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Raymond and Zeyd M. Ben-Halim<br> 49 updates since release 1.9.9e by Thomas Dickey 50 </blockquote> 51 52 <div class="nav"> 53 <h2>Contents</h2> 54 55 <ul> 56 <li> 57 <a href="#introduction">Introduction</a> 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 <ul> 70 <li> 71 <a href="#overview">An Overview of Curses</a> 72 <ul> 73 <li><a href="#compiling">Compiling Programs using 74 Curses</a></li> 75 76 <li><a href="#updating">Updating the Screen</a></li> 77 78 <li><a href="#stdscr">Standard Windows and Function 79 Naming Conventions</a></li> 80 81 <li><a href="#variables">Variables</a></li> 82 </ul> 83 </li> 84 85 <li> 86 <a href="#using">Using the Library</a> 87 <ul> 88 <li><a href="#starting">Starting up</a></li> 89 90 <li><a href="#output">Output</a></li> 91 92 <li><a href="#input">Input</a></li> 93 94 <li><a href="#formschars">Using Forms Characters</a></li> 95 96 <li><a href="#attributes">Character Attributes and 97 Color</a></li> 98 99 <li><a href="#mouse">Mouse Interfacing</a></li> 100 101 <li><a href="#finishing">Finishing Up</a></li> 102 </ul> 103 </li> 104 105 <li> 106 <a href="#functions">Function Descriptions</a> 107 <ul> 108 <li><a href="#init">Initialization and Wrapup</a></li> 109 110 <li><a href="#flush">Causing Output to the 111 Terminal</a></li> 112 113 <li><a href="#lowlevel">Low-Level Capability 114 Access</a></li> 115 116 <li><a href="#debugging">Debugging</a></li> 117 </ul> 118 </li> 119 120 <li> 121 <a href="#hints">Hints, Tips, and Tricks</a> 122 <ul> 123 <li><a href="#caution">Some Notes of Caution</a></li> 124 125 <li><a href="#leaving">Temporarily Leaving ncurses 126 Mode</a></li> 127 128 <li><a href="#xterm">Using <code>ncurses</code> under 129 <code>xterm</code></a></li> 130 131 <li><a href="#screens">Handling Multiple Terminal 132 Screens</a></li> 133 134 <li><a href="#testing">Testing for Terminal 135 Capabilities</a></li> 136 137 <li><a href="#tuning">Tuning for Speed</a></li> 138 139 <li><a href="#special">Special Features of 140 <code>ncurses</code></a></li> 141 </ul> 142 </li> 143 144 <li> 145 <a href="#compat">Compatibility with Older Versions</a> 146 <ul> 147 <li><a href="#refbug">Refresh of Overlapping 148 Windows</a></li> 149 150 <li><a href="#backbug">Background Erase</a></li> 151 </ul> 152 </li> 153 154 <li><a href="#xsifuncs">XSI Curses Conformance</a></li> 155 </ul> 156 </li> 157 158 <li> 159 <a href="#panels">The Panels Library</a> 160 <ul> 161 <li><a href="#pcompile">Compiling With the Panels 162 Library</a></li> 163 164 <li><a href="#poverview">Overview of Panels</a></li> 165 166 <li><a href="#pstdscr">Panels, Input, and the Standard 167 Screen</a></li> 168 169 <li><a href="#hiding">Hiding Panels</a></li> 170 171 <li><a href="#pmisc">Miscellaneous Other Facilities</a></li> 172 </ul> 173 </li> 174 175 <li> 176 <a href="#menu">The Menu Library</a> 177 <ul> 178 <li><a href="#mcompile">Compiling with the menu 179 Library</a></li> 180 181 <li><a href="#moverview">Overview of Menus</a></li> 182 183 <li><a href="#mselect">Selecting items</a></li> 184 185 <li><a href="#mdisplay">Menu Display</a></li> 186 187 <li><a href="#mwindows">Menu Windows</a></li> 188 189 <li><a href="#minput">Processing Menu Input</a></li> 190 191 <li><a href="#mmisc">Miscellaneous Other Features</a></li> 192 </ul> 193 </li> 194 195 <li> 196 <a href="#form">The Forms Library</a> 197 <ul> 198 <li><a href="#fcompile">Compiling with the forms 199 Library</a></li> 200 201 <li><a href="#foverview">Overview of Forms</a></li> 202 203 <li><a href="#fcreate">Creating and Freeing Fields and 204 Forms</a></li> 205 206 <li> 207 <a href="#fattributes">Fetching and Changing Field 208 Attributes</a> 209 <ul> 210 <li><a href="#fsizes">Fetching Size and Location 211 Data</a></li> 212 213 <li><a href="#flocation">Changing the Field 214 Location</a></li> 215 216 <li><a href="#fjust">The Justification Attribute</a></li> 217 218 <li><a href="#fdispatts">Field Display Attributes</a></li> 219 220 <li><a href="#foptions">Field Option Bits</a></li> 221 222 <li><a href="#fstatus">Field Status</a></li> 223 224 <li><a href="#fuser">Field User Pointer</a></li> 225 </ul> 226 </li> 227 228 <li><a href="#fdynamic">Variable-Sized Fields</a></li> 229 230 <li> 231 <a href="#fvalidation">Field Validation</a> 232 <ul> 233 <li><a href="#ftype_alpha">TYPE_ALPHA</a></li> 234 235 <li><a href="#ftype_alnum">TYPE_ALNUM</a></li> 236 237 <li><a href="#ftype_enum">TYPE_ENUM</a></li> 238 239 <li><a href="#ftype_integer">TYPE_INTEGER</a></li> 240 241 <li><a href="#ftype_numeric">TYPE_NUMERIC</a></li> 242 243 <li><a href="#ftype_regexp">TYPE_REGEXP</a></li> 244 </ul> 245 </li> 246 247 <li><a href="#fbuffer">Direct Field Buffer 248 Manipulation</a></li> 249 250 <li><a href="#formattrs">Attributes of Forms</a></li> 251 252 <li><a href="#fdisplay">Control of Form Display</a></li> 253 254 <li> 255 <a href="#fdriver">Input Processing in the Forms 256 Driver</a> 257 <ul> 258 <li><a href="#fpage">Page Navigation Requests</a></li> 259 260 <li><a href="#ffield">Inter-Field Navigation 261 Requests</a></li> 262 263 <li><a href="#fifield">Intra-Field Navigation 264 Requests</a></li> 265 266 <li><a href="#fscroll">Scrolling Requests</a></li> 267 268 <li><a href="#fedit">Field Editing Requests</a></li> 269 270 <li><a href="#forder">Order Requests</a></li> 271 272 <li><a href="#fappcmds">Application Commands</a></li> 273 </ul> 274 </li> 275 276 <li><a href="#fhooks">Field Change Hooks</a></li> 277 278 <li><a href="#ffocus">Field Change Commands</a></li> 279 280 <li><a href="#frmoptions">Form Options</a></li> 281 282 <li> 283 <a href="#fcustom">Custom Validation Types</a> 284 <ul> 285 <li><a href="#flinktypes">Union Types</a></li> 286 287 <li><a href="#fnewtypes">New Field Types</a></li> 288 289 <li><a href="#fcheckargs">Validation Function 290 Arguments</a></li> 291 292 <li><a href="#fcustorder">Order Functions For Custom 293 Types</a></li> 294 295 <li><a href="#fcustprobs">Avoiding Problems</a></li> 296 </ul> 297 </li> 298 </ul> 299 </li> 300 </ul> 301 </div> 302 303 <hr> 304 305 <h2><a name="introduction" id="introduction">Introduction</a></h2> 306 307 <p>This document is an introduction to programming with 308 <code>curses</code>. It is not an exhaustive reference for the 309 curses Application Programming Interface (API); that role is 310 filled by the <code>curses</code> manual pages. Rather, it is 311 intended to help C programmers ease into using the package.</p> 312 313 <p>This document is aimed at C applications programmers not yet 314 specifically familiar with ncurses. If you are already an 315 experienced <code>curses</code> programmer, you should 316 nevertheless read the sections on <a href="#mouse">Mouse 317 Interfacing</a>, <a href="#debugging">Debugging</a>, <a href= 318 "#compat">Compatibility with Older Versions</a>, and <a href= 319 "#hints">Hints, Tips, and Tricks</a>. These will bring you up to 320 speed on the special features and quirks of the 321 <code>ncurses</code> implementation. If you are not so 322 experienced, keep reading.</p> 323 324 <p>The <code>curses</code> package is a subroutine library for 325 terminal-independent screen-painting and input-event handling 326 which presents a high level screen model to the programmer, 327 hiding differences between terminal types and doing automatic 328 optimization of output to change one screen full of text into 329 another. <code>Curses</code> uses terminfo, which is a database 330 format that can describe the capabilities of thousands of 331 different terminals.</p> 332 333 <p>The <code>curses</code> API may seem something of an archaism 334 on UNIX desktops increasingly dominated by X, Motif, and Tcl/Tk. 335 Nevertheless, UNIX still supports tty lines and X supports 336 <em>xterm(1)</em>; the <code>curses</code> API has the advantage 337 of (a) back-portability to character-cell terminals, and (b) 338 simplicity. For an application that does not require bit-mapped 339 graphics and multiple fonts, an interface implementation using 340 <code>curses</code> will typically be a great deal simpler and 341 less expensive than one using an X toolkit.</p> 342 343 <h3><a name="history" id="history">A Brief History of Curses</a></h3> 344 345 <p>Historically, the first ancestor of <code>curses</code> was 346 the routines written to provide screen-handling for the 347 <code>vi</code> editor; these used the <code>termcap</code> 348 database facility (both released in 3BSD) for describing terminal 349 capabilities. These routines were abstracted into a documented 350 library and first released with the early BSD UNIX versions. All 351 of this work was done by students at the University of California 352 (Berkeley campus). The curses library was first published in 353 4.0BSD, a year after 3BSD (i.e., late 1980).</p> 354 355 <p>After graduation, one of those students went to work at 356 AT&T Bell Labs, and made an improved <code>termcap</code> 357 library called <code>terminfo</code> (i.e., 358 “libterm”), and adapted the curses library to use 359 this. That was subsequently released in System V Release 2 (early 360 1984). Thereafter, other developers added to the curses and 361 terminfo libraries. For instance, a student at Cornell University 362 wrote an improved terminfo library as well as a tool 363 (<code>tic</code>) to compile the terminal descriptions. As a 364 general rule, AT&T did not identify the developers in the 365 source-code or documentation; the <code>tic</code> and 366 <code>infocmp</code> programs are the exceptions.</p> 367 368 <p>System V Release 3 (System III UNIX) from Bell Labs featured a 369 rewritten and much-improved <code>curses</code> library, along 370 with the <code>tic</code> program (late 1986).</p> 371 372 <p>To recap, terminfo is based on Berkeley's termcap database, 373 but contains a number of improvements and extensions. 374 Parameterized capabilities strings were introduced, making it 375 possible to describe multiple video attributes, and colors and to 376 handle far more unusual terminals than possible with termcap. In 377 the later AT&T System V releases, <code>curses</code> evolved 378 to use more facilities and offer more capabilities, going far 379 beyond BSD curses in power and flexibility.</p> 380 381 <h3><a name="scope" id="scope">Scope of This Document</a></h3> 382 383 <p>This document describes <code>ncurses</code>, a free 384 implementation of the System V <code>curses</code> API with some 385 clearly marked extensions. It includes the following System V 386 curses features:</p> 387 388 <ul> 389 <li>Support for multiple screen highlights (BSD curses could 390 only handle one “standout” highlight, usually 391 reverse-video).</li> 392 393 <li>Support for line- and box-drawing using forms 394 characters.</li> 395 396 <li>Recognition of function keys on input.</li> 397 398 <li>Color support.</li> 399 400 <li>Support for pads (windows of larger than screen size on 401 which the screen or a subwindow defines a viewport).</li> 402 </ul> 403 404 <p>Also, this package makes use of the insert and delete line and 405 character features of terminals so equipped, and determines how 406 to optimally use these features with no help from the programmer. 407 It allows arbitrary combinations of video attributes to be 408 displayed, even on terminals that leave “magic 409 cookies” on the screen to mark changes in attributes.</p> 410 411 <p>The <code>ncurses</code> package can also capture and use 412 event reports from a mouse in some environments (notably, xterm 413 under the X window system). This document includes tips for using 414 the mouse.</p> 415 416 <p>The <code>ncurses</code> package was originated by Pavel 417 Curtis. The original maintainer of this package is <a href= 418 "mailto:zmbenhal@netcom.com">Zeyd Ben-Halim</a> 419 <zmbenhal@netcom.com>. <a href= 420 "mailto:esr@snark.thyrsus.com">Eric S. Raymond</a> 421 <esr@snark.thyrsus.com> wrote many of the new features in 422 versions after 1.8.1 and wrote most of this introduction. 423 Jürgen Pfeifer wrote all of the menu and forms code as well 424 as the <a href="http://www.adahome.com">Ada95</a> binding. 425 Ongoing work is being done by <a href= 426 "mailto:dickey@invisible-island.net">Thomas Dickey</a> 427 (maintainer). Contact the current maintainers at <a href= 428 "mailto:bug-ncurses@gnu.org">bug-ncurses@gnu.org</a>.</p> 429 430 <p>This document also describes the <a href="#panels">panels</a> 431 extension library, similarly modeled on the SVr4 panels facility. 432 This library allows you to associate backing store with each of a 433 stack or deck of overlapping windows, and provides operations for 434 moving windows around in the stack that change their visibility 435 in the natural way (handling window overlaps).</p> 436 437 <p>Finally, this document describes in detail the <a href= 438 "#menu">menus</a> and <a href="#form">forms</a> extension 439 libraries, also cloned from System V, which support easy 440 construction and sequences of menus and fill-in forms.</p> 441 442 <h3><a name="terminology" id="terminology">Terminology</a></h3> 443 444 <p>In this document, the following terminology is used with 445 reasonable consistency:</p> 446 447 <dl> 448 <dt>window</dt> 449 450 <dd>A data structure describing a sub-rectangle of the screen 451 (possibly the entire screen). You can write to a window as 452 though it were a miniature screen, scrolling independently of 453 other windows on the physical screen.</dd> 454 455 <dt>screens</dt> 456 457 <dd>A subset of windows which are as large as the terminal 458 screen, i.e., they start at the upper left hand corner and 459 encompass the lower right hand corner. One of these, 460 <code>stdscr</code>, is automatically provided for the 461 programmer.</dd> 462 463 <dt>terminal screen</dt> 464 465 <dd>The package's idea of what the terminal display currently 466 looks like, i.e., what the user sees now. This is a special 467 screen.</dd> 468 </dl> 469 470 <h2><a name="curses" id="curses">The Curses Library</a></h2> 471 472 <h3><a name="overview" id="overview">An Overview of Curses</a></h3> 473 474 <h4><a name="compiling" id="compiling">Compiling Programs using 475 Curses</a></h4> 476 477 <p>In order to use the library, it is necessary to have certain 478 types and variables defined. Therefore, the programmer must have 479 a line:</p> 480 481 <pre class="code-block"> 482 #include <curses.h> 483</pre> 484 <p>at the top of the program source. The screen package uses the 485 Standard I/O library, so <code><curses.h></code> includes 486 <code><stdio.h></code>. <code><curses.h></code> also 487 includes <code><termios.h></code>, 488 <code><termio.h></code>, or <code><sgtty.h></code> 489 depending on your system. It is redundant (but harmless) for the 490 programmer to do these includes, too. In linking with 491 <code>curses</code> you need to have <code>-lncurses</code> in 492 your LDFLAGS or on the command line. There is no need for any 493 other libraries.</p> 494 495 <h4><a name="updating" id="updating">Updating the Screen</a></h4> 496 497 <p>In order to update the screen optimally, it is necessary for 498 the routines to know what the screen currently looks like and 499 what the programmer wants it to look like next. For this purpose, 500 a data type (structure) named WINDOW is defined which describes a 501 window image to the routines, including its starting position on 502 the screen (the (y, x) coordinates of the upper left hand corner) 503 and its size. One of these (called <code>curscr</code>, for 504 current screen) is a screen image of what the terminal currently 505 looks like. Another screen (called <code>stdscr</code>, for 506 standard screen) is provided by default to make changes on.</p> 507 508 <p>A window is a purely internal representation. It is used to 509 build and store a potential image of a portion of the terminal. 510 It does not bear any necessary relation to what is really on the 511 terminal screen; it is more like a scratchpad or write 512 buffer.</p> 513 514 <p>To make the section of physical screen corresponding to a 515 window reflect the contents of the window structure, the routine 516 <code>refresh()</code> (or <code>wrefresh()</code> if the window 517 is not <code>stdscr</code>) is called.</p> 518 519 <p>A given physical screen section may be within the scope of any 520 number of overlapping windows. Also, changes can be made to 521 windows in any order, without regard to motion efficiency. Then, 522 at will, the programmer can effectively say “make it look 523 like this,” and let the package implementation determine 524 the most efficient way to repaint the screen.</p> 525 526 <h4><a name="stdscr" id="stdscr">Standard Windows and Function 527 Naming Conventions</a></h4> 528 529 <p>As hinted above, the routines can use several windows, but two 530 are automatically given: <code>curscr</code>, which knows what 531 the terminal looks like, and <code>stdscr</code>, which is what 532 the programmer wants the terminal to look like next. The user 533 should never actually access <code>curscr</code> directly. 