1<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 3.0//EN"> 2<!-- 3 $Id: ncurses-intro.html,v 1.35 2001/09/02 00:23:11 tom Exp $ 4--> 5<HTML> 6<HEAD> 7<TITLE>Writing Programs with NCURSES</TITLE> 8<link rev="made" href="mailto:bugs-ncurses@gnu.org"> 9</HEAD> 10<BODY> 11 12<H1>Writing Programs with NCURSES</H1> 13 14<BLOCKQUOTE> 15by Eric S. Raymond and Zeyd M. Ben-Halim<BR> 16updates since release 1.9.9e by Thomas Dickey 17</BLOCKQUOTE> 18 19<H1>Contents</H1> 20<UL> 21<LI><A HREF="#introduction">Introduction</A> 22<UL> 23<LI><A HREF="#history">A Brief History of Curses</A> 24<LI><A HREF="#scope">Scope of This Document</A> 25<LI><A HREF="#terminology">Terminology</A> 26</UL> 27<LI><A HREF="#curses">The Curses Library</A> 28<UL> 29<LI><A HREF="#overview">An Overview of Curses</A> 30<UL> 31<LI><A HREF="#compiling">Compiling Programs using Curses</A> 32<LI><A HREF="#updating">Updating the Screen</A> 33<LI><A HREF="#stdscr">Standard Windows and Function Naming Conventions</A> 34<LI><A HREF="#variables">Variables</A> 35</UL> 36<LI><A HREF="#using">Using the Library</A> 37<UL> 38<LI><A HREF="#starting">Starting up</A> 39<LI><A HREF="#output">Output</A> 40<LI><A HREF="#input">Input</A> 41<LI><A HREF="#formschars">Using Forms Characters</A> 42<LI><A HREF="#attributes">Character Attributes and Color</A> 43<LI><A HREF="#mouse">Mouse Interfacing</A> 44<LI><A HREF="#finishing">Finishing Up</A> 45</UL> 46<LI><A HREF="#functions">Function Descriptions</A> 47<UL> 48<LI><A HREF="#init">Initialization and Wrapup</A> 49<LI><A HREF="#flush">Causing Output to the Terminal</A> 50<LI><A HREF="#lowlevel">Low-Level Capability Access</A> 51<LI><A HREF="#debugging">Debugging</A> 52</UL> 53<LI><A HREF="#hints">Hints, Tips, and Tricks</A> 54<UL> 55<LI><A HREF="#caution">Some Notes of Caution</A> 56<LI><A HREF="#leaving">Temporarily Leaving ncurses Mode</A> 57<LI><A HREF="#xterm">Using <CODE>ncurses</CODE> under <CODE>xterm</CODE></A> 58<LI><A HREF="#screens">Handling Multiple Terminal Screens</A> 59<LI><A HREF="#testing">Testing for Terminal Capabilities</A> 60<LI><A HREF="#tuning">Tuning for Speed</A> 61<LI><A HREF="#special">Special Features of <CODE>ncurses</CODE></A> 62</UL> 63<LI><A HREF="#compat">Compatibility with Older Versions</A> 64<UL> 65<LI><A HREF="#refbug">Refresh of Overlapping Windows</A> 66<LI><A HREF="#backbug">Background Erase</A> 67</UL> 68<LI><A HREF="#xsifuncs">XSI Curses Conformance</A> 69</UL> 70<LI><A HREF="#panels">The Panels Library</A> 71<UL> 72<LI><A HREF="#pcompile">Compiling With the Panels Library</A> 73<LI><A HREF="#poverview">Overview of Panels</A> 74<LI><A HREF="#pstdscr">Panels, Input, and the Standard Screen</A> 75<LI><A HREF="#hiding">Hiding Panels</A> 76<LI><A HREF="#pmisc">Miscellaneous Other Facilities</A> 77</UL> 78<LI><A HREF="#menu">The Menu Library</A> 79<UL> 80<LI><A HREF="#mcompile">Compiling with the menu Library</A> 81<LI><A HREF="#moverview">Overview of Menus</A> 82<LI><A HREF="#mselect">Selecting items</A> 83<LI><A HREF="#mdisplay">Menu Display</A> 84<LI><A HREF="#mwindows">Menu Windows</A> 85<LI><A HREF="#minput">Processing Menu Input</A> 86<LI><A HREF="#mmisc">Miscellaneous Other Features</A> 87</UL> 88<LI><A HREF="#form">The Forms Library</A> 89<UL> 90<LI><A HREF="#fcompile">Compiling with the forms Library</A> 91<LI><A HREF="#foverview">Overview of Forms</A> 92<LI><A HREF="#fcreate">Creating and Freeing Fields and Forms</A> 93<LI><A HREF="#fattributes">Fetching and Changing Field Attributes</A> 94<UL> 95<LI><A HREF="#fsizes">Fetching Size and Location Data</A> 96<LI><A HREF="#flocation">Changing the Field Location</A> 97<LI><A HREF="#fjust">The Justification Attribute</A> 98<LI><A HREF="#fdispatts">Field Display Attributes</A> 99<LI><A HREF="#foptions">Field Option Bits</A> 100<LI><A HREF="#fstatus">Field Status</A> 101<LI><A HREF="#fuser">Field User Pointer</A> 102</UL> 103<LI><A HREF="#fdynamic">Variable-Sized Fields</A> 104<LI><A HREF="#fvalidation">Field Validation</A> 105<UL> 106<LI><A HREF="#ftype_alpha">TYPE_ALPHA</A> 107<LI><A HREF="#ftype_alnum">TYPE_ALNUM</A> 108<LI><A HREF="#ftype_enum">TYPE_ENUM</A> 109<LI><A HREF="#ftype_integer">TYPE_INTEGER</A> 110<LI><A HREF="#ftype_numeric">TYPE_NUMERIC</A> 111<LI><A HREF="#ftype_regexp">TYPE_REGEXP</A> 112</UL> 113<LI><A HREF="#fbuffer">Direct Field Buffer Manipulation</A> 114<LI><A HREF="#formattrs">Attributes of Forms</A> 115<LI><A HREF="#fdisplay">Control of Form Display</A> 116<LI><A HREF="#fdriver">Input Processing in the Forms Driver</A> 117<UL> 118<LI><A HREF="#fpage">Page Navigation Requests</A> 119<LI><A HREF="#ffield">Inter-Field Navigation Requests</A> 120<LI><A HREF="#fifield">Intra-Field Navigation Requests</A> 121<LI><A HREF="#fscroll">Scrolling Requests</A> 122<LI><A HREF="#fedit">Field Editing Requests</A> 123<LI><A HREF="#forder">Order Requests</A> 124<LI><A HREF="#fappcmds">Application Commands</A> 125</UL> 126<LI><A HREF="#fhooks">Field Change Hooks</A> 127<LI><A HREF="#ffocus">Field Change Commands</A> 128<LI><A HREF="#frmoptions">Form Options</A> 129<LI><A HREF="#fcustom">Custom Validation Types</A> 130<UL> 131<LI><A HREF="#flinktypes">Union Types</A> 132<LI><A HREF="#fnewtypes">New Field Types</A> 133<LI><A HREF="#fcheckargs">Validation Function Arguments</A> 134<LI><A HREF="#fcustorder">Order Functions For Custom Types</A> 135<LI><A HREF="#fcustprobs">Avoiding Problems</A> 136</UL> 137</UL> 138</UL> 139 140<HR> 141<H1><A NAME="introduction">Introduction</A></H1> 142 143This document is an introduction to programming with <CODE>curses</CODE>. It is 144not an exhaustive reference for the curses Application Programming Interface 145(API); that role is filled by the <CODE>curses</CODE> manual pages. Rather, it 146is intended to help C programmers ease into using the package. <P> 147 148This document is aimed at C applications programmers not yet specifically 149familiar with ncurses. If you are already an experienced <CODE>curses</CODE> 150programmer, you should nevertheless read the sections on 151<A HREF="#mouse">Mouse Interfacing</A>, <A HREF="#debugging">Debugging</A>, 152<A HREF="#compat">Compatibility with Older Versions</A>, 153and <A HREF="#hints">Hints, Tips, and Tricks</A>. These will bring you up 154to speed on the special features and quirks of the <CODE>ncurses</CODE> 155implementation. If you are not so experienced, keep reading. <P> 156 157The <CODE>curses</CODE> package is a subroutine library for 158terminal-independent screen-painting and input-event handling which 159presents a high level screen model to the programmer, hiding differences 160between terminal types and doing automatic optimization of output to change 161one screen full of text into another. <CODE>Curses</CODE> uses terminfo, which 162is a database format that can describe the capabilities of thousands of 163different terminals. <P> 164 165The <CODE>curses</CODE> API may seem something of an archaism on UNIX desktops 166increasingly dominated by X, Motif, and Tcl/Tk. Nevertheless, UNIX still 167supports tty lines and X supports <EM>xterm(1)</EM>; the <CODE>curses</CODE> 168API has the advantage of (a) back-portability to character-cell terminals, 169and (b) simplicity. For an application that does not require bit-mapped 170graphics and multiple fonts, an interface implementation using <CODE>curses</CODE> 171will typically be a great deal simpler and less expensive than one using an 172X toolkit. 173 174<H2><A NAME="history">A Brief History of Curses</A></H2> 175 176Historically, the first ancestor of <CODE>curses</CODE> was the routines written to 177provide screen-handling for the game <CODE>rogue</CODE>; these used the 178already-existing <CODE>termcap</CODE> database facility for describing terminal 179capabilities. These routines were abstracted into a documented library and 180first released with the early BSD UNIX versions. <P> 181 182System III UNIX from Bell Labs featured a rewritten and much-improved 183<CODE>curses</CODE> library. It introduced the terminfo format. Terminfo is based 184on Berkeley's termcap database, but contains a number of improvements and 185extensions. Parameterized capabilities strings were introduced, making it 186possible to describe multiple video attributes, and colors and to handle far 187more unusual terminals than possible with termcap. In the later AT&T 188System V releases, <CODE>curses</CODE> evolved to use more facilities and offer 189more capabilities, going far beyond BSD curses in power and flexibility. 190 191<H2><A NAME="scope">Scope of This Document</A></H2> 192 193This document describes <CODE>ncurses</CODE>, a free implementation of 194the System V <CODE>curses</CODE> API with some clearly marked extensions. 195It includes the following System V curses features: 196<UL> 197<LI>Support for multiple screen highlights (BSD curses could only 198handle one `standout' highlight, usually reverse-video). 199<LI>Support for line- and box-drawing using forms characters. 200<LI>Recognition of function keys on input. 201<LI>Color support. 202<LI>Support for pads (windows of larger than screen size on which the 203screen or a subwindow defines a viewport). 204</UL> 205 206Also, this package makes use of the insert and delete line and character 207features of terminals so equipped, and determines how to optimally use these 208features with no help from the programmer. It allows arbitrary combinations of 209video attributes to be displayed, even on terminals that leave ``magic 210cookies'' on the screen to mark changes in attributes. <P> 211 212The <CODE>ncurses</CODE> package can also capture and use event reports from a 213mouse in some environments (notably, xterm under the X window system). This 214document includes tips for using the mouse. <P> 215 216The <CODE>ncurses</CODE> package was originated by Pavel Curtis. The original 217maintainer of this package is 218<A HREF="mailto:zmbenhal@netcom.com">Zeyd Ben-Halim</A> 219<zmbenhal@netcom.com>. 220<A HREF="mailto:esr@snark.thyrsus.com">Eric S. Raymond</A> 221<esr@snark.thyrsus.com> 222wrote many of the new features in versions after 1.8.1 223and wrote most of this introduction. 224<A HREF="mailto:juergen.pfeifer@gmx.net">Jürgen Pfeifer</A> 225wrote all of the menu and forms code as well as the 226<A HREF="http://www.adahome.com">Ada95</A> binding. 227Ongoing work is being done by 228<A HREF="mailto:dickey@herndon4.his.com">Thomas Dickey</A> 229and 230<A HREF="mailto:juergen.pfeifer@gmx.net">Jürgen Pfeifer</A>. 231<A HREF="mailto:florian@gnu.org">Florian La Roche</A> 232acts as the maintainer for the Free Software Foundation, which holds the 233copyright on ncurses. 234Contact the current maintainers at 235<A HREF="mailto:bug-ncurses@gnu.org">bug-ncurses@gnu.org</A>. 236<P> 237 238This document also describes the <A HREF="#panels">panels</A> extension library, 239similarly modeled on the SVr4 panels facility. This library allows you to 240associate backing store with each of a stack or deck of overlapping windows, 241and provides operations for moving windows around in the stack that change 242their visibility in the natural way (handling window overlaps). <P> 243 244Finally, this document describes in detail the <A HREF="#menu">menus</A> and <A 245HREF="#form">forms</A> extension libraries, also cloned from System V, 246which support easy construction and sequences of menus and fill-in 247forms. 248 249 250<H2><A NAME="terminology">Terminology</A></H2> 251 252In this document, the following terminology is used with reasonable 253consistency: 254 255<DL> 256<DT> window 257<DD> 258A data structure describing a sub-rectangle of the screen (possibly the 259entire screen). You can write to a window as though it were a miniature 260screen, scrolling independently of other windows on the physical screen. 261<DT> screens 262<DD> 263A subset of windows which are as large as the terminal screen, i.e., they start 264at the upper left hand corner and encompass the lower right hand corner. One 265of these, <CODE>stdscr</CODE>, is automatically provided for the programmer. 266<DT> terminal screen 267<DD> 268The package's idea of what the terminal display currently looks like, i.e., 269what the user sees now. This is a special screen. 270</DL> 271 272<H1><A NAME="curses">The Curses Library</A></H1> 273 274<H2><A NAME="overview">An Overview of Curses</A></H2> 275 276<H3><A NAME="compiling">Compiling Programs using Curses</A></H3> 277 278In order to use the library, it is necessary to have certain types and 279variables defined. Therefore, the programmer must have a line: 280 281<PRE> 282 #include <curses.h> 283</PRE> 284 285at the top of the program source. The screen package uses the Standard I/O 286library, so <CODE><curses.h></CODE> includes 287<CODE><stdio.h></CODE>. <CODE><curses.h></CODE> also includes 288<CODE><termios.h></CODE>, <CODE><termio.h></CODE>, or 289<CODE><sgtty.h></CODE> depending on your system. It is redundant (but 290harmless) for the programmer to do these includes, too. In linking with 291<CODE>curses</CODE> you need to have <CODE>-lncurses</CODE> in your LDFLAGS or on the 292command line. There is no need for any other libraries. 