591 pointer, it is always the first parameter passed.</p> 592 593 <h3><a name="variables" id="variables">Variables</a></h3> 594 595 <p>The <code>curses</code> library sets some variables describing 596 the terminal capabilities.</p> 597 598 <pre> 599 type name description 600 ------------------------------------------------------------------ 601 int LINES number of lines on the terminal 602 int COLS number of columns on the terminal 603</pre> 604 605 <p>The <code>curses.h</code> also introduces some 606 <code>#define</code> constants and types of general 607 usefulness:</p> 608 609 <dl> 610 <dt><code>bool</code> 611 </dt> 612 613 <dd>boolean type, actually a “char” (e.g., 614 <code>bool doneit;</code>)</dd> 615 616 <dt><code>TRUE</code> 617 </dt> 618 619 <dd>boolean “true” flag (1).</dd> 620 621 <dt><code>FALSE</code> 622 </dt> 623 624 <dd>boolean “false” flag (0).</dd> 625 626 <dt><code>ERR</code> 627 </dt> 628 629 <dd>error flag returned by routines on a failure (-1).</dd> 630 631 <dt><code>OK</code> 632 </dt> 633 634 <dd>error flag returned by routines when things go right.</dd> 635 </dl> 636 637 <h2><a name="using" id="using">Using the Library</a></h2> 638 639 <p>Now we describe how to actually use the screen package. In it, 640 we assume all updating, reading, etc. is applied to 641 <code>stdscr</code>. These instructions will work on any window, 642 providing you change the function names and parameters as 643 mentioned above.</p> 644 645 <p>Here is a sample program to motivate the discussion:</p> 646 647 <pre> 648#include <stdlib.h> 649#include <curses.h> 650#include <signal.h> 651 652static void finish(int sig); 653 654int 655main(int argc, char *argv[]) 656{ 657 int num = 0; 658 659 /* initialize your non-curses data structures here */ 660 661 (void) signal(SIGINT, finish); /* arrange interrupts to terminate */ 662 663 (void) initscr(); /* initialize the curses library */ 664 keypad(stdscr, TRUE); /* enable keyboard mapping */ 665 (void) nonl(); /* tell curses not to do NL->CR/NL on output */ 666 (void) cbreak(); /* take input chars one at a time, no wait for \n */ 667 (void) echo(); /* echo input - in color */ 668 669 if (has_colors()) 670 { 671 start_color(); 672 673 /* 674 * Simple color assignment, often all we need. Color pair 0 cannot 675 * be redefined. This example uses the same value for the color 676 * pair as for the foreground color, though of course that is not 677 * necessary: 678 */ 679 init_pair(1, COLOR_RED, COLOR_BLACK); 680 init_pair(2, COLOR_GREEN, COLOR_BLACK); 681 init_pair(3, COLOR_YELLOW, COLOR_BLACK); 682 init_pair(4, COLOR_BLUE, COLOR_BLACK); 683 init_pair(5, COLOR_CYAN, COLOR_BLACK); 684 init_pair(6, COLOR_MAGENTA, COLOR_BLACK); 685 init_pair(7, COLOR_WHITE, COLOR_BLACK); 686 } 687 688 for (;;) 689 { 690 int c = getch(); /* refresh, accept single keystroke of input */ 691 attrset(COLOR_PAIR(num % 8)); 692 num++; 693 694 /* process the command keystroke */ 695 } 696 697 finish(0); /* we are done */ 698} 699 700static void finish(int sig) 701{ 702 endwin(); 703 704 /* do your non-curses wrapup here */ 705 706 exit(0); 707} 708</pre> 709 710 <h3><a name="starting" id="starting">Starting up</a></h3> 711 712 <p>In order to use the screen package, the routines must know 713 about terminal characteristics, and the space for 714 <code>curscr</code> and <code>stdscr</code> must be allocated. 715 These function <code>initscr()</code> does both these things. 716 Since it must allocate space for the windows, it can overflow 717 memory when attempting to do so. On the rare occasions this 718 happens, <code>initscr()</code> will terminate the program with 719 an error message. <code>initscr()</code> must always be called 720 before any of the routines which affect windows are used. If it 721 is not, the program will core dump as soon as either 722 <code>curscr</code> or <code>stdscr</code> are referenced. 723 However, it is usually best to wait to call it until after you 724 are sure you will need it, like after checking for startup 725 errors. Terminal status changing routines like <code>nl()</code> 726 and <code>cbreak()</code> should be called after 727 <code>initscr()</code>.</p> 728 729 <p>Once the screen windows have been allocated, you can set them 730 up for your program. If you want to, say, allow a screen to 731 scroll, use <code>scrollok()</code>. If you want the cursor to be 732 left in place after the last change, use <code>leaveok()</code>. 733 If this is not done, <code>refresh()</code> will move the cursor 734 to the window's current (y, x) coordinates after updating it.</p> 735 736 <p>You can create new windows of your own using the functions 737 <code>newwin()</code>, <code>derwin()</code>, and 738 <code>subwin()</code>. The routine <code>delwin()</code> will 739 allow you to get rid of old windows. All the options described 740 above can be applied to any window.</p> 741 742 <h3><a name="output" id="output">Output</a></h3> 743 744 <p>Now that we have set things up, we will want to actually 745 update the terminal. The basic functions used to change what will 746 go on a window are <code>addch()</code> and <code>move()</code>. 747 <code>addch()</code> adds a character at the current (y, x) 748 coordinates. <code>move()</code> changes the current (y, x) 749 coordinates to whatever you want them to be. It returns 750 <code>ERR</code> if you try to move off the window. As mentioned 751 above, you can combine the two into <code>mvaddch()</code> to do 752 both things at once.</p> 753 754 <p>The other output functions, such as <code>addstr()</code> and 755 <code>printw()</code>, all call <code>addch()</code> to add 756 characters to the window.</p> 757 758 <p>After you have put on the window what you want there, when you 759 want the portion of the terminal covered by the window to be made 760 to look like it, you must call <code>refresh()</code>. In order 761 to optimize finding changes, <code>refresh()</code> assumes that 762 any part of the window not changed since the last 763 <code>refresh()</code> of that window has not been changed on the 764 terminal, i.e., that you have not refreshed a portion of the 765 terminal with an overlapping window. If this is not the case, the 766 routine <code>touchwin()</code> is provided to make it look like 767 the entire window has been changed, thus making 768 <code>refresh()</code> check the whole subsection of the terminal 769 for changes.</p> 770 771 <p>If you call <code>wrefresh()</code> with <code>curscr</code> 772 as its argument, it will make the screen look like 773 <code>curscr</code> thinks it looks like. This is useful for 774 implementing a command which would redraw the screen in case it 775 get messed up.</p> 776 777 <h3><a name="input" id="input">Input</a></h3> 778 779 <p>The complementary function to <code>addch()</code> is 780 <code>getch()</code> which, if echo is set, will call 781 <code>addch()</code> to echo the character. Since the screen 782 package needs to know what is on the terminal at all times, if 783 characters are to be echoed, the tty must be in raw or cbreak 784 mode. Since initially the terminal has echoing enabled and is in 785 ordinary “cooked” mode, one or the other has to 786 changed before calling <code>getch()</code>; otherwise, the 787 program's output will be unpredictable.</p> 788 789 <p>When you need to accept line-oriented input in a window, the 790 functions <code>wgetstr()</code> and friends are available. There 791 is even a <code>wscanw()</code> function that can do 792 <code>scanf()</code>(3)-style multi-field parsing on window 793 input. These pseudo-line-oriented functions turn on echoing while 794 they execute.</p> 795 796 <p>The example code above uses the call <code>keypad(stdscr, 797 TRUE)</code> to enable support for function-key mapping. With 798 this feature, the <code>getch()</code> code watches the input 799 stream for character sequences that correspond to arrow and 800 function keys. These sequences are returned as pseudo-character 801 values. The <code>#define</code> values returned are listed in 802 the <code>curses.h</code> The mapping from sequences to 803 <code>#define</code> values is determined by <code>key_</code> 804 capabilities in the terminal's terminfo entry.</p> 805 806 <h3><a name="formschars" id="formschars">Using Forms 807 Characters</a></h3> 808 809 <p>The <code>addch()</code> function (and some others, including 810 <code>box()</code> and <code>border()</code>) can accept some 811 pseudo-character arguments which are specially defined by 812 <code>ncurses</code>. These are <code>#define</code> values set 813 up in the <code>curses.h</code> header; see there for a complete 814 list (look for the prefix <code>ACS_</code>).</p> 815 816 <p>The most useful of the ACS defines are the forms-drawing 817 characters. You can use these to draw boxes and simple graphs on 818 the screen. If the terminal does not have such characters, 819 <code>curses.h</code> will map them to a recognizable (though 820 ugly) set of ASCII defaults.</p> 821 822 <h3><a name="attributes" id="attributes">Character Attributes and 823 Color</a></h3> 824 825 <p>The <code>ncurses</code> package supports screen highlights 826 including standout, reverse-video, underline, and blink. It also 827 supports color, which is treated as another kind of 828 highlight.</p> 829 830 <p>Highlights are encoded, internally, as high bits of the 831 pseudo-character type (<code>chtype</code>) that 832 <code>curses.h</code> uses to represent the contents of a screen 833 cell. See the <code>curses.h</code> header file for a complete 834 list of highlight mask values (look for the prefix 835 <code>A_</code>).</p> 836 837 <p>There are two ways to make highlights. One is to logical-or 838 the value of the highlights you want into the character argument 839 of an <code>addch()</code> call, or any other output call that 840 takes a <code>chtype</code> argument.</p> 841 842 <p>The other is to set the current-highlight value. This is 843 <em>logical-OR</em>ed with any highlight you specify the first 844 way. You do this with the functions <code>attron()</code>, 845 <code>attroff()</code>, and <code>attrset()</code>; see the 846 manual pages for details. Color is a special kind of highlight. 847 The package actually thinks in terms of color pairs, combinations 848 of foreground and background colors. The sample code above sets 849 up eight color pairs, all of the guaranteed-available colors on 850 black. Note that each color pair is, in effect, given the name of 851 its foreground color. Any other range of eight non-conflicting 852 values could have been used as the first arguments of the 853 <code>init_pair()</code> values.</p> 854 855 <p>Once you have done an <code>init_pair()</code> that creates 856 color-pair N, you can use <code>COLOR_PAIR(N)</code> as a 857 highlight that invokes that particular color combination. Note 858 that <code>COLOR_PAIR(N)</code>, for constant N, is itself a 859 compile-time constant and can be used in initializers.</p> 860 861 <h3><a name="mouse" id="mouse">Mouse Interfacing</a></h3> 862 863 <p>The <code>ncurses</code> library also provides a mouse 864 interface.</p> 865 866 <blockquote> 867 <strong>NOTE:</strong> this facility is specific to 868 <code>ncurses</code>, it is not part of either the XSI Curses 869 standard, nor of System V Release 4, nor BSD curses. System V 870 Release 4 curses contains code with similar interface 871 definitions, however it is not documented. Other than by 872 disassembling the library, we have no way to determine exactly 873 how that mouse code works. Thus, we recommend that you wrap 874 mouse-related code in an #ifdef using the feature macro 875 NCURSES_MOUSE_VERSION so it will not be compiled and linked on 876 non-ncurses systems. 877 </blockquote> 878 879 <p>Presently, mouse event reporting works in the following 880 environments:</p> 881 882 <ul> 883 <li>xterm and similar programs such as rxvt.</li> 884 885 <li>Linux console, when configured with <code>gpm</code>(1), 886 Alessandro Rubini's mouse server.</li> 887 888 <li>FreeBSD sysmouse (console)</li> 889 890 <li>OS/2 EMX</li> 891 </ul> 892 893 <p>The mouse interface is very simple. To activate it, you use 894 the function <code>mousemask()</code>, passing it as first 895 argument a bit-mask that specifies what kinds of events you want 896 your program to be able to see. It will return the bit-mask of 897 events that actually become visible, which may differ from the 898 argument if the mouse device is not capable of reporting some of 899 the event types you specify.</p> 900 901 <p>Once the mouse is active, your application's command loop 902 should watch for a return value of <code>KEY_MOUSE</code> from 903 <code>wgetch()</code>. When you see this, a mouse event report 904 has been queued. To pick it off the queue, use the function 905 <code>getmouse()</code> (you must do this before the next 906 <code>wgetch()</code>, otherwise another mouse event might come 907 in and make the first one inaccessible).</p> 908 909 <p>Each call to <code>getmouse()</code> fills a structure (the 910 address of which you will pass it) with mouse event data. The 911 event data includes zero-origin, screen-relative character-cell 912 coordinates of the mouse pointer. It also includes an event mask. 913 Bits in this mask will be set, corresponding to the event type 914 being reported.</p> 915 916 <p>The mouse structure contains two additional fields which may 917 be significant in the future as ncurses interfaces to new kinds 918 of pointing device. In addition to x and y coordinates, there is 919 a slot for a z coordinate; this might be useful with 920 touch-screens that can return a pressure or duration parameter. 921 There is also a device ID field, which could be used to 922 distinguish between multiple pointing devices.</p> 923 924 <p>The class of visible events may be changed at any time via 925 <code>mousemask()</code>. Events that can be reported include 926 presses, releases, single-, double- and triple-clicks (you can 927 set the maximum button-down time for clicks). If you do not make 928 clicks visible, they will be reported as press-release pairs. In 929 some environments, the event mask may include bits reporting the 930 state of shift, alt, and ctrl keys on the keyboard during the 931 event.</p> 932 933 <p>A function to check whether a mouse event fell within a given 934 window is also supplied. You can use this to see whether a given 935 window should consider a mouse event relevant to it.