534 Changes should be made to through the API, and then the routine 535 <code>refresh()</code> (or <code>wrefresh()</code>) called.</p> 536 537 <p>Many functions are defined to use <code>stdscr</code> as a 538 default screen. For example, to add a character to 539 <code>stdscr</code>, one calls <code>addch()</code> with the 540 desired character as argument. To write to a different window. 541 use the routine <code>waddch()</code> (for 542 <strong>w</strong>indow-specific addch()) is provided. This 543 convention of prepending function names with a “w” 544 when they are to be applied to specific windows is consistent. 545 The only routines which do not follow it are those for which a 546 window must always be specified.</p> 547 548 <p>In order to move the current (y, x) coordinates from one point 549 to another, the routines <code>move()</code> and 550 <code>wmove()</code> are provided. However, it is often desirable 551 to first move and then perform some I/O operation. In order to 552 avoid clumsiness, most I/O routines can be preceded by the prefix 553 “mv” and the desired (y, x) coordinates prepended to 554 the arguments to the function. For example, the calls</p> 555 556 <pre class="code-block"> 557 move(y, x); 558 addch(ch); 559</pre> 560 <p>can be replaced by</p> 561 562 <pre class="code-block"> 563 mvaddch(y, x, ch); 564</pre> 565 <p>and</p> 566 567 <pre class="code-block"> 568 wmove(win, y, x); 569 waddch(win, ch); 570</pre> 571 <p>can be replaced by</p> 572 573 <pre class="code-block"> 574 mvwaddch(win, y, x, ch); 575</pre> 576 <p>Note that the window description pointer (win) comes before 577 the added (y, x) coordinates. If a function requires a window 578 pointer, it is always the first parameter passed.</p> 579 580 <h4><a name="variables" id="variables">Variables</a></h4> 581 582 <p>The <code>curses</code> library sets some variables describing 583 the terminal capabilities.</p> 584 585 <pre class="code-block"> 586 type name description 587 ------------------------------------------------------------------ 588 int LINES number of lines on the terminal 589 int COLS number of columns on the terminal 590</pre> 591 <p>The <code>curses.h</code> also introduces some 592 <code>#define</code> constants and types of general 593 usefulness:</p> 594 595 <dl> 596 <dt><code>bool</code> 597 </dt> 598 599 <dd>boolean type, actually a “char” (e.g., 600 <code>bool doneit;</code>)</dd> 601 602 <dt><code>TRUE</code> 603 </dt> 604 605 <dd>boolean “true” flag (1).</dd> 606 607 <dt><code>FALSE</code> 608 </dt> 609 610 <dd>boolean “false” flag (0).</dd> 611 612 <dt><code>ERR</code> 613 </dt> 614 615 <dd>error flag returned by routines on a failure (-1).</dd> 616 617 <dt><code>OK</code> 618 </dt> 619 620 <dd>error flag returned by routines when things go right.</dd> 621 </dl> 622 623 <h3><a name="using" id="using">Using the Library</a></h3> 624 625 <p>Now we describe how to actually use the screen package. In it, 626 we assume all updating, reading, etc. is applied to 627 <code>stdscr</code>. These instructions will work on any window, 628 providing you change the function names and parameters as 629 mentioned above.</p> 630 631 <p>Here is a sample program to motivate the discussion:</p> 632 633 <pre class="code-block"> 634#include <stdlib.h> 635#include <curses.h> 636#include <signal.h> 637 638static void finish(int sig); 639 640int 641main(int argc, char *argv[]) 642{ 643 int num = 0; 644 645 /* initialize your non-curses data structures here */ 646 647 (void) signal(SIGINT, finish); /* arrange interrupts to terminate */ 648 649 (void) initscr(); /* initialize the curses library */ 650 keypad(stdscr, TRUE); /* enable keyboard mapping */ 651 (void) nonl(); /* tell curses not to do NL->CR/NL on output */ 652 (void) cbreak(); /* take input chars one at a time, no wait for \n */ 653 (void) echo(); /* echo input - in color */ 654 655 if (has_colors()) 656 { 657 start_color(); 658 659 /* 660 * Simple color assignment, often all we need. Color pair 0 cannot 661 * be redefined. This example uses the same value for the color 662 * pair as for the foreground color, though of course that is not 663 * necessary: 664 */ 665 init_pair(1, COLOR_RED, COLOR_BLACK); 666 init_pair(2, COLOR_GREEN, COLOR_BLACK); 667 init_pair(3, COLOR_YELLOW, COLOR_BLACK); 668 init_pair(4, COLOR_BLUE, COLOR_BLACK); 669 init_pair(5, COLOR_CYAN, COLOR_BLACK); 670 init_pair(6, COLOR_MAGENTA, COLOR_BLACK); 671 init_pair(7, COLOR_WHITE, COLOR_BLACK); 672 } 673 674 for (;;) 675 { 676 int c = getch(); /* refresh, accept single keystroke of input */ 677 attrset(COLOR_PAIR(num % 8)); 678 num++; 679 680 /* process the command keystroke */ 681 } 682 683 finish(0); /* we are done */ 684} 685 686static void finish(int sig) 687{ 688 endwin(); 689 690 /* do your non-curses wrapup here */ 691 692 exit(0); 693} 694</pre> 695 <h4><a name="starting" id="starting">Starting up</a></h4> 696 697 <p>In order to use the screen package, the routines must know 698 about terminal characteristics, and the space for 699 <code>curscr</code> and <code>stdscr</code> must be allocated. 700 These function <code>initscr()</code> does both these things. 701 Since it must allocate space for the windows, it can overflow 702 memory when attempting to do so. On the rare occasions this 703 happens, <code>initscr()</code> will terminate the program with 704 an error message. <code>initscr()</code> must always be called 705 before any of the routines which affect windows are used. If it 706 is not, the program will core dump as soon as either 707 <code>curscr</code> or <code>stdscr</code> are referenced. 708 However, it is usually best to wait to call it until after you 709 are sure you will need it, like after checking for startup 710 errors. Terminal status changing routines like <code>nl()</code> 711 and <code>cbreak()</code> should be called after 712 <code>initscr()</code>.</p> 713 714 <p>Once the screen windows have been allocated, you can set them 715 up for your program. If you want to, say, allow a screen to 716 scroll, use <code>scrollok()</code>. If you want the cursor to be 717 left in place after the last change, use <code>leaveok()</code>. 718 If this is not done, <code>refresh()</code> will move the cursor 719 to the window's current (y, x) coordinates after updating it.</p> 720 721 <p>You can create new windows of your own using the functions 722 <code>newwin()</code>, <code>derwin()</code>, and 723 <code>subwin()</code>. The routine <code>delwin()</code> will 724 allow you to get rid of old windows. All the options described 725 above can be applied to any window.</p> 726 727 <h4><a name="output" id="output">Output</a></h4> 728 729 <p>Now that we have set things up, we will want to actually 730 update the terminal. The basic functions used to change what will 731 go on a window are <code>addch()</code> and <code>move()</code>. 732 <code>addch()</code> adds a character at the current (y, x) 733 coordinates. <code>move()</code> changes the current (y, x) 734 coordinates to whatever you want them to be. It returns 735 <code>ERR</code> if you try to move off the window. As mentioned 736 above, you can combine the two into <code>mvaddch()</code> to do 737 both things at once.</p> 738 739 <p>The other output functions, such as <code>addstr()</code> and 740 <code>printw()</code>, all call <code>addch()</code> to add 741 characters to the window.</p> 742 743 <p>After you have put on the window what you want there, when you 744 want the portion of the terminal covered by the window to be made 745 to look like it, you must call <code>refresh()</code>. In order 746 to optimize finding changes, <code>refresh()</code> assumes that 747 any part of the window not changed since the last 748 <code>refresh()</code> of that window has not been changed on the 749 terminal, i.e., that you have not refreshed a portion of the 750 terminal with an overlapping window. If this is not the case, the 751 routine <code>touchwin()</code> is provided to make it look like 752 the entire window has been changed, thus making 753 <code>refresh()</code> check the whole subsection of the terminal 754 for changes.</p> 755 756 <p>If you call <code>wrefresh()</code> with <code>curscr</code> 757 as its argument, it will make the screen look like 758 <code>curscr</code> thinks it looks like. This is useful for 759 implementing a command which would redraw the screen in case it 760 get messed up.</p> 761 762 <h4><a name="input" id="input">Input</a></h4> 763 764 <p>The complementary function to <code>addch()</code> is 765 <code>getch()</code> which, if echo is set, will call 766 <code>addch()</code> to echo the character. Since the screen 767 package needs to know what is on the terminal at all times, if 768 characters are to be echoed, the tty must be in raw or cbreak 769 mode. Since initially the terminal has echoing enabled and is in 770 ordinary “cooked” mode, one or the other has to 771 changed before calling <code>getch()</code>; otherwise, the 772 program's output will be unpredictable.</p> 773 774 <p>When you need to accept line-oriented input in a window, the 775 functions <code>wgetstr()</code> and friends are available. There 776 is even a <code>wscanw()</code> function that can do 777 <code>scanf()</code>(3)-style multi-field parsing on window 778 input. These pseudo-line-oriented functions turn on echoing while 779 they execute.</p> 780 781 <p>The example code above uses the call <code>keypad(stdscr, 782 TRUE)</code> to enable support for function-key mapping. With 783 this feature, the <code>getch()</code> code watches the input 784 stream for character sequences that correspond to arrow and 785 function keys. These sequences are returned as pseudo-character 786 values. The <code>#define</code> values returned are listed in 787 the <code>curses.h</code> The mapping from sequences to 788 <code>#define</code> values is determined by <code>key_</code> 789 capabilities in the terminal's terminfo entry.</p> 790 791 <h4><a name="formschars" id="formschars">Using Forms 792 Characters</a></h4> 793 794 <p>The <code>addch()</code> function (and some others, including 795 <code>box()</code> and <code>border()</code>) can accept some 796 pseudo-character arguments which are specially defined by 797 <code>ncurses</code>. These are <code>#define</code> values set 798 up in the <code>curses.h</code> header; see there for a complete 799 list (look for the prefix <code>ACS_</code>).</p> 800 801 <p>The most useful of the ACS defines are the forms-drawing 802 characters. You can use these to draw boxes and simple graphs on 803 the screen. If the terminal does not have such characters, 804 <code>curses.h</code> will map them to a recognizable (though 805 ugly) set of ASCII defaults.</p> 806 807 <h4><a name="attributes" id="attributes">Character Attributes and 808 Color</a></h4> 809 810 <p>The <code>ncurses</code> package supports screen highlights 811 including standout, reverse-video, underline, and blink. It also 812 supports color, which is treated as another kind of 813 highlight.</p> 814 815 <p>Highlights are encoded, internally, as high bits of the 816 pseudo-character type (<code>chtype</code>) that 817 <code>curses.h</code> uses to represent the contents of a screen 818 cell. See the <code>curses.h</code> header file for a complete 819 list of highlight mask values (look for the prefix 820 <code>A_</code>).</p> 821 822 <p>There are two ways to make highlights. One is to logical-or 823 the value of the highlights you want into the character argument 824 of an <code>addch()</code> call, or any other output call that 825 takes a <code>chtype</code> argument.</p> 826 827 <p>The other is to set the current-highlight value. This is 828 <em>logical-OR</em>ed with any highlight you specify the first 829 way. You do this with the functions <code>attron()</code>, 830 <code>attroff()</code>, and <code>attrset()</code>; see the 831 manual pages for details. Color is a special kind of highlight. 832 The package actually thinks in terms of color pairs, combinations 833 of foreground and background colors. The sample code above sets 834 up eight color pairs, all of the guaranteed-available colors on 835 black. Note that each color pair is, in effect, given the name of 836 its foreground color. Any other range of eight non-conflicting 837 values could have been used as the first arguments of the 838 <code>init_pair()</code> values.</p> 839 840 <p>Once you have done an <code>init_pair()</code> that creates 841 color-pair N, you can use <code>COLOR_PAIR(N)</code> as a 842 highlight that invokes that particular color combination. Note 843 that <code>COLOR_PAIR(N)</code>, for constant N, is itself a 844 compile-time constant and can be used in initializers.</p> 845 846 <h4><a name="mouse" id="mouse">Mouse Interfacing</a></h4> 847 848 <p>The <code>ncurses</code> library also provides a mouse 849 interface.</p> 850 851 <blockquote> 852 <strong>NOTE:</strong> this facility is specific to 853 <code>ncurses</code>, it is not part of either the XSI Curses 854 standard, nor of System V Release 4, nor BSD curses. System V 855 Release 4 curses contains code with similar interface 856 definitions, however it is not documented. Other than by 857 disassembling the library, we have no way to determine exactly 858 how that mouse code works. Thus, we recommend that you wrap 859 mouse-related code in an #ifdef using the feature macro 860 NCURSES_MOUSE_VERSION so it will not be compiled and linked on 861 non-ncurses systems. 862 </blockquote> 863 864 <p>Presently, mouse event reporting works in the following 865 environments:</p> 866 867 <ul> 868 <li>xterm and similar programs such as rxvt.</li> 869 870 <li>Linux console, when configured with <code>gpm</code>(1), 871 Alessandro Rubini's mouse server.</li> 872 873 <li>FreeBSD sysmouse (console)</li> 874 875 <li>OS/2 EMX</li> 876 </ul> 877 878 <p>The mouse interface is very simple. To activate it, you use 879 the function <code>mousemask()</code>, passing it as first 880 argument a bit-mask that specifies what kinds of events you want 881 your program to be able to see. It will return the bit-mask of 882 events that actually become visible, which may differ from the 883 argument if the mouse device is not capable of reporting some of 884 the event types you specify.</p> 885 886 <p>Once the mouse is active, your application's command loop 887 should watch for a return value of <code>KEY_MOUSE</code> from 888 <code>wgetch()</code>. When you see this, a mouse event report 889 has been queued. To pick it off the queue, use the function 890 <code>getmouse()</code> (you must do this before the next 891 <code>wgetch()</code>, otherwise another mouse event might come 892 in and make the first one inaccessible).</p> 893 894 <p>Each call to <code>getmouse()</code> fills a structure (the 895 address of which you will pass it) with mouse event data. The 896 event data includes zero-origin, screen-relative character-cell 897 coordinates of the mouse pointer. It also includes an event mask. 898 Bits in this mask will be set, corresponding to the event type 899 being reported.</p> 900 901 <p>The mouse structure contains two additional fields which may 902 be significant in the future as ncurses interfaces to new kinds 903 of pointing device. In addition to x and y coordinates, there is 904 a slot for a z coordinate; this might be useful with 905 touch-screens that can return a pressure or duration parameter. 906 There is also a device ID field, which could be used to 907 distinguish between multiple pointing devices.</p> 908 909 <p>The class of visible events may be changed at any time via 910 <code>mousemask()</code>. Events that can be reported include 911 presses, releases, single-, double- and triple-clicks (you can 912 set the maximum button-down time for clicks). If you do not make 913 clicks visible, they will be reported as press-release pairs. In 914 some environments, the event mask may include bits reporting the 915 state of shift, alt, and ctrl keys on the keyboard during the 916 event.</p> 917 918 <p>A function to check whether a mouse event fell within a given 919 window is also supplied. You can use this to see whether a given 920 window should consider a mouse event relevant to it.</p> 921 922 <p>Because mouse event reporting will not be available in all 923 environments, it would be unwise to build <code>ncurses</code> 924 applications that <em>require</em> the use of a mouse. Rather, 925 you should use the mouse as a shortcut for point-and-shoot 926 commands your application would normally accept from the 927 keyboard. Two of the test games in the <code>ncurses</code> 928 distribution (<code>bs</code> and <code>knight</code>) contain 929 code that illustrates how this can be done.</p> 930 931 <p>See the manual page <code>curs_mouse(3X)</code> for full 932 details of the mouse-interface functions.