293 294<H3><A NAME="updating">Updating the Screen</A></H3> 295 296In order to update the screen optimally, it is necessary for the routines to 297know what the screen currently looks like and what the programmer wants it to 298look like next. For this purpose, a data type (structure) named WINDOW is 299defined which describes a window image to the routines, including its starting 300position on the screen (the (y, x) coordinates of the upper left hand corner) 301and its size. One of these (called <CODE>curscr</CODE>, for current screen) is a 302screen image of what the terminal currently looks like. Another screen (called 303<CODE>stdscr</CODE>, for standard screen) is provided by default to make changes 304on. <P> 305 306A window is a purely internal representation. It is used to build and store a 307potential image of a portion of the terminal. It doesn't bear any necessary 308relation to what is really on the terminal screen; it's more like a 309scratchpad or write buffer. <P> 310 311To make the section of physical screen corresponding to a window reflect the 312contents of the window structure, the routine <CODE>refresh()</CODE> (or 313<CODE>wrefresh()</CODE> if the window is not <CODE>stdscr</CODE>) is called. <P> 314 315A given physical screen section may be within the scope of any number of 316overlapping windows. Also, changes can be made to windows in any order, 317without regard to motion efficiency. Then, at will, the programmer can 318effectively say ``make it look like this,'' and let the package implementation 319determine the most efficient way to repaint the screen. 320 321<H3><A NAME="stdscr">Standard Windows and Function Naming Conventions</A></H3> 322 323As hinted above, the routines can use several windows, but two are 324automatically given: <CODE>curscr</CODE>, which knows what the terminal looks like, 325and <CODE>stdscr</CODE>, which is what the programmer wants the terminal to look 326like next. The user should never actually access <CODE>curscr</CODE> directly. 327Changes should be made to through the API, and then the routine 328<CODE>refresh()</CODE> (or <CODE>wrefresh()</CODE>) called. <P> 329 330Many functions are defined to use <CODE>stdscr</CODE> as a default screen. For 331example, to add a character to <CODE>stdscr</CODE>, one calls <CODE>addch()</CODE> with 332the desired character as argument. To write to a different window. use the 333routine <CODE>waddch()</CODE> (for `w'indow-specific addch()) is provided. This 334convention of prepending function names with a `w' when they are to be 335applied to specific windows is consistent. The only routines which do not 336follow it are those for which a window must always be specified. <P> 337 338In order to move the current (y, x) coordinates from one point to another, the 339routines <CODE>move()</CODE> and <CODE>wmove()</CODE> are provided. However, it is 340often desirable to first move and then perform some I/O operation. In order to 341avoid clumsiness, most I/O routines can be preceded by the prefix 'mv' and 342the desired (y, x) coordinates prepended to the arguments to the function. For 343example, the calls 344 345<PRE> 346 move(y, x); 347 addch(ch); 348</PRE> 349 350can be replaced by 351 352<PRE> 353 mvaddch(y, x, ch); 354</PRE> 355 356and 357 358<PRE> 359 wmove(win, y, x); 360 waddch(win, ch); 361</PRE> 362 363can be replaced by 364 365<PRE> 366 mvwaddch(win, y, x, ch); 367</PRE> 368 369Note that the window description pointer (win) comes before the added (y, x) 370coordinates. If a function requires a window pointer, it is always the first 371parameter passed. 372 373<H3><A NAME="variables">Variables</A></H3> 374 375The <CODE>curses</CODE> library sets some variables describing the terminal 376capabilities. 377 378<PRE> 379 type name description 380 ------------------------------------------------------------------ 381 int LINES number of lines on the terminal 382 int COLS number of columns on the terminal 383</PRE> 384 385The <CODE>curses.h</CODE> also introduces some <CODE>#define</CODE> constants and types 386of general usefulness: 387 388<DL> 389<DT> <CODE>bool</CODE> 390<DD> boolean type, actually a `char' (e.g., <CODE>bool doneit;</CODE>) 391<DT> <CODE>TRUE</CODE> 392<DD> boolean `true' flag (1). 393<DT> <CODE>FALSE</CODE> 394<DD> boolean `false' flag (0). 395<DT> <CODE>ERR</CODE> 396<DD> error flag returned by routines on a failure (-1). 397<DT> <CODE>OK</CODE> 398<DD> error flag returned by routines when things go right. 399</DL> 400 401<H2><A NAME="using">Using the Library</A></H2> 402 403Now we describe how to actually use the screen package. In it, we assume all 404updating, reading, etc. is applied to <CODE>stdscr</CODE>. These instructions will 405work on any window, providing you change the function names and parameters as 406mentioned above. <P> 407 408Here is a sample program to motivate the discussion: 409 410<PRE> 411#include <curses.h> 412#include <signal.h> 413 414static void finish(int sig); 415 416int 417main(int argc, char *argv[]) 418{ 419 int num = 0; 420 421 /* initialize your non-curses data structures here */ 422 423 (void) signal(SIGINT, finish); /* arrange interrupts to terminate */ 424 425 (void) initscr(); /* initialize the curses library */ 426 keypad(stdscr, TRUE); /* enable keyboard mapping */ 427 (void) nonl(); /* tell curses not to do NL->CR/NL on output */ 428 (void) cbreak(); /* take input chars one at a time, no wait for \n */ 429 (void) echo(); /* echo input - in color */ 430 431 if (has_colors()) 432 { 433 start_color(); 434 435 /* 436 * Simple color assignment, often all we need. Color pair 0 cannot 437 * be redefined. This example uses the same value for the color 438 * pair as for the foreground color, though of course that is not 439 * necessary: 440 */ 441 init_pair(1, COLOR_RED, COLOR_BLACK); 442 init_pair(2, COLOR_GREEN, COLOR_BLACK); 443 init_pair(3, COLOR_YELLOW, COLOR_BLACK); 444 init_pair(4, COLOR_BLUE, COLOR_BLACK); 445 init_pair(5, COLOR_CYAN, COLOR_BLACK); 446 init_pair(6, COLOR_MAGENTA, COLOR_BLACK); 447 init_pair(7, COLOR_WHITE, COLOR_BLACK); 448 } 449 450 for (;;) 451 { 452 int c = getch(); /* refresh, accept single keystroke of input */ 453 attrset(COLOR_PAIR(num % 8)); 454 num++; 455 456 /* process the command keystroke */ 457 } 458 459 finish(0); /* we're done */ 460} 461 462static void finish(int sig) 463{ 464 endwin(); 465 466 /* do your non-curses wrapup here */ 467 468 exit(0); 469} 470</PRE> 471 472<H3><A NAME="starting">Starting up</A></H3> 473 474In order to use the screen package, the routines must know about terminal 475characteristics, and the space for <CODE>curscr</CODE> and <CODE>stdscr</CODE> must be 476allocated. These function <CODE>initscr()</CODE> does both these things. Since it 477must allocate space for the windows, it can overflow memory when attempting to 478do so. On the rare occasions this happens, <CODE>initscr()</CODE> will terminate 479the program with an error message. <CODE>initscr()</CODE> must always be called 480before any of the routines which affect windows are used. If it is not, the 481program will core dump as soon as either <CODE>curscr</CODE> or <CODE>stdscr</CODE> are 482referenced. However, it is usually best to wait to call it until after you are 483sure you will need it, like after checking for startup errors. Terminal status 484changing routines like <CODE>nl()</CODE> and <CODE>cbreak()</CODE> should be called 485after <CODE>initscr()</CODE>. <P> 486 487Once the screen windows have been allocated, you can set them up for 488your program. If you want to, say, allow a screen to scroll, use 489<CODE>scrollok()</CODE>. If you want the cursor to be left in place after 490the last change, use <CODE>leaveok()</CODE>. If this isn't done, 491<CODE>refresh()</CODE> will move the cursor to the window's current (y, x) 492coordinates after updating it. <P> 493 494You can create new windows of your own using the functions <CODE>newwin()</CODE>, 495<CODE>derwin()</CODE>, and <CODE>subwin()</CODE>. The routine <CODE>delwin()</CODE> will 496allow you to get rid of old windows. All the options described above can be 497applied to any window. 498 499<H3><A NAME="output">Output</A></H3> 500 501Now that we have set things up, we will want to actually update the terminal. 502The basic functions used to change what will go on a window are 503<CODE>addch()</CODE> and <CODE>move()</CODE>. <CODE>addch()</CODE> adds a character at the 504current (y, x) coordinates. <CODE>move()</CODE> changes the current (y, x) 505coordinates to whatever you want them to be. It returns <CODE>ERR</CODE> if you 506try to move off the window. As mentioned above, you can combine the two into 507<CODE>mvaddch()</CODE> to do both things at once. <P> 508 509The other output functions, such as <CODE>addstr()</CODE> and <CODE>printw()</CODE>, 510all call <CODE>addch()</CODE> to add characters to the window. <P> 511 512After you have put on the window what you want there, when you want the portion 513of the terminal covered by the window to be made to look like it, you must call 514<CODE>refresh()</CODE>. In order to optimize finding changes, <CODE>refresh()</CODE> 515assumes that any part of the window not changed since the last 516<CODE>refresh()</CODE> of that window has not been changed on the terminal, i.e., 517that you have not refreshed a portion of the terminal with an overlapping 518window. If this is not the case, the routine <CODE>touchwin()</CODE> is provided 519to make it look like the entire window has been changed, thus making 520<CODE>refresh()</CODE> check the whole subsection of the terminal for changes. <P> 521 522If you call <CODE>wrefresh()</CODE> with <CODE>curscr</CODE> as its argument, it will 523make the screen look like <CODE>curscr</CODE> thinks it looks like. This is useful 524for implementing a command which would redraw the screen in case it get messed 525up. 526 527<H3><A NAME="input">Input</A></H3> 528 529The complementary function to <CODE>addch()</CODE> is <CODE>getch()</CODE> which, if 530echo is set, will call <CODE>addch()</CODE> to echo the character. Since the 531screen package needs to know what is on the terminal at all times, if 532characters are to be echoed, the tty must be in raw or cbreak mode. Since 533initially the terminal has echoing enabled and is in ordinary ``cooked'' mode, 534one or the other has to changed before calling <CODE>getch()</CODE>; otherwise, 535the program's output will be unpredictable. <P> 536 537When you need to accept line-oriented input in a window, the functions 538<CODE>wgetstr()</CODE> and friends are available. There is even a <CODE>wscanw()</CODE> 539function that can do <CODE>scanf()</CODE>(3)-style multi-field parsing on window 540input. These pseudo-line-oriented functions turn on echoing while they 541execute. <P> 542 543The example code above uses the call <CODE>keypad(stdscr, TRUE)</CODE> to enable 544support for function-key mapping. With this feature, the <CODE>getch()</CODE> code 545watches the input stream for character sequences that correspond to arrow and 546function keys. These sequences are returned as pseudo-character values. The 547<CODE>#define</CODE> values returned are listed in the <CODE>curses.h</CODE> The 548mapping from sequences to <CODE>#define</CODE> values is determined by 549<CODE>key_</CODE> capabilities in the terminal's terminfo entry. 550 551<H3><A NAME="formschars">Using Forms Characters</A></H3> 552 553The <CODE>addch()</CODE> function (and some others, including <CODE>box()</CODE> and 554<CODE>border()</CODE>) can accept some pseudo-character arguments which are specially 555defined by <CODE>ncurses</CODE>. These are <CODE>#define</CODE> values set up in 556the <CODE>curses.h</CODE> header; see there for a complete list (look for 557the prefix <CODE>ACS_</CODE>). <P> 558 559The most useful of the ACS defines are the forms-drawing characters. You can 560use these to draw boxes and simple graphs on the screen. If the terminal 561does not have such characters, <CODE>curses.h</CODE> will map them to a 562recognizable (though ugly) set of ASCII defaults. 563 564<H3><A NAME="attributes">Character Attributes and Color</A></H3> 565 566The <CODE>ncurses</CODE> package supports screen highlights including standout, 567reverse-video, underline, and blink. It also supports color, which is treated 568as another kind of highlight. <P> 569 570Highlights are encoded, internally, as high bits of the pseudo-character type 571(<CODE>chtype</CODE>) that <CODE>curses.h</CODE> uses to represent the contents of a 572screen cell. See the <CODE>curses.h</CODE> header file for a complete list of 573highlight mask values (look for the prefix <CODE>A_</CODE>).<P> 574 575There are two ways to make highlights. One is to logical-or the value of the 576highlights you want into the character argument of an <CODE>addch()</CODE> call, 577or any other output call that takes a <CODE>chtype</CODE> argument. <P> 578 579The other is to set the current-highlight value. This is logical-or'ed with 580any highlight you specify the first way. You do this with the functions 581<CODE>attron()</CODE>, <CODE>attroff()</CODE>, and <CODE>attrset()</CODE>; see the manual 582pages for details. 583 584Color is a special kind of highlight. The package actually thinks in terms 585of color pairs, combinations of foreground and background colors. The sample 586code above sets up eight color pairs, all of the guaranteed-available colors 587on black. Note that each color pair is, in effect, given the name of its 588foreground color. Any other range of eight non-conflicting values could 589have been used as the first arguments of the <CODE>init_pair()</CODE> values. <P> 590 591Once you've done an <CODE>init_pair()</CODE> that creates color-pair N, you can 592use <CODE>COLOR_PAIR(N)</CODE> as a highlight that invokes that particular 593color combination. Note that <CODE>COLOR_PAIR(N)</CODE>, for constant N, 594is itself a compile-time constant and can be used in initializers. 