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Raymond and Zeyd M. Ben-Halim<br> 50 updates since release 1.9.9e by Thomas Dickey 51 </blockquote> 52 53 <h1>Contents</h1> 54 55 <ul> 56 <li> 57 <a href="#introduction">Introduction</a> 58 59 <ul> 60 <li><a href="#history">A Brief History of Curses</a></li> 61 62 <li><a href="#scope">Scope of This Document</a></li> 63 64 <li><a href="#terminology">Terminology</a></li> 65 </ul> 66 </li> 67 68 <li> 69 <a href="#curses">The Curses Library</a> 70 71 <ul> 72 <li> 73 <a href="#overview">An Overview of Curses</a> 74 75 <ul> 76 <li><a href="#compiling">Compiling Programs using 77 Curses</a></li> 78 79 <li><a href="#updating">Updating the Screen</a></li> 80 81 <li><a href="#stdscr">Standard Windows and Function 82 Naming Conventions</a></li> 83 84 <li><a href="#variables">Variables</a></li> 85 </ul> 86 </li> 87 88 <li> 89 <a href="#using">Using the Library</a> 90 91 <ul> 92 <li><a href="#starting">Starting up</a></li> 93 94 <li><a href="#output">Output</a></li> 95 96 <li><a href="#input">Input</a></li> 97 98 <li><a href="#formschars">Using Forms Characters</a></li> 99 100 <li><a href="#attributes">Character Attributes and 101 Color</a></li> 102 103 <li><a href="#mouse">Mouse Interfacing</a></li> 104 105 <li><a href="#finishing">Finishing Up</a></li> 106 </ul> 107 </li> 108 109 <li> 110 <a href="#functions">Function Descriptions</a> 111 112 <ul> 113 <li><a href="#init">Initialization and Wrapup</a></li> 114 115 <li><a href="#flush">Causing Output to the Terminal</a></li> 116 117 <li><a href="#lowlevel">Low-Level Capability Access</a></li> 118 119 <li><a href="#debugging">Debugging</a></li> 120 </ul> 121 </li> 122 123 <li> 124 <a href="#hints">Hints, Tips, and Tricks</a> 125 126 <ul> 127 <li><a href="#caution">Some Notes of Caution</a></li> 128 129 <li><a href="#leaving">Temporarily Leaving ncurses 130 Mode</a></li> 131 132 <li><a href="#xterm">Using <code>ncurses</code> under 133 <code>xterm</code></a></li> 134 135 <li><a href="#screens">Handling Multiple Terminal 136 Screens</a></li> 137 138 <li><a href="#testing">Testing for Terminal 139 Capabilities</a></li> 140 141 <li><a href="#tuning">Tuning for Speed</a></li> 142 143 <li><a href="#special">Special Features of 144 <code>ncurses</code></a></li> 145 </ul> 146 </li> 147 148 <li> 149 <a href="#compat">Compatibility with Older Versions</a> 150 151 <ul> 152 <li><a href="#refbug">Refresh of Overlapping 153 Windows</a></li> 154 155 <li><a href="#backbug">Background Erase</a></li> 156 </ul> 157 </li> 158 159 <li><a href="#xsifuncs">XSI Curses Conformance</a></li> 160 </ul> 161 </li> 162 163 <li> 164 <a href="#panels">The Panels Library</a> 165 166 <ul> 167 <li><a href="#pcompile">Compiling With the Panels 168 Library</a></li> 169 170 <li><a href="#poverview">Overview of Panels</a></li> 171 172 <li><a href="#pstdscr">Panels, Input, and the Standard 173 Screen</a></li> 174 175 <li><a href="#hiding">Hiding Panels</a></li> 176 177 <li><a href="#pmisc">Miscellaneous Other Facilities</a></li> 178 </ul> 179 </li> 180 181 <li> 182 <a href="#menu">The Menu Library</a> 183 184 <ul> 185 <li><a href="#mcompile">Compiling with the menu Library</a></li> 186 187 <li><a href="#moverview">Overview of Menus</a></li> 188 189 <li><a href="#mselect">Selecting items</a></li> 190 191 <li><a href="#mdisplay">Menu Display</a></li> 192 193 <li><a href="#mwindows">Menu Windows</a></li> 194 195 <li><a href="#minput">Processing Menu Input</a></li> 196 197 <li><a href="#mmisc">Miscellaneous Other Features</a></li> 198 </ul> 199 </li> 200 201 <li> 202 <a href="#form">The Forms Library</a> 203 204 <ul> 205 <li><a href="#fcompile">Compiling with the forms 206 Library</a></li> 207 208 <li><a href="#foverview">Overview of Forms</a></li> 209 210 <li><a href="#fcreate">Creating and Freeing Fields and 211 Forms</a></li> 212 213 <li> 214 <a href="#fattributes">Fetching and Changing Field 215 Attributes</a> 216 217 <ul> 218 <li><a href="#fsizes">Fetching Size and Location 219 Data</a></li> 220 221 <li><a href="#flocation">Changing the Field 222 Location</a></li> 223 224 <li><a href="#fjust">The Justification Attribute</a></li> 225 226 <li><a href="#fdispatts">Field Display Attributes</a></li> 227 228 <li><a href="#foptions">Field Option Bits</a></li> 229 230 <li><a href="#fstatus">Field Status</a></li> 231 232 <li><a href="#fuser">Field User Pointer</a></li> 233 </ul> 234 </li> 235 236 <li><a href="#fdynamic">Variable-Sized Fields</a></li> 237 238 <li> 239 <a href="#fvalidation">Field Validation</a> 240 241 <ul> 242 <li><a href="#ftype_alpha">TYPE_ALPHA</a></li> 243 244 <li><a href="#ftype_alnum">TYPE_ALNUM</a></li> 245 246 <li><a href="#ftype_enum">TYPE_ENUM</a></li> 247 248 <li><a href="#ftype_integer">TYPE_INTEGER</a></li> 249 250 <li><a href="#ftype_numeric">TYPE_NUMERIC</a></li> 251 252 <li><a href="#ftype_regexp">TYPE_REGEXP</a></li> 253 </ul> 254 </li> 255 256 <li><a href="#fbuffer">Direct Field Buffer Manipulation</a></li> 257 258 <li><a href="#formattrs">Attributes of Forms</a></li> 259 260 <li><a href="#fdisplay">Control of Form Display</a></li> 261 262 <li> 263 <a href="#fdriver">Input Processing in the Forms 264 Driver</a> 265 266 <ul> 267 <li><a href="#fpage">Page Navigation Requests</a></li> 268 269 <li><a href="#ffield">Inter-Field Navigation 270 Requests</a></li> 271 272 <li><a href="#fifield">Intra-Field Navigation 273 Requests</a></li> 274 275 <li><a href="#fscroll">Scrolling Requests</a></li> 276 277 <li><a href="#fedit">Field Editing Requests</a></li> 278 279 <li><a href="#forder">Order Requests</a></li> 280 281 <li><a href="#fappcmds">Application Commands</a></li> 282 </ul> 283 </li> 284 285 <li><a href="#fhooks">Field Change Hooks</a></li> 286 287 <li><a href="#ffocus">Field Change Commands</a></li> 288 289 <li><a href="#frmoptions">Form Options</a></li> 290 291 <li> 292 <a href="#fcustom">Custom Validation Types</a> 293 294 <ul> 295 <li><a href="#flinktypes">Union Types</a></li> 296 297 <li><a href="#fnewtypes">New Field Types</a></li> 298 299 <li><a href="#fcheckargs">Validation Function 300 Arguments</a></li> 301 302 <li><a href="#fcustorder">Order Functions For Custom 303 Types</a></li> 304 305 <li><a href="#fcustprobs">Avoiding Problems</a></li> 306 </ul> 307 </li> 308 </ul> 309 </li> 310 </ul> 311 312 <hr> 313 314 <h1><a name="introduction" id="introduction">Introduction</a></h1> 315 316 <p>This document is an introduction to programming with 317 <code>curses</code>. It is not an exhaustive reference for the 318 curses Application Programming Interface (API); that role is 319 filled by the <code>curses</code> manual pages. Rather, it is 320 intended to help C programmers ease into using the package.</p> 321 322 <p>This document is aimed at C applications programmers not yet 323 specifically familiar with ncurses. If you are already an 324 experienced <code>curses</code> programmer, you should 325 nevertheless read the sections on <a href="#mouse">Mouse 326 Interfacing</a>, <a href="#debugging">Debugging</a>, <a href= 327 "#compat">Compatibility with Older Versions</a>, and <a href= 328 "#hints">Hints, Tips, and Tricks</a>. These will bring you up to 329 speed on the special features and quirks of the 330 <code>ncurses</code> implementation. If you are not so 331 experienced, keep reading.</p> 332 333 <p>The <code>curses</code> package is a subroutine library for 334 terminal-independent screen-painting and input-event handling 335 which presents a high level screen model to the programmer, 336 hiding differences between terminal types and doing automatic 337 optimization of output to change one screen full of text into 338 another. <code>Curses</code> uses terminfo, which is a database 339 format that can describe the capabilities of thousands of 340 different terminals.</p> 341 342 <p>The <code>curses</code> API may seem something of an archaism 343 on UNIX desktops increasingly dominated by X, Motif, and Tcl/Tk. 344 Nevertheless, UNIX still supports tty lines and X supports 345 <em>xterm(1)</em>; the <code>curses</code> API has the advantage 346 of (a) back-portability to character-cell terminals, and (b) 347 simplicity. For an application that does not require bit-mapped 348 graphics and multiple fonts, an interface implementation using 349 <code>curses</code> will typically be a great deal simpler and 350 less expensive than one using an X toolkit.</p> 351 352 <h2><a name="history" id="history">A Brief History of Curses</a></h2> 353 354 <p>Historically, the first ancestor of <code>curses</code> was 355 the routines written to provide screen-handling for the 356 <code>vi</code> editor; these used the <code>termcap</code> 357 database facility (both released in 3BSD) for describing terminal 358 capabilities. These routines were abstracted into a documented 359 library and first released with the early BSD UNIX versions. All 360 of this work was done by students at the University of California 361 (Berkeley campus). The curses library was first published in 362 4.0BSD, a year after 3BSD (i.e., late 1980).</p> 363 364 <p>After graduation, one of those students went to work at 365 AT&T Bell Labs, and made an improved <code>termcap</code> 366 library called <code>terminfo</code> (i.e., 367 “libterm”), and adapted the curses library to use 368 this. That was subsequently released in System V Release 2 (early 369 1984). Thereafter, other developers added to the curses and 370 terminfo libraries. For instance, a student at Cornell University 371 wrote an improved terminfo library as well as a tool 372 (<code>tic</code>) to compile the terminal descriptions. As a 373 general rule, AT&T did not identify the developers in the 374 source-code or documentation; the <code>tic</code> and 375 <code>infocmp</code> programs are the exceptions.</p> 376 377 <p>System V Release 3 (System III UNIX) from Bell Labs featured a 378 rewritten and much-improved <code>curses</code> library, along 379 with the <code>tic</code> program (late 1986).</p> 380 381 <p>To recap, terminfo is based on Berkeley's termcap database, 382 but contains a number of improvements and extensions. 383 Parameterized capabilities strings were introduced, making it 384 possible to describe multiple video attributes, and colors and to 385 handle far more unusual terminals than possible with termcap. In 386 the later AT&T System V releases, <code>curses</code> evolved 387 to use more facilities and offer more capabilities, going far 388 beyond BSD curses in power and flexibility.</p> 389 390 <h2><a name="scope" id="scope">Scope of This Document</a></h2> 391 392 <p>This document describes <code>ncurses</code>, a free 393 implementation of the System V <code>curses</code> API with some 394 clearly marked extensions. It includes the following System V 395 curses features:</p> 396 397 <ul> 398 <li>Support for multiple screen highlights (BSD curses could 399 only handle one “standout” highlight, usually 400 reverse-video).</li> 401 402 <li>Support for line- and box-drawing using forms 403 characters.</li> 404 405 <li>Recognition of function keys on input.</li> 406 407 <li>Color support.</li> 408 409 <li>Support for pads (windows of larger than screen size on 410 which the screen or a subwindow defines a viewport).</li> 411 </ul> 412 413 <p>Also, this package makes use of the insert and delete line and 414 character features of terminals so equipped, and determines how 415 to optimally use these features with no help from the programmer. 416 It allows arbitrary combinations of video attributes to be 417 displayed, even on terminals that leave “magic 418 cookies” on the screen to mark changes in attributes.</p> 419 420 <p>The <code>ncurses</code> package can also capture and use 421 event reports from a mouse in some environments (notably, xterm 422 under the X window system). This document includes tips for using 423 the mouse.</p> 424 425 <p>The <code>ncurses</code> package was originated by Pavel 426 Curtis. The original maintainer of this package is <a href= 427 "mailto:zmbenhal@netcom.com">Zeyd Ben-Halim</a> 428 <zmbenhal@netcom.com>. <a href= 429 "mailto:esr@snark.thyrsus.com">Eric S. Raymond</a> 430 <esr@snark.thyrsus.com> wrote many of the new features in 431 versions after 1.8.1 and wrote most of this introduction. 432 Jürgen Pfeifer wrote all of the menu and forms code as well 433 as the <a href="http://www.adahome.com">Ada95</a> binding. 434 Ongoing work is being done by <a href= 435 "mailto:dickey@invisible-island.net">Thomas Dickey</a> 436 (maintainer). Contact the current maintainers at <a href= 437 "mailto:bug-ncurses@gnu.org">bug-ncurses@gnu.org</a>.</p> 438 439 <p>This document also describes the <a href="#panels">panels</a> 440 extension library, similarly modeled on the SVr4 panels facility. 441 This library allows you to associate backing store with each of a 442 stack or deck of overlapping windows, and provides operations for 443 moving windows around in the stack that change their visibility 444 in the natural way (handling window overlaps).</p> 445 446 <p>Finally, this document describes in detail the <a href= 447 "#menu">menus</a> and <a href="#form">forms</a> extension 448 libraries, also cloned from System V, which support easy 449 construction and sequences of menus and fill-in forms.</p> 450 451 <h2><a name="terminology" id="terminology">Terminology</a></h2> 452 453 <p>In this document, the following terminology is used with 454 reasonable consistency:</p> 455 456 <dl> 457 <dt>window</dt> 458 459 <dd>A data structure describing a sub-rectangle of the screen 460 (possibly the entire screen). You can write to a window as 461 though it were a miniature screen, scrolling independently of 462 other windows on the physical screen.</dd> 463 464 <dt>screens</dt> 465 466 <dd>A subset of windows which are as large as the terminal 467 screen, i.e., they start at the upper left hand corner and 468 encompass the lower right hand corner. One of these, 469 <code>stdscr</code>, is automatically provided for the 470 programmer.</dd> 471 472 <dt>terminal screen</dt> 473 474 <dd>The package's idea of what the terminal display currently 475 looks like, i.e., what the user sees now. This is a special 476 screen.</dd> 477 </dl> 478 479 <h1><a name="curses" id="curses">The Curses Library</a></h1> 480 481 <h2><a name="overview" id="overview">An Overview of Curses</a></h2> 482 483 <h3><a name="compiling" id="compiling">Compiling Programs using 484 Curses</a></h3> 485 486 <p>In order to use the library, it is necessary to have certain 487 types and variables defined. Therefore, the programmer must have 488 a line:</p> 489 490 <pre> 491 #include <curses.h> 492</pre> 493 494 <p>at the top of the program source. The screen package uses the 495 Standard I/O library, so <code><curses.h></code> includes 496 <code><stdio.h></code>. <code><curses.h></code> also 497 includes <code><termios.h></code>, 498 <code><termio.h></code>, or <code><sgtty.h></code> 499 depending on your system. It is redundant (but harmless) for the 500 programmer to do these includes, too. In linking with 501 <code>curses</code> you need to have <code>-lncurses</code> in 502 your LDFLAGS or on the command line. There is no need for any 503 other libraries.</p> 504 505 <h3><a name="updating" id="updating">Updating the Screen</a></h3> 506 507 <p>In order to update the screen optimally, it is necessary for 508 the routines to know what the screen currently looks like and 509 what the programmer wants it to look like next. For this purpose, 510 a data type (structure) named WINDOW is defined which describes a 511 window image to the routines, including its starting position on 512 the screen (the (y, x) coordinates of the upper left hand corner) 513 and its size. One of these (called <code>curscr</code>, for 514 current screen) is a screen image of what the terminal currently 515 looks like. Another screen (called <code>stdscr</code>, for 516 standard screen) is provided by default to make changes on.</p> 517 518 <p>A window is a purely internal representation. It is used to 519 build and store a potential image of a portion of the terminal. 520 It does not bear any necessary relation to what is really on the 521 terminal screen; it is more like a scratchpad or write 522 buffer.</p> 523 524 <p>To make the section of physical screen corresponding to a 525 window reflect the contents of the window structure, the routine 526 <code>refresh()</code> (or <code>wrefresh()</code> if the window 527 is not <code>stdscr</code>) is called.</p> 528 529 <p>A given physical screen section may be within the scope of any 530 number of overlapping windows. Also, changes can be made to 531 windows in any order, without regard to motion efficiency. Then, 532 at will, the programmer can effectively say “make it look 533 like this,” and let the package implementation determine 534 the most efficient way to repaint the screen.