</p> 933 934 <h4><a name="finishing" id="finishing">Finishing Up</a></h4> 935 936 <p>In order to clean up after the <code>ncurses</code> routines, 937 the routine <code>endwin()</code> is provided. It restores tty 938 modes to what they were when <code>initscr()</code> was first 939 called, and moves the cursor down to the lower-left corner. Thus, 940 anytime after the call to initscr, <code>endwin()</code> should 941 be called before exiting.</p> 942 943 <h3><a name="functions" id="functions">Function Descriptions</a></h3> 944 945 <p>We describe the detailed behavior of some important curses 946 functions here, as a supplement to the manual page 947 descriptions.</p> 948 949 <h4><a name="init" id="init">Initialization and Wrapup</a></h4> 950 951 <dl> 952 <dt><code>initscr()</code> 953 </dt> 954 955 <dd>The first function called should almost always be 956 <code>initscr()</code>. This will determine the terminal type 957 and initialize curses data structures. <code>initscr()</code> 958 also arranges that the first call to <code>refresh()</code> 959 will clear the screen. If an error occurs a message is written 960 to standard error and the program exits. Otherwise it returns a 961 pointer to stdscr. A few functions may be called before initscr 962 (<code>slk_init()</code>, <code>filter()</code>, 963 <code>ripoffline()</code>, <code>use_env()</code>, and, if you 964 are using multiple terminals, <code>newterm()</code>.)</dd> 965 966 <dt><code>endwin()</code> 967 </dt> 968 969 <dd>Your program should always call <code>endwin()</code> 970 before exiting or shelling out of the program. This function 971 will restore tty modes, move the cursor to the lower left 972 corner of the screen, reset the terminal into the proper 973 non-visual mode. Calling <code>refresh()</code> or 974 <code>doupdate()</code> after a temporary escape from the 975 program will restore the ncurses screen from before the 976 escape.</dd> 977 978 <dt><code>newterm(type, ofp, ifp)</code> 979 </dt> 980 981 <dd>A program which outputs to more than one terminal should 982 use <code>newterm()</code> instead of <code>initscr()</code>. 983 <code>newterm()</code> should be called once for each terminal. 984 It returns a variable of type <code>SCREEN *</code> which 985 should be saved as a reference to that terminal. (NOTE: a 986 SCREEN variable is not a <em>screen</em> in the sense we are 987 describing in this introduction, but a collection of parameters 988 used to assist in optimizing the display.) The arguments are 989 the type of the terminal (a string) and <code>FILE</code> 990 pointers for the output and input of the terminal. If type is 991 NULL then the environment variable <code>$TERM</code> is used. 992 <code>endwin()</code> should called once at wrapup time for 993 each terminal opened using this function.</dd> 994 995 <dt><code>set_term(new)</code> 996 </dt> 997 998 <dd>This function is used to switch to a different terminal 999 previously opened by <code>newterm()</code>. The screen 1000 reference for the new terminal is passed as the parameter. The 1001 previous terminal is returned by the function. All other calls 1002 affect only the current terminal.</dd> 1003 1004 <dt><code>delscreen(sp)</code> 1005 </dt> 1006 1007 <dd>The inverse of <code>newterm()</code>; deallocates the data 1008 structures associated with a given <code>SCREEN</code> 1009 reference.</dd> 1010 </dl> 1011 1012 <h4><a name="flush" id="flush">Causing Output to the Terminal</a></h4> 1013 1014 <dl> 1015 <dt><code>refresh()</code> and <code>wrefresh(win)</code></dt> 1016 1017 <dd>These functions must be called to actually get any output 1018 on the terminal, as other routines merely manipulate data 1019 structures. <code>wrefresh()</code> copies the named window to 1020 the physical terminal screen, taking into account what is 1021 already there in order to do optimizations. 1022 <code>refresh()</code> does a refresh of <code>stdscr</code>. 1023 Unless <code>leaveok()</code> has been enabled, the physical 1024 cursor of the terminal is left at the location of the window's 1025 cursor.</dd> 1026 1027 <dt><code>doupdate()</code> and 1028 <code>wnoutrefresh(win)</code></dt> 1029 1030 <dd>These two functions allow multiple updates with more 1031 efficiency than wrefresh. To use them, it is important to 1032 understand how curses works. In addition to all the window 1033 structures, curses keeps two data structures representing the 1034 terminal screen: a physical screen, describing what is actually 1035 on the screen, and a virtual screen, describing what the 1036 programmer wants to have on the screen. wrefresh works by first 1037 copying the named window to the virtual screen 1038 (<code>wnoutrefresh()</code>), and then calling the routine to 1039 update the screen (<code>doupdate()</code>). If the programmer 1040 wishes to output several windows at once, a series of calls to 1041 <code>wrefresh</code> will result in alternating calls to 1042 <code>wnoutrefresh()</code> and <code>doupdate()</code>, 1043 causing several bursts of output to the screen. By calling 1044 <code>wnoutrefresh()</code> for each window, it is then 1045 possible to call <code>doupdate()</code> once, resulting in 1046 only one burst of output, with fewer total characters 1047 transmitted (this also avoids a visually annoying flicker at 1048 each update).</dd> 1049 </dl> 1050 1051 <h4><a name="lowlevel" id="lowlevel">Low-Level Capability 1052 Access</a></h4> 1053 1054 <dl> 1055 <dt><code>setupterm(term, filenum, errret)</code> 1056 </dt> 1057 1058 <dd> 1059 This routine is called to initialize a terminal's 1060 description, without setting up the curses screen structures 1061 or changing the tty-driver mode bits. <code>term</code> is 1062 the character string representing the name of the terminal 1063 being used. <code>filenum</code> is the UNIX file descriptor 1064 of the terminal to be used for output. <code>errret</code> is 1065 a pointer to an integer, in which a success or failure 1066 indication is returned. The values returned can be 1 (all is 1067 well), 0 (no such terminal), or -1 (some problem locating the 1068 terminfo database). 1069 <p>The value of <code>term</code> can be given as NULL, which 1070 will cause the value of <code>TERM</code> in the environment 1071 to be used. The <code>errret</code> pointer can also be given 1072 as NULL, meaning no error code is wanted. If 1073 <code>errret</code> is defaulted, and something goes wrong, 1074 <code>setupterm()</code> will print an appropriate error 1075 message and exit, rather than returning. Thus, a simple 1076 program can call setupterm(0, 1, 0) and not worry about 1077 initialization errors.</p> 1078 1079 <p>After the call to <code>setupterm()</code>, the global 1080 variable <code>cur_term</code> is set to point to the current 1081 structure of terminal capabilities. By calling 1082 <code>setupterm()</code> for each terminal, and saving and 1083 restoring <code>cur_term</code>, it is possible for a program 1084 to use two or more terminals at once. 1085 <code>Setupterm()</code> also stores the names section of the 1086 terminal description in the global character array 1087 <code>ttytype[]</code>. Subsequent calls to 1088 <code>setupterm()</code> will overwrite this array, so you 1089 will have to save it yourself if need be.</p> 1090 </dd> 1091 </dl> 1092 1093 <h4><a name="debugging" id="debugging">Debugging</a></h4> 1094 1095 <blockquote> 1096 <strong>NOTE:</strong> These functions are not part of the 1097 standard curses API! 1098 </blockquote> 1099 1100 <dl> 1101 <dt><code>trace()</code> 1102 </dt> 1103 1104 <dd>This function can be used to explicitly set a trace level. 1105 If the trace level is nonzero, execution of your program will 1106 generate a file called “trace” in the current 1107 working directory containing a report on the library's actions. 1108 Higher trace levels enable more detailed (and verbose) 1109 reporting -- see comments attached to <code>TRACE_</code> 1110 defines in the <code>curses.h</code> file for details. (It is 1111 also possible to set a trace level by assigning a trace level 1112 value to the environment variable 1113 <code>NCURSES_TRACE</code>).</dd> 1114 1115 <dt><code>_tracef()</code> 1116 </dt> 1117 1118 <dd>This function can be used to output your own debugging 1119 information. It is only available only if you link with 1120 -lncurses_g. It can be used the same way as 1121 <code>printf()</code>, only it outputs a newline after the end 1122 of arguments. The output goes to a file called 1123 <code>trace</code> in the current directory.</dd> 1124 </dl> 1125 1126 <p>Trace logs can be difficult to interpret due to the sheer 1127 volume of data dumped in them. There is a script called 1128 <strong>tracemunch</strong> included with the 1129 <code>ncurses</code> distribution that can alleviate this problem 1130 somewhat; it compacts long sequences of similar operations into 1131 more succinct single-line pseudo-operations. These pseudo-ops can 1132 be distinguished by the fact that they are named in capital 1133 letters.</p> 1134 1135 <h3><a name="hints" id="hints">Hints, Tips, and Tricks</a></h3> 1136 1137 <p>The <code>ncurses</code> manual pages are a complete reference 1138 for this library. In the remainder of this document, we discuss 1139 various useful methods that may not be obvious from the manual 1140 page descriptions.</p> 1141 1142 <h4><a name="caution" id="caution">Some Notes of Caution</a></h4> 1143 1144 <p>If you find yourself thinking you need to use 1145 <code>noraw()</code> or <code>nocbreak()</code>, think again and 1146 move carefully. It is probably better design to use 1147 <code>getstr()</code> or one of its relatives to simulate cooked 1148 mode. The <code>noraw()</code> and <code>nocbreak()</code> 1149 functions try to restore cooked mode, but they may end up 1150 clobbering some control bits set before you started your 1151 application. Also, they have always been poorly documented, and 1152 are likely to hurt your application's usability with other curses 1153 libraries.</p> 1154 1155 <p>Bear in mind that <code>refresh()</code> is a synonym for 1156 <code>wrefresh(stdscr)</code>. Do not try to mix use of 1157 <code>stdscr</code> with use of windows declared by 1158 <code>newwin()</code>; a <code>refresh()</code> call will blow 1159 them off the screen. The right way to handle this is to use 1160 <code>subwin()</code>, or not touch <code>stdscr</code> at all 1161 and tile your screen with declared windows which you then 1162 <code>wnoutrefresh()</code> somewhere in your program event loop, 1163 with a single <code>doupdate()</code> call to trigger actual 1164 repainting.</p> 1165 1166 <p>You are much less likely to run into problems if you design 1167 your screen layouts to use tiled rather than overlapping windows. 1168 Historically, curses support for overlapping windows has been 1169 weak, fragile, and poorly documented. The <code>ncurses</code> 1170 library is not yet an exception to this rule.</p> 1171 1172 <p>There is a panels library included in the <code>ncurses</code> 1173 distribution that does a pretty good job of strengthening the 1174 overlapping-windows facilities.</p> 1175 1176 <p>Try to avoid using the global variables LINES and COLS. Use 1177 <code>getmaxyx()</code> on the <code>stdscr</code> context 1178 instead. Reason: your code may be ported to run in an environment 1179 with window resizes, in which case several screens could be open 1180 with different sizes.</p> 1181 1182 <h4><a name="leaving" id="leaving">Temporarily Leaving NCURSES 1183 Mode</a></h4> 1184 1185 <p>Sometimes you will want to write a program that spends most of 1186 its time in screen mode, but occasionally returns to ordinary 1187 “cooked” mode. A common reason for this is to support 1188 shell-out. This behavior is simple to arrange in 1189 <code>ncurses</code>.</p> 1190 1191 <p>To leave <code>ncurses</code> mode, call <code>endwin()</code> 1192 as you would if you were intending to terminate the program. This 1193 will take the screen back to cooked mode; you can do your 1194 shell-out. When you want to return to <code>ncurses</code> mode, 1195 simply call <code>refresh()</code> or <code>doupdate()</code>. 1196 This will repaint the screen.</p> 1197 1198 <p>There is a boolean function, <code>isendwin()</code>, which 1199 code can use to test whether <code>ncurses</code> screen mode is 1200 active. It returns <code>TRUE</code> in the interval between an 1201 <code>endwin()</code> call and the following 1202 <code>refresh()</code>, <code>FALSE</code> otherwise.</p> 1203 1204 <p>Here is some sample code for shellout:</p> 1205 1206 <pre class="code-block"> 1207 addstr("Shelling out..."); 1208 def_prog_mode(); /* save current tty modes */ 1209 endwin(); /* restore original tty modes */ 1210 system("sh"); /* run shell */ 1211 addstr("returned.\n"); /* prepare return message */ 1212 refresh(); /* restore save modes, repaint screen */ 1213</pre> 1214 <h4><a name="xterm" id="xterm">Using NCURSES under XTERM</a></h4> 1215 1216 <p>A resize operation in X sends <code>SIGWINCH</code> to the 1217 application running under xterm. The easiest way to handle 1218 <code>SIGWINCH</code> is to do an <code>endwin</code>, followed 1219 by an <code>refresh</code> and a screen repaint you code 1220 yourself. The <code>refresh</code> will pick up the new screen 1221 size from the xterm's environment.</p> 1222 1223 <p>That is the standard way, of course (it even works with some 1224 vendor's curses implementations). Its drawback is that it clears 1225 the screen to reinitialize the display, and does not resize 1226 subwindows which must be shrunk. <code>Ncurses</code> provides an 1227 extension which works better, the <code>resizeterm</code> 1228 function. That function ensures that all windows are limited to 1229 the new screen dimensions, and pads <code>stdscr</code> with 1230 blanks if the screen is larger.</p> 1231 1232 <p>The <code>ncurses</code> library provides a SIGWINCH signal 1233 handler, which pushes a <code>KEY_RESIZE</code> via the wgetch() 1234 calls. When <code>ncurses</code> returns that code, it calls 1235 <code>resizeterm</code> to update the size of the standard 1236 screen's window, repainting that (filling with blanks or 1237 truncating as needed). It also resizes other windows, but its 1238 effect may be less satisfactory because it cannot know how you 1239 want the screen re-painted. You will usually have to write 1240 special-purpose code to handle <code>KEY_RESIZE</code> 1241 yourself.</p> 1242 1243 <h4><a name="screens" id="screens">Handling Multiple Terminal 1244 Screens</a></h4> 1245 1246 <p>The <code>initscr()</code> function actually calls a function 1247 named <code>newterm()</code> to do most of its work. If you are 1248 writing a program that opens multiple terminals, use 1249 <code>newterm()</code> directly.</p> 1250 1251 <p>For each call, you will have to specify a terminal type and a 1252 pair of file pointers; each call will return a screen reference, 1253 and <code>stdscr</code> will be set to the last one allocated. 1254 You will switch between screens with the <code>set_term</code> 1255 call. Note that you will also have to call 1256 <code>def_shell_mode</code> and <code>def_prog_mode</code> on 1257 each tty yourself.</p> 1258 1259 <h4><a name="testing" id="testing">Testing for Terminal 1260 Capabilities</a></h4> 1261 1262 <p>Sometimes you may want to write programs that test for the 1263 presence of various capabilities before deciding whether to go 1264 into <code>ncurses</code> mode. An easy way to do this is to call 1265 <code>setupterm()</code>, then use the functions 1266 <code>tigetflag()</code>, <code>tigetnum()</code>, and 1267 <code>tigetstr()</code> to do your testing.</p> 1268 1269 <p>A particularly useful case of this often comes up when you 1270 want to test whether a given terminal type should be treated as 1271 “smart” (cursor-addressable) or “stupid”. 1272 The right way to test this is to see if the return value of 1273 <code>tigetstr("cup")</code> is non-NULL. Alternatively, you can 1274 include the <code>term.h</code> file and test the value of the 1275 macro <code>cursor_address</code>.</p> 1276 1277 <h4><a name="tuning" id="tuning">Tuning for Speed</a></h4> 1278 1279 <p>Use the <code>addchstr()</code> family of functions for fast 1280 screen-painting of text when you know the text does not contain 1281 any control characters. Try to make attribute changes infrequent 1282 on your screens. Do not use the <code>immedok()</code> 1283 option!</p> 1284 1285 <h4><a name="special" id="special">Special Features of 1286 NCURSES</a></h4> 1287 1288 <p>The <code>wresize()</code> function allows you to resize a 1289 window in place. The associated <code>resizeterm()</code> 1290 function simplifies the construction of <a href= 1291 "#xterm">SIGWINCH</a> handlers, for resizing all windows.</p> 1292 1293 <p>The <code>define_key()</code> function allows you to define at 1294 runtime function-key control sequences which are not in the 1295 terminal description. The <code>keyok()</code> function allows 1296 you to temporarily enable or disable interpretation of any 1297 function-key control sequence.