595 596<H3><A NAME="mouse">Mouse Interfacing</A></H3> 597 598The <CODE>ncurses</CODE> library also provides a mouse interface. 599<!-- The 'note' tag is not portable enough --> 600<blockquote> 601<strong>NOTE:</strong> this facility is specific to <CODE>ncurses</CODE>, it is not part of either 602the XSI Curses standard, nor of System V Release 4, nor BSD curses. 603System V Release 4 curses contains code with similar interface definitions, 604however it is not documented. Other than by disassembling the library, we 605have no way to determine exactly how that mouse code works. 606Thus, we recommend that you wrap mouse-related code in an #ifdef using the 607feature macro NCURSES_MOUSE_VERSION so it will not be compiled and linked 608on non-ncurses systems. 609</blockquote> 610 611Presently, mouse event reporting works in the following environments: 612<ul> 613<li>xterm and similar programs such as rxvt. 614<li>Linux console, when configured with <CODE>gpm</CODE>(1), Alessandro 615Rubini's mouse server. 616<li>OS/2 EMX 617</ul> 618<P> 619The mouse interface is very simple. To activate it, you use the function 620<CODE>mousemask()</CODE>, passing it as first argument a bit-mask that specifies 621what kinds of events you want your program to be able to see. It will 622return the bit-mask of events that actually become visible, which may differ 623from the argument if the mouse device is not capable of reporting some of 624the event types you specify. <P> 625 626Once the mouse is active, your application's command loop should watch 627for a return value of <CODE>KEY_MOUSE</CODE> from <CODE>wgetch()</CODE>. When 628you see this, a mouse event report has been queued. To pick it off 629the queue, use the function <CODE>getmouse()</CODE> (you must do this before 630the next <CODE>wgetch()</CODE>, otherwise another mouse event might come 631in and make the first one inaccessible). <P> 632 633Each call to <CODE>getmouse()</CODE> fills a structure (the address of which you'll 634pass it) with mouse event data. The event data includes zero-origin, 635screen-relative character-cell coordinates of the mouse pointer. It also 636includes an event mask. Bits in this mask will be set, corresponding 637to the event type being reported. <P> 638 639The mouse structure contains two additional fields which may be 640significant in the future as ncurses interfaces to new kinds of 641pointing device. In addition to x and y coordinates, there is a slot 642for a z coordinate; this might be useful with touch-screens that can 643return a pressure or duration parameter. There is also a device ID 644field, which could be used to distinguish between multiple pointing 645devices. <P> 646 647The class of visible events may be changed at any time via <CODE>mousemask()</CODE>. 648Events that can be reported include presses, releases, single-, double- and 649triple-clicks (you can set the maximum button-down time for clicks). If 650you don't make clicks visible, they will be reported as press-release 651pairs. In some environments, the event mask may include bits reporting 652the state of shift, alt, and ctrl keys on the keyboard during the event. <P> 653 654A function to check whether a mouse event fell within a given window is 655also supplied. You can use this to see whether a given window should 656consider a mouse event relevant to it. <P> 657 658Because mouse event reporting will not be available in all 659environments, it would be unwise to build <CODE>ncurses</CODE> 660applications that <EM>require</EM> the use of a mouse. Rather, you should 661use the mouse as a shortcut for point-and-shoot commands your application 662would normally accept from the keyboard. Two of the test games in the 663<CODE>ncurses</CODE> distribution (<CODE>bs</CODE> and <CODE>knight</CODE>) contain 664code that illustrates how this can be done. <P> 665 666See the manual page <CODE>curs_mouse(3X)</CODE> for full details of the 667mouse-interface functions. 668 669<H3><A NAME="finishing">Finishing Up</A></H3> 670 671In order to clean up after the <CODE>ncurses</CODE> routines, the routine 672<CODE>endwin()</CODE> is provided. It restores tty modes to what they were when 673<CODE>initscr()</CODE> was first called, and moves the cursor down to the 674lower-left corner. Thus, anytime after the call to initscr, <CODE>endwin()</CODE> 675should be called before exiting. 676 677<H2><A NAME="functions">Function Descriptions</A></H2> 678 679We describe the detailed behavior of some important curses functions here, as a 680supplement to the manual page descriptions. 681 682<H3><A NAME="init">Initialization and Wrapup</A></H3> 683 684<DL> 685<DT> <CODE>initscr()</CODE> 686<DD> The first function called should almost always be <CODE>initscr()</CODE>. 687This will determine the terminal type and 688initialize curses data structures. <CODE>initscr()</CODE> also arranges that 689the first call to <CODE>refresh()</CODE> will clear the screen. If an error 690occurs a message is written to standard error and the program 691exits. Otherwise it returns a pointer to stdscr. A few functions may be 692called before initscr (<CODE>slk_init()</CODE>, <CODE>filter()</CODE>, 693<CODE>ripofflines()</CODE>, <CODE>use_env()</CODE>, and, if you are using multiple 694terminals, <CODE>newterm()</CODE>.) 695<DT> <CODE>endwin()</CODE> 696<DD> Your program should always call <CODE>endwin()</CODE> before exiting or 697shelling out of the program. This function will restore tty modes, 698move the cursor to the lower left corner of the screen, reset the 699terminal into the proper non-visual mode. Calling <CODE>refresh()</CODE> 700or <CODE>doupdate()</CODE> after a temporary escape from the program will 701restore the ncurses screen from before the escape. 702<DT> <CODE>newterm(type, ofp, ifp)</CODE> 703<DD> A program which outputs to more than one terminal should use 704<CODE>newterm()</CODE> instead of <CODE>initscr()</CODE>. <CODE>newterm()</CODE> should 705be called once for each terminal. It returns a variable of type 706<CODE>SCREEN *</CODE> which should be saved as a reference to that 707terminal. 708(NOTE: a SCREEN variable is not a <em>screen</em> in the sense we 709are describing in this introduction, but a collection of 710parameters used to assist in optimizing the display.) 711The arguments are the type of the terminal (a string) and 712<CODE>FILE</CODE> pointers for the output and input of the terminal. If 713type is NULL then the environment variable <CODE>$TERM</CODE> is used. 714<CODE>endwin()</CODE> should called once at wrapup time for each terminal 715opened using this function. 716<DT> <CODE>set_term(new)</CODE> 717<DD> This function is used to switch to a different terminal previously 718opened by <CODE>newterm()</CODE>. The screen reference for the new terminal 719is passed as the parameter. The previous terminal is returned by the 720function. All other calls affect only the current terminal. 721<DT> <CODE>delscreen(sp)</CODE> 722<DD> The inverse of <CODE>newterm()</CODE>; deallocates the data structures 723associated with a given <CODE>SCREEN</CODE> reference. 724</DL> 725 726<H3><A NAME="flush">Causing Output to the Terminal</A></H3> 727 728<DL> 729<DT> <CODE>refresh()</CODE> and <CODE>wrefresh(win)</CODE> 730<DD> These functions must be called to actually get any output on 731the terminal, as other routines merely manipulate data 732structures. <CODE>wrefresh()</CODE> copies the named window to the physical 733terminal screen, taking into account what is already 734there in order to do optimizations. <CODE>refresh()</CODE> does a 735refresh of <CODE>stdscr()</CODE>. Unless <CODE>leaveok()</CODE> has been 736enabled, the physical cursor of the terminal is left at the 737location of the window's cursor. 738<DT> <CODE>doupdate()</CODE> and <CODE>wnoutrefresh(win)</CODE> 739<DD> These two functions allow multiple updates with more efficiency 740than wrefresh. To use them, it is important to understand how curses 741works. In addition to all the window structures, curses keeps two 742data structures representing the terminal screen: a physical screen, 743describing what is actually on the screen, and a virtual screen, 744describing what the programmer wants to have on the screen. wrefresh 745works by first copying the named window to the virtual screen 746(<CODE>wnoutrefresh()</CODE>), and then calling the routine to update the 747screen (<CODE>doupdate()</CODE>). If the programmer wishes to output 748several windows at once, a series of calls to <CODE>wrefresh</CODE> will result 749in alternating calls to <CODE>wnoutrefresh()</CODE> and <CODE>doupdate()</CODE>, 750causing several bursts of output to the screen. By calling 751<CODE>wnoutrefresh()</CODE> for each window, it is then possible to call 752<CODE>doupdate()</CODE> once, resulting in only one burst of output, with 753fewer total characters transmitted (this also avoids a visually annoying 754flicker at each update). 755</DL> 756 757<H3><A NAME="lowlevel">Low-Level Capability Access</A></H3> 758 759<DL> 760<DT> <CODE>setupterm(term, filenum, errret)</CODE> 761<DD> This routine is called to initialize a terminal's description, without setting 762up the curses screen structures or changing the tty-driver mode bits. 763<CODE>term</CODE> is the character string representing the name of the terminal 764being used. <CODE>filenum</CODE> is the UNIX file descriptor of the terminal to 765be used for output. <CODE>errret</CODE> is a pointer to an integer, in which a 766success or failure indication is returned. The values returned can be 1 (all 767is well), 0 (no such terminal), or -1 (some problem locating the terminfo 768database). <P> 769 770The value of <CODE>term</CODE> can be given as NULL, which will cause the value of 771<CODE>TERM</CODE> in the environment to be used. The <CODE>errret</CODE> pointer can 772also be given as NULL, meaning no error code is wanted. If <CODE>errret</CODE> is 773defaulted, and something goes wrong, <CODE>setupterm()</CODE> will print an 774appropriate error message and exit, rather than returning. Thus, a simple 775program can call setupterm(0, 1, 0) and not worry about initialization 776errors. <P> 777 778After the call to <CODE>setupterm()</CODE>, the global variable <CODE>cur_term</CODE> is 779set to point to the current structure of terminal capabilities. By calling 780<CODE>setupterm()</CODE> for each terminal, and saving and restoring 781<CODE>cur_term</CODE>, it is possible for a program to use two or more terminals at 782once. <CODE>Setupterm()</CODE> also stores the names section of the terminal 783description in the global character array <CODE>ttytype[]</CODE>. Subsequent calls 784to <CODE>setupterm()</CODE> will overwrite this array, so you'll have to save it 785yourself if need be. 786</DL> 787 788<H3><A NAME="debugging">Debugging</A></H3> 789 790<!-- The 'note' tag is not portable enough --> 791<blockquote> 792<strong>NOTE:</strong> These functions are not part of the standard curses API! 793</blockquote> 794 795<DL> 796<DT> <CODE>trace()</CODE> 797<DD> 798This function can be used to explicitly set a trace level. If the 799trace level is nonzero, execution of your program will generate a file 800called `trace' in the current working directory containing a report on 801the library's actions. Higher trace levels enable more detailed (and 802verbose) reporting -- see comments attached to <CODE>TRACE_</CODE> defines 803in the <CODE>curses.h</CODE> file for details. (It is also possible to set 804a trace level by assigning a trace level value to the environment variable 805<CODE>NCURSES_TRACE</CODE>). 806<DT> <CODE>_tracef()</CODE> 807<DD> 808This function can be used to output your own debugging information. It is only 809available only if you link with -lncurses_g. It can be used the same way as 810<CODE>printf()</CODE>, only it outputs a newline after the end of arguments. 811The output goes to a file called <CODE>trace</CODE> in the current directory. 812</DL> 813 814Trace logs can be difficult to interpret due to the sheer volume of 815data dumped in them. There is a script called <STRONG>tracemunch</STRONG> 816included with the <CODE>ncurses</CODE> distribution that can alleviate 817this problem somewhat; it compacts long sequences of similar operations into 818more succinct single-line pseudo-operations. These pseudo-ops can be 819distinguished by the fact that they are named in capital letters. 820 821<H2><A NAME="hints">Hints, Tips, and Tricks</A></H2> 822 823The <CODE>ncurses</CODE> manual pages are a complete reference for this library. 824In the remainder of this document, we discuss various useful methods that 825may not be obvious from the manual page descriptions. 826 827<H3><A NAME="caution">Some Notes of Caution</A></H3> 828 829If you find yourself thinking you need to use <CODE>noraw()</CODE> or 830<CODE>nocbreak()</CODE>, think again and move carefully. It's probably 831better design to use <CODE>getstr()</CODE> or one of its relatives to 832simulate cooked mode. The <CODE>noraw()</CODE> and <CODE>nocbreak()</CODE> 833functions try to restore cooked mode, but they may end up clobbering 834some control bits set before you started your application. Also, they 835have always been poorly documented, and are likely to hurt your 836application's usability with other curses libraries. <P> 837 838Bear in mind that <CODE>refresh()</CODE> is a synonym for <CODE>wrefresh(stdscr)</CODE>. 