</p> 936 937 <p>Because mouse event reporting will not be available in all 938 environments, it would be unwise to build <code>ncurses</code> 939 applications that <em>require</em> the use of a mouse. Rather, 940 you should use the mouse as a shortcut for point-and-shoot 941 commands your application would normally accept from the 942 keyboard. Two of the test games in the <code>ncurses</code> 943 distribution (<code>bs</code> and <code>knight</code>) contain 944 code that illustrates how this can be done.</p> 945 946 <p>See the manual page <code>curs_mouse(3X)</code> for full 947 details of the mouse-interface functions.</p> 948 949 <h3><a name="finishing" id="finishing">Finishing Up</a></h3> 950 951 <p>In order to clean up after the <code>ncurses</code> routines, 952 the routine <code>endwin()</code> is provided. It restores tty 953 modes to what they were when <code>initscr()</code> was first 954 called, and moves the cursor down to the lower-left corner. Thus, 955 anytime after the call to initscr, <code>endwin()</code> should 956 be called before exiting.</p> 957 958 <h2><a name="functions" id="functions">Function Descriptions</a></h2> 959 960 <p>We describe the detailed behavior of some important curses 961 functions here, as a supplement to the manual page 962 descriptions.</p> 963 964 <h3><a name="init" id="init">Initialization and Wrapup</a></h3> 965 966 <dl> 967 <dt><code>initscr()</code> 968 </dt> 969 970 <dd>The first function called should almost always be 971 <code>initscr()</code>. This will determine the terminal type 972 and initialize curses data structures. <code>initscr()</code> 973 also arranges that the first call to <code>refresh()</code> 974 will clear the screen. If an error occurs a message is written 975 to standard error and the program exits. Otherwise it returns a 976 pointer to stdscr. A few functions may be called before initscr 977 (<code>slk_init()</code>, <code>filter()</code>, 978 <code>ripoffline()</code>, <code>use_env()</code>, and, if you 979 are using multiple terminals, <code>newterm()</code>.)</dd> 980 981 <dt><code>endwin()</code> 982 </dt> 983 984 <dd>Your program should always call <code>endwin()</code> 985 before exiting or shelling out of the program. This function 986 will restore tty modes, move the cursor to the lower left 987 corner of the screen, reset the terminal into the proper 988 non-visual mode. Calling <code>refresh()</code> or 989 <code>doupdate()</code> after a temporary escape from the 990 program will restore the ncurses screen from before the 991 escape.</dd> 992 993 <dt><code>newterm(type, ofp, ifp)</code> 994 </dt> 995 996 <dd>A program which outputs to more than one terminal should 997 use <code>newterm()</code> instead of <code>initscr()</code>. 998 <code>newterm()</code> should be called once for each terminal. 999 It returns a variable of type <code>SCREEN *</code> which 1000 should be saved as a reference to that terminal. (NOTE: a 1001 SCREEN variable is not a <em>screen</em> in the sense we are 1002 describing in this introduction, but a collection of parameters 1003 used to assist in optimizing the display.) The arguments are 1004 the type of the terminal (a string) and <code>FILE</code> 1005 pointers for the output and input of the terminal. If type is 1006 NULL then the environment variable <code>$TERM</code> is used. 1007 <code>endwin()</code> should called once at wrapup time for 1008 each terminal opened using this function.</dd> 1009 1010 <dt><code>set_term(new)</code> 1011 </dt> 1012 1013 <dd>This function is used to switch to a different terminal 1014 previously opened by <code>newterm()</code>. The screen 1015 reference for the new terminal is passed as the parameter. The 1016 previous terminal is returned by the function. All other calls 1017 affect only the current terminal.</dd> 1018 1019 <dt><code>delscreen(sp)</code> 1020 </dt> 1021 1022 <dd>The inverse of <code>newterm()</code>; deallocates the data 1023 structures associated with a given <code>SCREEN</code> 1024 reference.</dd> 1025 </dl> 1026 1027 <h3><a name="flush" id="flush">Causing Output to the Terminal</a></h3> 1028 1029 <dl> 1030 <dt><code>refresh()</code> and <code>wrefresh(win)</code></dt> 1031 1032 <dd>These functions must be called to actually get any output 1033 on the terminal, as other routines merely manipulate data 1034 structures. <code>wrefresh()</code> copies the named window to 1035 the physical terminal screen, taking into account what is 1036 already there in order to do optimizations. 1037 <code>refresh()</code> does a refresh of <code>stdscr</code>. 1038 Unless <code>leaveok()</code> has been enabled, the physical 1039 cursor of the terminal is left at the location of the window's 1040 cursor.</dd> 1041 1042 <dt><code>doupdate()</code> and 1043 <code>wnoutrefresh(win)</code></dt> 1044 1045 <dd>These two functions allow multiple updates with more 1046 efficiency than wrefresh. To use them, it is important to 1047 understand how curses works. In addition to all the window 1048 structures, curses keeps two data structures representing the 1049 terminal screen: a physical screen, describing what is actually 1050 on the screen, and a virtual screen, describing what the 1051 programmer wants to have on the screen. wrefresh works by first 1052 copying the named window to the virtual screen 1053 (<code>wnoutrefresh()</code>), and then calling the routine to 1054 update the screen (<code>doupdate()</code>). If the programmer 1055 wishes to output several windows at once, a series of calls to 1056 <code>wrefresh</code> will result in alternating calls to 1057 <code>wnoutrefresh()</code> and <code>doupdate()</code>, 1058 causing several bursts of output to the screen. By calling 1059 <code>wnoutrefresh()</code> for each window, it is then 1060 possible to call <code>doupdate()</code> once, resulting in 1061 only one burst of output, with fewer total characters 1062 transmitted (this also avoids a visually annoying flicker at 1063 each update).</dd> 1064 </dl> 1065 1066 <h3><a name="lowlevel" id="lowlevel">Low-Level Capability 1067 Access</a></h3> 1068 1069 <dl> 1070 <dt><code>setupterm(term, filenum, errret)</code> 1071 </dt> 1072 1073 <dd> 1074 This routine is called to initialize a terminal's 1075 description, without setting up the curses screen structures 1076 or changing the tty-driver mode bits. <code>term</code> is 1077 the character string representing the name of the terminal 1078 being used. <code>filenum</code> is the UNIX file descriptor 1079 of the terminal to be used for output. <code>errret</code> is 1080 a pointer to an integer, in which a success or failure 1081 indication is returned. The values returned can be 1 (all is 1082 well), 0 (no such terminal), or -1 (some problem locating the 1083 terminfo database). 1084 1085 <p>The value of <code>term</code> can be given as NULL, which 1086 will cause the value of <code>TERM</code> in the environment 1087 to be used. The <code>errret</code> pointer can also be given 1088 as NULL, meaning no error code is wanted. If 1089 <code>errret</code> is defaulted, and something goes wrong, 1090 <code>setupterm()</code> will print an appropriate error 1091 message and exit, rather than returning. Thus, a simple 1092 program can call setupterm(0, 1, 0) and not worry about 1093 initialization errors.</p> 1094 1095 <p>After the call to <code>setupterm()</code>, the global 1096 variable <code>cur_term</code> is set to point to the current 1097 structure of terminal capabilities. By calling 1098 <code>setupterm()</code> for each terminal, and saving and 1099 restoring <code>cur_term</code>, it is possible for a program 1100 to use two or more terminals at once. 1101 <code>Setupterm()</code> also stores the names section of the 1102 terminal description in the global character array 1103 <code>ttytype[]</code>. Subsequent calls to 1104 <code>setupterm()</code> will overwrite this array, so you 1105 will have to save it yourself if need be.</p> 1106 </dd> 1107 </dl> 1108 1109 <h3><a name="debugging" id="debugging">Debugging</a></h3> 1110 1111 <blockquote> 1112 <strong>NOTE:</strong> These functions are not part of the 1113 standard curses API! 1114 </blockquote> 1115 1116 <dl> 1117 <dt><code>trace()</code> 1118 </dt> 1119 1120 <dd>This function can be used to explicitly set a trace level. 1121 If the trace level is nonzero, execution of your program will 1122 generate a file called “trace” in the current 1123 working directory containing a report on the library's actions. 1124 Higher trace levels enable more detailed (and verbose) 1125 reporting -- see comments attached to <code>TRACE_</code> 1126 defines in the <code>curses.h</code> file for details. (It is 1127 also possible to set a trace level by assigning a trace level 1128 value to the environment variable 1129 <code>NCURSES_TRACE</code>).</dd> 1130 1131 <dt><code>_tracef()</code> 1132 </dt> 1133 1134 <dd>This function can be used to output your own debugging 1135 information. It is only available only if you link with 1136 -lncurses_g. It can be used the same way as 1137 <code>printf()</code>, only it outputs a newline after the end 1138 of arguments. The output goes to a file called 1139 <code>trace</code> in the current directory.</dd> 1140 </dl> 1141 1142 <p>Trace logs can be difficult to interpret due to the sheer 1143 volume of data dumped in them. There is a script called 1144 <strong>tracemunch</strong> included with the 1145 <code>ncurses</code> distribution that can alleviate this problem 1146 somewhat; it compacts long sequences of similar operations into 1147 more succinct single-line pseudo-operations. These pseudo-ops can 1148 be distinguished by the fact that they are named in capital 1149 letters.</p> 1150 1151 <h2><a name="hints" id="hints">Hints, Tips, and Tricks</a></h2> 1152 1153 <p>The <code>ncurses</code> manual pages are a complete reference 1154 for this library. In the remainder of this document, we discuss 1155 various useful methods that may not be obvious from the manual 1156 page descriptions.</p> 1157 1158 <h3><a name="caution" id="caution">Some Notes of Caution</a></h3> 1159 1160 <p>If you find yourself thinking you need to use 1161 <code>noraw()</code> or <code>nocbreak()</code>, think again and 1162 move carefully. It is probably better design to use 1163 <code>getstr()</code> or one of its relatives to simulate cooked 1164 mode. The <code>noraw()</code> and <code>nocbreak()</code> 1165 functions try to restore cooked mode, but they may end up 1166 clobbering some control bits set before you started your 1167 application. Also, they have always been poorly documented, and 1168 are likely to hurt your application's usability with other curses 1169 libraries.</p> 1170 1171 <p>Bear in mind that <code>refresh()</code> is a synonym for 1172 <code>wrefresh(stdscr)</code>. Do not try to mix use of 1173 <code>stdscr</code> with use of windows declared by 1174 <code>newwin()</code>; a <code>refresh()</code> call will blow 1175 them off the screen. The right way to handle this is to use 1176 <code>subwin()</code>, or not touch <code>stdscr</code> at all 1177 and tile your screen with declared windows which you then 1178 <code>wnoutrefresh()</code> somewhere in your program event loop, 1179 with a single <code>doupdate()</code> call to trigger actual 1180 repainting.</p> 1181 1182 <p>You are much less likely to run into problems if you design 1183 your screen layouts to use tiled rather than overlapping windows. 1184 Historically, curses support for overlapping windows has been 1185 weak, fragile, and poorly documented. The <code>ncurses</code> 1186 library is not yet an exception to this rule.</p> 1187 1188 <p>There is a panels library included in the <code>ncurses</code> 1189 distribution that does a pretty good job of strengthening the 1190 overlapping-windows facilities.</p> 1191 1192 <p>Try to avoid using the global variables LINES and COLS. Use 1193 <code>getmaxyx()</code> on the <code>stdscr</code> context 1194 instead. Reason: your code may be ported to run in an environment 1195 with window resizes, in which case several screens could be open 1196 with different sizes.</p> 1197 1198 <h3><a name="leaving" id="leaving">Temporarily Leaving NCURSES 1199 Mode</a></h3> 1200 1201 <p>Sometimes you will want to write a program that spends most of 1202 its time in screen mode, but occasionally returns to ordinary 1203 “cooked” mode. A common reason for this is to support 1204 shell-out. This behavior is simple to arrange in 1205 <code>ncurses</code>.</p> 1206 1207 <p>To leave <code>ncurses</code> mode, call <code>endwin()</code> 1208 as you would if you were intending to terminate the program. This 1209 will take the screen back to cooked mode; you can do your 1210 shell-out. When you want to return to <code>ncurses</code> mode, 1211 simply call <code>refresh()</code> or <code>doupdate()</code>. 1212 This will repaint the screen.</p> 1213 1214 <p>There is a boolean function, <code>isendwin()</code>, which 1215 code can use to test whether <code>ncurses</code> screen mode is 1216 active. It returns <code>TRUE</code> in the interval between an 1217 <code>endwin()</code> call and the following 1218 <code>refresh()</code>, <code>FALSE</code> otherwise.</p> 1219 1220 <p>Here is some sample code for shellout:</p> 1221 1222 <pre> 1223 addstr("Shelling out..."); 1224 def_prog_mode(); /* save current tty modes */ 1225 endwin(); /* restore original tty modes */ 1226 system("sh"); /* run shell */ 1227 addstr("returned.\n"); /* prepare return message */ 1228 refresh(); /* restore save modes, repaint screen */ 1229</pre> 1230 1231 <h3><a name="xterm" id="xterm">Using NCURSES under XTERM</a></h3> 1232 1233 <p>A resize operation in X sends <code>SIGWINCH</code> to the 1234 application running under xterm. The easiest way to handle 1235 <code>SIGWINCH</code> is to do an <code>endwin</code>, followed 1236 by an <code>refresh</code> and a screen repaint you code 1237 yourself. The <code>refresh</code> will pick up the new screen 1238 size from the xterm's environment.</p> 1239 1240 <p>That is the standard way, of course (it even works with some 1241 vendor's curses implementations). Its drawback is that it clears 1242 the screen to reinitialize the display, and does not resize 1243 subwindows which must be shrunk. <code>Ncurses</code> provides an 1244 extension which works better, the <code>resizeterm</code> 1245 function. That function ensures that all windows are limited to 1246 the new screen dimensions, and pads <code>stdscr</code> with 1247 blanks if the screen is larger.