</p> 1298 1299 <p>The <code>use_default_colors()</code> function allows you to 1300 construct applications which can use the terminal's default 1301 foreground and background colors as an additional "default" 1302 color. Several terminal emulators support this feature, which is 1303 based on ISO 6429.</p> 1304 1305 <p>Ncurses supports up 16 colors, unlike SVr4 curses which 1306 defines only 8. While most terminals which provide color allow 1307 only 8 colors, about a quarter (including XFree86 xterm) support 1308 16 colors.</p> 1309 1310 <h3><a name="compat" id="compat">Compatibility with Older 1311 Versions</a></h3> 1312 1313 <p>Despite our best efforts, there are some differences between 1314 <code>ncurses</code> and the (undocumented!) behavior of older 1315 curses implementations. These arise from ambiguities or omissions 1316 in the documentation of the API.</p> 1317 1318 <h4><a name="refbug" id="refbug">Refresh of Overlapping 1319 Windows</a></h4> 1320 1321 <p>If you define two windows A and B that overlap, and then 1322 alternately scribble on and refresh them, the changes made to the 1323 overlapping region under historic <code>curses</code> versions 1324 were often not documented precisely.</p> 1325 1326 <p>To understand why this is a problem, remember that screen 1327 updates are calculated between two representations of the 1328 <em>entire</em> display. The documentation says that when you 1329 refresh a window, it is first copied to the virtual screen, and 1330 then changes are calculated to update the physical screen (and 1331 applied to the terminal). But "copied to" is not very specific, 1332 and subtle differences in how copying works can produce different 1333 behaviors in the case where two overlapping windows are each 1334 being refreshed at unpredictable intervals.</p> 1335 1336 <p>What happens to the overlapping region depends on what 1337 <code>wnoutrefresh()</code> does with its argument -- what 1338 portions of the argument window it copies to the virtual screen. 1339 Some implementations do "change copy", copying down only 1340 locations in the window that have changed (or been marked changed 1341 with <code>wtouchln()</code> and friends). Some implementations 1342 do "entire copy", copying <em>all</em> window locations to the 1343 virtual screen whether or not they have changed.</p> 1344 1345 <p>The <code>ncurses</code> library itself has not always been 1346 consistent on this score. Due to a bug, versions 1.8.7 to 1.9.8a 1347 did entire copy. Versions 1.8.6 and older, and versions 1.9.9 and 1348 newer, do change copy.</p> 1349 1350 <p>For most commercial curses implementations, it is not 1351 documented and not known for sure (at least not to the 1352 <code>ncurses</code> maintainers) whether they do change copy or 1353 entire copy. We know that System V release 3 curses has logic in 1354 it that looks like an attempt to do change copy, but the 1355 surrounding logic and data representations are sufficiently 1356 complex, and our knowledge sufficiently indirect, that it is hard 1357 to know whether this is reliable. It is not clear what the SVr4 1358 documentation and XSI standard intend. The XSI Curses standard 1359 barely mentions wnoutrefresh(); the SVr4 documents seem to be 1360 describing entire-copy, but it is possible with some effort and 1361 straining to read them the other way.</p> 1362 1363 <p>It might therefore be unwise to rely on either behavior in 1364 programs that might have to be linked with other curses 1365 implementations. Instead, you can do an explicit 1366 <code>touchwin()</code> before the <code>wnoutrefresh()</code> 1367 call to guarantee an entire-contents copy anywhere.</p> 1368 1369 <p>The really clean way to handle this is to use the panels 1370 library. If, when you want a screen update, you do 1371 <code>update_panels()</code>, it will do all the necessary 1372 <code>wnoutrefresh()</code> calls for whatever panel stacking 1373 order you have defined. Then you can do one 1374 <code>doupdate()</code> and there will be a <em>single</em> burst 1375 of physical I/O that will do all your updates.</p> 1376 1377 <h4><a name="backbug" id="backbug">Background Erase</a></h4> 1378 1379 <p>If you have been using a very old versions of 1380 <code>ncurses</code> (1.8.7 or older) you may be surprised by the 1381 behavior of the erase functions. In older versions, erased areas 1382 of a window were filled with a blank modified by the window's 1383 current attribute (as set by <strong>wattrset()</strong>, 1384 <strong>wattron()</strong>, <strong>wattroff()</strong> and 1385 friends).</p> 1386 1387 <p>In newer versions, this is not so. Instead, the attribute of 1388 erased blanks is normal unless and until it is modified by the 1389 functions <code>bkgdset()</code> or <code>wbkgdset()</code>.</p> 1390 1391 <p>This change in behavior conforms <code>ncurses</code> to 1392 System V Release 4 and the XSI Curses standard.</p> 1393 1394 <h3><a name="xsifuncs" id="xsifuncs">XSI Curses Conformance</a></h3> 1395 1396 <p>The <code>ncurses</code> library is intended to be base-level 1397 conformant with the XSI Curses standard from X/Open. Many 1398 extended-level features (in fact, almost all features not 1399 directly concerned with wide characters and internationalization) 1400 are also supported.</p> 1401 1402 <p>One effect of XSI conformance is the change in behavior 1403 described under <a href="#backbug">"Background Erase -- 1404 Compatibility with Old Versions"</a>.</p> 1405 1406 <p>Also, <code>ncurses</code> meets the XSI requirement that 1407 every macro entry point have a corresponding function which may 1408 be linked (and will be prototype-checked) if the macro definition 1409 is disabled with <code>#undef</code>.</p> 1410 1411 <h2><a name="panels" id="panels">The Panels Library</a></h2> 1412 1413 <p>The <code>ncurses</code> library by itself provides good 1414 support for screen displays in which the windows are tiled 1415 (non-overlapping). In the more general case that windows may 1416 overlap, you have to use a series of <code>wnoutrefresh()</code> 1417 calls followed by a <code>doupdate()</code>, and be careful about 1418 the order you do the window refreshes in. It has to be 1419 bottom-upwards, otherwise parts of windows that should be 1420 obscured will show through.</p> 1421 1422 <p>When your interface design is such that windows may dive 1423 deeper into the visibility stack or pop to the top at runtime, 1424 the resulting book-keeping can be tedious and difficult to get 1425 right. Hence the panels library.</p> 1426 1427 <p>The <code>panel</code> library first appeared in AT&T 1428 System V. The version documented here is the <code>panel</code> 1429 code distributed with <code>ncurses</code>.</p> 1430 1431 <h3><a name="pcompile" id="pcompile">Compiling With the Panels 1432 Library</a></h3> 1433 1434 <p>Your panels-using modules must import the panels library 1435 declarations with</p> 1436 1437 <pre class="code-block"> 1438 #include <panel.h> 1439</pre> 1440 <p>and must be linked explicitly with the panels library using an 1441 <code>-lpanel</code> argument. Note that they must also link the 1442 <code>ncurses</code> library with <code>-lncurses</code>. Many 1443 linkers are two-pass and will accept either order, but it is 1444 still good practice to put <code>-lpanel</code> first and 1445 <code>-lncurses</code> second.</p> 1446 1447 <h3><a name="poverview" id="poverview">Overview of Panels</a></h3> 1448 1449 <p>A panel object is a window that is implicitly treated as part 1450 of a <dfn>deck</dfn> including all other panel objects. The deck 1451 has an implicit bottom-to-top visibility order. The panels 1452 library includes an update function (analogous to 1453 <code>refresh()</code>) that displays all panels in the deck in 1454 the proper order to resolve overlaps. The standard window, 1455 <code>stdscr</code>, is considered below all panels.</p> 1456 1457 <p>Details on the panels functions are available in the man 1458 pages. We will just hit the highlights here.</p> 1459 1460 <p>You create a panel from a window by calling 1461 <code>new_panel()</code> on a window pointer. It then becomes the 1462 top of the deck. The panel's window is available as the value of 1463 <code>panel_window()</code> called with the panel pointer as 1464 argument.</p> 1465 1466 <p>You can delete a panel (removing it from the deck) with 1467 <code>del_panel</code>. This will not deallocate the associated 1468 window; you have to do that yourself. You can replace a panel's 1469 window with a different window by calling 1470 <code>replace_window</code>. The new window may be of different 1471 size; the panel code will re-compute all overlaps. This operation 1472 does not change the panel's position in the deck.</p> 1473 1474 <p>To move a panel's window, use <code>move_panel()</code>. The 1475 <code>mvwin()</code> function on the panel's window is not 1476 sufficient because it does not update the panels library's 1477 representation of where the windows are. This operation leaves 1478 the panel's depth, contents, and size unchanged.</p> 1479 1480 <p>Two functions (<code>top_panel()</code>, 1481 <code>bottom_panel()</code>) are provided for rearranging the 1482 deck. The first pops its argument window to the top of the deck; 1483 the second sends it to the bottom. Either operation leaves the 1484 panel's screen location, contents, and size unchanged.</p> 1485 1486 <p>The function <code>update_panels()</code> does all the 1487 <code>wnoutrefresh()</code> calls needed to prepare for 1488 <code>doupdate()</code> (which you must call yourself, 1489 afterwards).</p> 1490 1491 <p>Typically, you will want to call <code>update_panels()</code> 1492 and <code>doupdate()</code> just before accepting command input, 1493 once in each cycle of interaction with the user. If you call 1494 <code>update_panels()</code> after each and every panel write, 1495 you will generate a lot of unnecessary refresh activity and 1496 screen flicker.</p> 1497 1498 <h3><a name="pstdscr" id="pstdscr">Panels, Input, and the 1499 Standard Screen</a></h3> 1500 1501 <p>You should not mix <code>wnoutrefresh()</code> or 1502 <code>wrefresh()</code> operations with panels code; this will 1503 work only if the argument window is either in the top panel or 1504 unobscured by any other panels.</p> 1505 1506 <p>The <code>stsdcr</code> window is a special case. It is 1507 considered below all panels. Because changes to panels may 1508 obscure parts of <code>stdscr</code>, though, you should call 1509 <code>update_panels()</code> before <code>doupdate()</code> even 1510 when you only change <code>stdscr</code>.</p> 1511 1512 <p>Note that <code>wgetch</code> automatically calls 1513 <code>wrefresh</code>. Therefore, before requesting input from a 1514 panel window, you need to be sure that the panel is totally 1515 unobscured.</p> 1516 1517 <p>There is presently no way to display changes to one obscured 1518 panel without repainting all panels.</p> 1519 1520 <h3><a name="hiding" id="hiding">Hiding Panels</a></h3> 1521 1522 <p>It is possible to remove a panel from the deck temporarily; 1523 use <code>hide_panel</code> for this. Use 1524 <code>show_panel()</code> to render it visible again. The 1525 predicate function <code>panel_hidden</code> tests whether or not 1526 a panel is hidden.</p> 1527 1528 <p>The <code>panel_update</code> code ignores hidden panels. You 1529 cannot do <code>top_panel()</code> or <code>bottom_panel</code> 1530 on a hidden panel(). Other panels operations are applicable.</p> 1531 1532 <h3><a name="pmisc" id="pmisc">Miscellaneous Other Facilities</a></h3> 1533 1534 <p>It is possible to navigate the deck using the functions 1535 <code>panel_above()</code> and <code>panel_below</code>. Handed a 1536 panel pointer, they return the panel above or below that panel. 1537 Handed <code>NULL</code>, they return the bottom-most or top-most 1538 panel.</p> 1539 1540 <p>Every panel has an associated user pointer, not used by the 1541 panel code, to which you can attach application data. See the man 1542 page documentation of <code>set_panel_userptr()</code> and 1543 <code>panel_userptr</code> for details.</p> 1544 1545 <h2><a name="menu" id="menu">The Menu Library</a></h2> 1546 1547 <p>A menu is a screen display that assists the user to choose 1548 some subset of a given set of items. The <code>menu</code> 1549 library is a curses extension that supports easy programming of 1550 menu hierarchies with a uniform but flexible interface.</p> 1551 1552 <p>The <code>menu</code> library first appeared in AT&T 1553 System V. The version documented here is the <code>menu</code> 1554 code distributed with <code>ncurses</code>.</p> 1555 1556 <h3><a name="mcompile" id="mcompile">Compiling With the menu 1557 Library</a></h3> 1558 1559 <p>Your menu-using modules must import the menu library 1560 declarations with</p> 1561 1562 <pre class="code-block"> 1563 #include <menu.h> 1564</pre> 1565 <p>and must be linked explicitly with the menus library using an 1566 <code>-lmenu</code> argument. Note that they must also link the 1567 <code>ncurses</code> library with <code>-lncurses</code>. Many 1568 linkers are two-pass and will accept either order, but it is 1569 still good practice to put <code>-lmenu</code> first and 1570 <code>-lncurses</code> second.</p> 1571 1572 <h3><a name="moverview" id="moverview">Overview of Menus</a></h3> 1573 1574 <p>The menus created by this library consist of collections of 1575 <dfn>items</dfn> including a name string part and a description 1576 string part. To make menus, you create groups of these items and 1577 connect them with menu frame objects.</p> 1578 1579 <p>The menu can then by <dfn>posted</dfn>, that is written to an 1580 associated window. Actually, each menu has two associated 1581 windows; a containing window in which the programmer can scribble 1582 titles or borders, and a subwindow in which the menu items proper 1583 are displayed. If this subwindow is too small to display all the 1584 items, it will be a scrollable viewport on the collection of 1585 items.</p> 1586 1587 <p>A menu may also be <dfn>unposted</dfn> (that is, undisplayed), 1588 and finally freed to make the storage associated with it and its 1589 items available for re-use.</p> 1590 1591 <p>The general flow of control of a menu program looks like 1592 this:</p> 1593 1594 <ol> 1595 <li>Initialize <code>curses</code>.</li> 1596 1597 <li>Create the menu items, using <code>new_item()</code>.</li> 1598 1599 <li>Create the menu using <code>new_menu()</code>.</li> 1600 1601 <li>Post the menu using <code>post_menu()</code>.</li> 1602 1603 <li>Refresh the screen.</li> 1604 1605 <li>Process user requests via an input loop.</li> 1606 1607 <li>Unpost the menu using <code>unpost_menu()</code>.</li> 1608 1609 <li>Free the menu, using <code>free_menu()</code>.</li> 1610 1611 <li>Free the items using <code>free_item()</code>.</li> 1612 1613 <li>Terminate <code>curses</code>.</li> 1614 </ol> 1615 1616 <h3><a name="mselect" id="mselect">Selecting items</a></h3> 1617 1618 <p>Menus may be multi-valued or (the default) single-valued (see 1619 the manual page <code>menu_opts(3x)</code> to see how to change 1620 the default). Both types always have a <dfn>current 1621 item</dfn>.</p> 1622 1623 <p>From a single-valued menu you can read the selected value 1624 simply by looking at the current item. From a multi-valued menu, 1625 you get the selected set by looping through the items applying 1626 the <code>item_value()</code> predicate function. Your 1627 menu-processing code can use the function 1628 <code>set_item_value()</code> to flag the items in the select 1629 set.</p> 1630 1631 <p>Menu items can be made unselectable using 1632 <code>set_item_opts()</code> or <code>item_opts_off()</code> with 1633 the <code>O_SELECTABLE</code> argument. This is the only option 1634 so far defined for menus, but it is good practice to code as 1635 though other option bits might be on.</p> 1636 1637 <h3><a name="mdisplay" id="mdisplay">Menu Display</a></h3> 1638 1639 <p>The menu library calculates a minimum display size for your 1640 window, based on the following variables:</p> 1641 1642 <ul> 1643 <li>The number and maximum length of the menu items</li> 1644 1645 <li>Whether the O_ROWMAJOR option is enabled</li> 1646 1647 <li>Whether display of descriptions is enabled</li> 1648 1649 <li>Whatever menu format may have been set by the 1650 programmer</li> 1651 1652 <li>The length of the menu mark string used for highlighting 1653 selected items</li> 1654 </ul> 1655 1656 <p>The function <code>set_menu_format()</code> allows you to set 1657 the maximum size of the viewport or <dfn>menu page</dfn> that 1658 will be used to display menu items. You can retrieve any format 1659 associated with a menu with <code>menu_format()</code>. The 1660 default format is rows=16, columns=1.