</p> 535 536 <h3><a name="stdscr" id="stdscr">Standard Windows and Function 537 Naming Conventions</a></h3> 538 539 <p>As hinted above, the routines can use several windows, but two 540 are automatically given: <code>curscr</code>, which knows what 541 the terminal looks like, and <code>stdscr</code>, which is what 542 the programmer wants the terminal to look like next. The user 543 should never actually access <code>curscr</code> directly. 544 Changes should be made to through the API, and then the routine 545 <code>refresh()</code> (or <code>wrefresh()</code>) called.</p> 546 547 <p>Many functions are defined to use <code>stdscr</code> as a 548 default screen. For example, to add a character to 549 <code>stdscr</code>, one calls <code>addch()</code> with the 550 desired character as argument. To write to a different window. 551 use the routine <code>waddch()</code> (for 552 <strong>w</strong>indow-specific addch()) is provided. This 553 convention of prepending function names with a “w” 554 when they are to be applied to specific windows is consistent. 555 The only routines which do not follow it are those for which a 556 window must always be specified.</p> 557 558 <p>In order to move the current (y, x) coordinates from one point 559 to another, the routines <code>move()</code> and 560 <code>wmove()</code> are provided. However, it is often desirable 561 to first move and then perform some I/O operation. In order to 562 avoid clumsiness, most I/O routines can be preceded by the prefix 563 “mv” and the desired (y, x) coordinates prepended to 564 the arguments to the function. For example, the calls</p> 565 566 <pre> 567 move(y, x); 568 addch(ch); 569</pre> 570 571 <p>can be replaced by</p> 572 573 <pre> 574 mvaddch(y, x, ch); 575</pre> 576 577 <p>and</p> 578 579 <pre> 580 wmove(win, y, x); 581 waddch(win, ch); 582</pre> 583 584 <p>can be replaced by</p> 585 586 <pre> 587 mvwaddch(win, y, x, ch); 588</pre> 589 590 <p>Note that the window description pointer (win) comes before 591 the added (y, x) coordinates. If a function requires a window 592 pointer, it is always the first parameter passed.</p> 593 594 <h3><a name="variables" id="variables">Variables</a></h3> 595 596 <p>The <code>curses</code> library sets some variables describing 597 the terminal capabilities.</p> 598 599 <pre> 600 type name description 601 ------------------------------------------------------------------ 602 int LINES number of lines on the terminal 603 int COLS number of columns on the terminal 604</pre> 605 606 <p>The <code>curses.h</code> also introduces some 607 <code>#define</code> constants and types of general 608 usefulness:</p> 609 610 <dl> 611 <dt><code>bool</code> 612 </dt> 613 614 <dd>boolean type, actually a “char” (e.g., 615 <code>bool doneit;</code>)</dd> 616 617 <dt><code>TRUE</code> 618 </dt> 619 620 <dd>boolean “true” flag (1).</dd> 621 622 <dt><code>FALSE</code> 623 </dt> 624 625 <dd>boolean “false” flag (0).</dd> 626 627 <dt><code>ERR</code> 628 </dt> 629 630 <dd>error flag returned by routines on a failure (-1).</dd> 631 632 <dt><code>OK</code> 633 </dt> 634 635 <dd>error flag returned by routines when things go right.</dd> 636 </dl> 637 638 <h2><a name="using" id="using">Using the Library</a></h2> 639 640 <p>Now we describe how to actually use the screen package. In it, 641 we assume all updating, reading, etc. is applied to 642 <code>stdscr</code>. These instructions will work on any window, 643 providing you change the function names and parameters as 644 mentioned above.</p> 645 646 <p>Here is a sample program to motivate the discussion:</p> 647 648 <pre> 649#include <stdlib.h> 650#include <curses.h> 651#include <signal.h> 652 653static void finish(int sig); 654 655int 656main(int argc, char *argv[]) 657{ 658 int num = 0; 659 660 /* initialize your non-curses data structures here */ 661 662 (void) signal(SIGINT, finish); /* arrange interrupts to terminate */ 663 664 (void) initscr(); /* initialize the curses library */ 665 keypad(stdscr, TRUE); /* enable keyboard mapping */ 666 (void) nonl(); /* tell curses not to do NL->CR/NL on output */ 667 (void) cbreak(); /* take input chars one at a time, no wait for \n */ 668 (void) echo(); /* echo input - in color */ 669 670 if (has_colors()) 671 { 672 start_color(); 673 674 /* 675 * Simple color assignment, often all we need. Color pair 0 cannot 676 * be redefined. This example uses the same value for the color 677 * pair as for the foreground color, though of course that is not 678 * necessary: 679 */ 680 init_pair(1, COLOR_RED, COLOR_BLACK); 681 init_pair(2, COLOR_GREEN, COLOR_BLACK); 682 init_pair(3, COLOR_YELLOW, COLOR_BLACK); 683 init_pair(4, COLOR_BLUE, COLOR_BLACK); 684 init_pair(5, COLOR_CYAN, COLOR_BLACK); 685 init_pair(6, COLOR_MAGENTA, COLOR_BLACK); 686 init_pair(7, COLOR_WHITE, COLOR_BLACK); 687 } 688 689 for (;;) 690 { 691 int c = getch(); /* refresh, accept single keystroke of input */ 692 attrset(COLOR_PAIR(num % 8)); 693 num++; 694 695 /* process the command keystroke */ 696 } 697 698 finish(0); /* we are done */ 699} 700 701static void finish(int sig) 702{ 703 endwin(); 704 705 /* do your non-curses wrapup here */ 706 707 exit(0); 708} 709</pre> 710 711 <h3><a name="starting" id="starting">Starting up</a></h3> 712 713 <p>In order to use the screen package, the routines must know 714 about terminal characteristics, and the space for 715 <code>curscr</code> and <code>stdscr</code> must be allocated. 716 These function <code>initscr()</code> does both these things. 717 Since it must allocate space for the windows, it can overflow 718 memory when attempting to do so. On the rare occasions this 719 happens, <code>initscr()</code> will terminate the program with 720 an error message. <code>initscr()</code> must always be called 721 before any of the routines which affect windows are used. If it 722 is not, the program will core dump as soon as either 723 <code>curscr</code> or <code>stdscr</code> are referenced. 724 However, it is usually best to wait to call it until after you 725 are sure you will need it, like after checking for startup 726 errors. Terminal status changing routines like <code>nl()</code> 727 and <code>cbreak()</code> should be called after 728 <code>initscr()</code>.</p> 729 730 <p>Once the screen windows have been allocated, you can set them 731 up for your program. If you want to, say, allow a screen to 732 scroll, use <code>scrollok()</code>. If you want the cursor to be 733 left in place after the last change, use <code>leaveok()</code>. 734 If this is not done, <code>refresh()</code> will move the cursor 735 to the window's current (y, x) coordinates after updating it.</p> 736 737 <p>You can create new windows of your own using the functions 738 <code>newwin()</code>, <code>derwin()</code>, and 739 <code>subwin()</code>. The routine <code>delwin()</code> will 740 allow you to get rid of old windows. All the options described 741 above can be applied to any window.</p> 742 743 <h3><a name="output" id="output">Output</a></h3> 744 745 <p>Now that we have set things up, we will want to actually 746 update the terminal. The basic functions used to change what will 747 go on a window are <code>addch()</code> and <code>move()</code>. 748 <code>addch()</code> adds a character at the current (y, x) 749 coordinates. <code>move()</code> changes the current (y, x) 750 coordinates to whatever you want them to be. It returns 751 <code>ERR</code> if you try to move off the window. As mentioned 752 above, you can combine the two into <code>mvaddch()</code> to do 753 both things at once.</p> 754 755 <p>The other output functions, such as <code>addstr()</code> and 756 <code>printw()</code>, all call <code>addch()</code> to add 757 characters to the window.</p> 758 759 <p>After you have put on the window what you want there, when you 760 want the portion of the terminal covered by the window to be made 761 to look like it, you must call <code>refresh()</code>. In order 762 to optimize finding changes, <code>refresh()</code> assumes that 763 any part of the window not changed since the last 764 <code>refresh()</code> of that window has not been changed on the 765 terminal, i.e., that you have not refreshed a portion of the 766 terminal with an overlapping window. If this is not the case, the 767 routine <code>touchwin()</code> is provided to make it look like 768 the entire window has been changed, thus making 769 <code>refresh()</code> check the whole subsection of the terminal 770 for changes.</p> 771 772 <p>If you call <code>wrefresh()</code> with <code>curscr</code> 773 as its argument, it will make the screen look like 774 <code>curscr</code> thinks it looks like. This is useful for 775 implementing a command which would redraw the screen in case it 776 get messed up.</p> 777 778 <h3><a name="input" id="input">Input</a></h3> 779 780 <p>The complementary function to <code>addch()</code> is 781 <code>getch()</code> which, if echo is set, will call 782 <code>addch()</code> to echo the character. Since the screen 783 package needs to know what is on the terminal at all times, if 784 characters are to be echoed, the tty must be in raw or cbreak 785 mode. Since initially the terminal has echoing enabled and is in 786 ordinary “cooked” mode, one or the other has to 787 changed before calling <code>getch()</code>; otherwise, the 788 program's output will be unpredictable.</p> 789 790 <p>When you need to accept line-oriented input in a window, the 791 functions <code>wgetstr()</code> and friends are available. There 792 is even a <code>wscanw()</code> function that can do 793 <code>scanf()</code>(3)-style multi-field parsing on window 794 input. These pseudo-line-oriented functions turn on echoing while 795 they execute.</p> 796 797 <p>The example code above uses the call <code>keypad(stdscr, 798 TRUE)</code> to enable support for function-key mapping. With 799 this feature, the <code>getch()</code> code watches the input 800 stream for character sequences that correspond to arrow and 801 function keys. These sequences are returned as pseudo-character 802 values. The <code>#define</code> values returned are listed in 803 the <code>curses.h</code> The mapping from sequences to 804 <code>#define</code> values is determined by <code>key_</code> 805 capabilities in the terminal's terminfo entry.</p> 806 807 <h3><a name="formschars" id="formschars">Using Forms 808 Characters</a></h3> 809 810 <p>The <code>addch()</code> function (and some others, including 811 <code>box()</code> and <code>border()</code>) can accept some 812 pseudo-character arguments which are specially defined by 813 <code>ncurses</code>. These are <code>#define</code> values set 814 up in the <code>curses.h</code> header; see there for a complete 815 list (look for the prefix <code>ACS_</code>).</p> 816 817 <p>The most useful of the ACS defines are the forms-drawing 818 characters. You can use these to draw boxes and simple graphs on 819 the screen. If the terminal does not have such characters, 820 <code>curses.h</code> will map them to a recognizable (though 821 ugly) set of ASCII defaults.</p> 822 823 <h3><a name="attributes" id="attributes">Character Attributes and 824 Color</a></h3> 825 826 <p>The <code>ncurses</code> package supports screen highlights 827 including standout, reverse-video, underline, and blink. It also 828 supports color, which is treated as another kind of 829 highlight.</p> 830 831 <p>Highlights are encoded, internally, as high bits of the 832 pseudo-character type (<code>chtype</code>) that 833 <code>curses.h</code> uses to represent the contents of a screen 834 cell. See the <code>curses.h</code> header file for a complete 835 list of highlight mask values (look for the prefix 836 <code>A_</code>).</p> 837 838 <p>There are two ways to make highlights. One is to logical-or 839 the value of the highlights you want into the character argument 840 of an <code>addch()</code> call, or any other output call that 841 takes a <code>chtype</code> argument.</p> 842 843 <p>The other is to set the current-highlight value. This is 844 <em>logical-OR</em>ed with any highlight you specify the first 845 way. You do this with the functions <code>attron()</code>, 846 <code>attroff()</code>, and <code>attrset()</code>; see the 847 manual pages for details. Color is a special kind of highlight. 848 The package actually thinks in terms of color pairs, combinations 849 of foreground and background colors. The sample code above sets 850 up eight color pairs, all of the guaranteed-available colors on 851 black. Note that each color pair is, in effect, given the name of 852 its foreground color. Any other range of eight non-conflicting 853 values could have been used as the first arguments of the 854 <code>init_pair()</code> values.</p> 855 856 <p>Once you have done an <code>init_pair()</code> that creates 857 color-pair N, you can use <code>COLOR_PAIR(N)</code> as a 858 highlight that invokes that particular color combination. Note 859 that <code>COLOR_PAIR(N)</code>, for constant N, is itself a 860 compile-time constant and can be used in initializers.</p> 861 862 <h3><a name="mouse" id="mouse">Mouse Interfacing</a></h3> 863 864 <p>The <code>ncurses</code> library also provides a mouse 865 interface.</p> 866 867 <blockquote> 868 <strong>NOTE:</strong> this facility is specific to 869 <code>ncurses</code>, it is not part of either the XSI Curses 870 standard, nor of System V Release 4, nor BSD curses. System V 871 Release 4 curses contains code with similar interface 872 definitions, however it is not documented. Other than by 873 disassembling the library, we have no way to determine exactly 874 how that mouse code works. Thus, we recommend that you wrap 875 mouse-related code in an #ifdef using the feature macro 876 NCURSES_MOUSE_VERSION so it will not be compiled and linked on 877 non-ncurses systems. 878 </blockquote> 879 880 <p>Presently, mouse event reporting works in the following 881 environments:</p> 882 883 <ul> 884 <li>xterm and similar programs such as rxvt.</li> 885 886 <li>Linux console, when configured with <code>gpm</code>(1), 887 Alessandro Rubini's mouse server.</li> 888 889 <li>FreeBSD sysmouse (console)</li> 890 891 <li>OS/2 EMX</li> 892 </ul> 893 894 <p>The mouse interface is very simple. To activate it, you use 895 the function <code>mousemask()</code>, passing it as first 896 argument a bit-mask that specifies what kinds of events you want 897 your program to be able to see. It will return the bit-mask of 898 events that actually become visible, which may differ from the 899 argument if the mouse device is not capable of reporting some of 900 the event types you specify.</p> 901 902 <p>Once the mouse is active, your application's command loop 903 should watch for a return value of <code>KEY_MOUSE</code> from 904 <code>wgetch()</code>. When you see this, a mouse event report 905 has been queued. To pick it off the queue, use the function 906 <code>getmouse()</code> (you must do this before the next 907 <code>wgetch()</code>, otherwise another mouse event might come 908 in and make the first one inaccessible).</p> 909 910 <p>Each call to <code>getmouse()</code> fills a structure (the 911 address of which you will pass it) with mouse event data. The 912 event data includes zero-origin, screen-relative character-cell 913 coordinates of the mouse pointer. It also includes an event mask. 914 Bits in this mask will be set, corresponding to the event type 915 being reported.</p> 916 917 <p>The mouse structure contains two additional fields which may 918 be significant in the future as ncurses interfaces to new kinds 919 of pointing device. In addition to x and y coordinates, there is 920 a slot for a z coordinate; this might be useful with 921 touch-screens that can return a pressure or duration parameter. 922 There is also a device ID field, which could be used to 923 distinguish between multiple pointing devices.</p> 924 925 <p>The class of visible events may be changed at any time via 926 <code>mousemask()</code>. Events that can be reported include 927 presses, releases, single-, double- and triple-clicks (you can 928 set the maximum button-down time for clicks). If you do not make 929 clicks visible, they will be reported as press-release pairs. In 930 some environments, the event mask may include bits reporting the 931 state of shift, alt, and ctrl keys on the keyboard during the 932 event.</p> 933 934 <p>A function to check whether a mouse event fell within a given 935 window is also supplied. You can use this to see whether a given 936 window should consider a mouse event relevant to it.</p> 937 938 <p>Because mouse event reporting will not be available in all 939 environments, it would be unwise to build <code>ncurses</code> 940 applications that <em>require</em> the use of a mouse. Rather, 941 you should use the mouse as a shortcut for point-and-shoot 942 commands your application would normally accept from the 943 keyboard. Two of the test games in the <code>ncurses</code> 944 distribution (<code>bs</code> and <code>knight</code>) contain 945 code that illustrates how this can be done.