</p> 1248 1249 <p>The <code>ncurses</code> library provides a SIGWINCH signal 1250 handler, which pushes a <code>KEY_RESIZE</code> via the wgetch() 1251 calls. When <code>ncurses</code> returns that code, it calls 1252 <code>resizeterm</code> to update the size of the standard 1253 screen's window, repainting that (filling with blanks or 1254 truncating as needed). It also resizes other windows, but its 1255 effect may be less satisfactory because it cannot know how you 1256 want the screen re-painted. You will usually have to write 1257 special-purpose code to handle <code>KEY_RESIZE</code> 1258 yourself.</p> 1259 1260 <h3><a name="screens" id="screens">Handling Multiple Terminal 1261 Screens</a></h3> 1262 1263 <p>The <code>initscr()</code> function actually calls a function 1264 named <code>newterm()</code> to do most of its work. If you are 1265 writing a program that opens multiple terminals, use 1266 <code>newterm()</code> directly.</p> 1267 1268 <p>For each call, you will have to specify a terminal type and a 1269 pair of file pointers; each call will return a screen reference, 1270 and <code>stdscr</code> will be set to the last one allocated. 1271 You will switch between screens with the <code>set_term</code> 1272 call. Note that you will also have to call 1273 <code>def_shell_mode</code> and <code>def_prog_mode</code> on 1274 each tty yourself.</p> 1275 1276 <h3><a name="testing" id="testing">Testing for Terminal 1277 Capabilities</a></h3> 1278 1279 <p>Sometimes you may want to write programs that test for the 1280 presence of various capabilities before deciding whether to go 1281 into <code>ncurses</code> mode. An easy way to do this is to call 1282 <code>setupterm()</code>, then use the functions 1283 <code>tigetflag()</code>, <code>tigetnum()</code>, and 1284 <code>tigetstr()</code> to do your testing.</p> 1285 1286 <p>A particularly useful case of this often comes up when you 1287 want to test whether a given terminal type should be treated as 1288 “smart” (cursor-addressable) or “stupid”. 1289 The right way to test this is to see if the return value of 1290 <code>tigetstr("cup")</code> is non-NULL. Alternatively, you can 1291 include the <code>term.h</code> file and test the value of the 1292 macro <code>cursor_address</code>.</p> 1293 1294 <h3><a name="tuning" id="tuning">Tuning for Speed</a></h3> 1295 1296 <p>Use the <code>addchstr()</code> family of functions for fast 1297 screen-painting of text when you know the text does not contain 1298 any control characters. Try to make attribute changes infrequent 1299 on your screens. Do not use the <code>immedok()</code> 1300 option!</p> 1301 1302 <h3><a name="special" id="special">Special Features of 1303 NCURSES</a></h3> 1304 1305 <p>The <code>wresize()</code> function allows you to resize a 1306 window in place. The associated <code>resizeterm()</code> 1307 function simplifies the construction of <a href= 1308 "#xterm">SIGWINCH</a> handlers, for resizing all windows.</p> 1309 1310 <p>The <code>define_key()</code> function allows you to define at 1311 runtime function-key control sequences which are not in the 1312 terminal description. The <code>keyok()</code> function allows 1313 you to temporarily enable or disable interpretation of any 1314 function-key control sequence.</p> 1315 1316 <p>The <code>use_default_colors()</code> function allows you to 1317 construct applications which can use the terminal's default 1318 foreground and background colors as an additional "default" 1319 color. Several terminal emulators support this feature, which is 1320 based on ISO 6429.</p> 1321 1322 <p>Ncurses supports up 16 colors, unlike SVr4 curses which 1323 defines only 8. While most terminals which provide color allow 1324 only 8 colors, about a quarter (including XFree86 xterm) support 1325 16 colors.</p> 1326 1327 <h2><a name="compat" id="compat">Compatibility with Older 1328 Versions</a></h2> 1329 1330 <p>Despite our best efforts, there are some differences between 1331 <code>ncurses</code> and the (undocumented!) behavior of older 1332 curses implementations. These arise from ambiguities or omissions 1333 in the documentation of the API.</p> 1334 1335 <h3><a name="refbug" id="refbug">Refresh of Overlapping 1336 Windows</a></h3> 1337 1338 <p>If you define two windows A and B that overlap, and then 1339 alternately scribble on and refresh them, the changes made to the 1340 overlapping region under historic <code>curses</code> versions 1341 were often not documented precisely.</p> 1342 1343 <p>To understand why this is a problem, remember that screen 1344 updates are calculated between two representations of the 1345 <em>entire</em> display. The documentation says that when you 1346 refresh a window, it is first copied to the virtual screen, and 1347 then changes are calculated to update the physical screen (and 1348 applied to the terminal). But "copied to" is not very specific, 1349 and subtle differences in how copying works can produce different 1350 behaviors in the case where two overlapping windows are each 1351 being refreshed at unpredictable intervals.</p> 1352 1353 <p>What happens to the overlapping region depends on what 1354 <code>wnoutrefresh()</code> does with its argument -- what 1355 portions of the argument window it copies to the virtual screen. 1356 Some implementations do "change copy", copying down only 1357 locations in the window that have changed (or been marked changed 1358 with <code>wtouchln()</code> and friends). Some implementations 1359 do "entire copy", copying <em>all</em> window locations to the 1360 virtual screen whether or not they have changed.</p> 1361 1362 <p>The <code>ncurses</code> library itself has not always been 1363 consistent on this score. Due to a bug, versions 1.8.7 to 1.9.8a 1364 did entire copy. Versions 1.8.6 and older, and versions 1.9.9 and 1365 newer, do change copy.</p> 1366 1367 <p>For most commercial curses implementations, it is not 1368 documented and not known for sure (at least not to the 1369 <code>ncurses</code> maintainers) whether they do change copy or 1370 entire copy. We know that System V release 3 curses has logic in 1371 it that looks like an attempt to do change copy, but the 1372 surrounding logic and data representations are sufficiently 1373 complex, and our knowledge sufficiently indirect, that it is hard 1374 to know whether this is reliable. It is not clear what the SVr4 1375 documentation and XSI standard intend. The XSI Curses standard 1376 barely mentions wnoutrefresh(); the SVr4 documents seem to be 1377 describing entire-copy, but it is possible with some effort and 1378 straining to read them the other way.</p> 1379 1380 <p>It might therefore be unwise to rely on either behavior in 1381 programs that might have to be linked with other curses 1382 implementations. Instead, you can do an explicit 1383 <code>touchwin()</code> before the <code>wnoutrefresh()</code> 1384 call to guarantee an entire-contents copy anywhere.</p> 1385 1386 <p>The really clean way to handle this is to use the panels 1387 library. If, when you want a screen update, you do 1388 <code>update_panels()</code>, it will do all the necessary 1389 <code>wnoutrefresh()</code> calls for whatever panel stacking 1390 order you have defined. Then you can do one 1391 <code>doupdate()</code> and there will be a <em>single</em> burst 1392 of physical I/O that will do all your updates.</p> 1393 1394 <h3><a name="backbug" id="backbug">Background Erase</a></h3> 1395 1396 <p>If you have been using a very old versions of 1397 <code>ncurses</code> (1.8.7 or older) you may be surprised by the 1398 behavior of the erase functions. In older versions, erased areas 1399 of a window were filled with a blank modified by the window's 1400 current attribute (as set by <strong>wattrset()</strong>, 1401 <strong>wattron()</strong>, <strong>wattroff()</strong> and 1402 friends).</p> 1403 1404 <p>In newer versions, this is not so. Instead, the attribute of 1405 erased blanks is normal unless and until it is modified by the 1406 functions <code>bkgdset()</code> or <code>wbkgdset()</code>.</p> 1407 1408 <p>This change in behavior conforms <code>ncurses</code> to 1409 System V Release 4 and the XSI Curses standard.</p> 1410 1411 <h2><a name="xsifuncs" id="xsifuncs">XSI Curses Conformance</a></h2> 1412 1413 <p>The <code>ncurses</code> library is intended to be base-level 1414 conformant with the XSI Curses standard from X/Open. Many 1415 extended-level features (in fact, almost all features not 1416 directly concerned with wide characters and internationalization) 1417 are also supported.</p> 1418 1419 <p>One effect of XSI conformance is the change in behavior 1420 described under <a href="#backbug">"Background Erase -- 1421 Compatibility with Old Versions"</a>.</p> 1422 1423 <p>Also, <code>ncurses</code> meets the XSI requirement that 1424 every macro entry point have a corresponding function which may 1425 be linked (and will be prototype-checked) if the macro definition 1426 is disabled with <code>#undef</code>.</p> 1427 1428 <h1><a name="panels" id="panels">The Panels Library</a></h1> 1429 1430 <p>The <code>ncurses</code> library by itself provides good 1431 support for screen displays in which the windows are tiled 1432 (non-overlapping). In the more general case that windows may 1433 overlap, you have to use a series of <code>wnoutrefresh()</code> 1434 calls followed by a <code>doupdate()</code>, and be careful about 1435 the order you do the window refreshes in. It has to be 1436 bottom-upwards, otherwise parts of windows that should be 1437 obscured will show through.</p> 1438 1439 <p>When your interface design is such that windows may dive 1440 deeper into the visibility stack or pop to the top at runtime, 1441 the resulting book-keeping can be tedious and difficult to get 1442 right. Hence the panels library.</p> 1443 1444 <p>The <code>panel</code> library first appeared in AT&T 1445 System V. The version documented here is the <code>panel</code> 1446 code distributed with <code>ncurses</code>.</p> 1447 1448 <h2><a name="pcompile" id="pcompile">Compiling With the Panels 1449 Library</a></h2> 1450 1451 <p>Your panels-using modules must import the panels library 1452 declarations with</p> 1453 1454 <pre> 1455 #include <panel.h> 1456</pre> 1457 1458 <p>and must be linked explicitly with the panels library using an 1459 <code>-lpanel</code> argument. Note that they must also link the 1460 <code>ncurses</code> library with <code>-lncurses</code>. Many 1461 linkers are two-pass and will accept either order, but it is 1462 still good practice to put <code>-lpanel</code> first and 1463 <code>-lncurses</code> second.</p> 1464 1465 <h2><a name="poverview" id="poverview">Overview of Panels</a></h2> 1466 1467 <p>A panel object is a window that is implicitly treated as part 1468 of a <dfn>deck</dfn> including all other panel objects. The deck 1469 has an implicit bottom-to-top visibility order. The panels 1470 library includes an update function (analogous to 1471 <code>refresh()</code>) that displays all panels in the deck in 1472 the proper order to resolve overlaps. The standard window, 1473 <code>stdscr</code>, is considered below all panels.</p> 1474 1475 <p>Details on the panels functions are available in the man 1476 pages. We will just hit the highlights here.</p> 1477 1478 <p>You create a panel from a window by calling 1479 <code>new_panel()</code> on a window pointer. It then becomes the 1480 top of the deck. The panel's window is available as the value of 1481 <code>panel_window()</code> called with the panel pointer as 1482 argument.</p> 1483 1484 <p>You can delete a panel (removing it from the deck) with 1485 <code>del_panel</code>. This will not deallocate the associated 1486 window; you have to do that yourself. You can replace a panel's 1487 window with a different window by calling 1488 <code>replace_window</code>. The new window may be of different 1489 size; the panel code will re-compute all overlaps. This operation 1490 does not change the panel's position in the deck.</p> 1491 1492 <p>To move a panel's window, use <code>move_panel()</code>. The 1493 <code>mvwin()</code> function on the panel's window is not 1494 sufficient because it does not update the panels library's 1495 representation of where the windows are. This operation leaves 1496 the panel's depth, contents, and size unchanged.</p> 1497 1498 <p>Two functions (<code>top_panel()</code>, 1499 <code>bottom_panel()</code>) are provided for rearranging the 1500 deck. The first pops its argument window to the top of the deck; 1501 the second sends it to the bottom. Either operation leaves the 1502 panel's screen location, contents, and size unchanged.</p> 1503 1504 <p>The function <code>update_panels()</code> does all the 1505 <code>wnoutrefresh()</code> calls needed to prepare for 1506 <code>doupdate()</code> (which you must call yourself, 1507 afterwards).</p> 1508 1509 <p>Typically, you will want to call <code>update_panels()</code> 1510 and <code>doupdate()</code> just before accepting command input, 1511 once in each cycle of interaction with the user. If you call 1512 <code>update_panels()</code> after each and every panel write, 1513 you will generate a lot of unnecessary refresh activity and 1514 screen flicker.</p> 1515 1516 <h2><a name="pstdscr" id="pstdscr">Panels, Input, and the 1517 Standard Screen</a></h2> 1518 1519 <p>You should not mix <code>wnoutrefresh()</code> or 1520 <code>wrefresh()</code> operations with panels code; this will 1521 work only if the argument window is either in the top panel or 1522 unobscured by any other panels.</p> 1523 1524 <p>The <code>stsdcr</code> window is a special case. It is 1525 considered below all panels. Because changes to panels may 1526 obscure parts of <code>stdscr</code>, though, you should call 1527 <code>update_panels()</code> before <code>doupdate()</code> even 1528 when you only change <code>stdscr</code>.</p> 1529 1530 <p>Note that <code>wgetch</code> automatically calls 1531 <code>wrefresh</code>. Therefore, before requesting input from a 1532 panel window, you need to be sure that the panel is totally 1533 unobscured.</p> 1534 1535 <p>There is presently no way to display changes to one obscured 1536 panel without repainting all panels.</p> 1537 1538 <h2><a name="hiding" id="hiding">Hiding Panels</a></h2> 1539 1540 <p>It is possible to remove a panel from the deck temporarily; 1541 use <code>hide_panel</code> for this. Use 1542 <code>show_panel()</code> to render it visible again. The 1543 predicate function <code>panel_hidden</code> tests whether or not 1544 a panel is hidden.</p> 1545 1546 <p>The <code>panel_update</code> code ignores hidden panels. You 1547 cannot do <code>top_panel()</code> or <code>bottom_panel</code> 1548 on a hidden panel(). Other panels operations are applicable.