</p> 1661 1662 <p>The actual menu page may be smaller than the format size. This 1663 depends on the item number and size and whether O_ROWMAJOR is on. 1664 This option (on by default) causes menu items to be displayed in 1665 a “raster-scan” pattern, so that if more than one 1666 item will fit horizontally the first couple of items are 1667 side-by-side in the top row. The alternative is column-major 1668 display, which tries to put the first several items in the first 1669 column.</p> 1670 1671 <p>As mentioned above, a menu format not large enough to allow 1672 all items to fit on-screen will result in a menu display that is 1673 vertically scrollable.</p> 1674 1675 <p>You can scroll it with requests to the menu driver, which will 1676 be described in the section on <a href="#minput">menu input 1677 handling</a>.</p> 1678 1679 <p>Each menu has a <dfn>mark string</dfn> used to visually tag 1680 selected items; see the <code>menu_mark(3x)</code> manual page 1681 for details. The mark string length also influences the menu page 1682 size.</p> 1683 1684 <p>The function <code>scale_menu()</code> returns the minimum 1685 display size that the menu code computes from all these factors. 1686 There are other menu display attributes including a select 1687 attribute, an attribute for selectable items, an attribute for 1688 unselectable items, and a pad character used to separate item 1689 name text from description text. These have reasonable defaults 1690 which the library allows you to change (see the 1691 <code>menu_attribs(3x)</code> manual page.</p> 1692 1693 <h3><a name="mwindows" id="mwindows">Menu Windows</a></h3> 1694 1695 <p>Each menu has, as mentioned previously, a pair of associated 1696 windows. Both these windows are painted when the menu is posted 1697 and erased when the menu is unposted.</p> 1698 1699 <p>The outer or frame window is not otherwise touched by the menu 1700 routines. It exists so the programmer can associate a title, a 1701 border, or perhaps help text with the menu and have it properly 1702 refreshed or erased at post/unpost time. The inner window or 1703 <dfn>subwindow</dfn> is where the current menu page is 1704 displayed.</p> 1705 1706 <p>By default, both windows are <code>stdscr</code>. You can set 1707 them with the functions in <code>menu_win(3x)</code>.</p> 1708 1709 <p>When you call <code>post_menu()</code>, you write the menu to 1710 its subwindow. When you call <code>unpost_menu()</code>, you 1711 erase the subwindow, However, neither of these actually modifies 1712 the screen. To do that, call <code>wrefresh()</code> or some 1713 equivalent.</p> 1714 1715 <h3><a name="minput" id="minput">Processing Menu Input</a></h3> 1716 1717 <p>The main loop of your menu-processing code should call 1718 <code>menu_driver()</code> repeatedly. The first argument of this 1719 routine is a menu pointer; the second is a menu command code. You 1720 should write an input-fetching routine that maps input characters 1721 to menu command codes, and pass its output to 1722 <code>menu_driver()</code>. The menu command codes are fully 1723 documented in <code>menu_driver(3x)</code>.</p> 1724 1725 <p>The simplest group of command codes is 1726 <code>REQ_NEXT_ITEM</code>, <code>REQ_PREV_ITEM</code>, 1727 <code>REQ_FIRST_ITEM</code>, <code>REQ_LAST_ITEM</code>, 1728 <code>REQ_UP_ITEM</code>, <code>REQ_DOWN_ITEM</code>, 1729 <code>REQ_LEFT_ITEM</code>, <code>REQ_RIGHT_ITEM</code>. These 1730 change the currently selected item. These requests may cause 1731 scrolling of the menu page if it only partially displayed.</p> 1732 1733 <p>There are explicit requests for scrolling which also change 1734 the current item (because the select location does not change, 1735 but the item there does). These are <code>REQ_SCR_DLINE</code>, 1736 <code>REQ_SCR_ULINE</code>, <code>REQ_SCR_DPAGE</code>, and 1737 <code>REQ_SCR_UPAGE</code>.</p> 1738 1739 <p>The <code>REQ_TOGGLE_ITEM</code> selects or deselects the 1740 current item. It is for use in multi-valued menus; if you use it 1741 with <code>O_ONEVALUE</code> on, you will get an error return 1742 (<code>E_REQUEST_DENIED</code>).</p> 1743 1744 <p>Each menu has an associated pattern buffer. The 1745 <code>menu_driver()</code> logic tries to accumulate printable 1746 ASCII characters passed in in that buffer; when it matches a 1747 prefix of an item name, that item (or the next matching item) is 1748 selected. If appending a character yields no new match, that 1749 character is deleted from the pattern buffer, and 1750 <code>menu_driver()</code> returns <code>E_NO_MATCH</code>.</p> 1751 1752 <p>Some requests change the pattern buffer directly: 1753 <code>REQ_CLEAR_PATTERN</code>, <code>REQ_BACK_PATTERN</code>, 1754 <code>REQ_NEXT_MATCH</code>, <code>REQ_PREV_MATCH</code>. The 1755 latter two are useful when pattern buffer input matches more than 1756 one item in a multi-valued menu.</p> 1757 1758 <p>Each successful scroll or item navigation request clears the 1759 pattern buffer. It is also possible to set the pattern buffer 1760 explicitly with <code>set_menu_pattern()</code>.</p> 1761 1762 <p>Finally, menu driver requests above the constant 1763 <code>MAX_COMMAND</code> are considered application-specific 1764 commands. The <code>menu_driver()</code> code ignores them and 1765 returns <code>E_UNKNOWN_COMMAND</code>.</p> 1766 1767 <h3><a name="mmisc" id="mmisc">Miscellaneous Other Features</a></h3> 1768 1769 <p>Various menu options can affect the processing and visual 1770 appearance and input processing of menus. See <code>menu_opts(3x) 1771 for details.</code></p> 1772 1773 <p>It is possible to change the current item from application 1774 code; this is useful if you want to write your own navigation 1775 requests. It is also possible to explicitly set the top row of 1776 the menu display. See <code>mitem_current(3x)</code>. If your 1777 application needs to change the menu subwindow cursor for any 1778 reason, <code>pos_menu_cursor()</code> will restore it to the 1779 correct location for continuing menu driver processing.</p> 1780 1781 <p>It is possible to set hooks to be called at menu 1782 initialization and wrapup time, and whenever the selected item 1783 changes. See <code>menu_hook(3x)</code>.</p> 1784 1785 <p>Each item, and each menu, has an associated user pointer on 1786 which you can hang application data. See 1787 <code>mitem_userptr(3x)</code> and 1788 <code>menu_userptr(3x)</code>.</p> 1789 1790 <h2><a name="form" id="form">The Forms Library</a></h2> 1791 1792 <p>The <code>form</code> library is a curses extension that 1793 supports easy programming of on-screen forms for data entry and 1794 program control.</p> 1795 1796 <p>The <code>form</code> library first appeared in AT&T 1797 System V. The version documented here is the <code>form</code> 1798 code distributed with <code>ncurses</code>.</p> 1799 1800 <h3><a name="fcompile" id="fcompile">Compiling With the form 1801 Library</a></h3> 1802 1803 <p>Your form-using modules must import the form library 1804 declarations with</p> 1805 1806 <pre class="code-block"> 1807 #include <form.h> 1808</pre> 1809 <p>and must be linked explicitly with the forms library using an 1810 <code>-lform</code> argument. Note that they must also link the 1811 <code>ncurses</code> library with <code>-lncurses</code>. Many 1812 linkers are two-pass and will accept either order, but it is 1813 still good practice to put <code>-lform</code> first and 1814 <code>-lncurses</code> second.</p> 1815 1816 <h3><a name="foverview" id="foverview">Overview of Forms</a></h3> 1817 1818 <p>A form is a collection of fields; each field may be either a 1819 label (explanatory text) or a data-entry location. Long forms may 1820 be segmented into pages; each entry to a new page clears the 1821 screen.</p> 1822 1823 <p>To make forms, you create groups of fields and connect them 1824 with form frame objects; the form library makes this relatively 1825 simple.</p> 1826 1827 <p>Once defined, a form can be <dfn>posted</dfn>, that is written 1828 to an associated window. Actually, each form has two associated 1829 windows; a containing window in which the programmer can scribble 1830 titles or borders, and a subwindow in which the form fields 1831 proper are displayed.</p> 1832 1833 <p>As the form user fills out the posted form, navigation and 1834 editing keys support movement between fields, editing keys 1835 support modifying field, and plain text adds to or changes data 1836 in a current field. The form library allows you (the forms 1837 designer) to bind each navigation and editing key to any 1838 keystroke accepted by <code>curses</code> Fields may have 1839 validation conditions on them, so that they check input data for 1840 type and value. The form library supplies a rich set of 1841 pre-defined field types, and makes it relatively easy to define 1842 new ones.</p> 1843 1844 <p>Once its transaction is completed (or aborted), a form may be 1845 <dfn>unposted</dfn> (that is, undisplayed), and finally freed to 1846 make the storage associated with it and its items available for 1847 re-use.</p> 1848 1849 <p>The general flow of control of a form program looks like 1850 this:</p> 1851 1852 <ol> 1853 <li>Initialize <code>curses</code>.</li> 1854 1855 <li>Create the form fields, using 1856 <code>new_field()</code>.</li> 1857 1858 <li>Create the form using <code>new_form()</code>.</li> 1859 1860 <li>Post the form using <code>post_form()</code>.</li> 1861 1862 <li>Refresh the screen.</li> 1863 1864 <li>Process user requests via an input loop.</li> 1865 1866 <li>Unpost the form using <code>unpost_form()</code>.</li> 1867 1868 <li>Free the form, using <code>free_form()</code>.</li> 1869 1870 <li>Free the fields using <code>free_field()</code>.</li> 1871 1872 <li>Terminate <code>curses</code>.</li> 1873 </ol> 1874 1875 <p>Note that this looks much like a menu program; the form 1876 library handles tasks which are in many ways similar, and its 1877 interface was obviously designed to resemble that of the <a href= 1878 "#menu">menu library</a> wherever possible.</p> 1879 1880 <p>In forms programs, however, the “process user 1881 requests” is somewhat more complicated than for menus. 1882 Besides menu-like navigation operations, the menu driver loop has 1883 to support field editing and data validation.</p> 1884 1885 <h3><a name="fcreate" id="fcreate">Creating and Freeing Fields 1886 and Forms</a></h3> 1887 1888 <p>The basic function for creating fields is 1889 <code>new_field()</code>:</p> 1890 1891 <pre class="code-block"> 1892FIELD *new_field(int height, int width, /* new field size */ 1893 int top, int left, /* upper left corner */ 1894 int offscreen, /* number of offscreen rows */ 1895 int nbuf); /* number of working buffers */ 1896</pre> 1897 <p>Menu items always occupy a single row, but forms fields may 1898 have multiple rows. So <code>new_field()</code> requires you to 1899 specify a width and height (the first two arguments, which mist 1900 both be greater than zero).</p> 1901 1902 <p>You must also specify the location of the field's upper left 1903 corner on the screen (the third and fourth arguments, which must 1904 be zero or greater). Note that these coordinates are relative to 1905 the form subwindow, which will coincide with <code>stdscr</code> 1906 by default but need not be <code>stdscr</code> if you have done 1907 an explicit <code>set_form_win()</code> call.</p> 1908 1909 <p>The fifth argument allows you to specify a number of 1910 off-screen rows. If this is zero, the entire field will always be 1911 displayed. If it is nonzero, the form will be scrollable, with 1912 only one screen-full (initially the top part) displayed at any 1913 given time. If you make a field dynamic and grow it so it will no 1914 longer fit on the screen, the form will become scrollable even if 1915 the <code>offscreen</code> argument was initially zero.</p> 1916 1917 <p>The forms library allocates one working buffer per field; the 1918 size of each buffer is <code>((height + offscreen)*width + 1919 1</code>, one character for each position in the field plus a NUL 1920 terminator. The sixth argument is the number of additional data 1921 buffers to allocate for the field; your application can use them 1922 for its own purposes.</p> 1923 1924 <pre class="code-block"> 1925FIELD *dup_field(FIELD *field, /* field to copy */ 1926 int top, int left); /* location of new copy */ 1927</pre> 1928 <p>The function <code>dup_field()</code> duplicates an existing 1929 field at a new location. Size and buffering information are 1930 copied; some attribute flags and status bits are not (see the 1931 <code>form_field_new(3X)</code> for details).</p> 1932 1933 <pre class="code-block"> 1934FIELD *link_field(FIELD *field, /* field to copy */ 1935 int top, int left); /* location of new copy */ 1936</pre> 1937 <p>The function <code>link_field()</code> also duplicates an 1938 existing field at a new location. The difference from 1939 <code>dup_field()</code> is that it arranges for the new field's 1940 buffer to be shared with the old one.</p> 1941 1942 <p>Besides the obvious use in making a field editable from two 1943 different form pages, linked fields give you a way to hack in 1944 dynamic labels. If you declare several fields linked to an 1945 original, and then make them inactive, changes from the original 1946 will still be propagated to the linked fields.</p> 1947 1948 <p>As with duplicated fields, linked fields have attribute bits 1949 separate from the original.</p> 1950 1951 <p>As you might guess, all these field-allocations return 1952 <code>NULL</code> if the field allocation is not possible due to 1953 an out-of-memory error or out-of-bounds arguments.</p> 1954 1955 <p>To connect fields to a form, use</p> 1956 1957 <pre class="code-block"> 1958FORM *new_form(FIELD **fields); 1959</pre> 1960 <p>This function expects to see a NULL-terminated array of field 1961 pointers. Said fields are connected to a newly-allocated form 1962 object; its address is returned (or else NULL if the allocation 1963 fails).</p> 1964 1965 <p>Note that <code>new_field()</code> does <em>not</em> copy the 1966 pointer array into private storage; if you modify the contents of 1967 the pointer array during forms processing, all manner of bizarre 1968 things might happen. Also note that any given field may only be 1969 connected to one form.</p> 1970 1971 <p>The functions <code>free_field()</code> and 1972 <code>free_form</code> are available to free field and form 1973 objects. It is an error to attempt to free a field connected to a 1974 form, but not vice-versa; thus, you will generally free your form 1975 objects first.</p> 1976 1977 <h3><a name="fattributes" id="fattributes">Fetching and Changing 1978 Field Attributes</a></h3> 1979 1980 <p>Each form field has a number of location and size attributes 1981 associated with it. There are other field attributes used to 1982 control display and editing of the field. Some (for example, the 1983 <code>O_STATIC</code> bit) involve sufficient complications to be 1984 covered in sections of their own later on. We cover the functions 1985 used to get and set several basic attributes here.</p> 1986 1987 <p>When a field is created, the attributes not specified by the 1988 <code>new_field</code> function are copied from an invisible 1989 system default field. In attribute-setting and -fetching 1990 functions, the argument NULL is taken to mean this field. Changes 1991 to it persist as defaults until your forms application 1992 terminates.</p> 1993 1994 <h4><a name="fsizes" id="fsizes">Fetching Size and Location 1995 Data</a></h4> 1996 1997 <p>You can retrieve field sizes and locations through:</p> 1998 1999 <pre class="code-block"> 2000int field_info(FIELD *field, /* field from which to fetch */ 2001 int *height, *int width, /* field size */ 2002 int *top, int *left, /* upper left corner */ 2003 int *offscreen, /* number of offscreen rows */ 2004 int *nbuf); /* number of working buffers */ 2005</pre> 2006 <p>This function is a sort of inverse of 2007 <code>new_field()</code>; instead of setting size and location 2008 attributes of a new field, it fetches them from an existing 2009 one.</p> 2010 2011 <h4><a name="flocation" id="flocation">Changing the Field 2012 Location</a></h4> 2013 2014 <p>It is possible to move a field's location on the screen:</p> 2015 2016 <pre class="code-block"> 2017int move_field(FIELD *field, /* field to alter */ 2018 int top, int left); /* new upper-left corner */ 2019</pre> 2020 <p>You can, of course. query the current location through 2021 <code>field_info()</code>.</p> 2022 2023 <h4><a name="fjust" id="fjust">The Justification Attribute</a></h4> 2024 2025 <p>One-line fields may be unjustified, justified right, justified 2026 left, or centered. Here is how you manipulate this attribute:</p> 2027 2028 <pre class="code-block"> 2029int set_field_just(FIELD *field, /* field to alter */ 2030 int justmode); /* mode to set */ 2031 2032int field_just(FIELD *field); /* fetch mode of field */ 2033</pre> 2034 <p>The mode values accepted and returned by this functions are 2035 preprocessor macros <code>NO_JUSTIFICATION</code>, 2036 <code>JUSTIFY_RIGHT</code>, <code>JUSTIFY_LEFT</code>, or 2037 <code>JUSTIFY_CENTER</code>.