</p> 946 947 <p>See the manual page <code>curs_mouse(3X)</code> for full 948 details of the mouse-interface functions.</p> 949 950 <h3><a name="finishing" id="finishing">Finishing Up</a></h3> 951 952 <p>In order to clean up after the <code>ncurses</code> routines, 953 the routine <code>endwin()</code> is provided. It restores tty 954 modes to what they were when <code>initscr()</code> was first 955 called, and moves the cursor down to the lower-left corner. Thus, 956 anytime after the call to initscr, <code>endwin()</code> should 957 be called before exiting.</p> 958 959 <h2><a name="functions" id="functions">Function Descriptions</a></h2> 960 961 <p>We describe the detailed behavior of some important curses 962 functions here, as a supplement to the manual page 963 descriptions.</p> 964 965 <h3><a name="init" id="init">Initialization and Wrapup</a></h3> 966 967 <dl> 968 <dt><code>initscr()</code> 969 </dt> 970 971 <dd>The first function called should almost always be 972 <code>initscr()</code>. This will determine the terminal type 973 and initialize curses data structures. <code>initscr()</code> 974 also arranges that the first call to <code>refresh()</code> 975 will clear the screen. If an error occurs a message is written 976 to standard error and the program exits. Otherwise it returns a 977 pointer to stdscr. A few functions may be called before initscr 978 (<code>slk_init()</code>, <code>filter()</code>, 979 <code>ripoffline()</code>, <code>use_env()</code>, and, if you 980 are using multiple terminals, <code>newterm()</code>.)</dd> 981 982 <dt><code>endwin()</code> 983 </dt> 984 985 <dd>Your program should always call <code>endwin()</code> 986 before exiting or shelling out of the program. This function 987 will restore tty modes, move the cursor to the lower left 988 corner of the screen, reset the terminal into the proper 989 non-visual mode. Calling <code>refresh()</code> or 990 <code>doupdate()</code> after a temporary escape from the 991 program will restore the ncurses screen from before the 992 escape.</dd> 993 994 <dt><code>newterm(type, ofp, ifp)</code> 995 </dt> 996 997 <dd>A program which outputs to more than one terminal should 998 use <code>newterm()</code> instead of <code>initscr()</code>. 999 <code>newterm()</code> should be called once for each terminal. 1000 It returns a variable of type <code>SCREEN *</code> which 1001 should be saved as a reference to that terminal. (NOTE: a 1002 SCREEN variable is not a <em>screen</em> in the sense we are 1003 describing in this introduction, but a collection of parameters 1004 used to assist in optimizing the display.) The arguments are 1005 the type of the terminal (a string) and <code>FILE</code> 1006 pointers for the output and input of the terminal. If type is 1007 NULL then the environment variable <code>$TERM</code> is used. 1008 <code>endwin()</code> should called once at wrapup time for 1009 each terminal opened using this function.</dd> 1010 1011 <dt><code>set_term(new)</code> 1012 </dt> 1013 1014 <dd>This function is used to switch to a different terminal 1015 previously opened by <code>newterm()</code>. The screen 1016 reference for the new terminal is passed as the parameter. The 1017 previous terminal is returned by the function. All other calls 1018 affect only the current terminal.</dd> 1019 1020 <dt><code>delscreen(sp)</code> 1021 </dt> 1022 1023 <dd>The inverse of <code>newterm()</code>; deallocates the data 1024 structures associated with a given <code>SCREEN</code> 1025 reference.</dd> 1026 </dl> 1027 1028 <h3><a name="flush" id="flush">Causing Output to the Terminal</a></h3> 1029 1030 <dl> 1031 <dt><code>refresh()</code> and <code>wrefresh(win)</code></dt> 1032 1033 <dd>These functions must be called to actually get any output 1034 on the terminal, as other routines merely manipulate data 1035 structures. <code>wrefresh()</code> copies the named window to 1036 the physical terminal screen, taking into account what is 1037 already there in order to do optimizations. 1038 <code>refresh()</code> does a refresh of <code>stdscr</code>. 1039 Unless <code>leaveok()</code> has been enabled, the physical 1040 cursor of the terminal is left at the location of the window's 1041 cursor.</dd> 1042 1043 <dt><code>doupdate()</code> and 1044 <code>wnoutrefresh(win)</code></dt> 1045 1046 <dd>These two functions allow multiple updates with more 1047 efficiency than wrefresh. To use them, it is important to 1048 understand how curses works. In addition to all the window 1049 structures, curses keeps two data structures representing the 1050 terminal screen: a physical screen, describing what is actually 1051 on the screen, and a virtual screen, describing what the 1052 programmer wants to have on the screen. wrefresh works by first 1053 copying the named window to the virtual screen 1054 (<code>wnoutrefresh()</code>), and then calling the routine to 1055 update the screen (<code>doupdate()</code>). If the programmer 1056 wishes to output several windows at once, a series of calls to 1057 <code>wrefresh</code> will result in alternating calls to 1058 <code>wnoutrefresh()</code> and <code>doupdate()</code>, 1059 causing several bursts of output to the screen. By calling 1060 <code>wnoutrefresh()</code> for each window, it is then 1061 possible to call <code>doupdate()</code> once, resulting in 1062 only one burst of output, with fewer total characters 1063 transmitted (this also avoids a visually annoying flicker at 1064 each update).</dd> 1065 </dl> 1066 1067 <h3><a name="lowlevel" id="lowlevel">Low-Level Capability 1068 Access</a></h3> 1069 1070 <dl> 1071 <dt><code>setupterm(term, filenum, errret)</code> 1072 </dt> 1073 1074 <dd> 1075 This routine is called to initialize a terminal's 1076 description, without setting up the curses screen structures 1077 or changing the tty-driver mode bits. <code>term</code> is 1078 the character string representing the name of the terminal 1079 being used. <code>filenum</code> is the UNIX file descriptor 1080 of the terminal to be used for output. <code>errret</code> is 1081 a pointer to an integer, in which a success or failure 1082 indication is returned. The values returned can be 1 (all is 1083 well), 0 (no such terminal), or -1 (some problem locating the 1084 terminfo database). 1085 1086 <p>The value of <code>term</code> can be given as NULL, which 1087 will cause the value of <code>TERM</code> in the environment 1088 to be used. The <code>errret</code> pointer can also be given 1089 as NULL, meaning no error code is wanted. If 1090 <code>errret</code> is defaulted, and something goes wrong, 1091 <code>setupterm()</code> will print an appropriate error 1092 message and exit, rather than returning. Thus, a simple 1093 program can call setupterm(0, 1, 0) and not worry about 1094 initialization errors.</p> 1095 1096 <p>After the call to <code>setupterm()</code>, the global 1097 variable <code>cur_term</code> is set to point to the current 1098 structure of terminal capabilities. By calling 1099 <code>setupterm()</code> for each terminal, and saving and 1100 restoring <code>cur_term</code>, it is possible for a program 1101 to use two or more terminals at once. 1102 <code>Setupterm()</code> also stores the names section of the 1103 terminal description in the global character array 1104 <code>ttytype[]</code>. Subsequent calls to 1105 <code>setupterm()</code> will overwrite this array, so you 1106 will have to save it yourself if need be.</p> 1107 </dd> 1108 </dl> 1109 1110 <h3><a name="debugging" id="debugging">Debugging</a></h3> 1111 1112 <blockquote> 1113 <strong>NOTE:</strong> These functions are not part of the 1114 standard curses API! 1115 </blockquote> 1116 1117 <dl> 1118 <dt><code>trace()</code> 1119 </dt> 1120 1121 <dd>This function can be used to explicitly set a trace level. 1122 If the trace level is nonzero, execution of your program will 1123 generate a file called “trace” in the current 1124 working directory containing a report on the library's actions. 1125 Higher trace levels enable more detailed (and verbose) 1126 reporting -- see comments attached to <code>TRACE_</code> 1127 defines in the <code>curses.h</code> file for details. (It is 1128 also possible to set a trace level by assigning a trace level 1129 value to the environment variable 1130 <code>NCURSES_TRACE</code>).</dd> 1131 1132 <dt><code>_tracef()</code> 1133 </dt> 1134 1135 <dd>This function can be used to output your own debugging 1136 information. It is only available only if you link with 1137 -lncurses_g. It can be used the same way as 1138 <code>printf()</code>, only it outputs a newline after the end 1139 of arguments. The output goes to a file called 1140 <code>trace</code> in the current directory.</dd> 1141 </dl> 1142 1143 <p>Trace logs can be difficult to interpret due to the sheer 1144 volume of data dumped in them. There is a script called 1145 <strong>tracemunch</strong> included with the 1146 <code>ncurses</code> distribution that can alleviate this problem 1147 somewhat; it compacts long sequences of similar operations into 1148 more succinct single-line pseudo-operations. These pseudo-ops can 1149 be distinguished by the fact that they are named in capital 1150 letters.</p> 1151 1152 <h2><a name="hints" id="hints">Hints, Tips, and Tricks</a></h2> 1153 1154 <p>The <code>ncurses</code> manual pages are a complete reference 1155 for this library. In the remainder of this document, we discuss 1156 various useful methods that may not be obvious from the manual 1157 page descriptions.</p> 1158 1159 <h3><a name="caution" id="caution">Some Notes of Caution</a></h3> 1160 1161 <p>If you find yourself thinking you need to use 1162 <code>noraw()</code> or <code>nocbreak()</code>, think again and 1163 move carefully. It is probably better design to use 1164 <code>getstr()</code> or one of its relatives to simulate cooked 1165 mode. The <code>noraw()</code> and <code>nocbreak()</code> 1166 functions try to restore cooked mode, but they may end up 1167 clobbering some control bits set before you started your 1168 application. Also, they have always been poorly documented, and 1169 are likely to hurt your application's usability with other curses 1170 libraries.</p> 1171 1172 <p>Bear in mind that <code>refresh()</code> is a synonym for 1173 <code>wrefresh(stdscr)</code>. Do not try to mix use of 1174 <code>stdscr</code> with use of windows declared by 1175 <code>newwin()</code>; a <code>refresh()</code> call will blow 1176 them off the screen. The right way to handle this is to use 1177 <code>subwin()</code>, or not touch <code>stdscr</code> at all 1178 and tile your screen with declared windows which you then 1179 <code>wnoutrefresh()</code> somewhere in your program event loop, 1180 with a single <code>doupdate()</code> call to trigger actual 1181 repainting.</p> 1182 1183 <p>You are much less likely to run into problems if you design 1184 your screen layouts to use tiled rather than overlapping windows. 1185 Historically, curses support for overlapping windows has been 1186 weak, fragile, and poorly documented. The <code>ncurses</code> 1187 library is not yet an exception to this rule.</p> 1188 1189 <p>There is a panels library included in the <code>ncurses</code> 1190 distribution that does a pretty good job of strengthening the 1191 overlapping-windows facilities.</p> 1192 1193 <p>Try to avoid using the global variables LINES and COLS. Use 1194 <code>getmaxyx()</code> on the <code>stdscr</code> context 1195 instead. Reason: your code may be ported to run in an environment 1196 with window resizes, in which case several screens could be open 1197 with different sizes.</p> 1198 1199 <h3><a name="leaving" id="leaving">Temporarily Leaving NCURSES 1200 Mode</a></h3> 1201 1202 <p>Sometimes you will want to write a program that spends most of 1203 its time in screen mode, but occasionally returns to ordinary 1204 “cooked” mode. A common reason for this is to support 1205 shell-out. This behavior is simple to arrange in 1206 <code>ncurses</code>.</p> 1207 1208 <p>To leave <code>ncurses</code> mode, call <code>endwin()</code> 1209 as you would if you were intending to terminate the program. This 1210 will take the screen back to cooked mode; you can do your 1211 shell-out. When you want to return to <code>ncurses</code> mode, 1212 simply call <code>refresh()</code> or <code>doupdate()</code>. 1213 This will repaint the screen.</p> 1214 1215 <p>There is a boolean function, <code>isendwin()</code>, which 1216 code can use to test whether <code>ncurses</code> screen mode is 1217 active. It returns <code>TRUE</code> in the interval between an 1218 <code>endwin()</code> call and the following 1219 <code>refresh()</code>, <code>FALSE</code> otherwise.</p> 1220 1221 <p>Here is some sample code for shellout:</p> 1222 1223 <pre> 1224 addstr("Shelling out..."); 1225 def_prog_mode(); /* save current tty modes */ 1226 endwin(); /* restore original tty modes */ 1227 system("sh"); /* run shell */ 1228 addstr("returned.\n"); /* prepare return message */ 1229 refresh(); /* restore save modes, repaint screen */ 1230</pre> 1231 1232 <h3><a name="xterm" id="xterm">Using NCURSES under XTERM</a></h3> 1233 1234 <p>A resize operation in X sends <code>SIGWINCH</code> to the 1235 application running under xterm. The easiest way to handle 1236 <code>SIGWINCH</code> is to do an <code>endwin</code>, followed 1237 by an <code>refresh</code> and a screen repaint you code 1238 yourself. The <code>refresh</code> will pick up the new screen 1239 size from the xterm's environment.</p> 1240 1241 <p>That is the standard way, of course (it even works with some 1242 vendor's curses implementations). Its drawback is that it clears 1243 the screen to reinitialize the display, and does not resize 1244 subwindows which must be shrunk. <code>Ncurses</code> provides an 1245 extension which works better, the <code>resizeterm</code> 1246 function. That function ensures that all windows are limited to 1247 the new screen dimensions, and pads <code>stdscr</code> with 1248 blanks if the screen is larger.</p> 1249 1250 <p>The <code>ncurses</code> library provides a SIGWINCH signal 1251 handler, which pushes a <code>KEY_RESIZE</code> via the wgetch() 1252 calls. When <code>ncurses</code> returns that code, it calls 1253 <code>resizeterm</code> to update the size of the standard 1254 screen's window, repainting that (filling with blanks or 1255 truncating as needed). It also resizes other windows, but its 1256 effect may be less satisfactory because it cannot know how you 1257 want the screen re-painted. You will usually have to write 1258 special-purpose code to handle <code>KEY_RESIZE</code> 1259 yourself.</p> 1260 1261 <h3><a name="screens" id="screens">Handling Multiple Terminal 1262 Screens</a></h3> 1263 1264 <p>The <code>initscr()</code> function actually calls a function 1265 named <code>newterm()</code> to do most of its work. If you are 1266 writing a program that opens multiple terminals, use 1267 <code>newterm()</code> directly.</p> 1268 1269 <p>For each call, you will have to specify a terminal type and a 1270 pair of file pointers; each call will return a screen reference, 1271 and <code>stdscr</code> will be set to the last one allocated. 1272 You will switch between screens with the <code>set_term</code> 1273 call. Note that you will also have to call 1274 <code>def_shell_mode</code> and <code>def_prog_mode</code> on 1275 each tty yourself.</p> 1276 1277 <h3><a name="testing" id="testing">Testing for Terminal 1278 Capabilities</a></h3> 1279 1280 <p>Sometimes you may want to write programs that test for the 1281 presence of various capabilities before deciding whether to go 1282 into <code>ncurses</code> mode. An easy way to do this is to call 1283 <code>setupterm()</code>, then use the functions 1284 <code>tigetflag()</code>, <code>tigetnum()</code>, and 1285 <code>tigetstr()</code> to do your testing.</p> 1286 1287 <p>A particularly useful case of this often comes up when you 1288 want to test whether a given terminal type should be treated as 1289 “smart” (cursor-addressable) or “stupid”. 1290 The right way to test this is to see if the return value of 1291 <code>tigetstr("cup")</code> is non-NULL. Alternatively, you can 1292 include the <code>term.h</code> file and test the value of the 1293 macro <code>cursor_address</code>.</p> 1294 1295 <h3><a name="tuning" id="tuning">Tuning for Speed</a></h3> 1296 1297 <p>Use the <code>addchstr()</code> family of functions for fast 1298 screen-painting of text when you know the text does not contain 1299 any control characters. Try to make attribute changes infrequent 1300 on your screens. Do not use the <code>immedok()</code> 1301 option!</p> 1302 1303 <h3><a name="special" id="special">Special Features of 1304 NCURSES</a></h3> 1305 1306 <p>The <code>wresize()</code> function allows you to resize a 1307 window in place. The associated <code>resizeterm()</code> 1308 function simplifies the construction of <a href= 1309 "#xterm">SIGWINCH</a> handlers, for resizing all windows.