839Don't try to mix use of <CODE>stdscr</CODE> with use of windows declared 840by <CODE>newwin()</CODE>; a <CODE>refresh()</CODE> call will blow them off the 841screen. The right way to handle this is to use <CODE>subwin()</CODE>, or 842not touch <CODE>stdscr</CODE> at all and tile your screen with declared 843windows which you then <CODE>wnoutrefresh()</CODE> somewhere in your program 844event loop, with a single <CODE>doupdate()</CODE> call to trigger actual 845repainting. <P> 846 847You are much less likely to run into problems if you design your screen 848layouts to use tiled rather than overlapping windows. Historically, 849curses support for overlapping windows has been weak, fragile, and poorly 850documented. The <CODE>ncurses</CODE> library is not yet an exception to this 851rule. <P> 852 853There is a panels library included in the <CODE>ncurses</CODE> 854distribution that does a pretty good job of strengthening the 855overlapping-windows facilities. <P> 856 857Try to avoid using the global variables LINES and COLS. Use 858<CODE>getmaxyx()</CODE> on the <CODE>stdscr</CODE> context instead. Reason: 859your code may be ported to run in an environment with window resizes, 860in which case several screens could be open with different sizes. 861 862<H3><A NAME="leaving">Temporarily Leaving NCURSES Mode</A></H3> 863 864Sometimes you will want to write a program that spends most of its time in 865screen mode, but occasionally returns to ordinary `cooked' mode. A common 866reason for this is to support shell-out. This behavior is simple to arrange 867in <CODE>ncurses</CODE>. <P> 868 869To leave <CODE>ncurses</CODE> mode, call <CODE>endwin()</CODE> as you would if you 870were intending to terminate the program. This will take the screen back to 871cooked mode; you can do your shell-out. When you want to return to 872<CODE>ncurses</CODE> mode, simply call <CODE>refresh()</CODE> or <CODE>doupdate()</CODE>. 873This will repaint the screen. <P> 874 875There is a boolean function, <CODE>isendwin()</CODE>, which code can use to 876test whether <CODE>ncurses</CODE> screen mode is active. It returns <CODE>TRUE</CODE> 877in the interval between an <CODE>endwin()</CODE> call and the following 878<CODE>refresh()</CODE>, <CODE>FALSE</CODE> otherwise. <P> 879 880Here is some sample code for shellout: 881 882<PRE> 883 addstr("Shelling out..."); 884 def_prog_mode(); /* save current tty modes */ 885 endwin(); /* restore original tty modes */ 886 system("sh"); /* run shell */ 887 addstr("returned.\n"); /* prepare return message */ 888 refresh(); /* restore save modes, repaint screen */ 889</PRE> 890 891<H3><A NAME="xterm">Using NCURSES under XTERM</A></H3> 892 893A resize operation in X sends SIGWINCH to the application running under xterm. 894The <CODE>ncurses</CODE> library provides an experimental signal 895handler, but in general does not catch this signal, because it cannot 896know how you want the screen re-painted. You will usually have to write the 897SIGWINCH handler yourself. Ncurses can give you some help. <P> 898 899The easiest way to code your SIGWINCH handler is to have it do an 900<CODE>endwin</CODE>, followed by an <CODE>refresh</CODE> and a screen repaint you code 901yourself. The <CODE>refresh</CODE> will pick up the new screen size from the 902xterm's environment. <P> 903 904That is the standard way, of course (it even works with some vendor's curses 905implementations). 906Its drawback is that it clears the screen to reinitialize the display, and does 907not resize subwindows which must be shrunk. 908<CODE>Ncurses</CODE> provides an extension which works better, the 909<CODE>resizeterm</CODE> function. That function ensures that all windows 910are limited to the new screen dimensions, and pads <CODE>stdscr</CODE> 911with blanks if the screen is larger. <P> 912 913Finally, ncurses can be configured to provide its own SIGWINCH handler, 914based on <CODE>resizeterm</CODE>. 915 916<H3><A NAME="screens">Handling Multiple Terminal Screens</A></H3> 917 918The <CODE>initscr()</CODE> function actually calls a function named 919<CODE>newterm()</CODE> to do most of its work. If you are writing a program that 920opens multiple terminals, use <CODE>newterm()</CODE> directly. <P> 921 922For each call, you will have to specify a terminal type and a pair of file 923pointers; each call will return a screen reference, and <CODE>stdscr</CODE> will be 924set to the last one allocated. You will switch between screens with the 925<CODE>set_term</CODE> call. Note that you will also have to call 926<CODE>def_shell_mode</CODE> and <CODE>def_prog_mode</CODE> on each tty yourself. 927 928<H3><A NAME="testing">Testing for Terminal Capabilities</A></H3> 929 930Sometimes you may want to write programs that test for the presence of various 931capabilities before deciding whether to go into <CODE>ncurses</CODE> mode. An easy 932way to do this is to call <CODE>setupterm()</CODE>, then use the functions 933<CODE>tigetflag()</CODE>, <CODE>tigetnum()</CODE>, and <CODE>tigetstr()</CODE> to do your 934testing. <P> 935 936A particularly useful case of this often comes up when you want to 937test whether a given terminal type should be treated as `smart' 938(cursor-addressable) or `stupid'. The right way to test this is to see 939if the return value of <CODE>tigetstr("cup")</CODE> is non-NULL. Alternatively, 940you can include the <CODE>term.h</CODE> file and test the value of the 941macro <CODE>cursor_address</CODE>. 942 943<H3><A NAME="tuning">Tuning for Speed</A></H3> 944 945Use the <CODE>addchstr()</CODE> family of functions for fast 946screen-painting of text when you know the text doesn't contain any 947control characters. Try to make attribute changes infrequent on your 948screens. Don't use the <CODE>immedok()</CODE> option! 949 950<H3><A NAME="special">Special Features of NCURSES</A></H3> 951 952The <CODE>wresize()</CODE> function allows you to resize a window in place. 953The associated <CODE>resizeterm()</CODE> function simplifies the construction 954of <a HREF="#xterm">SIGWINCH</a> handlers, for resizing all windows. <P> 955 956The <CODE>define_key()</CODE> function allows you 957to define at runtime function-key control sequences which are not in the 958terminal description. 959The <CODE>keyok()</CODE> function allows you to temporarily 960enable or disable interpretation of any function-key control sequence. <P> 961 962The <CODE>use_default_colors()</CODE> function allows you to construct 963applications which can use the terminal's default foreground and 964background colors as an additional "default" color. 965Several terminal emulators support this feature, which is based on ISO 6429. <P> 966 967Ncurses supports up 16 colors, unlike SVr4 curses which defines only 8. 968While most terminals which provide color allow only 8 colors, about 969a quarter (including XFree86 xterm) support 16 colors. 970 971<H2><A NAME="compat">Compatibility with Older Versions</A></H2> 972 973Despite our best efforts, there are some differences between <CODE>ncurses</CODE> 974and the (undocumented!) behavior of older curses implementations. These arise 975from ambiguities or omissions in the documentation of the API. 976 977<H3><A NAME="refbug">Refresh of Overlapping Windows</A></H3> 978 979If you define two windows A and B that overlap, and then alternately scribble 980on and refresh them, the changes made to the overlapping region under historic 981<CODE>curses</CODE> versions were often not documented precisely. <P> 982 983To understand why this is a problem, remember that screen updates are 984calculated between two representations of the <EM>entire</EM> display. The 985documentation says that when you refresh a window, it is first copied to to the 986virtual screen, and then changes are calculated to update the physical screen 987(and applied to the terminal). But "copied to" is not very specific, and 988subtle differences in how copying works can produce different behaviors in the 989case where two overlapping windows are each being refreshed at unpredictable 990intervals. <P> 991 992What happens to the overlapping region depends on what <CODE>wnoutrefresh()</CODE> 993does with its argument -- what portions of the argument window it copies to the 994virtual screen. Some implementations do "change copy", copying down only 995locations in the window that have changed (or been marked changed with 996<CODE>wtouchln()</CODE> and friends). Some implementations do "entire copy", 997copying <EM>all</EM> window locations to the virtual screen whether or not 998they have changed. <P> 999 1000The <CODE>ncurses</CODE> library itself has not always been consistent on this 1001score. Due to a bug, versions 1.8.7 to 1.9.8a did entire copy. Versions 10021.8.6 and older, and versions 1.9.9 and newer, do change copy. <P> 1003 1004For most commercial curses implementations, it is not documented and not known 1005for sure (at least not to the <CODE>ncurses</CODE> maintainers) whether they do 1006change copy or entire copy. We know that System V release 3 curses has logic 1007in it that looks like an attempt to do change copy, but the surrounding logic 1008and data representations are sufficiently complex, and our knowledge 1009sufficiently indirect, that it's hard to know whether this is reliable. 1010 1011It is not clear what the SVr4 documentation and XSI standard intend. The XSI 1012Curses standard barely mentions wnoutrefresh(); the SVr4 documents seem to be 1013describing entire-copy, but it is possible with some effort and straining to 1014read them the other way. <P> 1015 1016It might therefore be unwise to rely on either behavior in programs that might 1017have to be linked with other curses implementations. Instead, you can do an 1018explicit <CODE>touchwin()</CODE> before the <CODE>wnoutrefresh()</CODE> call to 1019guarantee an entire-contents copy anywhere. <P> 1020 1021The really clean way to handle this is to use the panels library. If, 1022when you want a screen update, you do <CODE>update_panels()</CODE>, it will 1023do all the necessary <CODE>wnoutrfresh()</CODE> calls for whatever panel 1024stacking order you have defined. Then you can do one <CODE>doupdate()</CODE> 1025and there will be a <EM>single</EM> burst of physical I/O that will do 1026all your updates. 1027 1028<H3><A NAME="backbug">Background Erase</A></H3> 1029 1030If you have been using a very old versions of <CODE>ncurses</CODE> (1.8.7 or 1031older) you may be surprised by the behavior of the erase functions. In older 1032versions, erased areas of a window were filled with a blank modified by the 1033window's current attribute (as set by <STRONG>wattrset()</STRONG>, <STRONG>wattron()</STRONG>, 1034<STRONG>wattroff()</STRONG> and friends). <P> 1035 1036In newer versions, this is not so. Instead, the attribute of erased blanks 1037is normal unless and until it is modified by the functions <CODE>bkgdset()</CODE> 1038or <CODE>wbkgdset()</CODE>. <P> 1039 1040This change in behavior conforms <CODE>ncurses</CODE> to System V Release 4 and 1041the XSI Curses standard. 1042 1043<H2><A NAME="xsifuncs">XSI Curses Conformance</A></H2> 1044 1045The <CODE>ncurses</CODE> library is intended to be base-level conformant with the 1046XSI Curses standard from X/Open. Many extended-level features (in fact, almost 1047all features not directly concerned with wide characters and 1048internationalization) are also supported. <P> 1049 1050One effect of XSI conformance is the change in behavior described under 1051<A HREF="#backbug">"Background Erase -- Compatibility with Old Versions"</A>. <P> 1052 1053Also, <CODE>ncurses</CODE> meets the XSI requirement that every macro 1054entry point have a corresponding function which may be linked (and 1055will be prototype-checked) if the macro definition is disabled with 1056<CODE>#undef</CODE>. 1057 1058<H1><A NAME="panels">The Panels Library</A></H1> 1059 1060The <CODE>ncurses</CODE> library by itself provides good support for screen 1061displays in which the windows are tiled (non-overlapping). In the more 1062general case that windows may overlap, you have to use a series of 1063<CODE>wnoutrefresh()</CODE> calls followed by a <CODE>doupdate()</CODE>, and be 1064careful about the order you do the window refreshes in. It has to be 1065bottom-upwards, otherwise parts of windows that should be obscured will 1066show through. <P> 1067 1068When your interface design is such that windows may dive deeper into the 1069visibility stack or pop to the top at runtime, the resulting book-keeping 1070can be tedious and difficult to get right. Hence the panels library. <P> 1071 1072The <CODE>panel</CODE> library first appeared in AT&T System V. The 1073version documented here is the <CODE>panel</CODE> code distributed 1074with <CODE>ncurses</CODE>. 1075 1076<H2><A NAME="pcompile">Compiling With the Panels Library</A></H2> 1077 1078Your panels-using modules must import the panels library declarations with 1079 1080<PRE> 1081 #include <panel.h> 1082</PRE> 1083 1084and must be linked explicitly with the panels library using an 1085<CODE>-lpanel</CODE> argument. Note that they must also link the 1086<CODE>ncurses</CODE> library with <CODE>-lncurses</CODE>. Many linkers 1087are two-pass and will accept either order, but it is still good practice 1088to put <CODE>-lpanel</CODE> first and <CODE>-lncurses</CODE> second. 