</p> 1549 1550 <h2><a name="pmisc" id="pmisc">Miscellaneous Other Facilities</a></h2> 1551 1552 <p>It is possible to navigate the deck using the functions 1553 <code>panel_above()</code> and <code>panel_below</code>. Handed a 1554 panel pointer, they return the panel above or below that panel. 1555 Handed <code>NULL</code>, they return the bottom-most or top-most 1556 panel.</p> 1557 1558 <p>Every panel has an associated user pointer, not used by the 1559 panel code, to which you can attach application data. See the man 1560 page documentation of <code>set_panel_userptr()</code> and 1561 <code>panel_userptr</code> for details.</p> 1562 1563 <h1><a name="menu" id="menu">The Menu Library</a></h1> 1564 1565 <p>A menu is a screen display that assists the user to choose 1566 some subset of a given set of items. The <code>menu</code> 1567 library is a curses extension that supports easy programming of 1568 menu hierarchies with a uniform but flexible interface.</p> 1569 1570 <p>The <code>menu</code> library first appeared in AT&T 1571 System V. The version documented here is the <code>menu</code> 1572 code distributed with <code>ncurses</code>.</p> 1573 1574 <h2><a name="mcompile" id="mcompile">Compiling With the menu 1575 Library</a></h2> 1576 1577 <p>Your menu-using modules must import the menu library 1578 declarations with</p> 1579 1580 <pre> 1581 #include <menu.h> 1582</pre> 1583 1584 <p>and must be linked explicitly with the menus library using an 1585 <code>-lmenu</code> argument. Note that they must also link the 1586 <code>ncurses</code> library with <code>-lncurses</code>. Many 1587 linkers are two-pass and will accept either order, but it is 1588 still good practice to put <code>-lmenu</code> first and 1589 <code>-lncurses</code> second.</p> 1590 1591 <h2><a name="moverview" id="moverview">Overview of Menus</a></h2> 1592 1593 <p>The menus created by this library consist of collections of 1594 <dfn>items</dfn> including a name string part and a description 1595 string part. To make menus, you create groups of these items and 1596 connect them with menu frame objects.</p> 1597 1598 <p>The menu can then by <dfn>posted</dfn>, that is written to an 1599 associated window. Actually, each menu has two associated 1600 windows; a containing window in which the programmer can scribble 1601 titles or borders, and a subwindow in which the menu items proper 1602 are displayed. If this subwindow is too small to display all the 1603 items, it will be a scrollable viewport on the collection of 1604 items.</p> 1605 1606 <p>A menu may also be <dfn>unposted</dfn> (that is, undisplayed), 1607 and finally freed to make the storage associated with it and its 1608 items available for re-use.</p> 1609 1610 <p>The general flow of control of a menu program looks like 1611 this:</p> 1612 1613 <ol> 1614 <li>Initialize <code>curses</code>.</li> 1615 1616 <li>Create the menu items, using <code>new_item()</code>.</li> 1617 1618 <li>Create the menu using <code>new_menu()</code>.</li> 1619 1620 <li>Post the menu using <code>post_menu()</code>.</li> 1621 1622 <li>Refresh the screen.</li> 1623 1624 <li>Process user requests via an input loop.</li> 1625 1626 <li>Unpost the menu using <code>unpost_menu()</code>.</li> 1627 1628 <li>Free the menu, using <code>free_menu()</code>.</li> 1629 1630 <li>Free the items using <code>free_item()</code>.</li> 1631 1632 <li>Terminate <code>curses</code>.</li> 1633 </ol> 1634 1635 <h2><a name="mselect" id="mselect">Selecting items</a></h2> 1636 1637 <p>Menus may be multi-valued or (the default) single-valued (see 1638 the manual page <code>menu_opts(3x)</code> to see how to change 1639 the default). Both types always have a <dfn>current 1640 item</dfn>.</p> 1641 1642 <p>From a single-valued menu you can read the selected value 1643 simply by looking at the current item. From a multi-valued menu, 1644 you get the selected set by looping through the items applying 1645 the <code>item_value()</code> predicate function. Your 1646 menu-processing code can use the function 1647 <code>set_item_value()</code> to flag the items in the select 1648 set.</p> 1649 1650 <p>Menu items can be made unselectable using 1651 <code>set_item_opts()</code> or <code>item_opts_off()</code> with 1652 the <code>O_SELECTABLE</code> argument. This is the only option 1653 so far defined for menus, but it is good practice to code as 1654 though other option bits might be on.</p> 1655 1656 <h2><a name="mdisplay" id="mdisplay">Menu Display</a></h2> 1657 1658 <p>The menu library calculates a minimum display size for your 1659 window, based on the following variables:</p> 1660 1661 <ul> 1662 <li>The number and maximum length of the menu items</li> 1663 1664 <li>Whether the O_ROWMAJOR option is enabled</li> 1665 1666 <li>Whether display of descriptions is enabled</li> 1667 1668 <li>Whatever menu format may have been set by the 1669 programmer</li> 1670 1671 <li>The length of the menu mark string used for highlighting 1672 selected items</li> 1673 </ul> 1674 1675 <p>The function <code>set_menu_format()</code> allows you to set 1676 the maximum size of the viewport or <dfn>menu page</dfn> that 1677 will be used to display menu items. You can retrieve any format 1678 associated with a menu with <code>menu_format()</code>. The 1679 default format is rows=16, columns=1.</p> 1680 1681 <p>The actual menu page may be smaller than the format size. This 1682 depends on the item number and size and whether O_ROWMAJOR is on. 1683 This option (on by default) causes menu items to be displayed in 1684 a “raster-scan” pattern, so that if more than one 1685 item will fit horizontally the first couple of items are 1686 side-by-side in the top row. The alternative is column-major 1687 display, which tries to put the first several items in the first 1688 column.</p> 1689 1690 <p>As mentioned above, a menu format not large enough to allow 1691 all items to fit on-screen will result in a menu display that is 1692 vertically scrollable.</p> 1693 1694 <p>You can scroll it with requests to the menu driver, which will 1695 be described in the section on <a href="#minput">menu input 1696 handling</a>.</p> 1697 1698 <p>Each menu has a <dfn>mark string</dfn> used to visually tag 1699 selected items; see the <code>menu_mark(3x)</code> manual page 1700 for details. The mark string length also influences the menu page 1701 size.</p> 1702 1703 <p>The function <code>scale_menu()</code> returns the minimum 1704 display size that the menu code computes from all these factors. 1705 There are other menu display attributes including a select 1706 attribute, an attribute for selectable items, an attribute for 1707 unselectable items, and a pad character used to separate item 1708 name text from description text. These have reasonable defaults 1709 which the library allows you to change (see the 1710 <code>menu_attribs(3x)</code> manual page.</p> 1711 1712 <h2><a name="mwindows" id="mwindows">Menu Windows</a></h2> 1713 1714 <p>Each menu has, as mentioned previously, a pair of associated 1715 windows. Both these windows are painted when the menu is posted 1716 and erased when the menu is unposted.</p> 1717 1718 <p>The outer or frame window is not otherwise touched by the menu 1719 routines. It exists so the programmer can associate a title, a 1720 border, or perhaps help text with the menu and have it properly 1721 refreshed or erased at post/unpost time. The inner window or 1722 <dfn>subwindow</dfn> is where the current menu page is 1723 displayed.</p> 1724 1725 <p>By default, both windows are <code>stdscr</code>. You can set 1726 them with the functions in <code>menu_win(3x)</code>.</p> 1727 1728 <p>When you call <code>post_menu()</code>, you write the menu to 1729 its subwindow. When you call <code>unpost_menu()</code>, you 1730 erase the subwindow, However, neither of these actually modifies 1731 the screen. To do that, call <code>wrefresh()</code> or some 1732 equivalent.</p> 1733 1734 <h2><a name="minput" id="minput">Processing Menu Input</a></h2> 1735 1736 <p>The main loop of your menu-processing code should call 1737 <code>menu_driver()</code> repeatedly. The first argument of this 1738 routine is a menu pointer; the second is a menu command code. You 1739 should write an input-fetching routine that maps input characters 1740 to menu command codes, and pass its output to 1741 <code>menu_driver()</code>. The menu command codes are fully 1742 documented in <code>menu_driver(3x)</code>.</p> 1743 1744 <p>The simplest group of command codes is 1745 <code>REQ_NEXT_ITEM</code>, <code>REQ_PREV_ITEM</code>, 1746 <code>REQ_FIRST_ITEM</code>, <code>REQ_LAST_ITEM</code>, 1747 <code>REQ_UP_ITEM</code>, <code>REQ_DOWN_ITEM</code>, 1748 <code>REQ_LEFT_ITEM</code>, <code>REQ_RIGHT_ITEM</code>. These 1749 change the currently selected item. These requests may cause 1750 scrolling of the menu page if it only partially displayed.</p> 1751 1752 <p>There are explicit requests for scrolling which also change 1753 the current item (because the select location does not change, 1754 but the item there does). These are <code>REQ_SCR_DLINE</code>, 1755 <code>REQ_SCR_ULINE</code>, <code>REQ_SCR_DPAGE</code>, and 1756 <code>REQ_SCR_UPAGE</code>.</p> 1757 1758 <p>The <code>REQ_TOGGLE_ITEM</code> selects or deselects the 1759 current item. It is for use in multi-valued menus; if you use it 1760 with <code>O_ONEVALUE</code> on, you will get an error return 1761 (<code>E_REQUEST_DENIED</code>).</p> 1762 1763 <p>Each menu has an associated pattern buffer. The 1764 <code>menu_driver()</code> logic tries to accumulate printable 1765 ASCII characters passed in in that buffer; when it matches a 1766 prefix of an item name, that item (or the next matching item) is 1767 selected. If appending a character yields no new match, that 1768 character is deleted from the pattern buffer, and 1769 <code>menu_driver()</code> returns <code>E_NO_MATCH</code>.</p> 1770 1771 <p>Some requests change the pattern buffer directly: 1772 <code>REQ_CLEAR_PATTERN</code>, <code>REQ_BACK_PATTERN</code>, 1773 <code>REQ_NEXT_MATCH</code>, <code>REQ_PREV_MATCH</code>. The 1774 latter two are useful when pattern buffer input matches more than 1775 one item in a multi-valued menu.</p> 1776 1777 <p>Each successful scroll or item navigation request clears the 1778 pattern buffer. It is also possible to set the pattern buffer 1779 explicitly with <code>set_menu_pattern()</code>.</p> 1780 1781 <p>Finally, menu driver requests above the constant 1782 <code>MAX_COMMAND</code> are considered application-specific 1783 commands. The <code>menu_driver()</code> code ignores them and 1784 returns <code>E_UNKNOWN_COMMAND</code>.</p> 1785 1786 <h2><a name="mmisc" id="mmisc">Miscellaneous Other Features</a></h2> 1787 1788 <p>Various menu options can affect the processing and visual 1789 appearance and input processing of menus. See <code>menu_opts(3x) 1790 for details.</code></p> 1791 1792 <p>It is possible to change the current item from application 1793 code; this is useful if you want to write your own navigation 1794 requests. It is also possible to explicitly set the top row of 1795 the menu display. See <code>mitem_current(3x)</code>. If your 1796 application needs to change the menu subwindow cursor for any 1797 reason, <code>pos_menu_cursor()</code> will restore it to the 1798 correct location for continuing menu driver processing.</p> 1799 1800 <p>It is possible to set hooks to be called at menu 1801 initialization and wrapup time, and whenever the selected item 1802 changes. See <code>menu_hook(3x)</code>.</p> 1803 1804 <p>Each item, and each menu, has an associated user pointer on 1805 which you can hang application data. See 1806 <code>mitem_userptr(3x)</code> and 1807 <code>menu_userptr(3x)</code>.</p> 1808 1809 <h1><a name="form" id="form">The Forms Library</a></h1> 1810 1811 <p>The <code>form</code> library is a curses extension that 1812 supports easy programming of on-screen forms for data entry and 1813 program control.</p> 1814 1815 <p>The <code>form</code> library first appeared in AT&T 1816 System V. The version documented here is the <code>form</code> 1817 code distributed with <code>ncurses</code>.</p> 1818 1819 <h2><a name="fcompile" id="fcompile">Compiling With the form 1820 Library</a></h2> 1821 1822 <p>Your form-using modules must import the form library 1823 declarations with</p> 1824 1825 <pre> 1826 #include <form.h> 1827</pre> 1828 1829 <p>and must be linked explicitly with the forms library using an 1830 <code>-lform</code> argument. Note that they must also link the 1831 <code>ncurses</code> library with <code>-lncurses</code>. Many 1832 linkers are two-pass and will accept either order, but it is 1833 still good practice to put <code>-lform</code> first and 1834 <code>-lncurses</code> second.</p> 1835 1836 <h2><a name="foverview" id="foverview">Overview of Forms</a></h2> 1837 1838 <p>A form is a collection of fields; each field may be either a 1839 label (explanatory text) or a data-entry location. Long forms may 1840 be segmented into pages; each entry to a new page clears the 1841 screen.</p> 1842 1843 <p>To make forms, you create groups of fields and connect them 1844 with form frame objects; the form library makes this relatively 1845 simple.</p> 1846 1847 <p>Once defined, a form can be <dfn>posted</dfn>, that is written 1848 to an associated window. Actually, each form has two associated 1849 windows; a containing window in which the programmer can scribble 1850 titles or borders, and a subwindow in which the form fields 1851 proper are displayed.</p> 1852 1853 <p>As the form user fills out the posted form, navigation and 1854 editing keys support movement between fields, editing keys 1855 support modifying field, and plain text adds to or changes data 1856 in a current field. The form library allows you (the forms 1857 designer) to bind each navigation and editing key to any 1858 keystroke accepted by <code>curses</code> Fields may have 1859 validation conditions on them, so that they check input data for 1860 type and value. The form library supplies a rich set of 1861 pre-defined field types, and makes it relatively easy to define 1862 new ones.</p> 1863 1864 <p>Once its transaction is completed (or aborted), a form may be 1865 <dfn>unposted</dfn> (that is, undisplayed), and finally freed to 1866 make the storage associated with it and its items available for 1867 re-use.</p> 1868 1869 <p>The general flow of control of a form program looks like 1870 this:</p> 1871 1872 <ol> 1873 <li>Initialize <code>curses</code>.</li> 1874 1875 <li>Create the form fields, using 1876 <code>new_field()</code>.