</p> 1310 1311 <p>The <code>define_key()</code> function allows you to define at 1312 runtime function-key control sequences which are not in the 1313 terminal description. The <code>keyok()</code> function allows 1314 you to temporarily enable or disable interpretation of any 1315 function-key control sequence.</p> 1316 1317 <p>The <code>use_default_colors()</code> function allows you to 1318 construct applications which can use the terminal's default 1319 foreground and background colors as an additional "default" 1320 color. Several terminal emulators support this feature, which is 1321 based on ISO 6429.</p> 1322 1323 <p>Ncurses supports up 16 colors, unlike SVr4 curses which 1324 defines only 8. While most terminals which provide color allow 1325 only 8 colors, about a quarter (including XFree86 xterm) support 1326 16 colors.</p> 1327 1328 <h2><a name="compat" id="compat">Compatibility with Older 1329 Versions</a></h2> 1330 1331 <p>Despite our best efforts, there are some differences between 1332 <code>ncurses</code> and the (undocumented!) behavior of older 1333 curses implementations. These arise from ambiguities or omissions 1334 in the documentation of the API.</p> 1335 1336 <h3><a name="refbug" id="refbug">Refresh of Overlapping 1337 Windows</a></h3> 1338 1339 <p>If you define two windows A and B that overlap, and then 1340 alternately scribble on and refresh them, the changes made to the 1341 overlapping region under historic <code>curses</code> versions 1342 were often not documented precisely.</p> 1343 1344 <p>To understand why this is a problem, remember that screen 1345 updates are calculated between two representations of the 1346 <em>entire</em> display. The documentation says that when you 1347 refresh a window, it is first copied to the virtual screen, and 1348 then changes are calculated to update the physical screen (and 1349 applied to the terminal). But "copied to" is not very specific, 1350 and subtle differences in how copying works can produce different 1351 behaviors in the case where two overlapping windows are each 1352 being refreshed at unpredictable intervals.</p> 1353 1354 <p>What happens to the overlapping region depends on what 1355 <code>wnoutrefresh()</code> does with its argument -- what 1356 portions of the argument window it copies to the virtual screen. 1357 Some implementations do "change copy", copying down only 1358 locations in the window that have changed (or been marked changed 1359 with <code>wtouchln()</code> and friends). Some implementations 1360 do "entire copy", copying <em>all</em> window locations to the 1361 virtual screen whether or not they have changed.</p> 1362 1363 <p>The <code>ncurses</code> library itself has not always been 1364 consistent on this score. Due to a bug, versions 1.8.7 to 1.9.8a 1365 did entire copy. Versions 1.8.6 and older, and versions 1.9.9 and 1366 newer, do change copy.</p> 1367 1368 <p>For most commercial curses implementations, it is not 1369 documented and not known for sure (at least not to the 1370 <code>ncurses</code> maintainers) whether they do change copy or 1371 entire copy. We know that System V release 3 curses has logic in 1372 it that looks like an attempt to do change copy, but the 1373 surrounding logic and data representations are sufficiently 1374 complex, and our knowledge sufficiently indirect, that it is hard 1375 to know whether this is reliable. It is not clear what the SVr4 1376 documentation and XSI standard intend. The XSI Curses standard 1377 barely mentions wnoutrefresh(); the SVr4 documents seem to be 1378 describing entire-copy, but it is possible with some effort and 1379 straining to read them the other way.</p> 1380 1381 <p>It might therefore be unwise to rely on either behavior in 1382 programs that might have to be linked with other curses 1383 implementations. Instead, you can do an explicit 1384 <code>touchwin()</code> before the <code>wnoutrefresh()</code> 1385 call to guarantee an entire-contents copy anywhere.</p> 1386 1387 <p>The really clean way to handle this is to use the panels 1388 library. If, when you want a screen update, you do 1389 <code>update_panels()</code>, it will do all the necessary 1390 <code>wnoutrefresh()</code> calls for whatever panel stacking 1391 order you have defined. Then you can do one 1392 <code>doupdate()</code> and there will be a <em>single</em> burst 1393 of physical I/O that will do all your updates.</p> 1394 1395 <h3><a name="backbug" id="backbug">Background Erase</a></h3> 1396 1397 <p>If you have been using a very old versions of 1398 <code>ncurses</code> (1.8.7 or older) you may be surprised by the 1399 behavior of the erase functions. In older versions, erased areas 1400 of a window were filled with a blank modified by the window's 1401 current attribute (as set by <strong>wattrset()</strong>, 1402 <strong>wattron()</strong>, <strong>wattroff()</strong> and 1403 friends).</p> 1404 1405 <p>In newer versions, this is not so. Instead, the attribute of 1406 erased blanks is normal unless and until it is modified by the 1407 functions <code>bkgdset()</code> or <code>wbkgdset()</code>.</p> 1408 1409 <p>This change in behavior conforms <code>ncurses</code> to 1410 System V Release 4 and the XSI Curses standard.</p> 1411 1412 <h2><a name="xsifuncs" id="xsifuncs">XSI Curses Conformance</a></h2> 1413 1414 <p>The <code>ncurses</code> library is intended to be base-level 1415 conformant with the XSI Curses standard from X/Open. Many 1416 extended-level features (in fact, almost all features not 1417 directly concerned with wide characters and internationalization) 1418 are also supported.</p> 1419 1420 <p>One effect of XSI conformance is the change in behavior 1421 described under <a href="#backbug">"Background Erase -- 1422 Compatibility with Old Versions"</a>.</p> 1423 1424 <p>Also, <code>ncurses</code> meets the XSI requirement that 1425 every macro entry point have a corresponding function which may 1426 be linked (and will be prototype-checked) if the macro definition 1427 is disabled with <code>#undef</code>.</p> 1428 1429 <h1><a name="panels" id="panels">The Panels Library</a></h1> 1430 1431 <p>The <code>ncurses</code> library by itself provides good 1432 support for screen displays in which the windows are tiled 1433 (non-overlapping). In the more general case that windows may 1434 overlap, you have to use a series of <code>wnoutrefresh()</code> 1435 calls followed by a <code>doupdate()</code>, and be careful about 1436 the order you do the window refreshes in. It has to be 1437 bottom-upwards, otherwise parts of windows that should be 1438 obscured will show through.</p> 1439 1440 <p>When your interface design is such that windows may dive 1441 deeper into the visibility stack or pop to the top at runtime, 1442 the resulting book-keeping can be tedious and difficult to get 1443 right. Hence the panels library.</p> 1444 1445 <p>The <code>panel</code> library first appeared in AT&T 1446 System V. The version documented here is the <code>panel</code> 1447 code distributed with <code>ncurses</code>.</p> 1448 1449 <h2><a name="pcompile" id="pcompile">Compiling With the Panels 1450 Library</a></h2> 1451 1452 <p>Your panels-using modules must import the panels library 1453 declarations with</p> 1454 1455 <pre> 1456 #include <panel.h> 1457</pre> 1458 1459 <p>and must be linked explicitly with the panels library using an 1460 <code>-lpanel</code> argument. Note that they must also link the 1461 <code>ncurses</code> library with <code>-lncurses</code>. Many 1462 linkers are two-pass and will accept either order, but it is 1463 still good practice to put <code>-lpanel</code> first and 1464 <code>-lncurses</code> second.</p> 1465 1466 <h2><a name="poverview" id="poverview">Overview of Panels</a></h2> 1467 1468 <p>A panel object is a window that is implicitly treated as part 1469 of a <dfn>deck</dfn> including all other panel objects. The deck 1470 has an implicit bottom-to-top visibility order. The panels 1471 library includes an update function (analogous to 1472 <code>refresh()</code>) that displays all panels in the deck in 1473 the proper order to resolve overlaps. The standard window, 1474 <code>stdscr</code>, is considered below all panels.</p> 1475 1476 <p>Details on the panels functions are available in the man 1477 pages. We will just hit the highlights here.</p> 1478 1479 <p>You create a panel from a window by calling 1480 <code>new_panel()</code> on a window pointer. It then becomes the 1481 top of the deck. The panel's window is available as the value of 1482 <code>panel_window()</code> called with the panel pointer as 1483 argument.</p> 1484 1485 <p>You can delete a panel (removing it from the deck) with 1486 <code>del_panel</code>. This will not deallocate the associated 1487 window; you have to do that yourself. You can replace a panel's 1488 window with a different window by calling 1489 <code>replace_window</code>. The new window may be of different 1490 size; the panel code will re-compute all overlaps. This operation 1491 does not change the panel's position in the deck.</p> 1492 1493 <p>To move a panel's window, use <code>move_panel()</code>. The 1494 <code>mvwin()</code> function on the panel's window is not 1495 sufficient because it does not update the panels library's 1496 representation of where the windows are. This operation leaves 1497 the panel's depth, contents, and size unchanged.</p> 1498 1499 <p>Two functions (<code>top_panel()</code>, 1500 <code>bottom_panel()</code>) are provided for rearranging the 1501 deck. The first pops its argument window to the top of the deck; 1502 the second sends it to the bottom. Either operation leaves the 1503 panel's screen location, contents, and size unchanged.</p> 1504 1505 <p>The function <code>update_panels()</code> does all the 1506 <code>wnoutrefresh()</code> calls needed to prepare for 1507 <code>doupdate()</code> (which you must call yourself, 1508 afterwards).</p> 1509 1510 <p>Typically, you will want to call <code>update_panels()</code> 1511 and <code>doupdate()</code> just before accepting command input, 1512 once in each cycle of interaction with the user. If you call 1513 <code>update_panels()</code> after each and every panel write, 1514 you will generate a lot of unnecessary refresh activity and 1515 screen flicker.</p> 1516 1517 <h2><a name="pstdscr" id="pstdscr">Panels, Input, and the 1518 Standard Screen</a></h2> 1519 1520 <p>You should not mix <code>wnoutrefresh()</code> or 1521 <code>wrefresh()</code> operations with panels code; this will 1522 work only if the argument window is either in the top panel or 1523 unobscured by any other panels.</p> 1524 1525 <p>The <code>stsdcr</code> window is a special case. It is 1526 considered below all panels. Because changes to panels may 1527 obscure parts of <code>stdscr</code>, though, you should call 1528 <code>update_panels()</code> before <code>doupdate()</code> even 1529 when you only change <code>stdscr</code>.</p> 1530 1531 <p>Note that <code>wgetch</code> automatically calls 1532 <code>wrefresh</code>. Therefore, before requesting input from a 1533 panel window, you need to be sure that the panel is totally 1534 unobscured.</p> 1535 1536 <p>There is presently no way to display changes to one obscured 1537 panel without repainting all panels.</p> 1538 1539 <h2><a name="hiding" id="hiding">Hiding Panels</a></h2> 1540 1541 <p>It is possible to remove a panel from the deck temporarily; 1542 use <code>hide_panel</code> for this. Use 1543 <code>show_panel()</code> to render it visible again. The 1544 predicate function <code>panel_hidden</code> tests whether or not 1545 a panel is hidden.</p> 1546 1547 <p>The <code>panel_update</code> code ignores hidden panels. You 1548 cannot do <code>top_panel()</code> or <code>bottom_panel</code> 1549 on a hidden panel(). Other panels operations are applicable.</p> 1550 1551 <h2><a name="pmisc" id="pmisc">Miscellaneous Other Facilities</a></h2> 1552 1553 <p>It is possible to navigate the deck using the functions 1554 <code>panel_above()</code> and <code>panel_below</code>. Handed a 1555 panel pointer, they return the panel above or below that panel. 1556 Handed <code>NULL</code>, they return the bottom-most or top-most 1557 panel.</p> 1558 1559 <p>Every panel has an associated user pointer, not used by the 1560 panel code, to which you can attach application data. See the man 1561 page documentation of <code>set_panel_userptr()</code> and 1562 <code>panel_userptr</code> for details.</p> 1563 1564 <h1><a name="menu" id="menu">The Menu Library</a></h1> 1565 1566 <p>A menu is a screen display that assists the user to choose 1567 some subset of a given set of items. The <code>menu</code> 1568 library is a curses extension that supports easy programming of 1569 menu hierarchies with a uniform but flexible interface.</p> 1570 1571 <p>The <code>menu</code> library first appeared in AT&T 1572 System V. The version documented here is the <code>menu</code> 1573 code distributed with <code>ncurses</code>.</p> 1574 1575 <h2><a name="mcompile" id="mcompile">Compiling With the menu 1576 Library</a></h2> 1577 1578 <p>Your menu-using modules must import the menu library 1579 declarations with</p> 1580 1581 <pre> 1582 #include <menu.h> 1583</pre> 1584 1585 <p>and must be linked explicitly with the menus library using an 1586 <code>-lmenu</code> argument. Note that they must also link the 1587 <code>ncurses</code> library with <code>-lncurses</code>. Many 1588 linkers are two-pass and will accept either order, but it is 1589 still good practice to put <code>-lmenu</code> first and 1590 <code>-lncurses</code> second.</p> 1591 1592 <h2><a name="moverview" id="moverview">Overview of Menus</a></h2> 1593 1594 <p>The menus created by this library consist of collections of 1595 <dfn>items</dfn> including a name string part and a description 1596 string part. To make menus, you create groups of these items and 1597 connect them with menu frame objects.</p> 1598 1599 <p>The menu can then by <dfn>posted</dfn>, that is written to an 1600 associated window. Actually, each menu has two associated 1601 windows; a containing window in which the programmer can scribble 1602 titles or borders, and a subwindow in which the menu items proper 1603 are displayed. If this subwindow is too small to display all the 1604 items, it will be a scrollable viewport on the collection of 1605 items.</p> 1606 1607 <p>A menu may also be <dfn>unposted</dfn> (that is, undisplayed), 1608 and finally freed to make the storage associated with it and its 1609 items available for re-use.</p> 1610 1611 <p>The general flow of control of a menu program looks like 1612 this:</p> 1613 1614 <ol> 1615 <li>Initialize <code>curses</code>.</li> 1616 1617 <li>Create the menu items, using <code>new_item()</code>.</li> 1618 1619 <li>Create the menu using <code>new_menu()</code>.</li> 1620 1621 <li>Post the menu using <code>post_menu()</code>.</li> 1622 1623 <li>Refresh the screen.</li> 1624 1625 <li>Process user requests via an input loop.</li> 1626 1627 <li>Unpost the menu using <code>unpost_menu()</code>.</li> 1628 1629 <li>Free the menu, using <code>free_menu()</code>.</li> 1630 1631 <li>Free the items using <code>free_item()</code>.</li> 1632 1633 <li>Terminate <code>curses</code>.</li> 1634 </ol> 1635 1636 <h2><a name="mselect" id="mselect">Selecting items</a></h2> 1637 1638 <p>Menus may be multi-valued or (the default) single-valued (see 1639 the manual page <code>menu_opts(3x)</code> to see how to change 1640 the default). Both types always have a <dfn>current 1641 item</dfn>.</p> 1642 1643 <p>From a single-valued menu you can read the selected value 1644 simply by looking at the current item. From a multi-valued menu, 1645 you get the selected set by looping through the items applying 1646 the <code>item_value()</code> predicate function. Your 1647 menu-processing code can use the function 1648 <code>set_item_value()</code> to flag the items in the select 1649 set.</p> 1650 1651 <p>Menu items can be made unselectable using 1652 <code>set_item_opts()</code> or <code>item_opts_off()</code> with 1653 the <code>O_SELECTABLE</code> argument. This is the only option 1654 so far defined for menus, but it is good practice to code as 1655 though other option bits might be on.</p> 1656 1657 <h2><a name="mdisplay" id="mdisplay">Menu Display</a></h2> 1658 1659 <p>The menu library calculates a minimum display size for your 1660 window, based on the following variables:</p> 1661 1662 <ul> 1663 <li>The number and maximum length of the menu items</li> 1664 1665 <li>Whether the O_ROWMAJOR option is enabled</li> 1666 1667 <li>Whether display of descriptions is enabled</li> 1668 1669 <li>Whatever menu format may have been set by the 1670 programmer</li> 1671 1672 <li>The length of the menu mark string used for highlighting 1673 selected items</li> 1674 </ul> 1675 1676 <p>The function <code>set_menu_format()</code> allows you to set 1677 the maximum size of the viewport or <dfn>menu page</dfn> that 1678 will be used to display menu items. You can retrieve any format 1679 associated with a menu with <code>menu_format()</code>. The 1680 default format is rows=16, columns=1.