1089 1090<H2><A NAME="poverview">Overview of Panels</A></H2> 1091 1092A panel object is a window that is implicitly treated as part of a 1093<DFN>deck</DFN> including all other panel objects. The deck has an implicit 1094bottom-to-top visibility order. The panels library includes an update 1095function (analogous to <CODE>refresh()</CODE>) that displays all panels in the 1096deck in the proper order to resolve overlaps. The standard window, 1097<CODE>stdscr</CODE>, is considered below all panels. <P> 1098 1099Details on the panels functions are available in the man pages. We'll just 1100hit the highlights here. <P> 1101 1102You create a panel from a window by calling <CODE>new_panel()</CODE> on a 1103window pointer. It then becomes the top of the deck. The panel's window 1104is available as the value of <CODE>panel_window()</CODE> called with the 1105panel pointer as argument.<P> 1106 1107You can delete a panel (removing it from the deck) with <CODE>del_panel</CODE>. 1108This will not deallocate the associated window; you have to do that yourself. 1109 1110You can replace a panel's window with a different window by calling 1111<CODE>replace_window</CODE>. The new window may be of different size; 1112the panel code will re-compute all overlaps. This operation doesn't 1113change the panel's position in the deck. <P> 1114 1115To move a panel's window, use <CODE>move_panel()</CODE>. The 1116<CODE>mvwin()</CODE> function on the panel's window isn't sufficient because it 1117doesn't update the panels library's representation of where the windows are. 1118This operation leaves the panel's depth, contents, and size unchanged. <P> 1119 1120Two functions (<CODE>top_panel()</CODE>, <CODE>bottom_panel()</CODE>) are 1121provided for rearranging the deck. The first pops its argument window to the 1122top of the deck; the second sends it to the bottom. Either operation leaves 1123the panel's screen location, contents, and size unchanged. <P> 1124 1125The function <CODE>update_panels()</CODE> does all the 1126<CODE>wnoutrefresh()</CODE> calls needed to prepare for 1127<CODE>doupdate()</CODE> (which you must call yourself, afterwards). <P> 1128 1129Typically, you will want to call <CODE>update_panels()</CODE> and 1130<CODE>doupdate()</CODE> just before accepting command input, once in each cycle 1131of interaction with the user. If you call <CODE>update_panels()</CODE> after 1132each and every panel write, you'll generate a lot of unnecessary refresh 1133activity and screen flicker. 1134 1135<H2><A NAME="pstdscr">Panels, Input, and the Standard Screen</A></H2> 1136 1137You shouldn't mix <CODE>wnoutrefresh()</CODE> or <CODE>wrefresh()</CODE> 1138operations with panels code; this will work only if the argument window 1139is either in the top panel or unobscured by any other panels. <P> 1140 1141The <CODE>stsdcr</CODE> window is a special case. It is considered below all 1142panels. Because changes to panels may obscure parts of <CODE>stdscr</CODE>, 1143though, you should call <CODE>update_panels()</CODE> before 1144<CODE>doupdate()</CODE> even when you only change <CODE>stdscr</CODE>. <P> 1145 1146Note that <CODE>wgetch</CODE> automatically calls <CODE>wrefresh</CODE>. 1147Therefore, before requesting input from a panel window, you need to be sure 1148that the panel is totally unobscured. <P> 1149 1150There is presently no way to display changes to one obscured panel without 1151repainting all panels. 1152 1153<H2><A NAME="hiding">Hiding Panels</A></H2> 1154 1155It's possible to remove a panel from the deck temporarily; use 1156<CODE>hide_panel</CODE> for this. Use <CODE>show_panel()</CODE> to render it 1157visible again. The predicate function <CODE>panel_hidden</CODE> 1158tests whether or not a panel is hidden. <P> 1159 1160The <CODE>panel_update</CODE> code ignores hidden panels. You cannot do 1161<CODE>top_panel()</CODE> or <CODE>bottom_panel</CODE> on a hidden panel(). 1162Other panels operations are applicable. 1163 1164<H2><A NAME="pmisc">Miscellaneous Other Facilities</A></H2> 1165 1166It's possible to navigate the deck using the functions 1167<CODE>panel_above()</CODE> and <CODE>panel_below</CODE>. Handed a panel 1168pointer, they return the panel above or below that panel. Handed 1169<CODE>NULL</CODE>, they return the bottom-most or top-most panel. <P> 1170 1171Every panel has an associated user pointer, not used by the panel code, to 1172which you can attach application data. See the man page documentation 1173of <CODE>set_panel_userptr()</CODE> and <CODE>panel_userptr</CODE> for 1174details. 1175 1176<H1><A NAME="menu">The Menu Library</A></H1> 1177 1178A menu is a screen display that assists the user to choose some subset 1179of a given set of items. The <CODE>menu</CODE> library is a curses 1180extension that supports easy programming of menu hierarchies with a 1181uniform but flexible interface. <P> 1182 1183The <CODE>menu</CODE> library first appeared in AT&T System V. The 1184version documented here is the <CODE>menu</CODE> code distributed 1185with <CODE>ncurses</CODE>. 1186 1187<H2><A NAME="mcompile">Compiling With the menu Library</A></H2> 1188 1189Your menu-using modules must import the menu library declarations with 1190 1191<PRE> 1192 #include <menu.h> 1193</PRE> 1194 1195and must be linked explicitly with the menus library using an 1196<CODE>-lmenu</CODE> argument. Note that they must also link the 1197<CODE>ncurses</CODE> library with <CODE>-lncurses</CODE>. Many linkers 1198are two-pass and will accept either order, but it is still good practice 1199to put <CODE>-lmenu</CODE> first and <CODE>-lncurses</CODE> second. 1200 1201<H2><A NAME="moverview">Overview of Menus</A></H2> 1202 1203The menus created by this library consist of collections of 1204<DFN>items</DFN> including a name string part and a description string 1205part. To make menus, you create groups of these items and connect 1206them with menu frame objects. <P> 1207 1208The menu can then by <DFN>posted</DFN>, that is written to an 1209associated window. Actually, each menu has two associated windows; a 1210containing window in which the programmer can scribble titles or 1211borders, and a subwindow in which the menu items proper are displayed. 1212If this subwindow is too small to display all the items, it will be a 1213scrollable viewport on the collection of items. <P> 1214 1215A menu may also be <DFN>unposted</DFN> (that is, undisplayed), and finally 1216freed to make the storage associated with it and its items available for 1217re-use. <P> 1218 1219The general flow of control of a menu program looks like this: 1220 1221<OL> 1222<LI>Initialize <CODE>curses</CODE>. 1223<LI>Create the menu items, using <CODE>new_item()</CODE>. 1224<LI>Create the menu using <CODE>new_menu()</CODE>. 1225<LI>Post the menu using <CODE>menu_post()</CODE>. 1226<LI>Refresh the screen. 1227<LI>Process user requests via an input loop. 1228<LI>Unpost the menu using <CODE>menu_unpost()</CODE>. 1229<LI>Free the menu, using <CODE>free_menu()</CODE>. 1230<LI>Free the items using <CODE>free_item()</CODE>. 1231<LI>Terminate <CODE>curses</CODE>. 1232</OL> 1233 1234<H2><A NAME="mselect">Selecting items</A></H2> 1235 1236Menus may be multi-valued or (the default) single-valued (see the manual 1237page <CODE>menu_opts(3x)</CODE> to see how to change the default). 1238Both types always have a <DFN>current item</DFN>. <P> 1239 1240From a single-valued menu you can read the selected value simply by looking 1241at the current item. From a multi-valued menu, you get the selected set 1242by looping through the items applying the <CODE>item_value()</CODE> 1243predicate function. Your menu-processing code can use the function 1244<CODE>set_item_value()</CODE> to flag the items in the select set. <P> 1245 1246Menu items can be made unselectable using <CODE>set_item_opts()</CODE> 1247or <CODE>item_opts_off()</CODE> with the <CODE>O_SELECTABLE</CODE> 1248argument. This is the only option so far defined for menus, but it 1249is good practice to code as though other option bits might be on. 1250 1251<H2><A NAME="mdisplay">Menu Display</A></H2> 1252 1253The menu library calculates a minimum display size for your window, based 1254on the following variables: 1255 1256<UL> 1257<LI>The number and maximum length of the menu items 1258<LI>Whether the O_ROWMAJOR option is enabled 1259<LI>Whether display of descriptions is enabled 1260<LI>Whatever menu format may have been set by the programmer 1261<LI>The length of the menu mark string used for highlighting selected items 1262</UL> 1263 1264The function <CODE>set_menu_format()</CODE> allows you to set the 1265maximum size of the viewport or <DFN>menu page</DFN> that will be used 1266to display menu items. You can retrieve any format associated with a 1267menu with <CODE>menu_format()</CODE>. The default format is rows=16, 1268columns=1. <P> 1269 1270The actual menu page may be smaller than the format size. This depends 1271on the item number and size and whether O_ROWMAJOR is on. This option 1272(on by default) causes menu items to be displayed in a `raster-scan' 1273pattern, so that if more than one item will fit horizontally the first 1274couple of items are side-by-side in the top row. The alternative is 1275column-major display, which tries to put the first several items in 1276the first column. <P> 1277 1278As mentioned above, a menu format not large enough to allow all items to fit 1279on-screen will result in a menu display that is vertically scrollable. <P> 1280You can scroll it with requests to the menu driver, which will be described 1281in the section on <A HREF="#minput">menu input handling</A>. <P> 1282 1283Each menu has a <DFN>mark string</DFN> used to visually tag selected items; 1284see the <CODE>menu_mark(3x)</CODE> manual page for details. The mark 1285string length also influences the menu page size. <P> 1286 1287The function <CODE>scale_menu()</CODE> returns the minimum display size 1288that the menu code computes from all these factors. 1289 1290There are other menu display attributes including a select attribute, 1291an attribute for selectable items, an attribute for unselectable items, 1292and a pad character used to separate item name text from description 1293text. These have reasonable defaults which the library allows you to 1294change (see the <CODE>menu_attribs(3x)</CODE> manual page. 1295 1296<H2><A NAME="mwindows">Menu Windows</A></H2> 1297 1298Each menu has, as mentioned previously, a pair of associated windows. 1299Both these windows are painted when the menu is posted and erased when 1300the menu is unposted. <P> 1301 1302The outer or frame window is not otherwise touched by the menu 1303routines. It exists so the programmer can associate a title, a 1304border, or perhaps help text with the menu and have it properly 1305refreshed or erased at post/unpost time. The inner window or 1306<DFN>subwindow</DFN> is where the current menu page is displayed. <P> 1307 1308By default, both windows are <CODE>stdscr</CODE>. You can set them with the 1309functions in <CODE>menu_win(3x)</CODE>. <P> 1310 1311When you call <CODE>menu_post()</CODE>, you write the menu to its 1312subwindow. When you call <CODE>menu_unpost()</CODE>, you erase the 1313subwindow, However, neither of these actually modifies the screen. To 1314do that, call <CODE>wrefresh()</CODE> or some equivalent. 1315 1316<H2><A NAME="minput">Processing Menu Input</A></H2> 1317 1318The main loop of your menu-processing code should call 1319<CODE>menu_driver()</CODE> repeatedly. The first argument of this routine 1320is a menu pointer; the second is a menu command code. You should write an 1321input-fetching routine that maps input characters to menu command codes, and 1322pass its output to <CODE>menu_driver()</CODE>. The menu command codes are 1323fully documented in <CODE>menu_driver(3x)</CODE>. <P> 1324 1325The simplest group of command codes is <CODE>REQ_NEXT_ITEM</CODE>, 1326<CODE>REQ_PREV_ITEM</CODE>, <CODE>REQ_FIRST_ITEM</CODE>, 1327<CODE>REQ_LAST_ITEM</CODE>, <CODE>REQ_UP_ITEM</CODE>, 1328<CODE>REQ_DOWN_ITEM</CODE>, <CODE>REQ_LEFT_ITEM</CODE>, 1329<CODE>REQ_RIGHT_ITEM</CODE>. These change the currently selected 1330item. These requests may cause scrolling of the menu page if it only 1331partially displayed. <P> 1332 1333There are explicit requests for scrolling which also change the 1334current item (because the select location does not change, but the 1335item there does). These are <CODE>REQ_SCR_DLINE</CODE>, 1336<CODE>REQ_SCR_ULINE</CODE>, <CODE>REQ_SCR_DPAGE</CODE>, and 1337<CODE>REQ_SCR_UPAGE</CODE>. <P> 1338 1339The <CODE>REQ_TOGGLE_ITEM</CODE> selects or deselects the current item. 1340It is for use in multi-valued menus; if you use it with <CODE>O_ONEVALUE</CODE> 1341on, you'll get an error return (<CODE>E_REQUEST_DENIED</CODE>). <P> 1342 1343Each menu has an associated pattern buffer. The 1344<CODE>menu_driver()</CODE> logic tries to accumulate printable ASCII 1345characters passed in in that buffer; when it matches a prefix of an 1346item name, that item (or the next matching item) is selected. If 1347appending a character yields no new match, that character is deleted 1348from the pattern buffer, and <CODE>menu_driver()</CODE> returns 1349<CODE>E_NO_MATCH</CODE>. <P> 1350 1351Some requests change the pattern buffer directly: 1352<CODE>REQ_CLEAR_PATTERN</CODE>, <CODE>REQ_BACK_PATTERN</CODE>, 1353<CODE>REQ_NEXT_MATCH</CODE>, <CODE>REQ_PREV_MATCH</CODE>. The latter 1354two are useful when pattern buffer input matches more than one item 1355in a multi-valued menu. <P> 1356 1357Each successful scroll or item navigation request clears the pattern 1358buffer. It is also possible to set the pattern buffer explicitly 1359with <CODE>set_menu_pattern()</CODE>. <P> 1360 1361Finally, menu driver requests above the constant <CODE>MAX_COMMAND</CODE> 1362are considered application-specific commands. The <CODE>menu_driver()</CODE> 1363code ignores them and returns <CODE>E_UNKNOWN_COMMAND</CODE>. 