</li> 1877 1878 <li>Create the form using <code>new_form()</code>.</li> 1879 1880 <li>Post the form using <code>post_form()</code>.</li> 1881 1882 <li>Refresh the screen.</li> 1883 1884 <li>Process user requests via an input loop.</li> 1885 1886 <li>Unpost the form using <code>unpost_form()</code>.</li> 1887 1888 <li>Free the form, using <code>free_form()</code>.</li> 1889 1890 <li>Free the fields using <code>free_field()</code>.</li> 1891 1892 <li>Terminate <code>curses</code>.</li> 1893 </ol> 1894 1895 <p>Note that this looks much like a menu program; the form 1896 library handles tasks which are in many ways similar, and its 1897 interface was obviously designed to resemble that of the <a href= 1898 "#menu">menu library</a> wherever possible.</p> 1899 1900 <p>In forms programs, however, the “process user 1901 requests” is somewhat more complicated than for menus. 1902 Besides menu-like navigation operations, the menu driver loop has 1903 to support field editing and data validation.</p> 1904 1905 <h2><a name="fcreate" id="fcreate">Creating and Freeing Fields 1906 and Forms</a></h2> 1907 1908 <p>The basic function for creating fields is 1909 <code>new_field()</code>:</p> 1910 1911 <pre> 1912FIELD *new_field(int height, int width, /* new field size */ 1913 int top, int left, /* upper left corner */ 1914 int offscreen, /* number of offscreen rows */ 1915 int nbuf); /* number of working buffers */ 1916</pre> 1917 1918 <p>Menu items always occupy a single row, but forms fields may 1919 have multiple rows. So <code>new_field()</code> requires you to 1920 specify a width and height (the first two arguments, which mist 1921 both be greater than zero).</p> 1922 1923 <p>You must also specify the location of the field's upper left 1924 corner on the screen (the third and fourth arguments, which must 1925 be zero or greater). Note that these coordinates are relative to 1926 the form subwindow, which will coincide with <code>stdscr</code> 1927 by default but need not be <code>stdscr</code> if you have done 1928 an explicit <code>set_form_win()</code> call.</p> 1929 1930 <p>The fifth argument allows you to specify a number of 1931 off-screen rows. If this is zero, the entire field will always be 1932 displayed. If it is nonzero, the form will be scrollable, with 1933 only one screen-full (initially the top part) displayed at any 1934 given time. If you make a field dynamic and grow it so it will no 1935 longer fit on the screen, the form will become scrollable even if 1936 the <code>offscreen</code> argument was initially zero.</p> 1937 1938 <p>The forms library allocates one working buffer per field; the 1939 size of each buffer is <code>((height + offscreen)*width + 1940 1</code>, one character for each position in the field plus a NUL 1941 terminator. The sixth argument is the number of additional data 1942 buffers to allocate for the field; your application can use them 1943 for its own purposes.</p> 1944 1945 <pre> 1946FIELD *dup_field(FIELD *field, /* field to copy */ 1947 int top, int left); /* location of new copy */ 1948</pre> 1949 1950 <p>The function <code>dup_field()</code> duplicates an existing 1951 field at a new location. Size and buffering information are 1952 copied; some attribute flags and status bits are not (see the 1953 <code>form_field_new(3X)</code> for details).</p> 1954 1955 <pre> 1956FIELD *link_field(FIELD *field, /* field to copy */ 1957 int top, int left); /* location of new copy */ 1958</pre> 1959 1960 <p>The function <code>link_field()</code> also duplicates an 1961 existing field at a new location. The difference from 1962 <code>dup_field()</code> is that it arranges for the new field's 1963 buffer to be shared with the old one.</p> 1964 1965 <p>Besides the obvious use in making a field editable from two 1966 different form pages, linked fields give you a way to hack in 1967 dynamic labels. If you declare several fields linked to an 1968 original, and then make them inactive, changes from the original 1969 will still be propagated to the linked fields.</p> 1970 1971 <p>As with duplicated fields, linked fields have attribute bits 1972 separate from the original.</p> 1973 1974 <p>As you might guess, all these field-allocations return 1975 <code>NULL</code> if the field allocation is not possible due to 1976 an out-of-memory error or out-of-bounds arguments.</p> 1977 1978 <p>To connect fields to a form, use</p> 1979 1980 <pre> 1981FORM *new_form(FIELD **fields); 1982</pre> 1983 1984 <p>This function expects to see a NULL-terminated array of field 1985 pointers. Said fields are connected to a newly-allocated form 1986 object; its address is returned (or else NULL if the allocation 1987 fails).</p> 1988 1989 <p>Note that <code>new_field()</code> does <em>not</em> copy the 1990 pointer array into private storage; if you modify the contents of 1991 the pointer array during forms processing, all manner of bizarre 1992 things might happen. Also note that any given field may only be 1993 connected to one form.</p> 1994 1995 <p>The functions <code>free_field()</code> and 1996 <code>free_form</code> are available to free field and form 1997 objects. It is an error to attempt to free a field connected to a 1998 form, but not vice-versa; thus, you will generally free your form 1999 objects first.</p> 2000 2001 <h2><a name="fattributes" id="fattributes">Fetching and Changing 2002 Field Attributes</a></h2> 2003 2004 <p>Each form field has a number of location and size attributes 2005 associated with it. There are other field attributes used to 2006 control display and editing of the field. Some (for example, the 2007 <code>O_STATIC</code> bit) involve sufficient complications to be 2008 covered in sections of their own later on. We cover the functions 2009 used to get and set several basic attributes here.</p> 2010 2011 <p>When a field is created, the attributes not specified by the 2012 <code>new_field</code> function are copied from an invisible 2013 system default field. In attribute-setting and -fetching 2014 functions, the argument NULL is taken to mean this field. Changes 2015 to it persist as defaults until your forms application 2016 terminates.</p> 2017 2018 <h3><a name="fsizes" id="fsizes">Fetching Size and Location 2019 Data</a></h3> 2020 2021 <p>You can retrieve field sizes and locations through:</p> 2022 2023 <pre> 2024int field_info(FIELD *field, /* field from which to fetch */ 2025 int *height, *int width, /* field size */ 2026 int *top, int *left, /* upper left corner */ 2027 int *offscreen, /* number of offscreen rows */ 2028 int *nbuf); /* number of working buffers */ 2029</pre> 2030 2031 <p>This function is a sort of inverse of 2032 <code>new_field()</code>; instead of setting size and location 2033 attributes of a new field, it fetches them from an existing 2034 one.</p> 2035 2036 <h3><a name="flocation" id="flocation">Changing the Field 2037 Location</a></h3> 2038 2039 <p>It is possible to move a field's location on the screen:</p> 2040 2041 <pre> 2042int move_field(FIELD *field, /* field to alter */ 2043 int top, int left); /* new upper-left corner */ 2044</pre> 2045 2046 <p>You can, of course. query the current location through 2047 <code>field_info()</code>.</p> 2048 2049 <h3><a name="fjust" id="fjust">The Justification Attribute</a></h3> 2050 2051 <p>One-line fields may be unjustified, justified right, justified 2052 left, or centered. Here is how you manipulate this attribute:</p> 2053 2054 <pre> 2055int set_field_just(FIELD *field, /* field to alter */ 2056 int justmode); /* mode to set */ 2057 2058int field_just(FIELD *field); /* fetch mode of field */ 2059</pre> 2060 2061 <p>The mode values accepted and returned by this functions are 2062 preprocessor macros <code>NO_JUSTIFICATION</code>, 2063 <code>JUSTIFY_RIGHT</code>, <code>JUSTIFY_LEFT</code>, or 2064 <code>JUSTIFY_CENTER</code>.</p> 2065 2066 <h3><a name="fdispatts" id="fdispatts">Field Display 2067 Attributes</a></h3> 2068 2069 <p>For each field, you can set a foreground attribute for entered 2070 characters, a background attribute for the entire field, and a 2071 pad character for the unfilled portion of the field. You can also 2072 control pagination of the form.</p> 2073 2074 <p>This group of four field attributes controls the visual 2075 appearance of the field on the screen, without affecting in any 2076 way the data in the field buffer.</p> 2077 2078 <pre> 2079int set_field_fore(FIELD *field, /* field to alter */ 2080 chtype attr); /* attribute to set */ 2081 2082chtype field_fore(FIELD *field); /* field to query */ 2083 2084int set_field_back(FIELD *field, /* field to alter */ 2085 chtype attr); /* attribute to set */ 2086 2087chtype field_back(FIELD *field); /* field to query */ 2088 2089int set_field_pad(FIELD *field, /* field to alter */ 2090 int pad); /* pad character to set */ 2091 2092chtype field_pad(FIELD *field); 2093 2094int set_new_page(FIELD *field, /* field to alter */ 2095 int flag); /* TRUE to force new page */ 2096 2097chtype new_page(FIELD *field); /* field to query */ 2098</pre> 2099 2100 <p>The attributes set and returned by the first four functions 2101 are normal <code>curses(3x)</code> display attribute values 2102 (<code>A_STANDOUT</code>, <code>A_BOLD</code>, 2103 <code>A_REVERSE</code> etc). The page bit of a field controls 2104 whether it is displayed at the start of a new form screen.</p> 2105 2106 <h3><a name="foptions" id="foptions">Field Option Bits</a></h3> 2107 2108 <p>There is also a large collection of field option bits you can 2109 set to control various aspects of forms processing. You can 2110 manipulate them with these functions:</p> 2111 2112 <pre> 2113int set_field_opts(FIELD *field, /* field to alter */ 2114 int attr); /* attribute to set */ 2115 2116int field_opts_on(FIELD *field, /* field to alter */ 2117 int attr); /* attributes to turn on */ 2118 2119int field_opts_off(FIELD *field, /* field to alter */ 2120 int attr); /* attributes to turn off */ 2121 2122int field_opts(FIELD *field); /* field to query */ 2123</pre> 2124 2125 <p>By default, all options are on. Here are the available option 2126 bits:</p> 2127 2128 <dl> 2129 <dt>O_VISIBLE</dt> 2130 2131 <dd>Controls whether the field is visible on the screen. Can be 2132 used during form processing to hide or pop up fields depending 2133 on the value of parent fields.</dd> 2134 2135 <dt>O_ACTIVE</dt> 2136 2137 <dd>Controls whether the field is active during forms 2138 processing (i.e. visited by form navigation keys). Can be used 2139 to make labels or derived fields with buffer values alterable 2140 by the forms application, not the user.</dd> 2141 2142 <dt>O_PUBLIC</dt> 2143 2144 <dd>Controls whether data is displayed during field entry. If 2145 this option is turned off on a field, the library will accept 2146 and edit data in that field, but it will not be displayed and 2147 the visible field cursor will not move. You can turn off the 2148 O_PUBLIC bit to define password fields.</dd> 2149 2150 <dt>O_EDIT</dt> 2151 2152 <dd>Controls whether the field's data can be modified. When 2153 this option is off, all editing requests except 2154 <code>REQ_PREV_CHOICE</code> and <code>REQ_NEXT_CHOICE</code> 2155 will fail. Such read-only fields may be useful for help 2156 messages.</dd> 2157 2158 <dt>O_WRAP</dt> 2159 2160 <dd>Controls word-wrapping in multi-line fields. Normally, when 2161 any character of a (blank-separated) word reaches the end of 2162 the current line, the entire word is wrapped to the next line 2163 (assuming there is one). When this option is off, the word will 2164 be split across the line break.</dd> 2165 2166 <dt>O_BLANK</dt> 2167 2168 <dd>Controls field blanking. When this option is on, entering a 2169 character at the first field position erases the entire field 2170 (except for the just-entered character).</dd> 2171 2172 <dt>O_AUTOSKIP</dt> 2173 2174 <dd>Controls automatic skip to next field when this one fills. 2175 Normally, when the forms user tries to type more data into a 2176 field than will fit, the editing location jumps to next field. 2177 When this option is off, the user's cursor will hang at the end 2178 of the field. This option is ignored in dynamic fields that 2179 have not reached their size limit.</dd> 2180 2181 <dt>O_NULLOK</dt> 2182 2183 <dd>Controls whether <a href="#fvalidation">validation</a> is 2184 applied to blank fields. Normally, it is not; the user can 2185 leave a field blank without invoking the usual validation check 2186 on exit. If this option is off on a field, exit from it will 2187 invoke a validation check.</dd> 2188 2189 <dt>O_PASSOK</dt> 2190 2191 <dd>Controls whether validation occurs on every exit, or only 2192 after the field is modified. Normally the latter is true. 2193 Setting O_PASSOK may be useful if your field's validation 2194 function may change during forms processing.</dd> 2195 2196 <dt>O_STATIC</dt> 2197 2198 <dd>Controls whether the field is fixed to its initial 2199 dimensions. If you turn this off, the field becomes <a href= 2200 "#fdynamic">dynamic</a> and will stretch to fit entered 2201 data.</dd> 2202 </dl> 2203 2204 <p>A field's options cannot be changed while the field is 2205 currently selected. However, options may be changed on posted 2206 fields that are not current.</p> 2207 2208 <p>The option values are bit-masks and can be composed with 2209 logical-or in the obvious way.</p> 2210 2211 <h2><a name="fstatus" id="fstatus">Field Status</a></h2> 2212 2213 <p>Every field has a status flag, which is set to FALSE when the 2214 field is created and TRUE when the value in field buffer 0 2215 changes. This flag can be queried and set directly:</p> 2216 2217 <pre> 2218int set_field_status(FIELD *field, /* field to alter */ 2219 int status); /* mode to set */ 2220 2221int field_status(FIELD *field); /* fetch mode of field */ 2222</pre> 2223 2224 <p>Setting this flag under program control can be useful if you 2225 use the same form repeatedly, looking for modified fields each 2226 time.</p> 2227 2228 <p>Calling <code>field_status()</code> on a field not currently 2229 selected for input will return a correct value. Calling 2230 <code>field_status()</code> on a field that is currently selected 2231 for input may not necessarily give a correct field status value, 2232 because entered data is not necessarily copied to buffer zero 2233 before the exit validation check. To guarantee that the returned 2234 status value reflects reality, call <code>field_status()</code> 2235 either (1) in the field's exit validation check routine, (2) from 2236 the field's or form's initialization or termination hooks, or (3) 2237 just after a <code>REQ_VALIDATION</code> request has been 2238 processed by the forms driver.