</p> 1681 1682 <p>The actual menu page may be smaller than the format size. This 1683 depends on the item number and size and whether O_ROWMAJOR is on. 1684 This option (on by default) causes menu items to be displayed in 1685 a “raster-scan” pattern, so that if more than one 1686 item will fit horizontally the first couple of items are 1687 side-by-side in the top row. The alternative is column-major 1688 display, which tries to put the first several items in the first 1689 column.</p> 1690 1691 <p>As mentioned above, a menu format not large enough to allow 1692 all items to fit on-screen will result in a menu display that is 1693 vertically scrollable.</p> 1694 1695 <p>You can scroll it with requests to the menu driver, which will 1696 be described in the section on <a href="#minput">menu input 1697 handling</a>.</p> 1698 1699 <p>Each menu has a <dfn>mark string</dfn> used to visually tag 1700 selected items; see the <code>menu_mark(3x)</code> manual page 1701 for details. The mark string length also influences the menu page 1702 size.</p> 1703 1704 <p>The function <code>scale_menu()</code> returns the minimum 1705 display size that the menu code computes from all these factors. 1706 There are other menu display attributes including a select 1707 attribute, an attribute for selectable items, an attribute for 1708 unselectable items, and a pad character used to separate item 1709 name text from description text. These have reasonable defaults 1710 which the library allows you to change (see the 1711 <code>menu_attribs(3x)</code> manual page.</p> 1712 1713 <h2><a name="mwindows" id="mwindows">Menu Windows</a></h2> 1714 1715 <p>Each menu has, as mentioned previously, a pair of associated 1716 windows. Both these windows are painted when the menu is posted 1717 and erased when the menu is unposted.</p> 1718 1719 <p>The outer or frame window is not otherwise touched by the menu 1720 routines. It exists so the programmer can associate a title, a 1721 border, or perhaps help text with the menu and have it properly 1722 refreshed or erased at post/unpost time. The inner window or 1723 <dfn>subwindow</dfn> is where the current menu page is 1724 displayed.</p> 1725 1726 <p>By default, both windows are <code>stdscr</code>. You can set 1727 them with the functions in <code>menu_win(3x)</code>.</p> 1728 1729 <p>When you call <code>post_menu()</code>, you write the menu to 1730 its subwindow. When you call <code>unpost_menu()</code>, you 1731 erase the subwindow, However, neither of these actually modifies 1732 the screen. To do that, call <code>wrefresh()</code> or some 1733 equivalent.</p> 1734 1735 <h2><a name="minput" id="minput">Processing Menu Input</a></h2> 1736 1737 <p>The main loop of your menu-processing code should call 1738 <code>menu_driver()</code> repeatedly. The first argument of this 1739 routine is a menu pointer; the second is a menu command code. You 1740 should write an input-fetching routine that maps input characters 1741 to menu command codes, and pass its output to 1742 <code>menu_driver()</code>. The menu command codes are fully 1743 documented in <code>menu_driver(3x)</code>.</p> 1744 1745 <p>The simplest group of command codes is 1746 <code>REQ_NEXT_ITEM</code>, <code>REQ_PREV_ITEM</code>, 1747 <code>REQ_FIRST_ITEM</code>, <code>REQ_LAST_ITEM</code>, 1748 <code>REQ_UP_ITEM</code>, <code>REQ_DOWN_ITEM</code>, 1749 <code>REQ_LEFT_ITEM</code>, <code>REQ_RIGHT_ITEM</code>. These 1750 change the currently selected item. These requests may cause 1751 scrolling of the menu page if it only partially displayed.</p> 1752 1753 <p>There are explicit requests for scrolling which also change 1754 the current item (because the select location does not change, 1755 but the item there does). These are <code>REQ_SCR_DLINE</code>, 1756 <code>REQ_SCR_ULINE</code>, <code>REQ_SCR_DPAGE</code>, and 1757 <code>REQ_SCR_UPAGE</code>.</p> 1758 1759 <p>The <code>REQ_TOGGLE_ITEM</code> selects or deselects the 1760 current item. It is for use in multi-valued menus; if you use it 1761 with <code>O_ONEVALUE</code> on, you will get an error return 1762 (<code>E_REQUEST_DENIED</code>).</p> 1763 1764 <p>Each menu has an associated pattern buffer. The 1765 <code>menu_driver()</code> logic tries to accumulate printable 1766 ASCII characters passed in in that buffer; when it matches a 1767 prefix of an item name, that item (or the next matching item) is 1768 selected. If appending a character yields no new match, that 1769 character is deleted from the pattern buffer, and 1770 <code>menu_driver()</code> returns <code>E_NO_MATCH</code>.</p> 1771 1772 <p>Some requests change the pattern buffer directly: 1773 <code>REQ_CLEAR_PATTERN</code>, <code>REQ_BACK_PATTERN</code>, 1774 <code>REQ_NEXT_MATCH</code>, <code>REQ_PREV_MATCH</code>. The 1775 latter two are useful when pattern buffer input matches more than 1776 one item in a multi-valued menu.</p> 1777 1778 <p>Each successful scroll or item navigation request clears the 1779 pattern buffer. It is also possible to set the pattern buffer 1780 explicitly with <code>set_menu_pattern()</code>.</p> 1781 1782 <p>Finally, menu driver requests above the constant 1783 <code>MAX_COMMAND</code> are considered application-specific 1784 commands. The <code>menu_driver()</code> code ignores them and 1785 returns <code>E_UNKNOWN_COMMAND</code>.</p> 1786 1787 <h2><a name="mmisc" id="mmisc">Miscellaneous Other Features</a></h2> 1788 1789 <p>Various menu options can affect the processing and visual 1790 appearance and input processing of menus. See <code>menu_opts(3x) 1791 for details.</code></p> 1792 1793 <p>It is possible to change the current item from application 1794 code; this is useful if you want to write your own navigation 1795 requests. It is also possible to explicitly set the top row of 1796 the menu display. See <code>mitem_current(3x)</code>. If your 1797 application needs to change the menu subwindow cursor for any 1798 reason, <code>pos_menu_cursor()</code> will restore it to the 1799 correct location for continuing menu driver processing.</p> 1800 1801 <p>It is possible to set hooks to be called at menu 1802 initialization and wrapup time, and whenever the selected item 1803 changes. See <code>menu_hook(3x)</code>.</p> 1804 1805 <p>Each item, and each menu, has an associated user pointer on 1806 which you can hang application data. See 1807 <code>mitem_userptr(3x)</code> and 1808 <code>menu_userptr(3x)</code>.</p> 1809 1810 <h1><a name="form" id="form">The Forms Library</a></h1> 1811 1812 <p>The <code>form</code> library is a curses extension that 1813 supports easy programming of on-screen forms for data entry and 1814 program control.</p> 1815 1816 <p>The <code>form</code> library first appeared in AT&T 1817 System V. The version documented here is the <code>form</code> 1818 code distributed with <code>ncurses</code>.</p> 1819 1820 <h2><a name="fcompile" id="fcompile">Compiling With the form 1821 Library</a></h2> 1822 1823 <p>Your form-using modules must import the form library 1824 declarations with</p> 1825 1826 <pre> 1827 #include <form.h> 1828</pre> 1829 1830 <p>and must be linked explicitly with the forms library using an 1831 <code>-lform</code> argument. Note that they must also link the 1832 <code>ncurses</code> library with <code>-lncurses</code>. Many 1833 linkers are two-pass and will accept either order, but it is 1834 still good practice to put <code>-lform</code> first and 1835 <code>-lncurses</code> second.</p> 1836 1837 <h2><a name="foverview" id="foverview">Overview of Forms</a></h2> 1838 1839 <p>A form is a collection of fields; each field may be either a 1840 label (explanatory text) or a data-entry location. Long forms may 1841 be segmented into pages; each entry to a new page clears the 1842 screen.</p> 1843 1844 <p>To make forms, you create groups of fields and connect them 1845 with form frame objects; the form library makes this relatively 1846 simple.</p> 1847 1848 <p>Once defined, a form can be <dfn>posted</dfn>, that is written 1849 to an associated window. Actually, each form has two associated 1850 windows; a containing window in which the programmer can scribble 1851 titles or borders, and a subwindow in which the form fields 1852 proper are displayed.</p> 1853 1854 <p>As the form user fills out the posted form, navigation and 1855 editing keys support movement between fields, editing keys 1856 support modifying field, and plain text adds to or changes data 1857 in a current field. The form library allows you (the forms 1858 designer) to bind each navigation and editing key to any 1859 keystroke accepted by <code>curses</code> Fields may have 1860 validation conditions on them, so that they check input data for 1861 type and value. The form library supplies a rich set of 1862 pre-defined field types, and makes it relatively easy to define 1863 new ones.</p> 1864 1865 <p>Once its transaction is completed (or aborted), a form may be 1866 <dfn>unposted</dfn> (that is, undisplayed), and finally freed to 1867 make the storage associated with it and its items available for 1868 re-use.</p> 1869 1870 <p>The general flow of control of a form program looks like 1871 this:</p> 1872 1873 <ol> 1874 <li>Initialize <code>curses</code>.</li> 1875 1876 <li>Create the form fields, using 1877 <code>new_field()</code>.</li> 1878 1879 <li>Create the form using <code>new_form()</code>.</li> 1880 1881 <li>Post the form using <code>post_form()</code>.</li> 1882 1883 <li>Refresh the screen.</li> 1884 1885 <li>Process user requests via an input loop.</li> 1886 1887 <li>Unpost the form using <code>unpost_form()</code>.</li> 1888 1889 <li>Free the form, using <code>free_form()</code>.</li> 1890 1891 <li>Free the fields using <code>free_field()</code>.</li> 1892 1893 <li>Terminate <code>curses</code>.</li> 1894 </ol> 1895 1896 <p>Note that this looks much like a menu program; the form 1897 library handles tasks which are in many ways similar, and its 1898 interface was obviously designed to resemble that of the <a href= 1899 "#menu">menu library</a> wherever possible.</p> 1900 1901 <p>In forms programs, however, the “process user 1902 requests” is somewhat more complicated than for menus. 1903 Besides menu-like navigation operations, the menu driver loop has 1904 to support field editing and data validation.</p> 1905 1906 <h2><a name="fcreate" id="fcreate">Creating and Freeing Fields 1907 and Forms</a></h2> 1908 1909 <p>The basic function for creating fields is 1910 <code>new_field()</code>:</p> 1911 1912 <pre> 1913FIELD *new_field(int height, int width, /* new field size */ 1914 int top, int left, /* upper left corner */ 1915 int offscreen, /* number of offscreen rows */ 1916 int nbuf); /* number of working buffers */ 1917</pre> 1918 1919 <p>Menu items always occupy a single row, but forms fields may 1920 have multiple rows. So <code>new_field()</code> requires you to 1921 specify a width and height (the first two arguments, which mist 1922 both be greater than zero).</p> 1923 1924 <p>You must also specify the location of the field's upper left 1925 corner on the screen (the third and fourth arguments, which must 1926 be zero or greater). Note that these coordinates are relative to 1927 the form subwindow, which will coincide with <code>stdscr</code> 1928 by default but need not be <code>stdscr</code> if you have done 1929 an explicit <code>set_form_win()</code> call.</p> 1930 1931 <p>The fifth argument allows you to specify a number of 1932 off-screen rows. If this is zero, the entire field will always be 1933 displayed. If it is nonzero, the form will be scrollable, with 1934 only one screen-full (initially the top part) displayed at any 1935 given time. If you make a field dynamic and grow it so it will no 1936 longer fit on the screen, the form will become scrollable even if 1937 the <code>offscreen</code> argument was initially zero.</p> 1938 1939 <p>The forms library allocates one working buffer per field; the 1940 size of each buffer is <code>((height + offscreen)*width + 1941 1</code>, one character for each position in the field plus a NUL 1942 terminator. The sixth argument is the number of additional data 1943 buffers to allocate for the field; your application can use them 1944 for its own purposes.</p> 1945 1946 <pre> 1947FIELD *dup_field(FIELD *field, /* field to copy */ 1948 int top, int left); /* location of new copy */ 1949</pre> 1950 1951 <p>The function <code>dup_field()</code> duplicates an existing 1952 field at a new location. Size and buffering information are 1953 copied; some attribute flags and status bits are not (see the 1954 <code>form_field_new(3X)</code> for details).</p> 1955 1956 <pre> 1957FIELD *link_field(FIELD *field, /* field to copy */ 1958 int top, int left); /* location of new copy */ 1959</pre> 1960 1961 <p>The function <code>link_field()</code> also duplicates an 1962 existing field at a new location. The difference from 1963 <code>dup_field()</code> is that it arranges for the new field's 1964 buffer to be shared with the old one.</p> 1965 1966 <p>Besides the obvious use in making a field editable from two 1967 different form pages, linked fields give you a way to hack in 1968 dynamic labels. If you declare several fields linked to an 1969 original, and then make them inactive, changes from the original 1970 will still be propagated to the linked fields.</p> 1971 1972 <p>As with duplicated fields, linked fields have attribute bits 1973 separate from the original.</p> 1974 1975 <p>As you might guess, all these field-allocations return 1976 <code>NULL</code> if the field allocation is not possible due to 1977 an out-of-memory error or out-of-bounds arguments.</p> 1978 1979 <p>To connect fields to a form, use</p> 1980 1981 <pre> 1982FORM *new_form(FIELD **fields); 1983</pre> 1984 1985 <p>This function expects to see a NULL-terminated array of field 1986 pointers. Said fields are connected to a newly-allocated form 1987 object; its address is returned (or else NULL if the allocation 1988 fails).</p> 1989 1990 <p>Note that <code>new_field()</code> does <em>not</em> copy the 1991 pointer array into private storage; if you modify the contents of 1992 the pointer array during forms processing, all manner of bizarre 1993 things might happen. Also note that any given field may only be 1994 connected to one form.</p> 1995 1996 <p>The functions <code>free_field()</code> and 1997 <code>free_form</code> are available to free field and form 1998 objects. It is an error to attempt to free a field connected to a 1999 form, but not vice-versa; thus, you will generally free your form 2000 objects first.</p> 2001 2002 <h2><a name="fattributes" id="fattributes">Fetching and Changing 2003 Field Attributes</a></h2> 2004 2005 <p>Each form field has a number of location and size attributes 2006 associated with it. There are other field attributes used to 2007 control display and editing of the field. Some (for example, the 2008 <code>O_STATIC</code> bit) involve sufficient complications to be 2009 covered in sections of their own later on. We cover the functions 2010 used to get and set several basic attributes here.</p> 2011 2012 <p>When a field is created, the attributes not specified by the 2013 <code>new_field</code> function are copied from an invisible 2014 system default field. In attribute-setting and -fetching 2015 functions, the argument NULL is taken to mean this field. Changes 2016 to it persist as defaults until your forms application 2017 terminates.</p> 2018 2019 <h3><a name="fsizes" id="fsizes">Fetching Size and Location 2020 Data</a></h3> 2021 2022 <p>You can retrieve field sizes and locations through:</p> 2023 2024 <pre> 2025int field_info(FIELD *field, /* field from which to fetch */ 2026 int *height, *int width, /* field size */ 2027 int *top, int *left, /* upper left corner */ 2028 int *offscreen, /* number of offscreen rows */ 2029 int *nbuf); /* number of working buffers */ 2030</pre> 2031 2032 <p>This function is a sort of inverse of 2033 <code>new_field()</code>; instead of setting size and location 2034 attributes of a new field, it fetches them from an existing 2035 one.</p> 2036 2037 <h3><a name="flocation" id="flocation">Changing the Field 2038 Location</a></h3> 2039 2040 <p>It is possible to move a field's location on the screen:</p> 2041 2042 <pre> 2043int move_field(FIELD *field, /* field to alter */ 2044 int top, int left); /* new upper-left corner */ 2045</pre> 2046 2047 <p>You can, of course. query the current location through 2048 <code>field_info()</code>.