1364 1365<H2><A NAME="mmisc">Miscellaneous Other Features</A></H2> 1366 1367Various menu options can affect the processing and visual appearance 1368and input processing of menus. See <CODE>menu_opts(3x) for 1369details.</CODE> <P> 1370 1371It is possible to change the current item from application code; this 1372is useful if you want to write your own navigation requests. It is 1373also possible to explicitly set the top row of the menu display. See 1374<CODE>mitem_current(3x)</CODE>. 1375 1376If your application needs to change the menu subwindow cursor for 1377any reason, <CODE>pos_menu_cursor()</CODE> will restore it to the 1378correct location for continuing menu driver processing. <P> 1379 1380It is possible to set hooks to be called at menu initialization and 1381wrapup time, and whenever the selected item changes. See 1382<CODE>menu_hook(3x)</CODE>. <P> 1383 1384Each item, and each menu, has an associated user pointer on which you 1385can hang application data. See <CODE>mitem_userptr(3x)</CODE> and 1386<CODE>menu_userptr(3x)</CODE>. 1387 1388<H1><A NAME="form">The Forms Library</A></H1> 1389 1390The <CODE>form</CODE> library is a curses extension that supports easy 1391programming of on-screen forms for data entry and program control. <P> 1392 1393The <CODE>form</CODE> library first appeared in AT&T System V. The 1394version documented here is the <CODE>form</CODE> code distributed 1395with <CODE>ncurses</CODE>. 1396 1397<H2><A NAME="fcompile">Compiling With the form Library</A></H2> 1398 1399Your form-using modules must import the form library declarations with 1400 1401<PRE> 1402 #include <form.h> 1403</PRE> 1404 1405and must be linked explicitly with the forms library using an 1406<CODE>-lform</CODE> argument. Note that they must also link the 1407<CODE>ncurses</CODE> library with <CODE>-lncurses</CODE>. Many linkers 1408are two-pass and will accept either order, but it is still good practice 1409to put <CODE>-lform</CODE> first and <CODE>-lncurses</CODE> second. 1410 1411<H2><A NAME="foverview">Overview of Forms</A></H2> 1412 1413A form is a collection of fields; each field may be either a label 1414(explanatory text) or a data-entry location. Long forms may be 1415segmented into pages; each entry to a new page clears the screen. <P> 1416To make forms, you create groups of fields and connect them with form 1417frame objects; the form library makes this relatively simple. <P> 1418 1419Once defined, a form can be <DFN>posted</DFN>, that is written to an 1420associated window. Actually, each form has two associated windows; a 1421containing window in which the programmer can scribble titles or 1422borders, and a subwindow in which the form fields proper are displayed. <P> 1423 1424As the form user fills out the posted form, navigation and editing 1425keys support movement between fields, editing keys support modifying 1426field, and plain text adds to or changes data in a current field. The 1427form library allows you (the forms designer) to bind each navigation 1428and editing key to any keystroke accepted by <CODE>curses</CODE> 1429 1430Fields may have validation conditions on them, so that they check input 1431data for type and value. The form library supplies a rich set of 1432pre-defined field types, and makes it relatively easy to define new ones. <P> 1433 1434Once its transaction is completed (or aborted), a form may be 1435<DFN>unposted</DFN> (that is, undisplayed), and finally freed to make 1436the storage associated with it and its items available for re-use. <P> 1437 1438The general flow of control of a form program looks like this: 1439 1440<OL> 1441<LI>Initialize <CODE>curses</CODE>. 1442<LI>Create the form fields, using <CODE>new_field()</CODE>. 1443<LI>Create the form using <CODE>new_form()</CODE>. 1444<LI>Post the form using <CODE>form_post()</CODE>. 1445<LI>Refresh the screen. 1446<LI>Process user requests via an input loop. 1447<LI>Unpost the form using <CODE>form_unpost()</CODE>. 1448<LI>Free the form, using <CODE>free_form()</CODE>. 1449<LI>Free the fields using <CODE>free_field()</CODE>. 1450<LI>Terminate <CODE>curses</CODE>. 1451</OL> 1452 1453Note that this looks much like a menu program; the form library handles 1454tasks which are in many ways similar, and its interface was obviously 1455designed to resemble that of the <A HREF="#menu">menu library</A> 1456wherever possible. <P> 1457 1458In forms programs, however, the `process user requests' is somewhat more 1459complicated than for menus. Besides menu-like navigation operations, 1460the menu driver loop has to support field editing and data validation. 1461 1462<H2><A NAME="fcreate">Creating and Freeing Fields and Forms</A></H2> 1463 1464The basic function for creating fields is <CODE>new_field()</CODE>: 1465 1466<PRE> 1467FIELD *new_field(int height, int width, /* new field size */ 1468 int top, int left, /* upper left corner */ 1469 int offscreen, /* number of offscreen rows */ 1470 int nbuf); /* number of working buffers */ 1471</PRE> 1472 1473Menu items always occupy a single row, but forms fields may have 1474multiple rows. So <CODE>new_field()</CODE> requires you to specify a 1475width and height (the first two arguments, which mist both be greater 1476than zero). <P> 1477 1478You must also specify the location of the field's upper left corner on 1479the screen (the third and fourth arguments, which must be zero or 1480greater). Note that these coordinates are relative to the form 1481subwindow, which will coincide with <CODE>stdscr</CODE> by default but 1482need not be <CODE>stdscr</CODE> if you've done an explicit 1483<CODE>set_form_window()</CODE> call. <P> 1484 1485The fifth argument allows you to specify a number of off-screen rows. If 1486this is zero, the entire field will always be displayed. If it is 1487nonzero, the form will be scrollable, with only one screen-full (initially 1488the top part) displayed at any given time. If you make a field dynamic 1489and grow it so it will no longer fit on the screen, the form will become 1490scrollable even if the <CODE>offscreen</CODE> argument was initially zero. <P> 1491 1492The forms library allocates one working buffer per field; the size of 1493each buffer is <CODE>((height + offscreen)*width + 1</CODE>, one character 1494for each position in the field plus a NUL terminator. The sixth 1495argument is the number of additional data buffers to allocate for the 1496field; your application can use them for its own purposes. 1497 1498<PRE> 1499FIELD *dup_field(FIELD *field, /* field to copy */ 1500 int top, int left); /* location of new copy */ 1501</PRE> 1502 1503The function <CODE>dup_field()</CODE> duplicates an existing field at a 1504new location. Size and buffering information are copied; some 1505attribute flags and status bits are not (see the 1506<CODE>form_field_new(3X)</CODE> for details). 1507 1508<PRE> 1509FIELD *link_field(FIELD *field, /* field to copy */ 1510 int top, int left); /* location of new copy */ 1511</PRE> 1512 1513The function <CODE>link_field()</CODE> also duplicates an existing field 1514at a new location. The difference from <CODE>dup_field()</CODE> is that 1515it arranges for the new field's buffer to be shared with the old one. <P> 1516 1517Besides the obvious use in making a field editable from two different 1518form pages, linked fields give you a way to hack in dynamic labels. If 1519you declare several fields linked to an original, and then make them 1520inactive, changes from the original will still be propagated to the 1521linked fields. <P> 1522 1523As with duplicated fields, linked fields have attribute bits separate 1524from the original. <P> 1525 1526As you might guess, all these field-allocations return <CODE>NULL</CODE> if 1527the field allocation is not possible due to an out-of-memory error or 1528out-of-bounds arguments. <P> 1529 1530To connect fields to a form, use 1531 1532<PRE> 1533FORM *new_form(FIELD **fields); 1534</PRE> 1535 1536This function expects to see a NULL-terminated array of field pointers. 1537Said fields are connected to a newly-allocated form object; its address 1538is returned (or else NULL if the allocation fails). <P> 1539 1540Note that <CODE>new_field()</CODE> does <EM>not</EM> copy the pointer array 1541into private storage; if you modify the contents of the pointer array 1542during forms processing, all manner of bizarre things might happen. Also 1543note that any given field may only be connected to one form. <P> 1544 1545The functions <CODE>free_field()</CODE> and <CODE>free_form</CODE> are available 1546to free field and form objects. It is an error to attempt to free a field 1547connected to a form, but not vice-versa; thus, you will generally free 1548your form objects first. 1549 1550<H2><A NAME="fattributes">Fetching and Changing Field Attributes</A></H2> 1551 1552Each form field has a number of location and size attributes 1553associated with it. There are other field attributes used to control 1554display and editing of the field. Some (for example, the <CODE>O_STATIC</CODE> bit) 1555involve sufficient complications to be covered in sections of their own 1556later on. We cover the functions used to get and set several basic 1557attributes here. <P> 1558 1559When a field is created, the attributes not specified by the 1560<CODE>new_field</CODE> function are copied from an invisible system 1561default field. In attribute-setting and -fetching functions, the 1562argument NULL is taken to mean this field. Changes to it persist 1563as defaults until your forms application terminates. 1564 1565<H3><A NAME="fsizes">Fetching Size and Location Data</A></H3> 1566 1567You can retrieve field sizes and locations through: 1568 1569<PRE> 1570int field_info(FIELD *field, /* field from which to fetch */ 1571 int *height, *int width, /* field size */ 1572 int *top, int *left, /* upper left corner */ 1573 int *offscreen, /* number of offscreen rows */ 1574 int *nbuf); /* number of working buffers */ 1575</PRE> 1576 1577This function is a sort of inverse of <CODE>new_field()</CODE>; instead of 1578setting size and location attributes of a new field, it fetches them 1579from an existing one. 1580 1581<H3><A NAME="flocation">Changing the Field Location</A></H3> 1582 1583It is possible to move a field's location on the screen: 1584 1585<PRE> 1586int move_field(FIELD *field, /* field to alter */ 1587 int top, int left); /* new upper-left corner */ 1588</PRE> 1589 1590You can, of course. query the current location through <CODE>field_info()</CODE>. 1591 1592<H3><A NAME="fjust">The Justification Attribute</A></H3> 1593 1594One-line fields may be unjustified, justified right, justified left, 1595or centered. Here is how you manipulate this attribute: 1596 1597<PRE> 1598int set_field_just(FIELD *field, /* field to alter */ 1599 int justmode); /* mode to set */ 1600 1601int field_just(FIELD *field); /* fetch mode of field */ 1602</PRE> 1603 1604The mode values accepted and returned by this functions are 1605preprocessor macros <CODE>NO_JUSTIFICATION</CODE>, <CODE>JUSTIFY_RIGHT</CODE>, 1606<CODE>JUSTIFY_LEFT</CODE>, or <CODE>JUSTIFY_CENTER</CODE>. 1607 1608<H3><A NAME="fdispatts">Field Display Attributes</A></H3> 1609 1610For each field, you can set a foreground attribute for entered 1611characters, a background attribute for the entire field, and a pad 1612character for the unfilled portion of the field. You can also 1613control pagination of the form. <P> 1614 1615This group of four field attributes controls the visual appearance 1616of the field on the screen, without affecting in any way the data 1617in the field buffer. 1618 1619<PRE> 1620int set_field_fore(FIELD *field, /* field to alter */ 1621 chtype attr); /* attribute to set */ 1622 1623chtype field_fore(FIELD *field); /* field to query */ 1624 1625int set_field_back(FIELD *field, /* field to alter */ 1626 chtype attr); /* attribute to set */ 1627 1628chtype field_back(FIELD *field); /* field to query */ 1629 1630int set_field_pad(FIELD *field, /* field to alter */ 1631 int pad); /* pad character to set */ 1632 1633chtype field_pad(FIELD *field); 1634 1635int set_new_page(FIELD *field, /* field to alter */ 1636 int flag); /* TRUE to force new page */ 1637 1638chtype new_page(FIELD *field); /* field to query */ 1639</PRE> 1640 1641The attributes set and returned by the first four functions are normal 1642<CODE>curses(3x)</CODE> display attribute values (<CODE>A_STANDOUT</CODE>, 1643<CODE>A_BOLD</CODE>, <CODE>A_REVERSE</CODE> etc). 1644 1645The page bit of a field controls whether it is displayed at the start of 1646a new form screen. 1647 1648<H3><A NAME="foptions">Field Option Bits</A></H3> 1649 1650There is also a large collection of field option bits you can set to control 1651various aspects of forms processing. You can manipulate them with these 1652functions: 1653 1654<PRE> 1655int set_field_opts(FIELD *field, /* field to alter */ 1656 int attr); /* attribute to set */ 1657 1658int field_opts_on(FIELD *field, /* field to alter */ 1659 int attr); /* attributes to turn on */ 1660 1661int field_opts_off(FIELD *field, /* field to alter */ 1662 int attr); /* attributes to turn off */ 1663 1664int field_opts(FIELD *field); /* field to query */ 1665</PRE> 1666 1667By default, all options are on. Here are the available option bits: 1668<DL> 1669<DT> O_VISIBLE 1670<DD> Controls whether the field is visible on the screen. Can be used 1671during form processing to hide or pop up fields depending on the value 1672of parent fields. 