</p> 2239 2240 <h2><a name="fuser" id="fuser">Field User Pointer</a></h2> 2241 2242 <p>Each field structure contains one character pointer slot that 2243 is not used by the forms library. It is intended to be used by 2244 applications to store private per-field data. You can manipulate 2245 it with:</p> 2246 2247 <pre> 2248int set_field_userptr(FIELD *field, /* field to alter */ 2249 char *userptr); /* mode to set */ 2250 2251char *field_userptr(FIELD *field); /* fetch mode of field */ 2252</pre>(Properly, this user pointer field ought to have <code>(void 2253*)</code> type. The <code>(char *)</code> type is retained for 2254System V compatibility.) 2255 2256 <p>It is valid to set the user pointer of the default field (with 2257 a <code>set_field_userptr()</code> call passed a NULL field 2258 pointer.) When a new field is created, the default-field user 2259 pointer is copied to initialize the new field's user pointer.</p> 2260 2261 <h2><a name="fdynamic" id="fdynamic">Variable-Sized Fields</a></h2> 2262 2263 <p>Normally, a field is fixed at the size specified for it at 2264 creation time. If, however, you turn off its O_STATIC bit, it 2265 becomes <dfn>dynamic</dfn> and will automatically resize itself 2266 to accommodate data as it is entered. If the field has extra 2267 buffers associated with it, they will grow right along with the 2268 main input buffer.</p> 2269 2270 <p>A one-line dynamic field will have a fixed height (1) but 2271 variable width, scrolling horizontally to display data within the 2272 field area as originally dimensioned and located. A multi-line 2273 dynamic field will have a fixed width, but variable height 2274 (number of rows), scrolling vertically to display data within the 2275 field area as originally dimensioned and located.</p> 2276 2277 <p>Normally, a dynamic field is allowed to grow without limit. 2278 But it is possible to set an upper limit on the size of a dynamic 2279 field. You do it with this function:</p> 2280 2281 <pre> 2282int set_max_field(FIELD *field, /* field to alter (may not be NULL) */ 2283 int max_size); /* upper limit on field size */ 2284</pre> 2285 2286 <p>If the field is one-line, <code>max_size</code> is taken to be 2287 a column size limit; if it is multi-line, it is taken to be a 2288 line size limit. To disable any limit, use an argument of zero. 2289 The growth limit can be changed whether or not the O_STATIC bit 2290 is on, but has no effect until it is.</p> 2291 2292 <p>The following properties of a field change when it becomes 2293 dynamic:</p> 2294 2295 <ul> 2296 <li>If there is no growth limit, there is no final position of 2297 the field; therefore <code>O_AUTOSKIP</code> and 2298 <code>O_NL_OVERLOAD</code> are ignored.</li> 2299 2300 <li>Field justification will be ignored (though whatever 2301 justification is set up will be retained internally and can be 2302 queried).</li> 2303 2304 <li>The <code>dup_field()</code> and <code>link_field()</code> 2305 calls copy dynamic-buffer sizes. If the <code>O_STATIC</code> 2306 option is set on one of a collection of links, buffer resizing 2307 will occur only when the field is edited through that 2308 link.</li> 2309 2310 <li>The call <code>field_info()</code> will retrieve the 2311 original static size of the field; use 2312 <code>dynamic_field_info()</code> to get the actual dynamic 2313 size.</li> 2314 </ul> 2315 2316 <h2><a name="fvalidation" id="fvalidation">Field Validation</a></h2> 2317 2318 <p>By default, a field will accept any data that will fit in its 2319 input buffer. However, it is possible to attach a validation type 2320 to a field. If you do this, any attempt to leave the field while 2321 it contains data that does not match the validation type will 2322 fail. Some validation types also have a character-validity check 2323 for each time a character is entered in the field.</p> 2324 2325 <p>A field's validation check (if any) is not called when 2326 <code>set_field_buffer()</code> modifies the input buffer, nor 2327 when that buffer is changed through a linked field.</p> 2328 2329 <p>The <code>form</code> library provides a rich set of 2330 pre-defined validation types, and gives you the capability to 2331 define custom ones of your own. You can examine and change field 2332 validation attributes with the following functions:</p> 2333 2334 <pre> 2335int set_field_type(FIELD *field, /* field to alter */ 2336 FIELDTYPE *ftype, /* type to associate */ 2337 ...); /* additional arguments*/ 2338 2339FIELDTYPE *field_type(FIELD *field); /* field to query */ 2340</pre> 2341 2342 <p>The validation type of a field is considered an attribute of 2343 the field. As with other field attributes, Also, doing 2344 <code>set_field_type()</code> with a <code>NULL</code> field 2345 default will change the system default for validation of 2346 newly-created fields.</p> 2347 2348 <p>Here are the pre-defined validation types:</p> 2349 2350 <h3><a name="ftype_alpha" id="ftype_alpha">TYPE_ALPHA</a></h3> 2351 2352 <p>This field type accepts alphabetic data; no blanks, no digits, 2353 no special characters (this is checked at character-entry time). 2354 It is set up with:</p> 2355 2356 <pre> 2357int set_field_type(FIELD *field, /* field to alter */ 2358 TYPE_ALPHA, /* type to associate */ 2359 int width); /* maximum width of field */ 2360</pre> 2361 2362 <p>The <code>width</code> argument sets a minimum width of data. 2363 Typically you will want to set this to the field width; if it is 2364 greater than the field width, the validation check will always 2365 fail. A minimum width of zero makes field completion 2366 optional.</p> 2367 2368 <h3><a name="ftype_alnum" id="ftype_alnum">TYPE_ALNUM</a></h3> 2369 2370 <p>This field type accepts alphabetic data and digits; no blanks, 2371 no special characters (this is checked at character-entry time). 2372 It is set up with:</p> 2373 2374 <pre> 2375int set_field_type(FIELD *field, /* field to alter */ 2376 TYPE_ALNUM, /* type to associate */ 2377 int width); /* maximum width of field */ 2378</pre> 2379 2380 <p>The <code>width</code> argument sets a minimum width of data. 2381 As with TYPE_ALPHA, typically you will want to set this to the 2382 field width; if it is greater than the field width, the 2383 validation check will always fail. A minimum width of zero makes 2384 field completion optional.</p> 2385 2386 <h3><a name="ftype_enum" id="ftype_enum">TYPE_ENUM</a></h3> 2387 2388 <p>This type allows you to restrict a field's values to be among 2389 a specified set of string values (for example, the two-letter 2390 postal codes for U.S. states). It is set up with:</p> 2391 2392 <pre> 2393int set_field_type(FIELD *field, /* field to alter */ 2394 TYPE_ENUM, /* type to associate */ 2395 char **valuelist; /* list of possible values */ 2396 int checkcase; /* case-sensitive? */ 2397 int checkunique); /* must specify uniquely? */ 2398</pre> 2399 2400 <p>The <code>valuelist</code> parameter must point at a 2401 NULL-terminated list of valid strings. The <code>checkcase</code> 2402 argument, if true, makes comparison with the string 2403 case-sensitive.</p> 2404 2405 <p>When the user exits a TYPE_ENUM field, the validation 2406 procedure tries to complete the data in the buffer to a valid 2407 entry. If a complete choice string has been entered, it is of 2408 course valid. But it is also possible to enter a prefix of a 2409 valid string and have it completed for you.</p> 2410 2411 <p>By default, if you enter such a prefix and it matches more 2412 than one value in the string list, the prefix will be completed 2413 to the first matching value. But the <code>checkunique</code> 2414 argument, if true, requires prefix matches to be unique in order 2415 to be valid.</p> 2416 2417 <p>The <code>REQ_NEXT_CHOICE</code> and 2418 <code>REQ_PREV_CHOICE</code> input requests can be particularly 2419 useful with these fields.</p> 2420 2421 <h3><a name="ftype_integer" id="ftype_integer">TYPE_INTEGER</a></h3> 2422 2423 <p>This field type accepts an integer. It is set up as 2424 follows:</p> 2425 2426 <pre> 2427int set_field_type(FIELD *field, /* field to alter */ 2428 TYPE_INTEGER, /* type to associate */ 2429 int padding, /* # places to zero-pad to */ 2430 int vmin, int vmax); /* valid range */ 2431</pre> 2432 2433 <p>Valid characters consist of an optional leading minus and 2434 digits. The range check is performed on exit. If the range 2435 maximum is less than or equal to the minimum, the range is 2436 ignored.</p> 2437 2438 <p>If the value passes its range check, it is padded with as many 2439 leading zero digits as necessary to meet the padding 2440 argument.</p> 2441 2442 <p>A <code>TYPE_INTEGER</code> value buffer can conveniently be 2443 interpreted with the C library function <code>atoi(3)</code>.</p> 2444 2445 <h3><a name="ftype_numeric" id="ftype_numeric">TYPE_NUMERIC</a></h3> 2446 2447 <p>This field type accepts a decimal number. It is set up as 2448 follows:</p> 2449 2450 <pre> 2451int set_field_type(FIELD *field, /* field to alter */ 2452 TYPE_NUMERIC, /* type to associate */ 2453 int padding, /* # places of precision */ 2454 double vmin, double vmax); /* valid range */ 2455</pre> 2456 2457 <p>Valid characters consist of an optional leading minus and 2458 digits. possibly including a decimal point. If your system 2459 supports locale's, the decimal point character used must be the 2460 one defined by your locale. The range check is performed on exit. 2461 If the range maximum is less than or equal to the minimum, the 2462 range is ignored.</p> 2463 2464 <p>If the value passes its range check, it is padded with as many 2465 trailing zero digits as necessary to meet the padding 2466 argument.</p> 2467 2468 <p>A <code>TYPE_NUMERIC</code> value buffer can conveniently be 2469 interpreted with the C library function <code>atof(3)</code>.</p> 2470 2471 <h3><a name="ftype_regexp" id="ftype_regexp">TYPE_REGEXP</a></h3> 2472 2473 <p>This field type accepts data matching a regular expression. It 2474 is set up as follows:</p> 2475 2476 <pre> 2477int set_field_type(FIELD *field, /* field to alter */ 2478 TYPE_REGEXP, /* type to associate */ 2479 char *regexp); /* expression to match */ 2480</pre> 2481 2482 <p>The syntax for regular expressions is that of 2483 <code>regcomp(3)</code>. The check for regular-expression match 2484 is performed on exit.</p> 2485 2486 <h2><a name="fbuffer" id="fbuffer">Direct Field Buffer 2487 Manipulation</a></h2> 2488 2489 <p>The chief attribute of a field is its buffer contents. When a 2490 form has been completed, your application usually needs to know 2491 the state of each field buffer. You can find this out with:</p> 2492 2493 <pre> 2494char *field_buffer(FIELD *field, /* field to query */ 2495 int bufindex); /* number of buffer to query */ 2496</pre> 2497 2498 <p>Normally, the state of the zero-numbered buffer for each field 2499 is set by the user's editing actions on that field. It is 2500 sometimes useful to be able to set the value of the zero-numbered 2501 (or some other) buffer from your application:</p> 2502 2503 <pre> 2504int set_field_buffer(FIELD *field, /* field to alter */ 2505 int bufindex, /* number of buffer to alter */ 2506 char *value); /* string value to set */ 2507</pre> 2508 2509 <p>If the field is not large enough and cannot be resized to a 2510 sufficiently large size to contain the specified value, the value 2511 will be truncated to fit.</p> 2512 2513 <p>Calling <code>field_buffer()</code> with a null field pointer 2514 will raise an error. Calling <code>field_buffer()</code> on a 2515 field not currently selected for input will return a correct 2516 value. Calling <code>field_buffer()</code> on a field that is 2517 currently selected for input may not necessarily give a correct 2518 field buffer value, because entered data is not necessarily 2519 copied to buffer zero before the exit validation check. To 2520 guarantee that the returned buffer value reflects on-screen 2521 reality, call <code>field_buffer()</code> either (1) in the 2522 field's exit validation check routine, (2) from the field's or 2523 form's initialization or termination hooks, or (3) just after a 2524 <code>REQ_VALIDATION</code> request has been processed by the 2525 forms driver.</p> 2526 2527 <h2><a name="formattrs" id="formattrs">Attributes of Forms</a></h2> 2528 2529 <p>As with field attributes, form attributes inherit a default 2530 from a system default form structure. These defaults can be 2531 queried or set by of these functions using a form-pointer 2532 argument of <code>NULL</code>.</p> 2533 2534 <p>The principal attribute of a form is its field list. You can 2535 query and change this list with:</p> 2536 2537 <pre> 2538int set_form_fields(FORM *form, /* form to alter */ 2539 FIELD **fields); /* fields to connect */ 2540 2541char *form_fields(FORM *form); /* fetch fields of form */ 2542 2543int field_count(FORM *form); /* count connect fields */ 2544</pre> 2545 2546 <p>The second argument of <code>set_form_fields()</code> may be a 2547 NULL-terminated field pointer array like the one required by 2548 <code>new_form()</code>. In that case, the old fields of the form 2549 are disconnected but not freed (and eligible to be connected to 2550 other forms), then the new fields are connected.</p> 2551 2552 <p>It may also be null, in which case the old fields are 2553 disconnected (and not freed) but no new ones are connected.</p> 2554 2555 <p>The <code>field_count()</code> function simply counts the 2556 number of fields connected to a given from. It returns -1 if the 2557 form-pointer argument is NULL.</p> 2558 2559 <h2><a name="fdisplay" id="fdisplay">Control of Form Display</a></h2> 2560 2561 <p>In the overview section, you saw that to display a form you 2562 normally start by defining its size (and fields), posting it, and 2563 refreshing the screen. There is an hidden step before posting, 2564 which is the association of the form with a frame window 2565 (actually, a pair of windows) within which it will be displayed. 2566 By default, the forms library associates every form with the 2567 full-screen window <code>stdscr</code>.</p> 2568 2569 <p>By making this step explicit, you can associate a form with a 2570 declared frame window on your screen display. This can be useful 2571 if you want to adapt the form display to different screen sizes, 2572 dynamically tile forms on the screen, or use a form as part of an 2573 interface layout managed by <a href="#panels">panels</a>.