</p> 2049 2050 <h3><a name="fjust" id="fjust">The Justification Attribute</a></h3> 2051 2052 <p>One-line fields may be unjustified, justified right, justified 2053 left, or centered. Here is how you manipulate this attribute:</p> 2054 2055 <pre> 2056int set_field_just(FIELD *field, /* field to alter */ 2057 int justmode); /* mode to set */ 2058 2059int field_just(FIELD *field); /* fetch mode of field */ 2060</pre> 2061 2062 <p>The mode values accepted and returned by this functions are 2063 preprocessor macros <code>NO_JUSTIFICATION</code>, 2064 <code>JUSTIFY_RIGHT</code>, <code>JUSTIFY_LEFT</code>, or 2065 <code>JUSTIFY_CENTER</code>.</p> 2066 2067 <h3><a name="fdispatts" id="fdispatts">Field Display 2068 Attributes</a></h3> 2069 2070 <p>For each field, you can set a foreground attribute for entered 2071 characters, a background attribute for the entire field, and a 2072 pad character for the unfilled portion of the field. You can also 2073 control pagination of the form.</p> 2074 2075 <p>This group of four field attributes controls the visual 2076 appearance of the field on the screen, without affecting in any 2077 way the data in the field buffer.</p> 2078 2079 <pre> 2080int set_field_fore(FIELD *field, /* field to alter */ 2081 chtype attr); /* attribute to set */ 2082 2083chtype field_fore(FIELD *field); /* field to query */ 2084 2085int set_field_back(FIELD *field, /* field to alter */ 2086 chtype attr); /* attribute to set */ 2087 2088chtype field_back(FIELD *field); /* field to query */ 2089 2090int set_field_pad(FIELD *field, /* field to alter */ 2091 int pad); /* pad character to set */ 2092 2093chtype field_pad(FIELD *field); 2094 2095int set_new_page(FIELD *field, /* field to alter */ 2096 int flag); /* TRUE to force new page */ 2097 2098chtype new_page(FIELD *field); /* field to query */ 2099</pre> 2100 2101 <p>The attributes set and returned by the first four functions 2102 are normal <code>curses(3x)</code> display attribute values 2103 (<code>A_STANDOUT</code>, <code>A_BOLD</code>, 2104 <code>A_REVERSE</code> etc). The page bit of a field controls 2105 whether it is displayed at the start of a new form screen.</p> 2106 2107 <h3><a name="foptions" id="foptions">Field Option Bits</a></h3> 2108 2109 <p>There is also a large collection of field option bits you can 2110 set to control various aspects of forms processing. You can 2111 manipulate them with these functions:</p> 2112 2113 <pre> 2114int set_field_opts(FIELD *field, /* field to alter */ 2115 int attr); /* attribute to set */ 2116 2117int field_opts_on(FIELD *field, /* field to alter */ 2118 int attr); /* attributes to turn on */ 2119 2120int field_opts_off(FIELD *field, /* field to alter */ 2121 int attr); /* attributes to turn off */ 2122 2123int field_opts(FIELD *field); /* field to query */ 2124</pre> 2125 2126 <p>By default, all options are on. Here are the available option 2127 bits:</p> 2128 2129 <dl> 2130 <dt>O_VISIBLE</dt> 2131 2132 <dd>Controls whether the field is visible on the screen. Can be 2133 used during form processing to hide or pop up fields depending 2134 on the value of parent fields.</dd> 2135 2136 <dt>O_ACTIVE</dt> 2137 2138 <dd>Controls whether the field is active during forms 2139 processing (i.e. visited by form navigation keys). Can be used 2140 to make labels or derived fields with buffer values alterable 2141 by the forms application, not the user.</dd> 2142 2143 <dt>O_PUBLIC</dt> 2144 2145 <dd>Controls whether data is displayed during field entry. If 2146 this option is turned off on a field, the library will accept 2147 and edit data in that field, but it will not be displayed and 2148 the visible field cursor will not move. You can turn off the 2149 O_PUBLIC bit to define password fields.</dd> 2150 2151 <dt>O_EDIT</dt> 2152 2153 <dd>Controls whether the field's data can be modified. When 2154 this option is off, all editing requests except 2155 <code>REQ_PREV_CHOICE</code> and <code>REQ_NEXT_CHOICE</code> 2156 will fail. Such read-only fields may be useful for help 2157 messages.</dd> 2158 2159 <dt>O_WRAP</dt> 2160 2161 <dd>Controls word-wrapping in multi-line fields. Normally, when 2162 any character of a (blank-separated) word reaches the end of 2163 the current line, the entire word is wrapped to the next line 2164 (assuming there is one). When this option is off, the word will 2165 be split across the line break.</dd> 2166 2167 <dt>O_BLANK</dt> 2168 2169 <dd>Controls field blanking. When this option is on, entering a 2170 character at the first field position erases the entire field 2171 (except for the just-entered character).</dd> 2172 2173 <dt>O_AUTOSKIP</dt> 2174 2175 <dd>Controls automatic skip to next field when this one fills. 2176 Normally, when the forms user tries to type more data into a 2177 field than will fit, the editing location jumps to next field. 2178 When this option is off, the user's cursor will hang at the end 2179 of the field. This option is ignored in dynamic fields that 2180 have not reached their size limit.</dd> 2181 2182 <dt>O_NULLOK</dt> 2183 2184 <dd>Controls whether <a href="#fvalidation">validation</a> is 2185 applied to blank fields. Normally, it is not; the user can 2186 leave a field blank without invoking the usual validation check 2187 on exit. If this option is off on a field, exit from it will 2188 invoke a validation check.</dd> 2189 2190 <dt>O_PASSOK</dt> 2191 2192 <dd>Controls whether validation occurs on every exit, or only 2193 after the field is modified. Normally the latter is true. 2194 Setting O_PASSOK may be useful if your field's validation 2195 function may change during forms processing.</dd> 2196 2197 <dt>O_STATIC</dt> 2198 2199 <dd>Controls whether the field is fixed to its initial 2200 dimensions. If you turn this off, the field becomes <a href= 2201 "#fdynamic">dynamic</a> and will stretch to fit entered 2202 data.</dd> 2203 </dl> 2204 2205 <p>A field's options cannot be changed while the field is 2206 currently selected. However, options may be changed on posted 2207 fields that are not current.</p> 2208 2209 <p>The option values are bit-masks and can be composed with 2210 logical-or in the obvious way.</p> 2211 2212 <h2><a name="fstatus" id="fstatus">Field Status</a></h2> 2213 2214 <p>Every field has a status flag, which is set to FALSE when the 2215 field is created and TRUE when the value in field buffer 0 2216 changes. This flag can be queried and set directly:</p> 2217 2218 <pre> 2219int set_field_status(FIELD *field, /* field to alter */ 2220 int status); /* mode to set */ 2221 2222int field_status(FIELD *field); /* fetch mode of field */ 2223</pre> 2224 2225 <p>Setting this flag under program control can be useful if you 2226 use the same form repeatedly, looking for modified fields each 2227 time.</p> 2228 2229 <p>Calling <code>field_status()</code> on a field not currently 2230 selected for input will return a correct value. Calling 2231 <code>field_status()</code> on a field that is currently selected 2232 for input may not necessarily give a correct field status value, 2233 because entered data is not necessarily copied to buffer zero 2234 before the exit validation check. To guarantee that the returned 2235 status value reflects reality, call <code>field_status()</code> 2236 either (1) in the field's exit validation check routine, (2) from 2237 the field's or form's initialization or termination hooks, or (3) 2238 just after a <code>REQ_VALIDATION</code> request has been 2239 processed by the forms driver.</p> 2240 2241 <h2><a name="fuser" id="fuser">Field User Pointer</a></h2> 2242 2243 <p>Each field structure contains one character pointer slot that 2244 is not used by the forms library. It is intended to be used by 2245 applications to store private per-field data. You can manipulate 2246 it with:</p> 2247 2248 <pre> 2249int set_field_userptr(FIELD *field, /* field to alter */ 2250 char *userptr); /* mode to set */ 2251 2252char *field_userptr(FIELD *field); /* fetch mode of field */ 2253</pre>(Properly, this user pointer field ought to have <code>(void 2254*)</code> type. The <code>(char *)</code> type is retained for 2255System V compatibility.) 2256 2257 <p>It is valid to set the user pointer of the default field (with 2258 a <code>set_field_userptr()</code> call passed a NULL field 2259 pointer.) When a new field is created, the default-field user 2260 pointer is copied to initialize the new field's user pointer.</p> 2261 2262 <h2><a name="fdynamic" id="fdynamic">Variable-Sized Fields</a></h2> 2263 2264 <p>Normally, a field is fixed at the size specified for it at 2265 creation time. If, however, you turn off its O_STATIC bit, it 2266 becomes <dfn>dynamic</dfn> and will automatically resize itself 2267 to accommodate data as it is entered. If the field has extra 2268 buffers associated with it, they will grow right along with the 2269 main input buffer.</p> 2270 2271 <p>A one-line dynamic field will have a fixed height (1) but 2272 variable width, scrolling horizontally to display data within the 2273 field area as originally dimensioned and located. A multi-line 2274 dynamic field will have a fixed width, but variable height 2275 (number of rows), scrolling vertically to display data within the 2276 field area as originally dimensioned and located.</p> 2277 2278 <p>Normally, a dynamic field is allowed to grow without limit. 2279 But it is possible to set an upper limit on the size of a dynamic 2280 field. You do it with this function:</p> 2281 2282 <pre> 2283int set_max_field(FIELD *field, /* field to alter (may not be NULL) */ 2284 int max_size); /* upper limit on field size */ 2285</pre> 2286 2287 <p>If the field is one-line, <code>max_size</code> is taken to be 2288 a column size limit; if it is multi-line, it is taken to be a 2289 line size limit. To disable any limit, use an argument of zero. 2290 The growth limit can be changed whether or not the O_STATIC bit 2291 is on, but has no effect until it is.</p> 2292 2293 <p>The following properties of a field change when it becomes 2294 dynamic:</p> 2295 2296 <ul> 2297 <li>If there is no growth limit, there is no final position of 2298 the field; therefore <code>O_AUTOSKIP</code> and 2299 <code>O_NL_OVERLOAD</code> are ignored.</li> 2300 2301 <li>Field justification will be ignored (though whatever 2302 justification is set up will be retained internally and can be 2303 queried).</li> 2304 2305 <li>The <code>dup_field()</code> and <code>link_field()</code> 2306 calls copy dynamic-buffer sizes. If the <code>O_STATIC</code> 2307 option is set on one of a collection of links, buffer resizing 2308 will occur only when the field is edited through that 2309 link.</li> 2310 2311 <li>The call <code>field_info()</code> will retrieve the 2312 original static size of the field; use 2313 <code>dynamic_field_info()</code> to get the actual dynamic 2314 size.</li> 2315 </ul> 2316 2317 <h2><a name="fvalidation" id="fvalidation">Field Validation</a></h2> 2318 2319 <p>By default, a field will accept any data that will fit in its 2320 input buffer. However, it is possible to attach a validation type 2321 to a field. If you do this, any attempt to leave the field while 2322 it contains data that does not match the validation type will 2323 fail. Some validation types also have a character-validity check 2324 for each time a character is entered in the field.</p> 2325 2326 <p>A field's validation check (if any) is not called when 2327 <code>set_field_buffer()</code> modifies the input buffer, nor 2328 when that buffer is changed through a linked field.</p> 2329 2330 <p>The <code>form</code> library provides a rich set of 2331 pre-defined validation types, and gives you the capability to 2332 define custom ones of your own. You can examine and change field 2333 validation attributes with the following functions:</p> 2334 2335 <pre> 2336int set_field_type(FIELD *field, /* field to alter */ 2337 FIELDTYPE *ftype, /* type to associate */ 2338 ...); /* additional arguments*/ 2339 2340FIELDTYPE *field_type(FIELD *field); /* field to query */ 2341</pre> 2342 2343 <p>The validation type of a field is considered an attribute of 2344 the field. As with other field attributes, Also, doing 2345 <code>set_field_type()</code> with a <code>NULL</code> field 2346 default will change the system default for validation of 2347 newly-created fields.</p> 2348 2349 <p>Here are the pre-defined validation types:</p> 2350 2351 <h3><a name="ftype_alpha" id="ftype_alpha">TYPE_ALPHA</a></h3> 2352 2353 <p>This field type accepts alphabetic data; no blanks, no digits, 2354 no special characters (this is checked at character-entry time). 2355 It is set up with:</p> 2356 2357 <pre> 2358int set_field_type(FIELD *field, /* field to alter */ 2359 TYPE_ALPHA, /* type to associate */ 2360 int width); /* maximum width of field */ 2361</pre> 2362 2363 <p>The <code>width</code> argument sets a minimum width of data. 2364 Typically you will want to set this to the field width; if it is 2365 greater than the field width, the validation check will always 2366 fail. A minimum width of zero makes field completion 2367 optional.</p> 2368 2369 <h3><a name="ftype_alnum" id="ftype_alnum">TYPE_ALNUM</a></h3> 2370 2371 <p>This field type accepts alphabetic data and digits; no blanks, 2372 no special characters (this is checked at character-entry time). 2373 It is set up with:</p> 2374 2375 <pre> 2376int set_field_type(FIELD *field, /* field to alter */ 2377 TYPE_ALNUM, /* type to associate */ 2378 int width); /* maximum width of field */ 2379</pre> 2380 2381 <p>The <code>width</code> argument sets a minimum width of data. 2382 As with TYPE_ALPHA, typically you will want to set this to the 2383 field width; if it is greater than the field width, the 2384 validation check will always fail. A minimum width of zero makes 2385 field completion optional.</p> 2386 2387 <h3><a name="ftype_enum" id="ftype_enum">TYPE_ENUM</a></h3> 2388 2389 <p>This type allows you to restrict a field's values to be among 2390 a specified set of string values (for example, the two-letter 2391 postal codes for U.S. states). It is set up with:</p> 2392 2393 <pre> 2394int set_field_type(FIELD *field, /* field to alter */ 2395 TYPE_ENUM, /* type to associate */ 2396 char **valuelist; /* list of possible values */ 2397 int checkcase; /* case-sensitive? */ 2398 int checkunique); /* must specify uniquely? */ 2399</pre> 2400 2401 <p>The <code>valuelist</code> parameter must point at a 2402 NULL-terminated list of valid strings. The <code>checkcase</code> 2403 argument, if true, makes comparison with the string 2404 case-sensitive.</p> 2405 2406 <p>When the user exits a TYPE_ENUM field, the validation 2407 procedure tries to complete the data in the buffer to a valid 2408 entry. If a complete choice string has been entered, it is of 2409 course valid. But it is also possible to enter a prefix of a 2410 valid string and have it completed for you.</p> 2411 2412 <p>By default, if you enter such a prefix and it matches more 2413 than one value in the string list, the prefix will be completed 2414 to the first matching value. But the <code>checkunique</code> 2415 argument, if true, requires prefix matches to be unique in order 2416 to be valid.</p> 2417 2418 <p>The <code>REQ_NEXT_CHOICE</code> and 2419 <code>REQ_PREV_CHOICE</code> input requests can be particularly 2420 useful with these fields.</p> 2421 2422 <h3><a name="ftype_integer" id="ftype_integer">TYPE_INTEGER</a></h3> 2423 2424 <p>This field type accepts an integer. It is set up as 2425 follows:</p> 2426 2427 <pre> 2428int set_field_type(FIELD *field, /* field to alter */ 2429 TYPE_INTEGER, /* type to associate */ 2430 int padding, /* # places to zero-pad to */ 2431 int vmin, int vmax); /* valid range */ 2432</pre> 2433 2434 <p>Valid characters consist of an optional leading minus and 2435 digits. The range check is performed on exit. If the range 2436 maximum is less than or equal to the minimum, the range is 2437 ignored.</p> 2438 2439 <p>If the value passes its range check, it is padded with as many 2440 leading zero digits as necessary to meet the padding 2441 argument.</p> 2442 2443 <p>A <code>TYPE_INTEGER</code> value buffer can conveniently be 2444 interpreted with the C library function <code>atoi(3)</code>.</p> 2445 2446 <h3><a name="ftype_numeric" id="ftype_numeric">TYPE_NUMERIC</a></h3> 2447 2448 <p>This field type accepts a decimal number. It is set up as 2449 follows:</p> 2450 2451 <pre> 2452int set_field_type(FIELD *field, /* field to alter */ 2453 TYPE_NUMERIC, /* type to associate */ 2454 int padding, /* # places of precision */ 2455 double vmin, double vmax); /* valid range */ 2456</pre> 2457 2458 <p>Valid characters consist of an optional leading minus and 2459 digits. possibly including a decimal point. If your system 2460 supports locale's, the decimal point character used must be the 2461 one defined by your locale. The range check is performed on exit. 2462 If the range maximum is less than or equal to the minimum, the 2463 range is ignored.</p> 2464 2465 <p>If the value passes its range check, it is padded with as many 2466 trailing zero digits as necessary to meet the padding 2467 argument.</p> 2468 2469 <p>A <code>TYPE_NUMERIC</code> value buffer can conveniently be 2470 interpreted with the C library function <code>atof(3)</code>.