1673<DT> O_ACTIVE 1674<DD> Controls whether the field is active during forms processing (i.e. 1675visited by form navigation keys). Can be used to make labels or derived 1676fields with buffer values alterable by the forms application, not the user. 1677<DT> O_PUBLIC 1678<DD> Controls whether data is displayed during field entry. If this option is 1679turned off on a field, the library will accept and edit data in that field, 1680but it will not be displayed and the visible field cursor will not move. 1681You can turn off the O_PUBLIC bit to define password fields. 1682<DT> O_EDIT 1683<DD> Controls whether the field's data can be modified. When this option is 1684off, all editing requests except <CODE>REQ_PREV_CHOICE</CODE> and 1685<CODE>REQ_NEXT_CHOICE</CODE> will fail. Such read-only fields may be useful for 1686help messages. 1687<DT> O_WRAP 1688<DD> Controls word-wrapping in multi-line fields. Normally, when any 1689character of a (blank-separated) word reaches the end of the current line, the 1690entire word is wrapped to the next line (assuming there is one). When this 1691option is off, the word will be split across the line break. 1692<DT> O_BLANK 1693<DD> Controls field blanking. When this option is on, entering a character at 1694the first field position erases the entire field (except for the just-entered 1695character). 1696<DT> O_AUTOSKIP 1697<DD> Controls automatic skip to next field when this one fills. Normally, 1698when the forms user tries to type more data into a field than will fit, 1699the editing location jumps to next field. When this option is off, the 1700user's cursor will hang at the end of the field. This option is ignored 1701in dynamic fields that have not reached their size limit. 1702<DT> O_NULLOK 1703<DD> Controls whether <A HREF="#fvalidation">validation</A> is applied to 1704blank fields. Normally, it is not; the user can leave a field blank 1705without invoking the usual validation check on exit. If this option is 1706off on a field, exit from it will invoke a validation check. 1707<DT> O_PASSOK 1708<DD> Controls whether validation occurs on every exit, or only after 1709the field is modified. Normally the latter is true. Setting O_PASSOK 1710may be useful if your field's validation function may change during 1711forms processing. 1712<DT> O_STATIC 1713<DD> Controls whether the field is fixed to its initial dimensions. If you 1714turn this off, the field becomes <A HREF="#fdynamic">dynamic</A> and will 1715stretch to fit entered data. 1716</DL> 1717 1718A field's options cannot be changed while the field is currently selected. 1719However, options may be changed on posted fields that are not current. <P> 1720 1721The option values are bit-masks and can be composed with logical-or in 1722the obvious way. 1723 1724<H2><A NAME="fstatus">Field Status</A></H2> 1725 1726Every field has a status flag, which is set to FALSE when the field is 1727created and TRUE when the value in field buffer 0 changes. This flag can 1728be queried and set directly: 1729 1730<PRE> 1731int set_field_status(FIELD *field, /* field to alter */ 1732 int status); /* mode to set */ 1733 1734int field_status(FIELD *field); /* fetch mode of field */ 1735</PRE> 1736 1737Setting this flag under program control can be useful if you use the same 1738form repeatedly, looking for modified fields each time. <P> 1739 1740Calling <CODE>field_status()</CODE> on a field not currently selected 1741for input will return a correct value. Calling <CODE>field_status()</CODE> on a 1742field that is currently selected for input may not necessarily give a 1743correct field status value, because entered data isn't necessarily copied to 1744buffer zero before the exit validation check. 1745 1746To guarantee that the returned status value reflects reality, call 1747<CODE>field_status()</CODE> either (1) in the field's exit validation check 1748routine, (2) from the field's or form's initialization or termination 1749hooks, or (3) just after a <CODE>REQ_VALIDATION</CODE> request has been 1750processed by the forms driver. 1751 1752<H2><A NAME="fuser">Field User Pointer</A></H2> 1753 1754Each field structure contains one character pointer slot that is not used 1755by the forms library. It is intended to be used by applications to store 1756private per-field data. You can manipulate it with: 1757 1758<PRE> 1759int set_field_userptr(FIELD *field, /* field to alter */ 1760 char *userptr); /* mode to set */ 1761 1762char *field_userptr(FIELD *field); /* fetch mode of field */ 1763</PRE> 1764 1765(Properly, this user pointer field ought to have <CODE>(void *)</CODE> type. 1766The <CODE>(char *)</CODE> type is retained for System V compatibility.) <P> 1767 1768It is valid to set the user pointer of the default field (with a 1769<CODE>set_field_userptr()</CODE> call passed a NULL field pointer.) 1770When a new field is created, the default-field user pointer is copied 1771to initialize the new field's user pointer. 1772 1773<H2><A NAME="fdynamic">Variable-Sized Fields</A></H2> 1774 1775Normally, a field is fixed at the size specified for it at creation 1776time. If, however, you turn off its O_STATIC bit, it becomes 1777<DFN>dynamic</DFN> and will automatically resize itself to accommodate 1778data as it is entered. If the field has extra buffers associated with it, 1779they will grow right along with the main input buffer. <P> 1780 1781A one-line dynamic field will have a fixed height (1) but variable 1782width, scrolling horizontally to display data within the field area as 1783originally dimensioned and located. A multi-line dynamic field will 1784have a fixed width, but variable height (number of rows), scrolling 1785vertically to display data within the field area as originally 1786dimensioned and located. <P> 1787 1788Normally, a dynamic field is allowed to grow without limit. But it is 1789possible to set an upper limit on the size of a dynamic field. You do 1790it with this function: 1791 1792<PRE> 1793int set_max_field(FIELD *field, /* field to alter (may not be NULL) */ 1794 int max_size); /* upper limit on field size */ 1795</PRE> 1796 1797If the field is one-line, <CODE>max_size</CODE> is taken to be a column size 1798limit; if it is multi-line, it is taken to be a line size limit. To disable 1799any limit, use an argument of zero. The growth limit can be changed whether 1800or not the O_STATIC bit is on, but has no effect until it is. <P> 1801 1802The following properties of a field change when it becomes dynamic: 1803 1804<UL> 1805<LI>If there is no growth limit, there is no final position of the field; 1806therefore <CODE>O_AUTOSKIP</CODE> and <CODE>O_NL_OVERLOAD</CODE> are ignored. 1807<LI>Field justification will be ignored (though whatever justification is 1808set up will be retained internally and can be queried). 1809<LI>The <CODE>dup_field()</CODE> and <CODE>link_field()</CODE> calls copy 1810dynamic-buffer sizes. If the <CODE>O_STATIC</CODE> option is set on one of a 1811collection of links, buffer resizing will occur only when the field is 1812edited through that link. 1813<LI>The call <CODE>field_info()</CODE> will retrieve the original static size of 1814the field; use <CODE>dynamic_field_info()</CODE> to get the actual dynamic size. 1815</UL> 1816 1817<H2><A NAME="fvalidation">Field Validation</A></H2> 1818 1819By default, a field will accept any data that will fit in its input buffer. 1820However, it is possible to attach a validation type to a field. If you do 1821this, any attempt to leave the field while it contains data that doesn't 1822match the validation type will fail. Some validation types also have a 1823character-validity check for each time a character is entered in the field. <P> 1824 1825A field's validation check (if any) is not called when 1826<CODE>set_field_buffer()</CODE> modifies the input buffer, nor when that buffer 1827is changed through a linked field. <P> 1828 1829The <CODE>form</CODE> library provides a rich set of pre-defined validation 1830types, and gives you the capability to define custom ones of your own. You 1831can examine and change field validation attributes with the following 1832functions: 1833 1834<PRE> 1835int set_field_type(FIELD *field, /* field to alter */ 1836 FIELDTYPE *ftype, /* type to associate */ 1837 ...); /* additional arguments*/ 1838 1839FIELDTYPE *field_type(FIELD *field); /* field to query */ 1840</PRE> 1841 1842The validation type of a field is considered an attribute of the field. As 1843with other field attributes, Also, doing <CODE>set_field_type()</CODE> with a 1844<CODE>NULL</CODE> field default will change the system default for validation of 1845newly-created fields. <P> 1846 1847Here are the pre-defined validation types: 1848 1849<H3><A NAME="ftype_alpha">TYPE_ALPHA</A></H3> 1850 1851This field type accepts alphabetic data; no blanks, no digits, no special 1852characters (this is checked at character-entry time). It is set up with: 1853 1854<PRE> 1855int set_field_type(FIELD *field, /* field to alter */ 1856 TYPE_ALPHA, /* type to associate */ 1857 int width); /* maximum width of field */ 1858</PRE> 1859 1860The <CODE>width</CODE> argument sets a minimum width of data. Typically 1861you'll want to set this to the field width; if it's greater than the 1862field width, the validation check will always fail. A minimum width 1863of zero makes field completion optional. 1864 1865<H3><A NAME="ftype_alnum">TYPE_ALNUM</A></H3> 1866 1867This field type accepts alphabetic data and digits; no blanks, no special 1868characters (this is checked at character-entry time). It is set up with: 1869 1870<PRE> 1871int set_field_type(FIELD *field, /* field to alter */ 1872 TYPE_ALNUM, /* type to associate */ 1873 int width); /* maximum width of field */ 1874</PRE> 1875 1876The <CODE>width</CODE> argument sets a minimum width of data. As with 1877TYPE_ALPHA, typically you'll want to set this to the field width; if it's 1878greater than the field width, the validation check will always fail. A 1879minimum width of zero makes field completion optional. 1880 1881<H3><A NAME="ftype_enum">TYPE_ENUM</A></H3> 1882 1883This type allows you to restrict a field's values to be among a specified 1884set of string values (for example, the two-letter postal codes for U.S. 1885states). It is set up with: 1886 1887<PRE> 1888int set_field_type(FIELD *field, /* field to alter */ 1889 TYPE_ENUM, /* type to associate */ 1890 char **valuelist; /* list of possible values */ 1891 int checkcase; /* case-sensitive? */ 1892 int checkunique); /* must specify uniquely? */ 1893</PRE> 1894 1895The <CODE>valuelist</CODE> parameter must point at a NULL-terminated list of 1896valid strings. The <CODE>checkcase</CODE> argument, if true, makes comparison 1897with the string case-sensitive. <P> 1898 1899When the user exits a TYPE_ENUM field, the validation procedure tries to 1900complete the data in the buffer to a valid entry. If a complete choice string 1901has been entered, it is of course valid. But it is also possible to enter a 1902prefix of a valid string and have it completed for you. <P> 1903 1904By default, if you enter such a prefix and it matches more than one value 1905in the string list, the prefix will be completed to the first matching 1906value. But the <CODE>checkunique</CODE> argument, if true, requires prefix 1907matches to be unique in order to be valid. <P> 1908 1909The <CODE>REQ_NEXT_CHOICE</CODE> and <CODE>REQ_PREV_CHOICE</CODE> input requests 1910can be particularly useful with these fields. 1911 1912<H3><A NAME="ftype_integer">TYPE_INTEGER</A></H3> 1913 1914This field type accepts an integer. It is set up as follows: 1915 1916<PRE> 1917int set_field_type(FIELD *field, /* field to alter */ 1918 TYPE_INTEGER, /* type to associate */ 1919 int padding, /* # places to zero-pad to */ 1920 int vmin, int vmax); /* valid range */ 1921</PRE> 1922 1923Valid characters consist of an optional leading minus and digits. 1924The range check is performed on exit. If the range maximum is less 1925than or equal to the minimum, the range is ignored. <P> 1926 1927If the value passes its range check, it is padded with as many leading 1928zero digits as necessary to meet the padding argument. <P> 1929 1930A <CODE>TYPE_INTEGER</CODE> value buffer can conveniently be interpreted 1931with the C library function <CODE>atoi(3)</CODE>. 1932 1933<H3><A NAME="ftype_numeric">TYPE_NUMERIC</A></H3> 1934 1935This field type accepts a decimal number. It is set up as follows: 1936 1937<PRE> 1938int set_field_type(FIELD *field, /* field to alter */ 1939 TYPE_NUMERIC, /* type to associate */ 1940 int padding, /* # places of precision */ 1941 double vmin, double vmax); /* valid range */ 1942</PRE> 1943 1944Valid characters consist of an optional leading minus and digits. possibly 1945including a decimal point. If your system supports locale's, the decimal point 1946character used must be the one defined by your locale. The range check is 1947performed on exit. If the range maximum is less than or equal to the minimum, 1948the range is ignored. <P> 1949 1950If the value passes its range check, it is padded with as many trailing 1951zero digits as necessary to meet the padding argument. <P> 1952 1953A <CODE>TYPE_NUMERIC</CODE> value buffer can conveniently be interpreted 1954with the C library function <CODE>atof(3)</CODE>. 1955 1956<H3><A NAME="ftype_regexp">TYPE_REGEXP</A></H3> 1957 1958This field type accepts data matching a regular expression. It is set up 1959as follows: 1960 1961<PRE> 1962int set_field_type(FIELD *field, /* field to alter */ 1963 TYPE_REGEXP, /* type to associate */ 1964 char *regexp); /* expression to match */ 1965</PRE> 1966 1967The syntax for regular expressions is that of <CODE>regcomp(3)</CODE>. 