</p> 2574 2575 <p>The two windows associated with each form have the same 2576 functions as their analogues in the <a href="#menu">menu 2577 library</a>. Both these windows are painted when the form is 2578 posted and erased when the form is unposted.</p> 2579 2580 <p>The outer or frame window is not otherwise touched by the form 2581 routines. It exists so the programmer can associate a title, a 2582 border, or perhaps help text with the form and have it properly 2583 refreshed or erased at post/unpost time. The inner window or 2584 subwindow is where the current form page is actually 2585 displayed.</p> 2586 2587 <p>In order to declare your own frame window for a form, you will 2588 need to know the size of the form's bounding rectangle. You can 2589 get this information with:</p> 2590 2591 <pre> 2592int scale_form(FORM *form, /* form to query */ 2593 int *rows, /* form rows */ 2594 int *cols); /* form cols */ 2595</pre> 2596 2597 <p>The form dimensions are passed back in the locations pointed 2598 to by the arguments. Once you have this information, you can use 2599 it to declare of windows, then use one of these functions:</p> 2600 2601 <pre> 2602int set_form_win(FORM *form, /* form to alter */ 2603 WINDOW *win); /* frame window to connect */ 2604 2605WINDOW *form_win(FORM *form); /* fetch frame window of form */ 2606 2607int set_form_sub(FORM *form, /* form to alter */ 2608 WINDOW *win); /* form subwindow to connect */ 2609 2610WINDOW *form_sub(FORM *form); /* fetch form subwindow of form */ 2611</pre> 2612 2613 <p>Note that curses operations, including <code>refresh()</code>, 2614 on the form, should be done on the frame window, not the form 2615 subwindow.</p> 2616 2617 <p>It is possible to check from your application whether all of a 2618 scrollable field is actually displayed within the menu subwindow. 2619 Use these functions:</p> 2620 2621 <pre> 2622int data_ahead(FORM *form); /* form to be queried */ 2623 2624int data_behind(FORM *form); /* form to be queried */ 2625</pre> 2626 2627 <p>The function <code>data_ahead()</code> returns TRUE if (a) the 2628 current field is one-line and has undisplayed data off to the 2629 right, (b) the current field is multi-line and there is data 2630 off-screen below it.</p> 2631 2632 <p>The function <code>data_behind()</code> returns TRUE if the 2633 first (upper left hand) character position is off-screen (not 2634 being displayed).</p> 2635 2636 <p>Finally, there is a function to restore the form window's 2637 cursor to the value expected by the forms driver:</p> 2638 2639 <pre> 2640int pos_form_cursor(FORM *) /* form to be queried */ 2641</pre> 2642 2643 <p>If your application changes the form window cursor, call this 2644 function before handing control back to the forms driver in order 2645 to re-synchronize it.</p> 2646 2647 <h2><a name="fdriver" id="fdriver">Input Processing in the Forms 2648 Driver</a></h2> 2649 2650 <p>The function <code>form_driver()</code> handles virtualized 2651 input requests for form navigation, editing, and validation 2652 requests, just as <code>menu_driver</code> does for menus (see 2653 the section on <a href="#minput">menu input handling</a>).</p> 2654 2655 <pre> 2656int form_driver(FORM *form, /* form to pass input to */ 2657 int request); /* form request code */ 2658</pre> 2659 2660 <p>Your input virtualization function needs to take input and 2661 then convert it to either an alphanumeric character (which is 2662 treated as data to be entered in the currently-selected field), 2663 or a forms processing request.</p> 2664 2665 <p>The forms driver provides hooks (through input-validation and 2666 field-termination functions) with which your application code can 2667 check that the input taken by the driver matched what was 2668 expected.</p> 2669 2670 <h3><a name="fpage" id="fpage">Page Navigation Requests</a></h3> 2671 2672 <p>These requests cause page-level moves through the form, 2673 triggering display of a new form screen.</p> 2674 2675 <dl> 2676 <dt><code>REQ_NEXT_PAGE</code> 2677 </dt> 2678 2679 <dd>Move to the next form page.</dd> 2680 2681 <dt><code>REQ_PREV_PAGE</code> 2682 </dt> 2683 2684 <dd>Move to the previous form page.</dd> 2685 2686 <dt><code>REQ_FIRST_PAGE</code> 2687 </dt> 2688 2689 <dd>Move to the first form page.</dd> 2690 2691 <dt><code>REQ_LAST_PAGE</code> 2692 </dt> 2693 2694 <dd>Move to the last form page.</dd> 2695 </dl> 2696 2697 <p>These requests treat the list as cyclic; that is, 2698 <code>REQ_NEXT_PAGE</code> from the last page goes to the first, 2699 and <code>REQ_PREV_PAGE</code> from the first page goes to the 2700 last.</p> 2701 2702 <h3><a name="ffield" id="ffield">Inter-Field Navigation 2703 Requests</a></h3> 2704 2705 <p>These requests handle navigation between fields on the same 2706 page.</p> 2707 2708 <dl> 2709 <dt><code>REQ_NEXT_FIELD</code> 2710 </dt> 2711 2712 <dd>Move to next field.</dd> 2713 2714 <dt><code>REQ_PREV_FIELD</code> 2715 </dt> 2716 2717 <dd>Move to previous field.</dd> 2718 2719 <dt><code>REQ_FIRST_FIELD</code> 2720 </dt> 2721 2722 <dd>Move to the first field.</dd> 2723 2724 <dt><code>REQ_LAST_FIELD</code> 2725 </dt> 2726 2727 <dd>Move to the last field.</dd> 2728 2729 <dt><code>REQ_SNEXT_FIELD</code> 2730 </dt> 2731 2732 <dd>Move to sorted next field.</dd> 2733 2734 <dt><code>REQ_SPREV_FIELD</code> 2735 </dt> 2736 2737 <dd>Move to sorted previous field.</dd> 2738 2739 <dt><code>REQ_SFIRST_FIELD</code> 2740 </dt> 2741 2742 <dd>Move to the sorted first field.</dd> 2743 2744 <dt><code>REQ_SLAST_FIELD</code> 2745 </dt> 2746 2747 <dd>Move to the sorted last field.</dd> 2748 2749 <dt><code>REQ_LEFT_FIELD</code> 2750 </dt> 2751 2752 <dd>Move left to field.</dd> 2753 2754 <dt><code>REQ_RIGHT_FIELD</code> 2755 </dt> 2756 2757 <dd>Move right to field.</dd> 2758 2759 <dt><code>REQ_UP_FIELD</code> 2760 </dt> 2761 2762 <dd>Move up to field.</dd> 2763 2764 <dt><code>REQ_DOWN_FIELD</code> 2765 </dt> 2766 2767 <dd>Move down to field.</dd> 2768 </dl> 2769 2770 <p>These requests treat the list of fields on a page as cyclic; 2771 that is, <code>REQ_NEXT_FIELD</code> from the last field goes to 2772 the first, and <code>REQ_PREV_FIELD</code> from the first field 2773 goes to the last. The order of the fields for these (and the 2774 <code>REQ_FIRST_FIELD</code> and <code>REQ_LAST_FIELD</code> 2775 requests) is simply the order of the field pointers in the form 2776 array (as set up by <code>new_form()</code> or 2777 <code>set_form_fields()</code></p> 2778 2779 <p>It is also possible to traverse the fields as if they had been 2780 sorted in screen-position order, so the sequence goes 2781 left-to-right and top-to-bottom. To do this, use the second group 2782 of four sorted-movement requests.</p> 2783 2784 <p>Finally, it is possible to move between fields using visual 2785 directions up, down, right, and left. To accomplish this, use the 2786 third group of four requests. Note, however, that the position of 2787 a form for purposes of these requests is its upper-left 2788 corner.</p> 2789 2790 <p>For example, suppose you have a multi-line field B, and two 2791 single-line fields A and C on the same line with B, with A to the 2792 left of B and C to the right of B. A <code>REQ_MOVE_RIGHT</code> 2793 from A will go to B only if A, B, and C <em>all</em> share the 2794 same first line; otherwise it will skip over B to C.</p> 2795 2796 <h3><a name="fifield" id="fifield">Intra-Field Navigation 2797 Requests</a></h3> 2798 2799 <p>These requests drive movement of the edit cursor within the 2800 currently selected field.</p> 2801 2802 <dl> 2803 <dt><code>REQ_NEXT_CHAR</code> 2804 </dt> 2805 2806 <dd>Move to next character.</dd> 2807 2808 <dt><code>REQ_PREV_CHAR</code> 2809 </dt> 2810 2811 <dd>Move to previous character.</dd> 2812 2813 <dt><code>REQ_NEXT_LINE</code> 2814 </dt> 2815 2816 <dd>Move to next line.</dd> 2817 2818 <dt><code>REQ_PREV_LINE</code> 2819 </dt> 2820 2821 <dd>Move to previous line.</dd> 2822 2823 <dt><code>REQ_NEXT_WORD</code> 2824 </dt> 2825 2826 <dd>Move to next word.</dd> 2827 2828 <dt><code>REQ_PREV_WORD</code> 2829 </dt> 2830 2831 <dd>Move to previous word.</dd> 2832 2833 <dt><code>REQ_BEG_FIELD</code> 2834 </dt> 2835 2836 <dd>Move to beginning of field.</dd> 2837 2838 <dt><code>REQ_END_FIELD</code> 2839 </dt> 2840 2841 <dd>Move to end of field.</dd> 2842 2843 <dt><code>REQ_BEG_LINE</code> 2844 </dt> 2845 2846 <dd>Move to beginning of line.</dd> 2847 2848 <dt><code>REQ_END_LINE</code> 2849 </dt> 2850 2851 <dd>Move to end of line.</dd> 2852 2853 <dt><code>REQ_LEFT_CHAR</code> 2854 </dt> 2855 2856 <dd>Move left in field.</dd> 2857 2858 <dt><code>REQ_RIGHT_CHAR</code> 2859 </dt> 2860 2861 <dd>Move right in field.</dd> 2862 2863 <dt><code>REQ_UP_CHAR</code> 2864 </dt> 2865 2866 <dd>Move up in field.</dd> 2867 2868 <dt><code>REQ_DOWN_CHAR</code> 2869 </dt> 2870 2871 <dd>Move down in field.</dd> 2872 </dl> 2873 2874 <p>Each <em>word</em> is separated from the previous and next 2875 characters by whitespace. The commands to move to beginning and 2876 end of line or field look for the first or last non-pad character 2877 in their ranges.</p> 2878 2879 <h3><a name="fscroll" id="fscroll">Scrolling Requests</a></h3> 2880 2881 <p>Fields that are dynamic and have grown and fields explicitly 2882 created with offscreen rows are scrollable. One-line fields 2883 scroll horizontally; multi-line fields scroll vertically. Most 2884 scrolling is triggered by editing and intra-field movement (the 2885 library scrolls the field to keep the cursor visible). It is 2886 possible to explicitly request scrolling with the following 2887 requests:</p> 2888 2889 <dl> 2890 <dt><code>REQ_SCR_FLINE</code> 2891 </dt> 2892 2893 <dd>Scroll vertically forward a line.</dd> 2894 2895 <dt><code>REQ_SCR_BLINE</code> 2896 </dt> 2897 2898 <dd>Scroll vertically backward a line.</dd> 2899 2900 <dt><code>REQ_SCR_FPAGE</code> 2901 </dt> 2902 2903 <dd>Scroll vertically forward a page.</dd> 2904 2905 <dt><code>REQ_SCR_BPAGE</code> 2906 </dt> 2907 2908 <dd>Scroll vertically backward a page.</dd> 2909 2910 <dt><code>REQ_SCR_FHPAGE</code> 2911 </dt> 2912 2913 <dd>Scroll vertically forward half a page.</dd> 2914 2915 <dt><code>REQ_SCR_BHPAGE</code> 2916 </dt> 2917 2918 <dd>Scroll vertically backward half a page.</dd> 2919 2920 <dt><code>REQ_SCR_FCHAR</code> 2921 </dt> 2922 2923 <dd>Scroll horizontally forward a character.</dd> 2924 2925 <dt><code>REQ_SCR_BCHAR</code> 2926 </dt> 2927 2928 <dd>Scroll horizontally backward a character.</dd> 2929 2930 <dt><code>REQ_SCR_HFLINE</code> 2931 </dt> 2932 2933 <dd>Scroll horizontally one field width forward.</dd> 2934 2935 <dt><code>REQ_SCR_HBLINE</code> 2936 </dt> 2937 2938 <dd>Scroll horizontally one field width backward.</dd> 2939 2940 <dt><code>REQ_SCR_HFHALF</code> 2941 </dt> 2942 2943 <dd>Scroll horizontally one half field width forward.</dd> 2944 2945 <dt><code>REQ_SCR_HBHALF</code> 2946 </dt> 2947 2948 <dd>Scroll horizontally one half field width backward.</dd> 2949 </dl> 2950 2951 <p>For scrolling purposes, a <em>page</em> of a field is the 2952 height of its visible part.</p> 2953 2954 <h3><a name="fedit" id="fedit">Editing Requests</a></h3> 2955 2956 <p>When you pass the forms driver an ASCII character, it is 2957 treated as a request to add the character to the field's data 2958 buffer. Whether this is an insertion or a replacement depends on 2959 the field's edit mode (insertion is the default.</p> 2960 2961 <p>The following requests support editing the field and changing 2962 the edit mode:</p> 2963 2964 <dl> 2965 <dt><code>REQ_INS_MODE</code> 2966 </dt> 2967 2968 <dd>Set insertion mode.</dd> 2969 2970 <dt><code>REQ_OVL_MODE</code> 2971 </dt> 2972 2973 <dd>Set overlay mode.</dd> 2974 2975 <dt><code>REQ_NEW_LINE</code> 2976 </dt> 2977 2978 <dd>New line request (see below for explanation).</dd> 2979 2980 <dt><code>REQ_INS_CHAR</code> 2981 </dt> 2982 2983 <dd>Insert space at character location.</dd> 2984 2985 <dt><code>REQ_INS_LINE</code> 2986 </dt> 2987 2988 <dd>Insert blank line at character location.</dd> 2989 2990 <dt><code>REQ_DEL_CHAR</code> 2991 </dt> 2992 2993 <dd>Delete character at cursor.</dd> 2994 2995 <dt><code>REQ_DEL_PREV</code> 2996 </dt> 2997 2998 <dd>Delete previous word at cursor.</dd> 2999 3000 <dt><code>REQ_DEL_LINE</code> 3001 </dt> 3002 3003 <dd>Delete line at cursor.</dd> 3004 3005 <dt><code>REQ_DEL_WORD</code> 3006 </dt> 3007 3008 <dd>Delete word at cursor.</dd> 3009 3010 <dt><code>REQ_CLR_EOL</code> 3011 </dt> 3012 3013 <dd>Clear to end of line.</dd> 3014 3015 <dt><code>REQ_CLR_EOF</code> 3016 </dt> 3017 3018 <dd>Clear to end of field.</dd> 3019 3020 <dt><code>REQ_CLEAR_FIELD</code> 3021 </dt> 3022 3023 <dd>Clear entire field.</dd> 3024 </dl> 3025 3026 <p>The behavior of the <code>REQ_NEW_LINE</code> and 3027 <code>REQ_DEL_PREV</code> requests is complicated and partly 3028 controlled by a pair of forms options. The special cases are 3029 triggered when the cursor is at the beginning of a field, or on 3030 the last line of the field.</p> 3031 3032 <p>First, we consider <code>REQ_NEW_LINE</code>:</p> 3033 3034 <p>The normal behavior of <code>REQ_NEW_LINE</code> in insert 3035 mode is to break the current line at the position of the edit 3036 cursor, inserting the portion of the current line after the 3037 cursor as a new line following the current and moving the cursor 3038 to the beginning of that new line (you may think of this as 3039 inserting a newline in the field buffer).</p> 3040 3041 <p>The normal behavior of <code>REQ_NEW_LINE</code> in overlay 3042 mode is to clear the current line from the position of the edit 3043 cursor to end of line. The cursor is then moved to the beginning 3044 of the next line.</p> 3045 3046 <p>However, <code>REQ_NEW_LINE</code> at the beginning of a 3047 field, or on the last line of a field, instead does a 3048 <code>REQ_NEXT_FIELD</code>. <code>O_NL_OVERLOAD</code> option is 3049 off, this special action is disabled.</p> 3050 3051 <p>Now, let us consider <code>REQ_DEL_PREV</code>:</p> 3052 3053 <p>The normal behavior of <code>REQ_DEL_PREV</code> is to delete 3054 the previous character. If insert mode is on, and the cursor is 3055 at the start of a line, and the text on that line will fit on the 3056 previous one, it instead appends the contents of the current line 3057 to the previous one and deletes the current line (you may think 3058 of this as deleting a newline from the field buffer).</p> 3059 3060 <p>However, <code>REQ_DEL_PREV</code> at the beginning of a field 3061 is instead treated as a <code>REQ_PREV_FIELD</code>.</p> 3062 3063 <p>If the <code>O_BS_OVERLOAD</code> option is off, this special 3064 action is disabled and the forms driver just returns 3065 <code>E_REQUEST_DENIED</code>.