</p> 2471 2472 <h3><a name="ftype_regexp" id="ftype_regexp">TYPE_REGEXP</a></h3> 2473 2474 <p>This field type accepts data matching a regular expression. It 2475 is set up as follows:</p> 2476 2477 <pre> 2478int set_field_type(FIELD *field, /* field to alter */ 2479 TYPE_REGEXP, /* type to associate */ 2480 char *regexp); /* expression to match */ 2481</pre> 2482 2483 <p>The syntax for regular expressions is that of 2484 <code>regcomp(3)</code>. The check for regular-expression match 2485 is performed on exit.</p> 2486 2487 <h2><a name="fbuffer" id="fbuffer">Direct Field Buffer 2488 Manipulation</a></h2> 2489 2490 <p>The chief attribute of a field is its buffer contents. When a 2491 form has been completed, your application usually needs to know 2492 the state of each field buffer. You can find this out with:</p> 2493 2494 <pre> 2495char *field_buffer(FIELD *field, /* field to query */ 2496 int bufindex); /* number of buffer to query */ 2497</pre> 2498 2499 <p>Normally, the state of the zero-numbered buffer for each field 2500 is set by the user's editing actions on that field. It is 2501 sometimes useful to be able to set the value of the zero-numbered 2502 (or some other) buffer from your application:</p> 2503 2504 <pre> 2505int set_field_buffer(FIELD *field, /* field to alter */ 2506 int bufindex, /* number of buffer to alter */ 2507 char *value); /* string value to set */ 2508</pre> 2509 2510 <p>If the field is not large enough and cannot be resized to a 2511 sufficiently large size to contain the specified value, the value 2512 will be truncated to fit.</p> 2513 2514 <p>Calling <code>field_buffer()</code> with a null field pointer 2515 will raise an error. Calling <code>field_buffer()</code> on a 2516 field not currently selected for input will return a correct 2517 value. Calling <code>field_buffer()</code> on a field that is 2518 currently selected for input may not necessarily give a correct 2519 field buffer value, because entered data is not necessarily 2520 copied to buffer zero before the exit validation check. To 2521 guarantee that the returned buffer value reflects on-screen 2522 reality, call <code>field_buffer()</code> either (1) in the 2523 field's exit validation check routine, (2) from the field's or 2524 form's initialization or termination hooks, or (3) just after a 2525 <code>REQ_VALIDATION</code> request has been processed by the 2526 forms driver.</p> 2527 2528 <h2><a name="formattrs" id="formattrs">Attributes of Forms</a></h2> 2529 2530 <p>As with field attributes, form attributes inherit a default 2531 from a system default form structure. These defaults can be 2532 queried or set by of these functions using a form-pointer 2533 argument of <code>NULL</code>.</p> 2534 2535 <p>The principal attribute of a form is its field list. You can 2536 query and change this list with:</p> 2537 2538 <pre> 2539int set_form_fields(FORM *form, /* form to alter */ 2540 FIELD **fields); /* fields to connect */ 2541 2542char *form_fields(FORM *form); /* fetch fields of form */ 2543 2544int field_count(FORM *form); /* count connect fields */ 2545</pre> 2546 2547 <p>The second argument of <code>set_form_fields()</code> may be a 2548 NULL-terminated field pointer array like the one required by 2549 <code>new_form()</code>. In that case, the old fields of the form 2550 are disconnected but not freed (and eligible to be connected to 2551 other forms), then the new fields are connected.</p> 2552 2553 <p>It may also be null, in which case the old fields are 2554 disconnected (and not freed) but no new ones are connected.</p> 2555 2556 <p>The <code>field_count()</code> function simply counts the 2557 number of fields connected to a given from. It returns -1 if the 2558 form-pointer argument is NULL.</p> 2559 2560 <h2><a name="fdisplay" id="fdisplay">Control of Form Display</a></h2> 2561 2562 <p>In the overview section, you saw that to display a form you 2563 normally start by defining its size (and fields), posting it, and 2564 refreshing the screen. There is an hidden step before posting, 2565 which is the association of the form with a frame window 2566 (actually, a pair of windows) within which it will be displayed. 2567 By default, the forms library associates every form with the 2568 full-screen window <code>stdscr</code>.</p> 2569 2570 <p>By making this step explicit, you can associate a form with a 2571 declared frame window on your screen display. This can be useful 2572 if you want to adapt the form display to different screen sizes, 2573 dynamically tile forms on the screen, or use a form as part of an 2574 interface layout managed by <a href="#panels">panels</a>.</p> 2575 2576 <p>The two windows associated with each form have the same 2577 functions as their analogues in the <a href="#menu">menu 2578 library</a>. Both these windows are painted when the form is 2579 posted and erased when the form is unposted.</p> 2580 2581 <p>The outer or frame window is not otherwise touched by the form 2582 routines. It exists so the programmer can associate a title, a 2583 border, or perhaps help text with the form and have it properly 2584 refreshed or erased at post/unpost time. The inner window or 2585 subwindow is where the current form page is actually 2586 displayed.</p> 2587 2588 <p>In order to declare your own frame window for a form, you will 2589 need to know the size of the form's bounding rectangle. You can 2590 get this information with:</p> 2591 2592 <pre> 2593int scale_form(FORM *form, /* form to query */ 2594 int *rows, /* form rows */ 2595 int *cols); /* form cols */ 2596</pre> 2597 2598 <p>The form dimensions are passed back in the locations pointed 2599 to by the arguments. Once you have this information, you can use 2600 it to declare of windows, then use one of these functions:</p> 2601 2602 <pre> 2603int set_form_win(FORM *form, /* form to alter */ 2604 WINDOW *win); /* frame window to connect */ 2605 2606WINDOW *form_win(FORM *form); /* fetch frame window of form */ 2607 2608int set_form_sub(FORM *form, /* form to alter */ 2609 WINDOW *win); /* form subwindow to connect */ 2610 2611WINDOW *form_sub(FORM *form); /* fetch form subwindow of form */ 2612</pre> 2613 2614 <p>Note that curses operations, including <code>refresh()</code>, 2615 on the form, should be done on the frame window, not the form 2616 subwindow.</p> 2617 2618 <p>It is possible to check from your application whether all of a 2619 scrollable field is actually displayed within the menu subwindow. 2620 Use these functions:</p> 2621 2622 <pre> 2623int data_ahead(FORM *form); /* form to be queried */ 2624 2625int data_behind(FORM *form); /* form to be queried */ 2626</pre> 2627 2628 <p>The function <code>data_ahead()</code> returns TRUE if (a) the 2629 current field is one-line and has undisplayed data off to the 2630 right, (b) the current field is multi-line and there is data 2631 off-screen below it.</p> 2632 2633 <p>The function <code>data_behind()</code> returns TRUE if the 2634 first (upper left hand) character position is off-screen (not 2635 being displayed).</p> 2636 2637 <p>Finally, there is a function to restore the form window's 2638 cursor to the value expected by the forms driver:</p> 2639 2640 <pre> 2641int pos_form_cursor(FORM *) /* form to be queried */ 2642</pre> 2643 2644 <p>If your application changes the form window cursor, call this 2645 function before handing control back to the forms driver in order 2646 to re-synchronize it.</p> 2647 2648 <h2><a name="fdriver" id="fdriver">Input Processing in the Forms 2649 Driver</a></h2> 2650 2651 <p>The function <code>form_driver()</code> handles virtualized 2652 input requests for form navigation, editing, and validation 2653 requests, just as <code>menu_driver</code> does for menus (see 2654 the section on <a href="#minput">menu input handling</a>).</p> 2655 2656 <pre> 2657int form_driver(FORM *form, /* form to pass input to */ 2658 int request); /* form request code */ 2659</pre> 2660 2661 <p>Your input virtualization function needs to take input and 2662 then convert it to either an alphanumeric character (which is 2663 treated as data to be entered in the currently-selected field), 2664 or a forms processing request.</p> 2665 2666 <p>The forms driver provides hooks (through input-validation and 2667 field-termination functions) with which your application code can 2668 check that the input taken by the driver matched what was 2669 expected.</p> 2670 2671 <h3><a name="fpage" id="fpage">Page Navigation Requests</a></h3> 2672 2673 <p>These requests cause page-level moves through the form, 2674 triggering display of a new form screen.</p> 2675 2676 <dl> 2677 <dt><code>REQ_NEXT_PAGE</code> 2678 </dt> 2679 2680 <dd>Move to the next form page.</dd> 2681 2682 <dt><code>REQ_PREV_PAGE</code> 2683 </dt> 2684 2685 <dd>Move to the previous form page.</dd> 2686 2687 <dt><code>REQ_FIRST_PAGE</code> 2688 </dt> 2689 2690 <dd>Move to the first form page.</dd> 2691 2692 <dt><code>REQ_LAST_PAGE</code> 2693 </dt> 2694 2695 <dd>Move to the last form page.</dd> 2696 </dl> 2697 2698 <p>These requests treat the list as cyclic; that is, 2699 <code>REQ_NEXT_PAGE</code> from the last page goes to the first, 2700 and <code>REQ_PREV_PAGE</code> from the first page goes to the 2701 last.</p> 2702 2703 <h3><a name="ffield" id="ffield">Inter-Field Navigation 2704 Requests</a></h3> 2705 2706 <p>These requests handle navigation between fields on the same 2707 page.</p> 2708 2709 <dl> 2710 <dt><code>REQ_NEXT_FIELD</code> 2711 </dt> 2712 2713 <dd>Move to next field.</dd> 2714 2715 <dt><code>REQ_PREV_FIELD</code> 2716 </dt> 2717 2718 <dd>Move to previous field.</dd> 2719 2720 <dt><code>REQ_FIRST_FIELD</code> 2721 </dt> 2722 2723 <dd>Move to the first field.</dd> 2724 2725 <dt><code>REQ_LAST_FIELD</code> 2726 </dt> 2727 2728 <dd>Move to the last field.</dd> 2729 2730 <dt><code>REQ_SNEXT_FIELD</code> 2731 </dt> 2732 2733 <dd>Move to sorted next field.</dd> 2734 2735 <dt><code>REQ_SPREV_FIELD</code> 2736 </dt> 2737 2738 <dd>Move to sorted previous field.</dd> 2739 2740 <dt><code>REQ_SFIRST_FIELD</code> 2741 </dt> 2742 2743 <dd>Move to the sorted first field.</dd> 2744 2745 <dt><code>REQ_SLAST_FIELD</code> 2746 </dt> 2747 2748 <dd>Move to the sorted last field.</dd> 2749 2750 <dt><code>REQ_LEFT_FIELD</code> 2751 </dt> 2752 2753 <dd>Move left to field.</dd> 2754 2755 <dt><code>REQ_RIGHT_FIELD</code> 2756 </dt> 2757 2758 <dd>Move right to field.</dd> 2759 2760 <dt><code>REQ_UP_FIELD</code> 2761 </dt> 2762 2763 <dd>Move up to field.</dd> 2764 2765 <dt><code>REQ_DOWN_FIELD</code> 2766 </dt> 2767 2768 <dd>Move down to field.</dd> 2769 </dl> 2770 2771 <p>These requests treat the list of fields on a page as cyclic; 2772 that is, <code>REQ_NEXT_FIELD</code> from the last field goes to 2773 the first, and <code>REQ_PREV_FIELD</code> from the first field 2774 goes to the last. The order of the fields for these (and the 2775 <code>REQ_FIRST_FIELD</code> and <code>REQ_LAST_FIELD</code> 2776 requests) is simply the order of the field pointers in the form 2777 array (as set up by <code>new_form()</code> or 2778 <code>set_form_fields()</code></p> 2779 2780 <p>It is also possible to traverse the fields as if they had been 2781 sorted in screen-position order, so the sequence goes 2782 left-to-right and top-to-bottom. To do this, use the second group 2783 of four sorted-movement requests.</p> 2784 2785 <p>Finally, it is possible to move between fields using visual 2786 directions up, down, right, and left. To accomplish this, use the 2787 third group of four requests. Note, however, that the position of 2788 a form for purposes of these requests is its upper-left 2789 corner.</p> 2790 2791 <p>For example, suppose you have a multi-line field B, and two 2792 single-line fields A and C on the same line with B, with A to the 2793 left of B and C to the right of B. A <code>REQ_MOVE_RIGHT</code> 2794 from A will go to B only if A, B, and C <em>all</em> share the 2795 same first line; otherwise it will skip over B to C.</p> 2796 2797 <h3><a name="fifield" id="fifield">Intra-Field Navigation 2798 Requests</a></h3> 2799 2800 <p>These requests drive movement of the edit cursor within the 2801 currently selected field.</p> 2802 2803 <dl> 2804 <dt><code>REQ_NEXT_CHAR</code> 2805 </dt> 2806 2807 <dd>Move to next character.</dd> 2808 2809 <dt><code>REQ_PREV_CHAR</code> 2810 </dt> 2811 2812 <dd>Move to previous character.</dd> 2813 2814 <dt><code>REQ_NEXT_LINE</code> 2815 </dt> 2816 2817 <dd>Move to next line.</dd> 2818 2819 <dt><code>REQ_PREV_LINE</code> 2820 </dt> 2821 2822 <dd>Move to previous line.</dd> 2823 2824 <dt><code>REQ_NEXT_WORD</code> 2825 </dt> 2826 2827 <dd>Move to next word.</dd> 2828 2829 <dt><code>REQ_PREV_WORD</code> 2830 </dt> 2831 2832 <dd>Move to previous word.</dd> 2833 2834 <dt><code>REQ_BEG_FIELD</code> 2835 </dt> 2836 2837 <dd>Move to beginning of field.</dd> 2838 2839 <dt><code>REQ_END_FIELD</code> 2840 </dt> 2841 2842 <dd>Move to end of field.</dd> 2843 2844 <dt><code>REQ_BEG_LINE</code> 2845 </dt> 2846 2847 <dd>Move to beginning of line.</dd> 2848 2849 <dt><code>REQ_END_LINE</code> 2850 </dt> 2851 2852 <dd>Move to end of line.</dd> 2853 2854 <dt><code>REQ_LEFT_CHAR</code> 2855 </dt> 2856 2857 <dd>Move left in field.</dd> 2858 2859 <dt><code>REQ_RIGHT_CHAR</code> 2860 </dt> 2861 2862 <dd>Move right in field.</dd> 2863 2864 <dt><code>REQ_UP_CHAR</code> 2865 </dt> 2866 2867 <dd>Move up in field.</dd> 2868 2869 <dt><code>REQ_DOWN_CHAR</code> 2870 </dt> 2871 2872 <dd>Move down in field.</dd> 2873 </dl> 2874 2875 <p>Each <em>word</em> is separated from the previous and next 2876 characters by whitespace. The commands to move to beginning and 2877 end of line or field look for the first or last non-pad character 2878 in their ranges.</p> 2879 2880 <h3><a name="fscroll" id="fscroll">Scrolling Requests</a></h3> 2881 2882 <p>Fields that are dynamic and have grown and fields explicitly 2883 created with offscreen rows are scrollable. One-line fields 2884 scroll horizontally; multi-line fields scroll vertically. Most 2885 scrolling is triggered by editing and intra-field movement (the 2886 library scrolls the field to keep the cursor visible). It is 2887 possible to explicitly request scrolling with the following 2888 requests:</p> 2889 2890 <dl> 2891 <dt><code>REQ_SCR_FLINE</code> 2892 </dt> 2893 2894 <dd>Scroll vertically forward a line.</dd> 2895 2896 <dt><code>REQ_SCR_BLINE</code> 2897 </dt> 2898 2899 <dd>Scroll vertically backward a line.</dd> 2900 2901 <dt><code>REQ_SCR_FPAGE</code> 2902 </dt> 2903 2904 <dd>Scroll vertically forward a page.</dd> 2905 2906 <dt><code>REQ_SCR_BPAGE</code> 2907 </dt> 2908 2909 <dd>Scroll vertically backward a page.</dd> 2910 2911 <dt><code>REQ_SCR_FHPAGE</code> 2912 </dt> 2913 2914 <dd>Scroll vertically forward half a page.</dd> 2915 2916 <dt><code>REQ_SCR_BHPAGE</code> 2917 </dt> 2918 2919 <dd>Scroll vertically backward half a page.</dd> 2920 2921 <dt><code>REQ_SCR_FCHAR</code> 2922 </dt> 2923 2924 <dd>Scroll horizontally forward a character.</dd> 2925 2926 <dt><code>REQ_SCR_BCHAR</code> 2927 </dt> 2928 2929 <dd>Scroll horizontally backward a character.</dd> 2930 2931 <dt><code>REQ_SCR_HFLINE</code> 2932 </dt> 2933 2934 <dd>Scroll horizontally one field width forward.</dd> 2935 2936 <dt><code>REQ_SCR_HBLINE</code> 2937 </dt> 2938 2939 <dd>Scroll horizontally one field width backward.</dd> 2940 2941 <dt><code>REQ_SCR_HFHALF</code> 2942 </dt> 2943 2944 <dd>Scroll horizontally one half field width forward.</dd> 2945 2946 <dt><code>REQ_SCR_HBHALF</code> 2947 </dt> 2948 2949 <dd>Scroll horizontally one half field width backward.</dd> 2950 </dl> 2951 2952 <p>For scrolling purposes, a <em>page</em> of a field is the 2953 height of its visible part.</p> 2954 2955 <h3><a name="fedit" id="fedit">Editing Requests</a></h3> 2956 2957 <p>When you pass the forms driver an ASCII character, it is 2958 treated as a request to add the character to the field's data 2959 buffer. Whether this is an insertion or a replacement depends on 2960 the field's edit mode (insertion is the default.</p> 2961 2962 <p>The following requests support editing the field and changing 2963 the edit mode:</p> 2964 2965 <dl> 2966 <dt><code>REQ_INS_MODE</code> 2967 </dt> 2968 2969 <dd>Set insertion mode.</dd> 2970 2971 <dt><code>REQ_OVL_MODE</code> 2972 </dt> 2973 2974 <dd>Set overlay mode.</dd> 2975 2976 <dt><code>REQ_NEW_LINE</code> 2977 </dt> 2978 2979 <dd>New line request (see below for explanation).</dd> 2980 2981 <dt><code>REQ_INS_CHAR</code> 2982 </dt> 2983 2984 <dd>Insert space at character location.</dd> 2985 2986 <dt><code>REQ_INS_LINE</code> 2987 </dt> 2988 2989 <dd>Insert blank line at character location.</dd> 2990 2991 <dt><code>REQ_DEL_CHAR</code> 2992 </dt> 2993 2994 <dd>Delete character at cursor.</dd> 2995 2996 <dt><code>REQ_DEL_PREV</code> 2997 </dt> 2998 2999 <dd>Delete previous word at cursor.</dd> 3000 3001 <dt><code>REQ_DEL_LINE</code> 3002 </dt> 3003 3004 <dd>Delete line at cursor.