</p> 2038 2039 <h4><a name="fdispatts" id="fdispatts">Field Display 2040 Attributes</a></h4> 2041 2042 <p>For each field, you can set a foreground attribute for entered 2043 characters, a background attribute for the entire field, and a 2044 pad character for the unfilled portion of the field. You can also 2045 control pagination of the form.</p> 2046 2047 <p>This group of four field attributes controls the visual 2048 appearance of the field on the screen, without affecting in any 2049 way the data in the field buffer.</p> 2050 2051 <pre class="code-block"> 2052int set_field_fore(FIELD *field, /* field to alter */ 2053 chtype attr); /* attribute to set */ 2054 2055chtype field_fore(FIELD *field); /* field to query */ 2056 2057int set_field_back(FIELD *field, /* field to alter */ 2058 chtype attr); /* attribute to set */ 2059 2060chtype field_back(FIELD *field); /* field to query */ 2061 2062int set_field_pad(FIELD *field, /* field to alter */ 2063 int pad); /* pad character to set */ 2064 2065chtype field_pad(FIELD *field); 2066 2067int set_new_page(FIELD *field, /* field to alter */ 2068 int flag); /* TRUE to force new page */ 2069 2070chtype new_page(FIELD *field); /* field to query */ 2071</pre> 2072 <p>The attributes set and returned by the first four functions 2073 are normal <code>curses(3x)</code> display attribute values 2074 (<code>A_STANDOUT</code>, <code>A_BOLD</code>, 2075 <code>A_REVERSE</code> etc). The page bit of a field controls 2076 whether it is displayed at the start of a new form screen.</p> 2077 2078 <h4><a name="foptions" id="foptions">Field Option Bits</a></h4> 2079 2080 <p>There is also a large collection of field option bits you can 2081 set to control various aspects of forms processing. You can 2082 manipulate them with these functions:</p> 2083 2084 <pre class="code-block"> 2085int set_field_opts(FIELD *field, /* field to alter */ 2086 int attr); /* attribute to set */ 2087 2088int field_opts_on(FIELD *field, /* field to alter */ 2089 int attr); /* attributes to turn on */ 2090 2091int field_opts_off(FIELD *field, /* field to alter */ 2092 int attr); /* attributes to turn off */ 2093 2094int field_opts(FIELD *field); /* field to query */ 2095</pre> 2096 <p>By default, all options are on. Here are the available option 2097 bits:</p> 2098 2099 <dl> 2100 <dt>O_VISIBLE</dt> 2101 2102 <dd>Controls whether the field is visible on the screen. Can be 2103 used during form processing to hide or pop up fields depending 2104 on the value of parent fields.</dd> 2105 2106 <dt>O_ACTIVE</dt> 2107 2108 <dd>Controls whether the field is active during forms 2109 processing (i.e. visited by form navigation keys). Can be used 2110 to make labels or derived fields with buffer values alterable 2111 by the forms application, not the user.</dd> 2112 2113 <dt>O_PUBLIC</dt> 2114 2115 <dd>Controls whether data is displayed during field entry. If 2116 this option is turned off on a field, the library will accept 2117 and edit data in that field, but it will not be displayed and 2118 the visible field cursor will not move. You can turn off the 2119 O_PUBLIC bit to define password fields.</dd> 2120 2121 <dt>O_EDIT</dt> 2122 2123 <dd>Controls whether the field's data can be modified. When 2124 this option is off, all editing requests except 2125 <code>REQ_PREV_CHOICE</code> and <code>REQ_NEXT_CHOICE</code> 2126 will fail. Such read-only fields may be useful for help 2127 messages.</dd> 2128 2129 <dt>O_WRAP</dt> 2130 2131 <dd>Controls word-wrapping in multi-line fields. Normally, when 2132 any character of a (blank-separated) word reaches the end of 2133 the current line, the entire word is wrapped to the next line 2134 (assuming there is one). When this option is off, the word will 2135 be split across the line break.</dd> 2136 2137 <dt>O_BLANK</dt> 2138 2139 <dd>Controls field blanking. When this option is on, entering a 2140 character at the first field position erases the entire field 2141 (except for the just-entered character).</dd> 2142 2143 <dt>O_AUTOSKIP</dt> 2144 2145 <dd>Controls automatic skip to next field when this one fills. 2146 Normally, when the forms user tries to type more data into a 2147 field than will fit, the editing location jumps to next field. 2148 When this option is off, the user's cursor will hang at the end 2149 of the field. This option is ignored in dynamic fields that 2150 have not reached their size limit.</dd> 2151 2152 <dt>O_NULLOK</dt> 2153 2154 <dd>Controls whether <a href="#fvalidation">validation</a> is 2155 applied to blank fields. Normally, it is not; the user can 2156 leave a field blank without invoking the usual validation check 2157 on exit. If this option is off on a field, exit from it will 2158 invoke a validation check.</dd> 2159 2160 <dt>O_PASSOK</dt> 2161 2162 <dd>Controls whether validation occurs on every exit, or only 2163 after the field is modified. Normally the latter is true. 2164 Setting O_PASSOK may be useful if your field's validation 2165 function may change during forms processing.</dd> 2166 2167 <dt>O_STATIC</dt> 2168 2169 <dd>Controls whether the field is fixed to its initial 2170 dimensions. If you turn this off, the field becomes <a href= 2171 "#fdynamic">dynamic</a> and will stretch to fit entered 2172 data.</dd> 2173 </dl> 2174 2175 <p>A field's options cannot be changed while the field is 2176 currently selected. However, options may be changed on posted 2177 fields that are not current.</p> 2178 2179 <p>The option values are bit-masks and can be composed with 2180 logical-or in the obvious way.</p> 2181 2182 <h3><a name="fstatus" id="fstatus">Field Status</a></h3> 2183 2184 <p>Every field has a status flag, which is set to FALSE when the 2185 field is created and TRUE when the value in field buffer 0 2186 changes. This flag can be queried and set directly:</p> 2187 2188 <pre class="code-block"> 2189int set_field_status(FIELD *field, /* field to alter */ 2190 int status); /* mode to set */ 2191 2192int field_status(FIELD *field); /* fetch mode of field */ 2193</pre> 2194 <p>Setting this flag under program control can be useful if you 2195 use the same form repeatedly, looking for modified fields each 2196 time.</p> 2197 2198 <p>Calling <code>field_status()</code> on a field not currently 2199 selected for input will return a correct value. Calling 2200 <code>field_status()</code> on a field that is currently selected 2201 for input may not necessarily give a correct field status value, 2202 because entered data is not necessarily copied to buffer zero 2203 before the exit validation check. To guarantee that the returned 2204 status value reflects reality, call <code>field_status()</code> 2205 either (1) in the field's exit validation check routine, (2) from 2206 the field's or form's initialization or termination hooks, or (3) 2207 just after a <code>REQ_VALIDATION</code> request has been 2208 processed by the forms driver.</p> 2209 2210 <h3><a name="fuser" id="fuser">Field User Pointer</a></h3> 2211 2212 <p>Each field structure contains one character pointer slot that 2213 is not used by the forms library. It is intended to be used by 2214 applications to store private per-field data. You can manipulate 2215 it with:</p> 2216 2217 <pre class="code-block"> 2218int set_field_userptr(FIELD *field, /* field to alter */ 2219 char *userptr); /* mode to set */ 2220 2221char *field_userptr(FIELD *field); /* fetch mode of field */ 2222</pre>(Properly, this user pointer field ought to have <code>(void 2223*)</code> type. The <code>(char *)</code> type is retained for 2224System V compatibility.) 2225 <p>It is valid to set the user pointer of the default field (with 2226 a <code>set_field_userptr()</code> call passed a NULL field 2227 pointer.) When a new field is created, the default-field user 2228 pointer is copied to initialize the new field's user pointer.</p> 2229 2230 <h3><a name="fdynamic" id="fdynamic">Variable-Sized Fields</a></h3> 2231 2232 <p>Normally, a field is fixed at the size specified for it at 2233 creation time. If, however, you turn off its O_STATIC bit, it 2234 becomes <dfn>dynamic</dfn> and will automatically resize itself 2235 to accommodate data as it is entered. If the field has extra 2236 buffers associated with it, they will grow right along with the 2237 main input buffer.</p> 2238 2239 <p>A one-line dynamic field will have a fixed height (1) but 2240 variable width, scrolling horizontally to display data within the 2241 field area as originally dimensioned and located. A multi-line 2242 dynamic field will have a fixed width, but variable height 2243 (number of rows), scrolling vertically to display data within the 2244 field area as originally dimensioned and located.</p> 2245 2246 <p>Normally, a dynamic field is allowed to grow without limit. 2247 But it is possible to set an upper limit on the size of a dynamic 2248 field. You do it with this function:</p> 2249 2250 <pre class="code-block"> 2251int set_max_field(FIELD *field, /* field to alter (may not be NULL) */ 2252 int max_size); /* upper limit on field size */ 2253</pre> 2254 <p>If the field is one-line, <code>max_size</code> is taken to be 2255 a column size limit; if it is multi-line, it is taken to be a 2256 line size limit. To disable any limit, use an argument of zero. 2257 The growth limit can be changed whether or not the O_STATIC bit 2258 is on, but has no effect until it is.</p> 2259 2260 <p>The following properties of a field change when it becomes 2261 dynamic:</p> 2262 2263 <ul> 2264 <li>If there is no growth limit, there is no final position of 2265 the field; therefore <code>O_AUTOSKIP</code> and 2266 <code>O_NL_OVERLOAD</code> are ignored.</li> 2267 2268 <li>Field justification will be ignored (though whatever 2269 justification is set up will be retained internally and can be 2270 queried).</li> 2271 2272 <li>The <code>dup_field()</code> and <code>link_field()</code> 2273 calls copy dynamic-buffer sizes. If the <code>O_STATIC</code> 2274 option is set on one of a collection of links, buffer resizing 2275 will occur only when the field is edited through that 2276 link.</li> 2277 2278 <li>The call <code>field_info()</code> will retrieve the 2279 original static size of the field; use 2280 <code>dynamic_field_info()</code> to get the actual dynamic 2281 size.</li> 2282 </ul> 2283 2284 <h3><a name="fvalidation" id="fvalidation">Field Validation</a></h3> 2285 2286 <p>By default, a field will accept any data that will fit in its 2287 input buffer. However, it is possible to attach a validation type 2288 to a field. If you do this, any attempt to leave the field while 2289 it contains data that does not match the validation type will 2290 fail. Some validation types also have a character-validity check 2291 for each time a character is entered in the field.</p> 2292 2293 <p>A field's validation check (if any) is not called when 2294 <code>set_field_buffer()</code> modifies the input buffer, nor 2295 when that buffer is changed through a linked field.</p> 2296 2297 <p>The <code>form</code> library provides a rich set of 2298 pre-defined validation types, and gives you the capability to 2299 define custom ones of your own. You can examine and change field 2300 validation attributes with the following functions:</p> 2301 2302 <pre class="code-block"> 2303int set_field_type(FIELD *field, /* field to alter */ 2304 FIELDTYPE *ftype, /* type to associate */ 2305 ...); /* additional arguments*/ 2306 2307FIELDTYPE *field_type(FIELD *field); /* field to query */ 2308</pre> 2309 <p>The validation type of a field is considered an attribute of 2310 the field. As with other field attributes, Also, doing 2311 <code>set_field_type()</code> with a <code>NULL</code> field 2312 default will change the system default for validation of 2313 newly-created fields.</p> 2314 2315 <p>Here are the pre-defined validation types:</p> 2316 2317 <h4><a name="ftype_alpha" id="ftype_alpha">TYPE_ALPHA</a></h4> 2318 2319 <p>This field type accepts alphabetic data; no blanks, no digits, 2320 no special characters (this is checked at character-entry time). 2321 It is set up with:</p> 2322 2323 <pre class="code-block"> 2324int set_field_type(FIELD *field, /* field to alter */ 2325 TYPE_ALPHA, /* type to associate */ 2326 int width); /* maximum width of field */ 2327</pre> 2328 <p>The <code>width</code> argument sets a minimum width of data. 2329 Typically you will want to set this to the field width; if it is 2330 greater than the field width, the validation check will always 2331 fail. A minimum width of zero makes field completion 2332 optional.</p> 2333 2334 <h4><a name="ftype_alnum" id="ftype_alnum">TYPE_ALNUM</a></h4> 2335 2336 <p>This field type accepts alphabetic data and digits; no blanks, 2337 no special characters (this is checked at character-entry time). 2338 It is set up with:</p> 2339 2340 <pre class="code-block"> 2341int set_field_type(FIELD *field, /* field to alter */ 2342 TYPE_ALNUM, /* type to associate */ 2343 int width); /* maximum width of field */ 2344</pre> 2345 <p>The <code>width</code> argument sets a minimum width of data. 2346 As with TYPE_ALPHA, typically you will want to set this to the 2347 field width; if it is greater than the field width, the 2348 validation check will always fail. A minimum width of zero makes 2349 field completion optional.</p> 2350 2351 <h4><a name="ftype_enum" id="ftype_enum">TYPE_ENUM</a></h4> 2352 2353 <p>This type allows you to restrict a field's values to be among 2354 a specified set of string values (for example, the two-letter 2355 postal codes for U.S. states). It is set up with:</p> 2356 2357 <pre class="code-block"> 2358int set_field_type(FIELD *field, /* field to alter */ 2359 TYPE_ENUM, /* type to associate */ 2360 char **valuelist; /* list of possible values */ 2361 int checkcase; /* case-sensitive? */ 2362 int checkunique); /* must specify uniquely? */ 2363</pre> 2364 <p>The <code>valuelist</code> parameter must point at a 2365 NULL-terminated list of valid strings. The <code>checkcase</code> 2366 argument, if true, makes comparison with the string 2367 case-sensitive.</p> 2368 2369 <p>When the user exits a TYPE_ENUM field, the validation 2370 procedure tries to complete the data in the buffer to a valid 2371 entry. If a complete choice string has been entered, it is of 2372 course valid. But it is also possible to enter a prefix of a 2373 valid string and have it completed for you.</p> 2374 2375 <p>By default, if you enter such a prefix and it matches more 2376 than one value in the string list, the prefix will be completed 2377 to the first matching value. But the <code>checkunique</code> 2378 argument, if true, requires prefix matches to be unique in order 2379 to be valid.</p> 2380 2381 <p>The <code>REQ_NEXT_CHOICE</code> and 2382 <code>REQ_PREV_CHOICE</code> input requests can be particularly 2383 useful with these fields.</p> 2384 2385 <h4><a name="ftype_integer" id="ftype_integer">TYPE_INTEGER</a></h4> 2386 2387 <p>This field type accepts an integer. It is set up as 2388 follows:</p> 2389 2390 <pre class="code-block"> 2391int set_field_type(FIELD *field, /* field to alter */ 2392 TYPE_INTEGER, /* type to associate */ 2393 int padding, /* # places to zero-pad to */ 2394 int vmin, int vmax); /* valid range */ 2395</pre> 2396 <p>Valid characters consist of an optional leading minus and 2397 digits. The range check is performed on exit. If the range 2398 maximum is less than or equal to the minimum, the range is 2399 ignored.</p> 2400 2401 <p>If the value passes its range check, it is padded with as many 2402 leading zero digits as necessary to meet the padding 2403 argument.</p> 2404 2405 <p>A <code>TYPE_INTEGER</code> value buffer can conveniently be 2406 interpreted with the C library function <code>atoi(3)</code>.</p> 2407 2408 <h4><a name="ftype_numeric" id="ftype_numeric">TYPE_NUMERIC</a></h4> 2409 2410 <p>This field type accepts a decimal number. It is set up as 2411 follows:</p> 2412 2413 <pre class="code-block"> 2414int set_field_type(FIELD *field, /* field to alter */ 2415 TYPE_NUMERIC, /* type to associate */ 2416 int padding, /* # places of precision */ 2417 double vmin, double vmax); /* valid range */ 2418</pre> 2419 <p>Valid characters consist of an optional leading minus and 2420 digits. possibly including a decimal point. If your system 2421 supports locale's, the decimal point character used must be the 2422 one defined by your locale. The range check is performed on exit. 2423 If the range maximum is less than or equal to the minimum, the 2424 range is ignored.</p> 2425 2426 <p>If the value passes its range check, it is padded with as many 2427 trailing zero digits as necessary to meet the padding 2428 argument.</p> 2429 2430 <p>A <code>TYPE_NUMERIC</code> value buffer can conveniently be 2431 interpreted with the C library function <code>atof(3)</code>.