</p> 3066 3067 <p>See <a href="#frmoptions">Form Options</a> for discussion of 3068 how to set and clear the overload options.</p> 3069 3070 <h3><a name="forder" id="forder">Order Requests</a></h3> 3071 3072 <p>If the type of your field is ordered, and has associated 3073 functions for getting the next and previous values of the type 3074 from a given value, there are requests that can fetch that value 3075 into the field buffer:</p> 3076 3077 <dl> 3078 <dt><code>REQ_NEXT_CHOICE</code> 3079 </dt> 3080 3081 <dd>Place the successor value of the current value in the 3082 buffer.</dd> 3083 3084 <dt><code>REQ_PREV_CHOICE</code> 3085 </dt> 3086 3087 <dd>Place the predecessor value of the current value in the 3088 buffer.</dd> 3089 </dl> 3090 3091 <p>Of the built-in field types, only <code>TYPE_ENUM</code> has 3092 built-in successor and predecessor functions. When you define a 3093 field type of your own (see <a href="#fcustom">Custom Validation 3094 Types</a>), you can associate our own ordering functions.</p> 3095 3096 <h3><a name="fappcmds" id="fappcmds">Application Commands</a></h3> 3097 3098 <p>Form requests are represented as integers above the 3099 <code>curses</code> value greater than <code>KEY_MAX</code> and 3100 less than or equal to the constant <code>MAX_COMMAND</code>. If 3101 your input-virtualization routine returns a value above 3102 <code>MAX_COMMAND</code>, the forms driver will ignore it.</p> 3103 3104 <h2><a name="fhooks" id="fhooks">Field Change Hooks</a></h2> 3105 3106 <p>It is possible to set function hooks to be executed whenever 3107 the current field or form changes. Here are the functions that 3108 support this:</p> 3109 3110 <pre> 3111typedef void (*HOOK)(); /* pointer to function returning void */ 3112 3113int set_form_init(FORM *form, /* form to alter */ 3114 HOOK hook); /* initialization hook */ 3115 3116HOOK form_init(FORM *form); /* form to query */ 3117 3118int set_form_term(FORM *form, /* form to alter */ 3119 HOOK hook); /* termination hook */ 3120 3121HOOK form_term(FORM *form); /* form to query */ 3122 3123int set_field_init(FORM *form, /* form to alter */ 3124 HOOK hook); /* initialization hook */ 3125 3126HOOK field_init(FORM *form); /* form to query */ 3127 3128int set_field_term(FORM *form, /* form to alter */ 3129 HOOK hook); /* termination hook */ 3130 3131HOOK field_term(FORM *form); /* form to query */ 3132</pre> 3133 3134 <p>These functions allow you to either set or query four 3135 different hooks. In each of the set functions, the second 3136 argument should be the address of a hook function. These 3137 functions differ only in the timing of the hook call.</p> 3138 3139 <dl> 3140 <dt>form_init</dt> 3141 3142 <dd>This hook is called when the form is posted; also, just 3143 after each page change operation.</dd> 3144 3145 <dt>field_init</dt> 3146 3147 <dd>This hook is called when the form is posted; also, just 3148 after each field change</dd> 3149 3150 <dt>field_term</dt> 3151 3152 <dd>This hook is called just after field validation; that is, 3153 just before the field is altered. It is also called when the 3154 form is unposted.</dd> 3155 3156 <dt>form_term</dt> 3157 3158 <dd>This hook is called when the form is unposted; also, just 3159 before each page change operation.</dd> 3160 </dl> 3161 3162 <p>Calls to these hooks may be triggered</p> 3163 3164 <ol> 3165 <li>When user editing requests are processed by the forms 3166 driver</li> 3167 3168 <li>When the current page is changed by 3169 <code>set_current_field()</code> call</li> 3170 3171 <li>When the current field is changed by a 3172 <code>set_form_page()</code> call</li> 3173 </ol> 3174 3175 <p>See <a name="ffocus" id="ffocus">Field Change Commands</a> for 3176 discussion of the latter two cases.</p> 3177 3178 <p>You can set a default hook for all fields by passing one of 3179 the set functions a NULL first argument.</p> 3180 3181 <p>You can disable any of these hooks by (re)setting them to 3182 NULL, the default value.</p> 3183 3184 <h2><a href="#ffocus">Field Change Commands</a></h2> 3185 3186 <p>Normally, navigation through the form will be driven by the 3187 user's input requests. But sometimes it is useful to be able to 3188 move the focus for editing and viewing under control of your 3189 application, or ask which field it currently is in. The following 3190 functions help you accomplish this:</p> 3191 3192 <pre> 3193int set_current_field(FORM *form, /* form to alter */ 3194 FIELD *field); /* field to shift to */ 3195 3196FIELD *current_field(FORM *form); /* form to query */ 3197 3198int field_index(FORM *form, /* form to query */ 3199 FIELD *field); /* field to get index of */ 3200</pre> 3201 3202 <p>The function <code>field_index()</code> returns the index of 3203 the given field in the given form's field array (the array passed 3204 to <code>new_form()</code> or 3205 <code>set_form_fields()</code>).</p> 3206 3207 <p>The initial current field of a form is the first active field 3208 on the first page. The function <code>set_form_fields()</code> 3209 resets this.</p> 3210 3211 <p>It is also possible to move around by pages.</p> 3212 3213 <pre> 3214int set_form_page(FORM *form, /* form to alter */ 3215 int page); /* page to go to (0-origin) */ 3216 3217int form_page(FORM *form); /* return form's current page */ 3218</pre> 3219 3220 <p>The initial page of a newly-created form is 0. The function 3221 <code>set_form_fields()</code> resets this.</p> 3222 3223 <h2><a name="frmoptions" id="frmoptions">Form Options</a></h2> 3224 3225 <p>Like fields, forms may have control option bits. They can be 3226 changed or queried with these functions:</p> 3227 3228 <pre> 3229int set_form_opts(FORM *form, /* form to alter */ 3230 int attr); /* attribute to set */ 3231 3232int form_opts_on(FORM *form, /* form to alter */ 3233 int attr); /* attributes to turn on */ 3234 3235int form_opts_off(FORM *form, /* form to alter */ 3236 int attr); /* attributes to turn off */ 3237 3238int form_opts(FORM *form); /* form to query */ 3239</pre> 3240 3241 <p>By default, all options are on. Here are the available option 3242 bits:</p> 3243 3244 <dl> 3245 <dt>O_NL_OVERLOAD</dt> 3246 3247 <dd>Enable overloading of <code>REQ_NEW_LINE</code> as 3248 described in <a href="#fedit">Editing Requests</a>. The value 3249 of this option is ignored on dynamic fields that have not 3250 reached their size limit; these have no last line, so the 3251 circumstances for triggering a <code>REQ_NEXT_FIELD</code> 3252 never arise.</dd> 3253 3254 <dt>O_BS_OVERLOAD</dt> 3255 3256 <dd>Enable overloading of <code>REQ_DEL_PREV</code> as 3257 described in <a href="#fedit">Editing Requests</a>.</dd> 3258 </dl> 3259 3260 <p>The option values are bit-masks and can be composed with 3261 logical-or in the obvious way.</p> 3262 3263 <h2><a name="fcustom" id="fcustom">Custom Validation Types</a></h2> 3264 3265 <p>The <code>form</code> library gives you the capability to 3266 define custom validation types of your own. Further, the optional 3267 additional arguments of <code>set_field_type</code> effectively 3268 allow you to parameterize validation types. Most of the 3269 complications in the validation-type interface have to do with 3270 the handling of the additional arguments within custom validation 3271 functions.</p> 3272 3273 <h3><a name="flinktypes" id="flinktypes">Union Types</a></h3> 3274 3275 <p>The simplest way to create a custom data type is to compose it 3276 from two preexisting ones:</p> 3277 3278 <pre> 3279FIELD *link_fieldtype(FIELDTYPE *type1, 3280 FIELDTYPE *type2); 3281</pre> 3282 3283 <p>This function creates a field type that will accept any of the 3284 values legal for either of its argument field types (which may be 3285 either predefined or programmer-defined). If a 3286 <code>set_field_type()</code> call later requires arguments, the 3287 new composite type expects all arguments for the first type, than 3288 all arguments for the second. Order functions (see <a href= 3289 "#forder">Order Requests</a>) associated with the component types 3290 will work on the composite; what it does is check the validation 3291 function for the first type, then for the second, to figure what 3292 type the buffer contents should be treated as.</p> 3293 3294 <h3><a name="fnewtypes" id="fnewtypes">New Field Types</a></h3> 3295 3296 <p>To create a field type from scratch, you need to specify one 3297 or both of the following things:</p> 3298 3299 <ul> 3300 <li>A character-validation function, to check each character as 3301 it is entered.</li> 3302 3303 <li>A field-validation function to be applied on exit from the 3304 field.</li> 3305 </ul> 3306 3307 <p>Here is how you do that:</p> 3308 3309 <pre> 3310typedef int (*HOOK)(); /* pointer to function returning int */ 3311 3312FIELDTYPE *new_fieldtype(HOOK f_validate, /* field validator */ 3313 HOOK c_validate) /* character validator */ 3314 3315int free_fieldtype(FIELDTYPE *ftype); /* type to free */ 3316</pre> 3317 3318 <p>At least one of the arguments of <code>new_fieldtype()</code> 3319 must be non-NULL. The forms driver will automatically call the 3320 new type's validation functions at appropriate points in 3321 processing a field of the new type.</p> 3322 3323 <p>The function <code>free_fieldtype()</code> deallocates the 3324 argument fieldtype, freeing all storage associated with it.</p> 3325 3326 <p>Normally, a field validator is called when the user attempts 3327 to leave the field. Its first argument is a field pointer, from 3328 which it can get to field buffer 0 and test it. If the function 3329 returns TRUE, the operation succeeds; if it returns FALSE, the 3330 edit cursor stays in the field.</p> 3331 3332 <p>A character validator gets the character passed in as a first 3333 argument. It too should return TRUE if the character is valid, 3334 FALSE otherwise.</p> 3335 3336 <h3><a name="fcheckargs" id="fcheckargs">Validation Function 3337 Arguments</a></h3> 3338 3339 <p>Your field- and character- validation functions will be passed 3340 a second argument as well. This second argument is the address of 3341 a structure (which we will call a <em>pile</em>) built from any 3342 of the field-type-specific arguments passed to 3343 <code>set_field_type()</code>. If no such arguments are defined 3344 for the field type, this pile pointer argument will be NULL.</p> 3345 3346 <p>In order to arrange for such arguments to be passed to your 3347 validation functions, you must associate a small set of 3348 storage-management functions with the type. The forms driver will 3349 use these to synthesize a pile from the trailing arguments of 3350 each <code>set_field_type()</code> argument, and a pointer to the 3351 pile will be passed to the validation functions.</p> 3352 3353 <p>Here is how you make the association:</p> 3354 3355 <pre> 3356typedef char *(*PTRHOOK)(); /* pointer to function returning (char *) */ 3357typedef void (*VOIDHOOK)(); /* pointer to function returning void */ 3358 3359int set_fieldtype_arg(FIELDTYPE *type, /* type to alter */ 3360 PTRHOOK make_str, /* make structure from args */ 3361 PTRHOOK copy_str, /* make copy of structure */ 3362 VOIDHOOK free_str); /* free structure storage */ 3363</pre> 3364 3365 <p>Here is how the storage-management hooks are used:</p> 3366 3367 <dl> 3368 <dt><code>make_str</code> 3369 </dt> 3370 3371 <dd>This function is called by <code>set_field_type()</code>. 3372 It gets one argument, a <code>va_list</code> of the 3373 type-specific arguments passed to 3374 <code>set_field_type()</code>. It is expected to return a pile 3375 pointer to a data structure that encapsulates those 3376 arguments.</dd> 3377 3378 <dt><code>copy_str</code> 3379 </dt> 3380 3381 <dd>This function is called by form library functions that 3382 allocate new field instances. It is expected to take a pile 3383 pointer, copy the pile to allocated storage, and return the 3384 address of the pile copy.</dd> 3385 3386 <dt><code>free_str</code> 3387 </dt> 3388 3389 <dd>This function is called by field- and type-deallocation 3390 routines in the library. It takes a pile pointer argument, and 3391 is expected to free the storage of that pile.</dd> 3392 </dl> 3393 3394 <p>The <code>make_str</code> and <code>copy_str</code> functions 3395 may return NULL to signal allocation failure. The library 3396 routines will that call them will return error indication when 3397 this happens. Thus, your validation functions should never see a 3398 NULL file pointer and need not check specially for it.</p> 3399 3400 <h3><a name="fcustorder" id="fcustorder">Order Functions For 3401 Custom Types</a></h3> 3402 3403 <p>Some custom field types are simply ordered in the same 3404 well-defined way that <code>TYPE_ENUM</code> is. For such types, 3405 it is possible to define successor and predecessor functions to 3406 support the <code>REQ_NEXT_CHOICE</code> and 3407 <code>REQ_PREV_CHOICE</code> requests. Here is how:</p> 3408 3409 <pre> 3410typedef int (*INTHOOK)(); /* pointer to function returning int */ 3411 3412int set_fieldtype_arg(FIELDTYPE *type, /* type to alter */ 3413 INTHOOK succ, /* get successor value */ 3414 INTHOOK pred); /* get predecessor value */ 3415</pre> 3416 3417 <p>The successor and predecessor arguments will each be passed 3418 two arguments; a field pointer, and a pile pointer (as for the 3419 validation functions). They are expected to use the function 3420 <code>field_buffer()</code> to read the current value, and 3421 <code>set_field_buffer()</code> on buffer 0 to set the next or 3422 previous value. Either hook may return TRUE to indicate success 3423 (a legal next or previous value was set) or FALSE to indicate 3424 failure.</p> 3425 3426 <h3><a name="fcustprobs" id="fcustprobs">Avoiding Problems</a></h3> 3427 3428 <p>The interface for defining custom types is complicated and 3429 tricky. Rather than attempting to create a custom type entirely 3430 from scratch, you should start by studying the library source 3431 code for whichever of the pre-defined types seems to be closest 3432 to what you want.</p> 3433 3434 <p>Use that code as a model, and evolve it towards what you 3435 really want. You will avoid many problems and annoyances that 3436 way. The code in the <code>ncurses</code> library has been 3437 specifically exempted from the package copyright to support 3438 this.</p> 3439 3440 <p>If your custom type defines order functions, have do something 3441 intuitive with a blank field. A useful convention is to make the 3442 successor of a blank field the types minimum value, and its 3443 predecessor the maximum.</p> 3444</body> 3445</html> 3446