</dd> 3005 3006 <dt><code>REQ_DEL_WORD</code> 3007 </dt> 3008 3009 <dd>Delete word at cursor.</dd> 3010 3011 <dt><code>REQ_CLR_EOL</code> 3012 </dt> 3013 3014 <dd>Clear to end of line.</dd> 3015 3016 <dt><code>REQ_CLR_EOF</code> 3017 </dt> 3018 3019 <dd>Clear to end of field.</dd> 3020 3021 <dt><code>REQ_CLEAR_FIELD</code> 3022 </dt> 3023 3024 <dd>Clear entire field.</dd> 3025 </dl> 3026 3027 <p>The behavior of the <code>REQ_NEW_LINE</code> and 3028 <code>REQ_DEL_PREV</code> requests is complicated and partly 3029 controlled by a pair of forms options. The special cases are 3030 triggered when the cursor is at the beginning of a field, or on 3031 the last line of the field.</p> 3032 3033 <p>First, we consider <code>REQ_NEW_LINE</code>:</p> 3034 3035 <p>The normal behavior of <code>REQ_NEW_LINE</code> in insert 3036 mode is to break the current line at the position of the edit 3037 cursor, inserting the portion of the current line after the 3038 cursor as a new line following the current and moving the cursor 3039 to the beginning of that new line (you may think of this as 3040 inserting a newline in the field buffer).</p> 3041 3042 <p>The normal behavior of <code>REQ_NEW_LINE</code> in overlay 3043 mode is to clear the current line from the position of the edit 3044 cursor to end of line. The cursor is then moved to the beginning 3045 of the next line.</p> 3046 3047 <p>However, <code>REQ_NEW_LINE</code> at the beginning of a 3048 field, or on the last line of a field, instead does a 3049 <code>REQ_NEXT_FIELD</code>. <code>O_NL_OVERLOAD</code> option is 3050 off, this special action is disabled.</p> 3051 3052 <p>Now, let us consider <code>REQ_DEL_PREV</code>:</p> 3053 3054 <p>The normal behavior of <code>REQ_DEL_PREV</code> is to delete 3055 the previous character. If insert mode is on, and the cursor is 3056 at the start of a line, and the text on that line will fit on the 3057 previous one, it instead appends the contents of the current line 3058 to the previous one and deletes the current line (you may think 3059 of this as deleting a newline from the field buffer).</p> 3060 3061 <p>However, <code>REQ_DEL_PREV</code> at the beginning of a field 3062 is instead treated as a <code>REQ_PREV_FIELD</code>.</p> 3063 3064 <p>If the <code>O_BS_OVERLOAD</code> option is off, this special 3065 action is disabled and the forms driver just returns 3066 <code>E_REQUEST_DENIED</code>.</p> 3067 3068 <p>See <a href="#frmoptions">Form Options</a> for discussion of 3069 how to set and clear the overload options.</p> 3070 3071 <h3><a name="forder" id="forder">Order Requests</a></h3> 3072 3073 <p>If the type of your field is ordered, and has associated 3074 functions for getting the next and previous values of the type 3075 from a given value, there are requests that can fetch that value 3076 into the field buffer:</p> 3077 3078 <dl> 3079 <dt><code>REQ_NEXT_CHOICE</code> 3080 </dt> 3081 3082 <dd>Place the successor value of the current value in the 3083 buffer.</dd> 3084 3085 <dt><code>REQ_PREV_CHOICE</code> 3086 </dt> 3087 3088 <dd>Place the predecessor value of the current value in the 3089 buffer.</dd> 3090 </dl> 3091 3092 <p>Of the built-in field types, only <code>TYPE_ENUM</code> has 3093 built-in successor and predecessor functions. When you define a 3094 field type of your own (see <a href="#fcustom">Custom Validation 3095 Types</a>), you can associate our own ordering functions.</p> 3096 3097 <h3><a name="fappcmds" id="fappcmds">Application Commands</a></h3> 3098 3099 <p>Form requests are represented as integers above the 3100 <code>curses</code> value greater than <code>KEY_MAX</code> and 3101 less than or equal to the constant <code>MAX_COMMAND</code>. If 3102 your input-virtualization routine returns a value above 3103 <code>MAX_COMMAND</code>, the forms driver will ignore it.</p> 3104 3105 <h2><a name="fhooks" id="fhooks">Field Change Hooks</a></h2> 3106 3107 <p>It is possible to set function hooks to be executed whenever 3108 the current field or form changes. Here are the functions that 3109 support this:</p> 3110 3111 <pre> 3112typedef void (*HOOK)(); /* pointer to function returning void */ 3113 3114int set_form_init(FORM *form, /* form to alter */ 3115 HOOK hook); /* initialization hook */ 3116 3117HOOK form_init(FORM *form); /* form to query */ 3118 3119int set_form_term(FORM *form, /* form to alter */ 3120 HOOK hook); /* termination hook */ 3121 3122HOOK form_term(FORM *form); /* form to query */ 3123 3124int set_field_init(FORM *form, /* form to alter */ 3125 HOOK hook); /* initialization hook */ 3126 3127HOOK field_init(FORM *form); /* form to query */ 3128 3129int set_field_term(FORM *form, /* form to alter */ 3130 HOOK hook); /* termination hook */ 3131 3132HOOK field_term(FORM *form); /* form to query */ 3133</pre> 3134 3135 <p>These functions allow you to either set or query four 3136 different hooks. In each of the set functions, the second 3137 argument should be the address of a hook function. These 3138 functions differ only in the timing of the hook call.</p> 3139 3140 <dl> 3141 <dt>form_init</dt> 3142 3143 <dd>This hook is called when the form is posted; also, just 3144 after each page change operation.</dd> 3145 3146 <dt>field_init</dt> 3147 3148 <dd>This hook is called when the form is posted; also, just 3149 after each field change</dd> 3150 3151 <dt>field_term</dt> 3152 3153 <dd>This hook is called just after field validation; that is, 3154 just before the field is altered. It is also called when the 3155 form is unposted.</dd> 3156 3157 <dt>form_term</dt> 3158 3159 <dd>This hook is called when the form is unposted; also, just 3160 before each page change operation.</dd> 3161 </dl> 3162 3163 <p>Calls to these hooks may be triggered</p> 3164 3165 <ol> 3166 <li>When user editing requests are processed by the forms 3167 driver</li> 3168 3169 <li>When the current page is changed by 3170 <code>set_current_field()</code> call</li> 3171 3172 <li>When the current field is changed by a 3173 <code>set_form_page()</code> call</li> 3174 </ol> 3175 3176 <p>See <a name="ffocus" id="ffocus">Field Change Commands</a> for 3177 discussion of the latter two cases.</p> 3178 3179 <p>You can set a default hook for all fields by passing one of 3180 the set functions a NULL first argument.</p> 3181 3182 <p>You can disable any of these hooks by (re)setting them to 3183 NULL, the default value.</p> 3184 3185 <h2><a href="#ffocus">Field Change Commands</a></h2> 3186 3187 <p>Normally, navigation through the form will be driven by the 3188 user's input requests. But sometimes it is useful to be able to 3189 move the focus for editing and viewing under control of your 3190 application, or ask which field it currently is in. The following 3191 functions help you accomplish this:</p> 3192 3193 <pre> 3194int set_current_field(FORM *form, /* form to alter */ 3195 FIELD *field); /* field to shift to */ 3196 3197FIELD *current_field(FORM *form); /* form to query */ 3198 3199int field_index(FORM *form, /* form to query */ 3200 FIELD *field); /* field to get index of */ 3201</pre> 3202 3203 <p>The function <code>field_index()</code> returns the index of 3204 the given field in the given form's field array (the array passed 3205 to <code>new_form()</code> or 3206 <code>set_form_fields()</code>).</p> 3207 3208 <p>The initial current field of a form is the first active field 3209 on the first page. The function <code>set_form_fields()</code> 3210 resets this.</p> 3211 3212 <p>It is also possible to move around by pages.</p> 3213 3214 <pre> 3215int set_form_page(FORM *form, /* form to alter */ 3216 int page); /* page to go to (0-origin) */ 3217 3218int form_page(FORM *form); /* return form's current page */ 3219</pre> 3220 3221 <p>The initial page of a newly-created form is 0. The function 3222 <code>set_form_fields()</code> resets this.</p> 3223 3224 <h2><a name="frmoptions" id="frmoptions">Form Options</a></h2> 3225 3226 <p>Like fields, forms may have control option bits. They can be 3227 changed or queried with these functions:</p> 3228 3229 <pre> 3230int set_form_opts(FORM *form, /* form to alter */ 3231 int attr); /* attribute to set */ 3232 3233int form_opts_on(FORM *form, /* form to alter */ 3234 int attr); /* attributes to turn on */ 3235 3236int form_opts_off(FORM *form, /* form to alter */ 3237 int attr); /* attributes to turn off */ 3238 3239int form_opts(FORM *form); /* form to query */ 3240</pre> 3241 3242 <p>By default, all options are on. Here are the available option 3243 bits:</p> 3244 3245 <dl> 3246 <dt>O_NL_OVERLOAD</dt> 3247 3248 <dd>Enable overloading of <code>REQ_NEW_LINE</code> as 3249 described in <a href="#fedit">Editing Requests</a>. The value 3250 of this option is ignored on dynamic fields that have not 3251 reached their size limit; these have no last line, so the 3252 circumstances for triggering a <code>REQ_NEXT_FIELD</code> 3253 never arise.</dd> 3254 3255 <dt>O_BS_OVERLOAD</dt> 3256 3257 <dd>Enable overloading of <code>REQ_DEL_PREV</code> as 3258 described in <a href="#fedit">Editing Requests</a>.</dd> 3259 </dl> 3260 3261 <p>The option values are bit-masks and can be composed with 3262 logical-or in the obvious way.</p> 3263 3264 <h2><a name="fcustom" id="fcustom">Custom Validation Types</a></h2> 3265 3266 <p>The <code>form</code> library gives you the capability to 3267 define custom validation types of your own. Further, the optional 3268 additional arguments of <code>set_field_type</code> effectively 3269 allow you to parameterize validation types. Most of the 3270 complications in the validation-type interface have to do with 3271 the handling of the additional arguments within custom validation 3272 functions.</p> 3273 3274 <h3><a name="flinktypes" id="flinktypes">Union Types</a></h3> 3275 3276 <p>The simplest way to create a custom data type is to compose it 3277 from two preexisting ones:</p> 3278 3279 <pre> 3280FIELD *link_fieldtype(FIELDTYPE *type1, 3281 FIELDTYPE *type2); 3282</pre> 3283 3284 <p>This function creates a field type that will accept any of the 3285 values legal for either of its argument field types (which may be 3286 either predefined or programmer-defined). If a 3287 <code>set_field_type()</code> call later requires arguments, the 3288 new composite type expects all arguments for the first type, than 3289 all arguments for the second. Order functions (see <a href= 3290 "#forder">Order Requests</a>) associated with the component types 3291 will work on the composite; what it does is check the validation 3292 function for the first type, then for the second, to figure what 3293 type the buffer contents should be treated as.</p> 3294 3295 <h3><a name="fnewtypes" id="fnewtypes">New Field Types</a></h3> 3296 3297 <p>To create a field type from scratch, you need to specify one 3298 or both of the following things:</p> 3299 3300 <ul> 3301 <li>A character-validation function, to check each character as 3302 it is entered.</li> 3303 3304 <li>A field-validation function to be applied on exit from the 3305 field.</li> 3306 </ul> 3307 3308 <p>Here is how you do that:</p> 3309 3310 <pre> 3311typedef int (*HOOK)(); /* pointer to function returning int */ 3312 3313FIELDTYPE *new_fieldtype(HOOK f_validate, /* field validator */ 3314 HOOK c_validate) /* character validator */ 3315 3316int free_fieldtype(FIELDTYPE *ftype); /* type to free */ 3317</pre> 3318 3319 <p>At least one of the arguments of <code>new_fieldtype()</code> 3320 must be non-NULL. The forms driver will automatically call the 3321 new type's validation functions at appropriate points in 3322 processing a field of the new type.</p> 3323 3324 <p>The function <code>free_fieldtype()</code> deallocates the 3325 argument fieldtype, freeing all storage associated with it.</p> 3326 3327 <p>Normally, a field validator is called when the user attempts 3328 to leave the field. Its first argument is a field pointer, from 3329 which it can get to field buffer 0 and test it. If the function 3330 returns TRUE, the operation succeeds; if it returns FALSE, the 3331 edit cursor stays in the field.</p> 3332 3333 <p>A character validator gets the character passed in as a first 3334 argument. It too should return TRUE if the character is valid, 3335 FALSE otherwise.</p> 3336 3337 <h3><a name="fcheckargs" id="fcheckargs">Validation Function 3338 Arguments</a></h3> 3339 3340 <p>Your field- and character- validation functions will be passed 3341 a second argument as well. This second argument is the address of 3342 a structure (which we will call a <em>pile</em>) built from any 3343 of the field-type-specific arguments passed to 3344 <code>set_field_type()</code>. If no such arguments are defined 3345 for the field type, this pile pointer argument will be NULL.</p> 3346 3347 <p>In order to arrange for such arguments to be passed to your 3348 validation functions, you must associate a small set of 3349 storage-management functions with the type. The forms driver will 3350 use these to synthesize a pile from the trailing arguments of 3351 each <code>set_field_type()</code> argument, and a pointer to the 3352 pile will be passed to the validation functions.</p> 3353 3354 <p>Here is how you make the association:</p> 3355 3356 <pre> 3357typedef char *(*PTRHOOK)(); /* pointer to function returning (char *) */ 3358typedef void (*VOIDHOOK)(); /* pointer to function returning void */ 3359 3360int set_fieldtype_arg(FIELDTYPE *type, /* type to alter */ 3361 PTRHOOK make_str, /* make structure from args */ 3362 PTRHOOK copy_str, /* make copy of structure */ 3363 VOIDHOOK free_str); /* free structure storage */ 3364</pre> 3365 3366 <p>Here is how the storage-management hooks are used:</p> 3367 3368 <dl> 3369 <dt><code>make_str</code> 3370 </dt> 3371 3372 <dd>This function is called by <code>set_field_type()</code>. 3373 It gets one argument, a <code>va_list</code> of the 3374 type-specific arguments passed to 3375 <code>set_field_type()</code>. It is expected to return a pile 3376 pointer to a data structure that encapsulates those 3377 arguments.</dd> 3378 3379 <dt><code>copy_str</code> 3380 </dt> 3381 3382 <dd>This function is called by form library functions that 3383 allocate new field instances. It is expected to take a pile 3384 pointer, copy the pile to allocated storage, and return the 3385 address of the pile copy.</dd> 3386 3387 <dt><code>free_str</code> 3388 </dt> 3389 3390 <dd>This function is called by field- and type-deallocation 3391 routines in the library. It takes a pile pointer argument, and 3392 is expected to free the storage of that pile.</dd> 3393 </dl> 3394 3395 <p>The <code>make_str</code> and <code>copy_str</code> functions 3396 may return NULL to signal allocation failure. The library 3397 routines will that call them will return error indication when 3398 this happens. Thus, your validation functions should never see a 3399 NULL file pointer and need not check specially for it.</p> 3400 3401 <h3><a name="fcustorder" id="fcustorder">Order Functions For 3402 Custom Types</a></h3> 3403 3404 <p>Some custom field types are simply ordered in the same 3405 well-defined way that <code>TYPE_ENUM</code> is. For such types, 3406 it is possible to define successor and predecessor functions to 3407 support the <code>REQ_NEXT_CHOICE</code> and 3408 <code>REQ_PREV_CHOICE</code> requests. Here is how:</p> 3409 3410 <pre> 3411typedef int (*INTHOOK)(); /* pointer to function returning int */ 3412 3413int set_fieldtype_arg(FIELDTYPE *type, /* type to alter */ 3414 INTHOOK succ, /* get successor value */ 3415 INTHOOK pred); /* get predecessor value */ 3416</pre> 3417 3418 <p>The successor and predecessor arguments will each be passed 3419 two arguments; a field pointer, and a pile pointer (as for the 3420 validation functions). They are expected to use the function 3421 <code>field_buffer()</code> to read the current value, and 3422 <code>set_field_buffer()</code> on buffer 0 to set the next or 3423 previous value. Either hook may return TRUE to indicate success 3424 (a legal next or previous value was set) or FALSE to indicate 3425 failure.</p> 3426 3427 <h3><a name="fcustprobs" id="fcustprobs">Avoiding Problems</a></h3> 3428 3429 <p>The interface for defining custom types is complicated and 3430 tricky. Rather than attempting to create a custom type entirely 3431 from scratch, you should start by studying the library source 3432 code for whichever of the pre-defined types seems to be closest 3433 to what you want.</p> 3434 3435 <p>Use that code as a model, and evolve it towards what you 3436 really want. You will avoid many problems and annoyances that 3437 way. The code in the <code>ncurses</code> library has been 3438 specifically exempted from the package copyright to support 3439 this.</p> 3440 3441 <p>If your custom type defines order functions, have do something 3442 intuitive with a blank field. A useful convention is to make the 3443 successor of a blank field the types minimum value, and its 3444 predecessor the maximum.</p> 3445</body> 3446</html> 3447