</p> 2432 2433 <h4><a name="ftype_regexp" id="ftype_regexp">TYPE_REGEXP</a></h4> 2434 2435 <p>This field type accepts data matching a regular expression. It 2436 is set up as follows:</p> 2437 2438 <pre class="code-block"> 2439int set_field_type(FIELD *field, /* field to alter */ 2440 TYPE_REGEXP, /* type to associate */ 2441 char *regexp); /* expression to match */ 2442</pre> 2443 <p>The syntax for regular expressions is that of 2444 <code>regcomp(3)</code>. The check for regular-expression match 2445 is performed on exit.</p> 2446 2447 <h3><a name="fbuffer" id="fbuffer">Direct Field Buffer 2448 Manipulation</a></h3> 2449 2450 <p>The chief attribute of a field is its buffer contents. When a 2451 form has been completed, your application usually needs to know 2452 the state of each field buffer. You can find this out with:</p> 2453 2454 <pre class="code-block"> 2455char *field_buffer(FIELD *field, /* field to query */ 2456 int bufindex); /* number of buffer to query */ 2457</pre> 2458 <p>Normally, the state of the zero-numbered buffer for each field 2459 is set by the user's editing actions on that field. It is 2460 sometimes useful to be able to set the value of the zero-numbered 2461 (or some other) buffer from your application:</p> 2462 2463 <pre class="code-block"> 2464int set_field_buffer(FIELD *field, /* field to alter */ 2465 int bufindex, /* number of buffer to alter */ 2466 char *value); /* string value to set */ 2467</pre> 2468 <p>If the field is not large enough and cannot be resized to a 2469 sufficiently large size to contain the specified value, the value 2470 will be truncated to fit.</p> 2471 2472 <p>Calling <code>field_buffer()</code> with a null field pointer 2473 will raise an error. Calling <code>field_buffer()</code> on a 2474 field not currently selected for input will return a correct 2475 value. Calling <code>field_buffer()</code> on a field that is 2476 currently selected for input may not necessarily give a correct 2477 field buffer value, because entered data is not necessarily 2478 copied to buffer zero before the exit validation check. To 2479 guarantee that the returned buffer value reflects on-screen 2480 reality, call <code>field_buffer()</code> either (1) in the 2481 field's exit validation check routine, (2) from the field's or 2482 form's initialization or termination hooks, or (3) just after a 2483 <code>REQ_VALIDATION</code> request has been processed by the 2484 forms driver.</p> 2485 2486 <h3><a name="formattrs" id="formattrs">Attributes of Forms</a></h3> 2487 2488 <p>As with field attributes, form attributes inherit a default 2489 from a system default form structure. These defaults can be 2490 queried or set by of these functions using a form-pointer 2491 argument of <code>NULL</code>.</p> 2492 2493 <p>The principal attribute of a form is its field list. You can 2494 query and change this list with:</p> 2495 2496 <pre class="code-block"> 2497int set_form_fields(FORM *form, /* form to alter */ 2498 FIELD **fields); /* fields to connect */ 2499 2500char *form_fields(FORM *form); /* fetch fields of form */ 2501 2502int field_count(FORM *form); /* count connect fields */ 2503</pre> 2504 <p>The second argument of <code>set_form_fields()</code> may be a 2505 NULL-terminated field pointer array like the one required by 2506 <code>new_form()</code>. In that case, the old fields of the form 2507 are disconnected but not freed (and eligible to be connected to 2508 other forms), then the new fields are connected.</p> 2509 2510 <p>It may also be null, in which case the old fields are 2511 disconnected (and not freed) but no new ones are connected.</p> 2512 2513 <p>The <code>field_count()</code> function simply counts the 2514 number of fields connected to a given from. It returns -1 if the 2515 form-pointer argument is NULL.</p> 2516 2517 <h3><a name="fdisplay" id="fdisplay">Control of Form Display</a></h3> 2518 2519 <p>In the overview section, you saw that to display a form you 2520 normally start by defining its size (and fields), posting it, and 2521 refreshing the screen. There is an hidden step before posting, 2522 which is the association of the form with a frame window 2523 (actually, a pair of windows) within which it will be displayed. 2524 By default, the forms library associates every form with the 2525 full-screen window <code>stdscr</code>.</p> 2526 2527 <p>By making this step explicit, you can associate a form with a 2528 declared frame window on your screen display. This can be useful 2529 if you want to adapt the form display to different screen sizes, 2530 dynamically tile forms on the screen, or use a form as part of an 2531 interface layout managed by <a href="#panels">panels</a>.</p> 2532 2533 <p>The two windows associated with each form have the same 2534 functions as their analogues in the <a href="#menu">menu 2535 library</a>. Both these windows are painted when the form is 2536 posted and erased when the form is unposted.</p> 2537 2538 <p>The outer or frame window is not otherwise touched by the form 2539 routines. It exists so the programmer can associate a title, a 2540 border, or perhaps help text with the form and have it properly 2541 refreshed or erased at post/unpost time. The inner window or 2542 subwindow is where the current form page is actually 2543 displayed.</p> 2544 2545 <p>In order to declare your own frame window for a form, you will 2546 need to know the size of the form's bounding rectangle. You can 2547 get this information with:</p> 2548 2549 <pre class="code-block"> 2550int scale_form(FORM *form, /* form to query */ 2551 int *rows, /* form rows */ 2552 int *cols); /* form cols */ 2553</pre> 2554 <p>The form dimensions are passed back in the locations pointed 2555 to by the arguments. Once you have this information, you can use 2556 it to declare of windows, then use one of these functions:</p> 2557 2558 <pre class="code-block"> 2559int set_form_win(FORM *form, /* form to alter */ 2560 WINDOW *win); /* frame window to connect */ 2561 2562WINDOW *form_win(FORM *form); /* fetch frame window of form */ 2563 2564int set_form_sub(FORM *form, /* form to alter */ 2565 WINDOW *win); /* form subwindow to connect */ 2566 2567WINDOW *form_sub(FORM *form); /* fetch form subwindow of form */ 2568</pre> 2569 <p>Note that curses operations, including <code>refresh()</code>, 2570 on the form, should be done on the frame window, not the form 2571 subwindow.</p> 2572 2573 <p>It is possible to check from your application whether all of a 2574 scrollable field is actually displayed within the menu subwindow. 2575 Use these functions:</p> 2576 2577 <pre class="code-block"> 2578int data_ahead(FORM *form); /* form to be queried */ 2579 2580int data_behind(FORM *form); /* form to be queried */ 2581</pre> 2582 <p>The function <code>data_ahead()</code> returns TRUE if (a) the 2583 current field is one-line and has undisplayed data off to the 2584 right, (b) the current field is multi-line and there is data 2585 off-screen below it.</p> 2586 2587 <p>The function <code>data_behind()</code> returns TRUE if the 2588 first (upper left hand) character position is off-screen (not 2589 being displayed).</p> 2590 2591 <p>Finally, there is a function to restore the form window's 2592 cursor to the value expected by the forms driver:</p> 2593 2594 <pre class="code-block"> 2595int pos_form_cursor(FORM *) /* form to be queried */ 2596</pre> 2597 <p>If your application changes the form window cursor, call this 2598 function before handing control back to the forms driver in order 2599 to re-synchronize it.</p> 2600 2601 <h3><a name="fdriver" id="fdriver">Input Processing in the Forms 2602 Driver</a></h3> 2603 2604 <p>The function <code>form_driver()</code> handles virtualized 2605 input requests for form navigation, editing, and validation 2606 requests, just as <code>menu_driver</code> does for menus (see 2607 the section on <a href="#minput">menu input handling</a>).</p> 2608 2609 <pre class="code-block"> 2610int form_driver(FORM *form, /* form to pass input to */ 2611 int request); /* form request code */ 2612</pre> 2613 <p>Your input virtualization function needs to take input and 2614 then convert it to either an alphanumeric character (which is 2615 treated as data to be entered in the currently-selected field), 2616 or a forms processing request.</p> 2617 2618 <p>The forms driver provides hooks (through input-validation and 2619 field-termination functions) with which your application code can 2620 check that the input taken by the driver matched what was 2621 expected.</p> 2622 2623 <h4><a name="fpage" id="fpage">Page Navigation Requests</a></h4> 2624 2625 <p>These requests cause page-level moves through the form, 2626 triggering display of a new form screen.</p> 2627 2628 <dl> 2629 <dt><code>REQ_NEXT_PAGE</code> 2630 </dt> 2631 2632 <dd>Move to the next form page.</dd> 2633 2634 <dt><code>REQ_PREV_PAGE</code> 2635 </dt> 2636 2637 <dd>Move to the previous form page.</dd> 2638 2639 <dt><code>REQ_FIRST_PAGE</code> 2640 </dt> 2641 2642 <dd>Move to the first form page.</dd> 2643 2644 <dt><code>REQ_LAST_PAGE</code> 2645 </dt> 2646 2647 <dd>Move to the last form page.</dd> 2648 </dl> 2649 2650 <p>These requests treat the list as cyclic; that is, 2651 <code>REQ_NEXT_PAGE</code> from the last page goes to the first, 2652 and <code>REQ_PREV_PAGE</code> from the first page goes to the 2653 last.</p> 2654 2655 <h4><a name="ffield" id="ffield">Inter-Field Navigation 2656 Requests</a></h4> 2657 2658 <p>These requests handle navigation between fields on the same 2659 page.</p> 2660 2661 <dl> 2662 <dt><code>REQ_NEXT_FIELD</code> 2663 </dt> 2664 2665 <dd>Move to next field.</dd> 2666 2667 <dt><code>REQ_PREV_FIELD</code> 2668 </dt> 2669 2670 <dd>Move to previous field.</dd> 2671 2672 <dt><code>REQ_FIRST_FIELD</code> 2673 </dt> 2674 2675 <dd>Move to the first field.</dd> 2676 2677 <dt><code>REQ_LAST_FIELD</code> 2678 </dt> 2679 2680 <dd>Move to the last field.</dd> 2681 2682 <dt><code>REQ_SNEXT_FIELD</code> 2683 </dt> 2684 2685 <dd>Move to sorted next field.</dd> 2686 2687 <dt><code>REQ_SPREV_FIELD</code> 2688 </dt> 2689 2690 <dd>Move to sorted previous field.</dd> 2691 2692 <dt><code>REQ_SFIRST_FIELD</code> 2693 </dt> 2694 2695 <dd>Move to the sorted first field.</dd> 2696 2697 <dt><code>REQ_SLAST_FIELD</code> 2698 </dt> 2699 2700 <dd>Move to the sorted last field.</dd> 2701 2702 <dt><code>REQ_LEFT_FIELD</code> 2703 </dt> 2704 2705 <dd>Move left to field.</dd> 2706 2707 <dt><code>REQ_RIGHT_FIELD</code> 2708 </dt> 2709 2710 <dd>Move right to field.</dd> 2711 2712 <dt><code>REQ_UP_FIELD</code> 2713 </dt> 2714 2715 <dd>Move up to field.</dd> 2716 2717 <dt><code>REQ_DOWN_FIELD</code> 2718 </dt> 2719 2720 <dd>Move down to field.</dd> 2721 </dl> 2722 2723 <p>These requests treat the list of fields on a page as cyclic; 2724 that is, <code>REQ_NEXT_FIELD</code> from the last field goes to 2725 the first, and <code>REQ_PREV_FIELD</code> from the first field 2726 goes to the last. The order of the fields for these (and the 2727 <code>REQ_FIRST_FIELD</code> and <code>REQ_LAST_FIELD</code> 2728 requests) is simply the order of the field pointers in the form 2729 array (as set up by <code>new_form()</code> or 2730 <code>set_form_fields()</code></p> 2731 2732 <p>It is also possible to traverse the fields as if they had been 2733 sorted in screen-position order, so the sequence goes 2734 left-to-right and top-to-bottom. To do this, use the second group 2735 of four sorted-movement requests.</p> 2736 2737 <p>Finally, it is possible to move between fields using visual 2738 directions up, down, right, and left. To accomplish this, use the 2739 third group of four requests. Note, however, that the position of 2740 a form for purposes of these requests is its upper-left 2741 corner.</p> 2742 2743 <p>For example, suppose you have a multi-line field B, and two 2744 single-line fields A and C on the same line with B, with A to the 2745 left of B and C to the right of B. A <code>REQ_MOVE_RIGHT</code> 2746 from A will go to B only if A, B, and C <em>all</em> share the 2747 same first line; otherwise it will skip over B to C.</p> 2748 2749 <h4><a name="fifield" id="fifield">Intra-Field Navigation 2750 Requests</a></h4> 2751 2752 <p>These requests drive movement of the edit cursor within the 2753 currently selected field.</p> 2754 2755 <dl> 2756 <dt><code>REQ_NEXT_CHAR</code> 2757 </dt> 2758 2759 <dd>Move to next character.</dd> 2760 2761 <dt><code>REQ_PREV_CHAR</code> 2762 </dt> 2763 2764 <dd>Move to previous character.</dd> 2765 2766 <dt><code>REQ_NEXT_LINE</code> 2767 </dt> 2768 2769 <dd>Move to next line.</dd> 2770 2771 <dt><code>REQ_PREV_LINE</code> 2772 </dt> 2773 2774 <dd>Move to previous line.</dd> 2775 2776 <dt><code>REQ_NEXT_WORD</code> 2777 </dt> 2778 2779 <dd>Move to next word.</dd> 2780 2781 <dt><code>REQ_PREV_WORD</code> 2782 </dt> 2783 2784 <dd>Move to previous word.</dd> 2785 2786 <dt><code>REQ_BEG_FIELD</code> 2787 </dt> 2788 2789 <dd>Move to beginning of field.</dd> 2790 2791 <dt><code>REQ_END_FIELD</code> 2792 </dt> 2793 2794 <dd>Move to end of field.</dd> 2795 2796 <dt><code>REQ_BEG_LINE</code> 2797 </dt> 2798 2799 <dd>Move to beginning of line.</dd> 2800 2801 <dt><code>REQ_END_LINE</code> 2802 </dt> 2803 2804 <dd>Move to end of line.</dd> 2805 2806 <dt><code>REQ_LEFT_CHAR</code> 2807 </dt> 2808 2809 <dd>Move left in field.</dd> 2810 2811 <dt><code>REQ_RIGHT_CHAR</code> 2812 </dt> 2813 2814 <dd>Move right in field.</dd> 2815 2816 <dt><code>REQ_UP_CHAR</code> 2817 </dt> 2818 2819 <dd>Move up in field.</dd> 2820 2821 <dt><code>REQ_DOWN_CHAR</code> 2822 </dt> 2823 2824 <dd>Move down in field.</dd> 2825 </dl> 2826 2827 <p>Each <em>word</em> is separated from the previous and next 2828 characters by whitespace. The commands to move to beginning and 2829 end of line or field look for the first or last non-pad character 2830 in their ranges.</p> 2831 2832 <h4><a name="fscroll" id="fscroll">Scrolling Requests</a></h4> 2833 2834 <p>Fields that are dynamic and have grown and fields explicitly 2835 created with offscreen rows are scrollable. One-line fields 2836 scroll horizontally; multi-line fields scroll vertically. Most 2837 scrolling is triggered by editing and intra-field movement (the 2838 library scrolls the field to keep the cursor visible). It is 2839 possible to explicitly request scrolling with the following 2840 requests:</p> 2841 2842 <dl> 2843 <dt><code>REQ_SCR_FLINE</code> 2844 </dt> 2845 2846 <dd>Scroll vertically forward a line.</dd> 2847 2848 <dt><code>REQ_SCR_BLINE</code> 2849 </dt> 2850 2851 <dd>Scroll vertically backward a line.</dd> 2852 2853 <dt><code>REQ_SCR_FPAGE</code> 2854 </dt> 2855 2856 <dd>Scroll vertically forward a page.</dd> 2857 2858 <dt><code>REQ_SCR_BPAGE</code> 2859 </dt> 2860 2861 <dd>Scroll vertically backward a page.</dd> 2862 2863 <dt><code>REQ_SCR_FHPAGE</code> 2864 </dt> 2865 2866 <dd>Scroll vertically forward half a page.</dd> 2867 2868 <dt><code>REQ_SCR_BHPAGE</code> 2869 </dt> 2870 2871 <dd>Scroll vertically backward half a page.</dd> 2872 2873 <dt><code>REQ_SCR_FCHAR</code> 2874 </dt> 2875 2876 <dd>Scroll horizontally forward a character.</dd> 2877 2878 <dt><code>REQ_SCR_BCHAR</code> 2879 </dt> 2880 2881 <dd>Scroll horizontally backward a character.</dd> 2882 2883 <dt><code>REQ_SCR_HFLINE</code> 2884 </dt> 2885 2886 <dd>Scroll horizontally one field width forward.</dd> 2887 2888 <dt><code>REQ_SCR_HBLINE</code> 2889 </dt> 2890 2891 <dd>Scroll horizontally one field width backward.</dd> 2892 2893 <dt><code>REQ_SCR_HFHALF</code> 2894 </dt> 2895 2896 <dd>Scroll horizontally one half field width forward.</dd> 2897 2898 <dt><code>REQ_SCR_HBHALF</code> 2899 </dt> 2900 2901 <dd>Scroll horizontally one half field width backward.</dd> 2902 </dl> 2903 2904 <p>For scrolling purposes, a <em>page</em> of a field is the 2905 height of its visible part.</p> 2906 2907 <h4><a name="fedit" id="fedit">Editing Requests</a></h4> 2908 2909 <p>When you pass the forms driver an ASCII character, it is 2910 treated as a request to add the character to the field's data 2911 buffer. Whether this is an insertion or a replacement depends on 2912 the field's edit mode (insertion is the default.</p> 2913 2914 <p>The following requests support editing the field and changing 2915 the edit mode:</p> 2916 2917 <dl> 2918 <dt><code>REQ_INS_MODE</code> 2919 </dt> 2920 2921 <dd>Set insertion mode.</dd> 2922 2923 <dt><code>REQ_OVL_MODE</code> 2924 </dt> 2925 2926 <dd>Set overlay mode.</dd> 2927 2928 <dt><code>REQ_NEW_LINE</code> 2929 </dt> 2930 2931 <dd>New line request (see below for explanation).</dd> 2932 2933 <dt><code>REQ_INS_CHAR</code> 2934 </dt> 2935 2936 <dd>Insert space at character location.</dd> 2937 2938 <dt><code>REQ_INS_LINE</code> 2939 </dt> 2940 2941 <dd>Insert blank line at character location.</dd> 2942 2943 <dt><code>REQ_DEL_CHAR</code> 2944 </dt> 2945 2946 <dd>Delete character at cursor.</dd> 2947 2948 <dt><code>REQ_DEL_PREV</code> 2949 </dt> 2950 2951 <dd>Delete previous word at cursor.</dd> 2952 2953 <dt><code>REQ_DEL_LINE</code> 2954 </dt> 2955 2956 <dd>Delete line at cursor.</dd> 2957 2958 <dt><code>REQ_DEL_WORD</code> 2959 </dt> 2960 2961 <dd>Delete word at cursor.</dd> 2962 2963 <dt><code>REQ_CLR_EOL</code> 2964 </dt> 2965 2966 <dd>Clear to end of line.</dd> 2967 2968 <dt><code>REQ_CLR_EOF</code> 2969 </dt> 2970 2971 <dd>Clear to end of field.</dd> 2972 2973 <dt><code>REQ_CLEAR_FIELD</code> 2974 </dt> 2975 2976 <dd>Clear entire field.</dd> 2977 </dl> 2978 2979 <p>The behavior of the <code>REQ_NEW_LINE</code> and 2980 <code>REQ_DEL_PREV</code> requests is complicated and partly 2981 controlled by a pair of forms options. The special cases are 2982 triggered when the cursor is at the beginning of a field, or on 2983 the last line of the field.</p> 2984 2985 <p>First, we consider <code>REQ_NEW_LINE</code>:</p> 2986 2987 <p>The normal behavior of <code>REQ_NEW_LINE</code> in insert 2988 mode is to break the current line at the position of the edit 2989 cursor, inserting the portion of the current line after the 2990 cursor as a new line following the current and moving the cursor 2991 to the beginning of that new line (you may think of this as 2992 inserting a newline in the field buffer).</p> 2993 2994 <p>The normal behavior of <code>REQ_NEW_LINE</code> in overlay 2995 mode is to clear the current line from the position of the edit 2996 cursor to end of line. The cursor is then moved to the beginning 2997 of the next line.</p> 2998 2999 <p>However, <code>REQ_NEW_LINE</code> at the beginning of a 3000 field, or on the last line of a field, instead does a 3001 <code>REQ_NEXT_FIELD</code>. <code>O_NL_OVERLOAD</code> option is 3002 off, this special action is disabled.</p> 3003 3004 <p>Now, let us consider <code>REQ_DEL_PREV</code>:</p> 3005 3006 <p>The normal behavior of <code>REQ_DEL_PREV</code> is to delete 3007 the previous character. If insert mode is on, and the cursor is 3008 at the start of a line, and the text on that line will fit on the 3009 previous one, it instead appends the contents of the current line 3010 to the previous one and deletes the current line (you may think 3011 of this as deleting a newline from the field buffer).</p> 3012 3013 <p>However, <code>REQ_DEL_PREV</code> at the beginning of a field 3014 is instead treated as a <code>REQ_PREV_FIELD</code>.</p> 3015 3016 <p>If the <code>O_BS_OVERLOAD</code> option is off, this special 3017 action is disabled and the forms driver just returns 3018 <code>E_REQUEST_DENIED</code>.</p> 3019 3020 <p>See <a href="#frmoptions">Form Options</a> for discussion of 3021 how to set and clear the overload options.</p> 3022 3023 <h4><a name="forder" id="forder">Order Requests</a></h4> 3024 3025 <p>If the type of your field is ordered, and has associated 3026 functions for getting the next and previous values of the type 3027 from a given value, there are requests that can fetch that value 3028 into the field buffer:</p> 3029 3030 <dl> 3031 <dt><code>REQ_NEXT_CHOICE</code> 3032 </dt> 3033 3034 <dd>Place the successor value of the current value in the 3035 buffer.</dd> 3036 3037 <dt><code>REQ_PREV_CHOICE</code> 3038 </dt> 3039 3040 <dd>Place the predecessor value of the current value in the 3041 buffer.</dd> 3042 </dl> 3043 3044 <p>Of the built-in field types, only <code>TYPE_ENUM</code> has 3045 built-in successor and predecessor functions. When you define a 3046 field type of your own (see <a href="#fcustom">Custom Validation 3047 Types</a>), you can associate our own ordering functions.</p> 3048 3049 <h4><a name="fappcmds" id="fappcmds">Application Commands</a></h4> 3050 3051 <p>Form requests are represented as integers above the 3052 <code>curses</code> value greater than <code>KEY_MAX</code> and 3053 less than or equal to the constant <code>MAX_COMMAND</code>. If 3054 your input-virtualization routine returns a value above 3055 <code>MAX_COMMAND</code>, the forms driver will ignore it.</p> 3056 3057 <h3><a name="fhooks" id="fhooks">Field Change Hooks</a></h3> 3058 3059 <p>It is possible to set function hooks to be executed whenever 3060 the current field or form changes. Here are the functions that 3061 support this:</p> 3062 3063 <pre class="code-block"> 3064typedef void (*HOOK)(); /* pointer to function returning void */ 3065 3066int set_form_init(FORM *form, /* form to alter */ 3067 HOOK hook); /* initialization hook */ 3068 3069HOOK form_init(FORM *form); /* form to query */ 3070 3071int set_form_term(FORM *form, /* form to alter */ 3072 HOOK hook); /* termination hook */ 3073 3074HOOK form_term(FORM *form); /* form to query */ 3075 3076int set_field_init(FORM *form, /* form to alter */ 3077 HOOK hook); /* initialization hook */ 3078 3079HOOK field_init(FORM *form); /* form to query */ 3080 3081int set_field_term(FORM *form, /* form to alter */ 3082 HOOK hook); /* termination hook */ 3083 3084HOOK field_term(FORM *form); /* form to query */ 3085</pre> 3086 <p>These functions allow you to either set or query four 3087 different hooks. In each of the set functions, the second 3088 argument should be the address of a hook function. These 3089 functions differ only in the timing of the hook call.</p> 3090 3091 <dl> 3092 <dt>form_init</dt> 3093 3094 <dd>This hook is called when the form is posted; also, just 3095 after each page change operation.</dd> 3096 3097 <dt>field_init</dt> 3098 3099 <dd>This hook is called when the form is posted; also, just 3100 after each field change</dd> 3101 3102 <dt>field_term</dt> 3103 3104 <dd>This hook is called just after field validation; that is, 3105 just before the field is altered. It is also called when the 3106 form is unposted.</dd> 3107 3108 <dt>form_term</dt> 3109 3110 <dd>This hook is called when the form is unposted; also, just 3111 before each page change operation.</dd> 3112 </dl> 3113 3114 <p>Calls to these hooks may be triggered</p> 3115 3116 <ol> 3117 <li>When user editing requests are processed by the forms 3118 driver</li> 3119 3120 <li>When the current page is changed by 3121 <code>set_current_field()</code> call</li> 3122 3123 <li>When the current field is changed by a 3124 <code>set_form_page()</code> call</li> 3125 </ol> 3126 3127 <p>See <a name="ffocus" id="ffocus">Field Change Commands</a> for 3128 discussion of the latter two cases.</p> 3129 3130 <p>You can set a default hook for all fields by passing one of 3131 the set functions a NULL first argument.</p> 3132 3133 <p>You can disable any of these hooks by (re)setting them to 3134 NULL, the default value.</p> 3135 3136 <h3><a href="#ffocus">Field Change Commands</a></h3> 3137 3138 <p>Normally, navigation through the form will be driven by the 3139 user's input requests. But sometimes it is useful to be able to 3140 move the focus for editing and viewing under control of your 3141 application, or ask which field it currently is in. The following 3142 functions help you accomplish this:</p> 3143 3144 <pre class="code-block"> 3145int set_current_field(FORM *form, /* form to alter */ 3146 FIELD *field); /* field to shift to */ 3147 3148FIELD *current_field(FORM *form); /* form to query */ 3149 3150int field_index(FORM *form, /* form to query */ 3151 FIELD *field); /* field to get index of */ 3152</pre> 3153 <p>The function <code>field_index()</code> returns the index of 3154 the given field in the given form's field array (the array passed 3155 to <code>new_form()</code> or 3156 <code>set_form_fields()</code>).</p> 3157 3158 <p>The initial current field of a form is the first active field 3159 on the first page. The function <code>set_form_fields()</code> 3160 resets this.</p> 3161 3162 <p>It is also possible to move around by pages.</p> 3163 3164 <pre class="code-block"> 3165int set_form_page(FORM *form, /* form to alter */ 3166 int page); /* page to go to (0-origin) */ 3167 3168int form_page(FORM *form); /* return form's current page */ 3169</pre> 3170 <p>The initial page of a newly-created form is 0. The function 3171 <code>set_form_fields()</code> resets this.</p> 3172 3173 <h3><a name="frmoptions" id="frmoptions">Form Options</a></h3> 3174 3175 <p>Like fields, forms may have control option bits. They can be 3176 changed or queried with these functions:</p> 3177 3178 <pre class="code-block"> 3179int set_form_opts(FORM *form, /* form to alter */ 3180 int attr); /* attribute to set */ 3181 3182int form_opts_on(FORM *form, /* form to alter */ 3183 int attr); /* attributes to turn on */ 3184 3185int form_opts_off(FORM *form, /* form to alter */ 3186 int attr); /* attributes to turn off */ 3187 3188int form_opts(FORM *form); /* form to query */ 3189</pre> 3190 <p>By default, all options are on. Here are the available option 3191 bits:</p> 3192 3193 <dl> 3194 <dt>O_NL_OVERLOAD</dt> 3195 3196 <dd>Enable overloading of <code>REQ_NEW_LINE</code> as 3197 described in <a href="#fedit">Editing Requests</a>. The value 3198 of this option is ignored on dynamic fields that have not 3199 reached their size limit; these have no last line, so the 3200 circumstances for triggering a <code>REQ_NEXT_FIELD</code> 3201 never arise.</dd> 3202 3203 <dt>O_BS_OVERLOAD</dt> 3204 3205 <dd>Enable overloading of <code>REQ_DEL_PREV</code> as 3206 described in <a href="#fedit">Editing Requests</a>.</dd> 3207 </dl> 3208 3209 <p>The option values are bit-masks and can be composed with 3210 logical-or in the obvious way.</p> 3211 3212 <h3><a name="fcustom" id="fcustom">Custom Validation Types</a></h3> 3213 3214 <p>The <code>form</code> library gives you the capability to 3215 define custom validation types of your own. Further, the optional 3216 additional arguments of <code>set_field_type</code> effectively 3217 allow you to parameterize validation types. Most of the 3218 complications in the validation-type interface have to do with 3219 the handling of the additional arguments within custom validation 3220 functions.</p> 3221 3222 <h4><a name="flinktypes" id="flinktypes">Union Types</a></h4> 3223 3224 <p>The simplest way to create a custom data type is to compose it 3225 from two preexisting ones:</p> 3226 3227 <pre class="code-block"> 3228FIELD *link_fieldtype(FIELDTYPE *type1, 3229 FIELDTYPE *type2); 3230</pre> 3231 <p>This function creates a field type that will accept any of the 3232 values legal for either of its argument field types (which may be 3233 either predefined or programmer-defined). If a 3234 <code>set_field_type()</code> call later requires arguments, the 3235 new composite type expects all arguments for the first type, than 3236 all arguments for the second. Order functions (see <a href= 3237 "#forder">Order Requests</a>) associated with the component types 3238 will work on the composite; what it does is check the validation 3239 function for the first type, then for the second, to figure what 3240 type the buffer contents should be treated as.</p> 3241 3242 <h4><a name="fnewtypes" id="fnewtypes">New Field Types</a></h4> 3243 3244 <p>To create a field type from scratch, you need to specify one 3245 or both of the following things:</p> 3246 3247 <ul> 3248 <li>A character-validation function, to check each character as 3249 it is entered.</li> 3250 3251 <li>A field-validation function to be applied on exit from the 3252 field.</li> 3253 </ul> 3254 3255 <p>Here is how you do that:</p> 3256 3257 <pre class="code-block"> 3258typedef int (*HOOK)(); /* pointer to function returning int */ 3259 3260FIELDTYPE *new_fieldtype(HOOK f_validate, /* field validator */ 3261 HOOK c_validate) /* character validator */ 3262 3263int free_fieldtype(FIELDTYPE *ftype); /* type to free */ 3264</pre> 3265 <p>At least one of the arguments of <code>new_fieldtype()</code> 3266 must be non-NULL. The forms driver will automatically call the 3267 new type's validation functions at appropriate points in 3268 processing a field of the new type.</p> 3269 3270 <p>The function <code>free_fieldtype()</code> deallocates the 3271 argument fieldtype, freeing all storage associated with it.</p> 3272 3273 <p>Normally, a field validator is called when the user attempts 3274 to leave the field. Its first argument is a field pointer, from 3275 which it can get to field buffer 0 and test it. If the function 3276 returns TRUE, the operation succeeds; if it returns FALSE, the 3277 edit cursor stays in the field.</p> 3278 3279 <p>A character validator gets the character passed in as a first 3280 argument. It too should return TRUE if the character is valid, 3281 FALSE otherwise.</p> 3282 3283 <h4><a name="fcheckargs" id="fcheckargs">Validation Function 3284 Arguments</a></h4> 3285 3286 <p>Your field- and character- validation functions will be passed 3287 a second argument as well. This second argument is the address of 3288 a structure (which we will call a <em>pile</em>) built from any 3289 of the field-type-specific arguments passed to 3290 <code>set_field_type()</code>. If no such arguments are defined 3291 for the field type, this pile pointer argument will be NULL.</p> 3292 3293 <p>In order to arrange for such arguments to be passed to your 3294 validation functions, you must associate a small set of 3295 storage-management functions with the type. The forms driver will 3296 use these to synthesize a pile from the trailing arguments of 3297 each <code>set_field_type()</code> argument, and a pointer to the 3298 pile will be passed to the validation functions.</p> 3299 3300 <p>Here is how you make the association:</p> 3301 3302 <pre class="code-block"> 3303typedef char *(*PTRHOOK)(); /* pointer to function returning (char *) */ 3304typedef void (*VOIDHOOK)(); /* pointer to function returning void */ 3305 3306int set_fieldtype_arg(FIELDTYPE *type, /* type to alter */ 3307 PTRHOOK make_str, /* make structure from args */ 3308 PTRHOOK copy_str, /* make copy of structure */ 3309 VOIDHOOK free_str); /* free structure storage */ 3310</pre> 3311 <p>Here is how the storage-management hooks are used:</p> 3312 3313 <dl> 3314 <dt><code>make_str</code> 3315 </dt> 3316 3317 <dd>This function is called by <code>set_field_type()</code>. 3318 It gets one argument, a <code>va_list</code> of the 3319 type-specific arguments passed to 3320 <code>set_field_type()</code>. It is expected to return a pile 3321 pointer to a data structure that encapsulates those 3322 arguments.</dd> 3323 3324 <dt><code>copy_str</code> 3325 </dt> 3326 3327 <dd>This function is called by form library functions that 3328 allocate new field instances. It is expected to take a pile 3329 pointer, copy the pile to allocated storage, and return the 3330 address of the pile copy.</dd> 3331 3332 <dt><code>free_str</code> 3333 </dt> 3334 3335 <dd>This function is called by field- and type-deallocation 3336 routines in the library. It takes a pile pointer argument, and 3337 is expected to free the storage of that pile.</dd> 3338 </dl> 3339 3340 <p>The <code>make_str</code> and <code>copy_str</code> functions 3341 may return NULL to signal allocation failure. The library 3342 routines will that call them will return error indication when 3343 this happens. Thus, your validation functions should never see a 3344 NULL file pointer and need not check specially for it.</p> 3345 3346 <h4><a name="fcustorder" id="fcustorder">Order Functions For 3347 Custom Types</a></h4> 3348 3349 <p>Some custom field types are simply ordered in the same 3350 well-defined way that <code>TYPE_ENUM</code> is. For such types, 3351 it is possible to define successor and predecessor functions to 3352 support the <code>REQ_NEXT_CHOICE</code> and 3353 <code>REQ_PREV_CHOICE</code> requests. Here is how:</p> 3354 3355 <pre class="code-block"> 3356typedef int (*INTHOOK)(); /* pointer to function returning int */ 3357 3358int set_fieldtype_arg(FIELDTYPE *type, /* type to alter */ 3359 INTHOOK succ, /* get successor value */ 3360 INTHOOK pred); /* get predecessor value */ 3361</pre> 3362 <p>The successor and predecessor arguments will each be passed 3363 two arguments; a field pointer, and a pile pointer (as for the 3364 validation functions). They are expected to use the function 3365 <code>field_buffer()</code> to read the current value, and 3366 <code>set_field_buffer()</code> on buffer 0 to set the next or 3367 previous value. Either hook may return TRUE to indicate success 3368 (a legal next or previous value was set) or FALSE to indicate 3369 failure.</p> 3370 3371 <h4><a name="fcustprobs" id="fcustprobs">Avoiding Problems</a></h4> 3372 3373 <p>The interface for defining custom types is complicated and 3374 tricky. Rather than attempting to create a custom type entirely 3375 from scratch, you should start by studying the library source 3376 code for whichever of the pre-defined types seems to be closest 3377 to what you want.</p> 3378 3379 <p>Use that code as a model, and evolve it towards what you 3380 really want. You will avoid many problems and annoyances that 3381 way. The code in the <code>ncurses</code> library has been 3382 specifically exempted from the package copyright to support 3383 this.</p> 3384 3385 <p>If your custom type defines order functions, have do something 3386 intuitive with a blank field. A useful convention is to make the 3387 successor of a blank field the types minimum value, and its 3388 predecessor the maximum.</p> 3389</body> 3390</html> 3391