1968The check for regular-expression match is performed on exit. 1969 1970<H2><A NAME="fbuffer">Direct Field Buffer Manipulation</A></H2> 1971 1972The chief attribute of a field is its buffer contents. When a form has 1973been completed, your application usually needs to know the state of each 1974field buffer. You can find this out with: 1975 1976<PRE> 1977char *field_buffer(FIELD *field, /* field to query */ 1978 int bufindex); /* number of buffer to query */ 1979</PRE> 1980 1981Normally, the state of the zero-numbered buffer for each field is set by 1982the user's editing actions on that field. It's sometimes useful to be able 1983to set the value of the zero-numbered (or some other) buffer from your 1984application: 1985 1986<PRE> 1987int set_field_buffer(FIELD *field, /* field to alter */ 1988 int bufindex, /* number of buffer to alter */ 1989 char *value); /* string value to set */ 1990</PRE> 1991 1992If the field is not large enough and cannot be resized to a sufficiently 1993large size to contain the specified value, the value will be truncated 1994to fit. <P> 1995 1996Calling <CODE>field_buffer()</CODE> with a null field pointer will raise an 1997error. Calling <CODE>field_buffer()</CODE> on a field not currently selected 1998for input will return a correct value. Calling <CODE>field_buffer()</CODE> on a 1999field that is currently selected for input may not necessarily give a 2000correct field buffer value, because entered data isn't necessarily copied to 2001buffer zero before the exit validation check. 2002 2003To guarantee that the returned buffer value reflects on-screen reality, 2004call <CODE>field_buffer()</CODE> either (1) in the field's exit validation 2005check routine, (2) from the field's or form's initialization or termination 2006hooks, or (3) just after a <CODE>REQ_VALIDATION</CODE> request has been processed 2007by the forms driver. 2008 2009<H2><A NAME="formattrs">Attributes of Forms</A></H2> 2010 2011As with field attributes, form attributes inherit a default from a 2012system default form structure. These defaults can be queried or set by 2013of these functions using a form-pointer argument of <CODE>NULL</CODE>. <P> 2014 2015The principal attribute of a form is its field list. You can query 2016and change this list with: 2017 2018<PRE> 2019int set_form_fields(FORM *form, /* form to alter */ 2020 FIELD **fields); /* fields to connect */ 2021 2022char *form_fields(FORM *form); /* fetch fields of form */ 2023 2024int field_count(FORM *form); /* count connect fields */ 2025</PRE> 2026 2027The second argument of <CODE>set_form_fields()</CODE> may be a 2028NULL-terminated field pointer array like the one required by 2029<CODE>new_form()</CODE>. In that case, the old fields of the form are 2030disconnected but not freed (and eligible to be connected to other 2031forms), then the new fields are connected. <P> 2032 2033It may also be null, in which case the old fields are disconnected 2034(and not freed) but no new ones are connected. <P> 2035 2036The <CODE>field_count()</CODE> function simply counts the number of fields 2037connected to a given from. It returns -1 if the form-pointer argument 2038is NULL. 2039 2040<H2><A NAME="fdisplay">Control of Form Display</A></H2> 2041 2042In the overview section, you saw that to display a form you normally 2043start by defining its size (and fields), posting it, and refreshing 2044the screen. There is an hidden step before posting, which is the 2045association of the form with a frame window (actually, a pair of 2046windows) within which it will be displayed. By default, the forms 2047library associates every form with the full-screen window 2048<CODE>stdscr</CODE>. <P> 2049 2050By making this step explicit, you can associate a form with a declared 2051frame window on your screen display. This can be useful if you want to 2052adapt the form display to different screen sizes, dynamically tile 2053forms on the screen, or use a form as part of an interface layout 2054managed by <A HREF="#panels">panels</A>. <P> 2055 2056The two windows associated with each form have the same functions as 2057their analogues in the <A HREF="#menu">menu library</A>. Both these 2058windows are painted when the form is posted and erased when the form 2059is unposted. <P> 2060 2061The outer or frame window is not otherwise touched by the form 2062routines. It exists so the programmer can associate a title, a 2063border, or perhaps help text with the form and have it properly 2064refreshed or erased at post/unpost time. The inner window or subwindow 2065is where the current form page is actually displayed. <P> 2066 2067In order to declare your own frame window for a form, you'll need to 2068know the size of the form's bounding rectangle. You can get this 2069information with: 2070 2071<PRE> 2072int scale_form(FORM *form, /* form to query */ 2073 int *rows, /* form rows */ 2074 int *cols); /* form cols */ 2075</PRE> 2076 2077The form dimensions are passed back in the locations pointed to by 2078the arguments. Once you have this information, you can use it to 2079declare of windows, then use one of these functions: 2080 2081<PRE> 2082int set_form_win(FORM *form, /* form to alter */ 2083 WINDOW *win); /* frame window to connect */ 2084 2085WINDOW *form_win(FORM *form); /* fetch frame window of form */ 2086 2087int set_form_sub(FORM *form, /* form to alter */ 2088 WINDOW *win); /* form subwindow to connect */ 2089 2090WINDOW *form_sub(FORM *form); /* fetch form subwindow of form */ 2091</PRE> 2092 2093Note that curses operations, including <CODE>refresh()</CODE>, on the form, 2094should be done on the frame window, not the form subwindow. <P> 2095 2096It is possible to check from your application whether all of a 2097scrollable field is actually displayed within the menu subwindow. Use 2098these functions: 2099 2100<PRE> 2101int data_ahead(FORM *form); /* form to be queried */ 2102 2103int data_behind(FORM *form); /* form to be queried */ 2104</PRE> 2105 2106The function <CODE>data_ahead()</CODE> returns TRUE if (a) the current 2107field is one-line and has undisplayed data off to the right, (b) the current 2108field is multi-line and there is data off-screen below it. <P> 2109 2110The function <CODE>data_behind()</CODE> returns TRUE if the first (upper 2111left hand) character position is off-screen (not being displayed). <P> 2112 2113Finally, there is a function to restore the form window's cursor to the 2114value expected by the forms driver: 2115 2116<PRE> 2117int pos_form_cursor(FORM *) /* form to be queried */ 2118</PRE> 2119 2120If your application changes the form window cursor, call this function before 2121handing control back to the forms driver in order to re-synchronize it. 2122 2123<H2><A NAME="fdriver">Input Processing in the Forms Driver</A></H2> 2124 2125The function <CODE>form_driver()</CODE> handles virtualized input requests 2126for form navigation, editing, and validation requests, just as 2127<CODE>menu_driver</CODE> does for menus (see the section on <A 2128HREF="#minput">menu input handling</A>). 2129 2130<PRE> 2131int form_driver(FORM *form, /* form to pass input to */ 2132 int request); /* form request code */ 2133</PRE> 2134 2135Your input virtualization function needs to take input and then convert it 2136to either an alphanumeric character (which is treated as data to be 2137entered in the currently-selected field), or a forms processing request. <P> 2138 2139The forms driver provides hooks (through input-validation and 2140field-termination functions) with which your application code can check 2141that the input taken by the driver matched what was expected. 2142 2143<H3><A NAME="fpage">Page Navigation Requests</A></H3> 2144 2145These requests cause page-level moves through the form, 2146triggering display of a new form screen. 2147 2148<DL> 2149<DT> <CODE>REQ_NEXT_PAGE</CODE> 2150<DD> Move to the next form page. 2151<DT> <CODE>REQ_PREV_PAGE</CODE> 2152<DD> Move to the previous form page. 2153<DT> <CODE>REQ_FIRST_PAGE</CODE> 2154<DD> Move to the first form page. 2155<DT> <CODE>REQ_LAST_PAGE</CODE> 2156<DD> Move to the last form page. 2157</DL> 2158 2159These requests treat the list as cyclic; that is, <CODE>REQ_NEXT_PAGE</CODE> 2160from the last page goes to the first, and <CODE>REQ_PREV_PAGE</CODE> from 2161the first page goes to the last. 2162 2163<H3><A NAME="#ffield">Inter-Field Navigation Requests</A></H3> 2164 2165These requests handle navigation between fields on the same page. 2166 2167<DL> 2168<DT> <CODE>REQ_NEXT_FIELD</CODE> 2169<DD> Move to next field. 2170<DT> <CODE>REQ_PREV_FIELD</CODE> 2171<DD> Move to previous field. 2172<DT> <CODE>REQ_FIRST_FIELD</CODE> 2173<DD> Move to the first field. 2174<DT> <CODE>REQ_LAST_FIELD</CODE> 2175<DD> Move to the last field. 2176<DT> <CODE>REQ_SNEXT_FIELD</CODE> 2177<DD> Move to sorted next field. 2178<DT> <CODE>REQ_SPREV_FIELD</CODE> 2179<DD> Move to sorted previous field. 2180<DT> <CODE>REQ_SFIRST_FIELD</CODE> 2181<DD> Move to the sorted first field. 2182<DT> <CODE>REQ_SLAST_FIELD</CODE> 2183<DD> Move to the sorted last field. 2184<DT> <CODE>REQ_LEFT_FIELD</CODE> 2185<DD> Move left to field. 2186<DT> <CODE>REQ_RIGHT_FIELD</CODE> 2187<DD> Move right to field. 2188<DT> <CODE>REQ_UP_FIELD</CODE> 2189<DD> Move up to field. 2190<DT> <CODE>REQ_DOWN_FIELD</CODE> 2191<DD> Move down to field. 2192</DL> 2193 2194These requests treat the list of fields on a page as cyclic; that is, 2195<CODE>REQ_NEXT_FIELD</CODE> from the last field goes to the first, and 2196<CODE>REQ_PREV_FIELD</CODE> from the first field goes to the last. The 2197order of the fields for these (and the <CODE>REQ_FIRST_FIELD</CODE> and 2198<CODE>REQ_LAST_FIELD</CODE> requests) is simply the order of the field 2199pointers in the form array (as set up by <CODE>new_form()</CODE> or 2200<CODE>set_form_fields()</CODE> <P> 2201 2202It is also possible to traverse the fields as if they had been sorted in 2203screen-position order, so the sequence goes left-to-right and top-to-bottom. 2204To do this, use the second group of four sorted-movement requests. <P> 2205 2206Finally, it is possible to move between fields using visual directions up, 2207down, right, and left. To accomplish this, use the third group of four 2208requests. Note, however, that the position of a form for purposes of these 2209requests is its upper-left corner. <P> 2210 2211For example, suppose you have a multi-line field B, and two 2212single-line fields A and C on the same line with B, with A to the left 2213of B and C to the right of B. A <CODE>REQ_MOVE_RIGHT</CODE> from A will 2214go to B only if A, B, and C <EM>all</EM> share the same first line; 2215otherwise it will skip over B to C. 2216 2217<H3><A NAME="#fifield">Intra-Field Navigation Requests</A></H3> 2218 2219These requests drive movement of the edit cursor within the currently 2220selected field. 2221 2222<DL> 2223<DT> <CODE>REQ_NEXT_CHAR</CODE> 2224<DD> Move to next character. 2225<DT> <CODE>REQ_PREV_CHAR</CODE> 2226<DD> Move to previous character. 2227<DT> <CODE>REQ_NEXT_LINE</CODE> 2228<DD> Move to next line. 2229<DT> <CODE>REQ_PREV_LINE</CODE> 2230<DD> Move to previous line. 2231<DT> <CODE>REQ_NEXT_WORD</CODE> 2232<DD> Move to next word. 2233<DT> <CODE>REQ_PREV_WORD</CODE> 2234<DD> Move to previous word. 2235<DT> <CODE>REQ_BEG_FIELD</CODE> 2236<DD> Move to beginning of field. 2237<DT> <CODE>REQ_END_FIELD</CODE> 2238<DD> Move to end of field. 2239<DT> <CODE>REQ_BEG_LINE</CODE> 2240<DD> Move to beginning of line. 2241<DT> <CODE>REQ_END_LINE</CODE> 2242<DD> Move to end of line. 2243<DT> <CODE>REQ_LEFT_CHAR</CODE> 2244<DD> Move left in field. 2245<DT> <CODE>REQ_RIGHT_CHAR</CODE> 2246<DD> Move right in field. 2247<DT> <CODE>REQ_UP_CHAR</CODE> 2248<DD> Move up in field. 2249<DT> <CODE>REQ_DOWN_CHAR</CODE> 2250<DD> Move down in field. 2251</DL> 2252 2253Each <EM>word</EM> is separated from the previous and next characters 2254by whitespace. The commands to move to beginning and end of line or field 2255look for the first or last non-pad character in their ranges. 2256 2257<H3><A NAME="fscroll">Scrolling Requests</A></H3> 2258 2259Fields that are dynamic and have grown and fields explicitly created 2260with offscreen rows are scrollable. One-line fields scroll horizontally; 2261multi-line fields scroll vertically. Most scrolling is triggered by 2262editing and intra-field movement (the library scrolls the field to keep the 2263cursor visible). It is possible to explicitly request scrolling with the 2264following requests: 2265 2266<DL> 2267<DT> <CODE>REQ_SCR_FLINE</CODE> 2268<DD> Scroll vertically forward a line. 2269<DT> <CODE>REQ_SCR_BLINE</CODE> 2270<DD> Scroll vertically backward a line. 2271<DT> <CODE>REQ_SCR_FPAGE</CODE> 2272<DD> Scroll vertically forward a page. 2273<DT> <CODE>REQ_SCR_BPAGE</CODE> 2274<DD> Scroll vertically backward a page. 2275<DT> <CODE>REQ_SCR_FHPAGE</CODE> 2276<DD> Scroll vertically forward half a page. 2277<DT> <CODE>REQ_SCR_BHPAGE</CODE> 2278<DD> Scroll vertically backward half a page. 2279<DT> <CODE>REQ_SCR_FCHAR</CODE> 2280<DD> Scroll horizontally forward a character. 2281<DT> <CODE>REQ_SCR_BCHAR</CODE> 2282<DD> Scroll horizontally backward a character. 2283<DT> <CODE>REQ_SCR_HFLINE</CODE> 2284<DD> Scroll horizontally one field width forward. 2285<DT> <CODE>REQ_SCR_HBLINE</CODE> 2286<DD> Scroll horizontally one field width backward. 2287<DT> <CODE>REQ_SCR_HFHALF</CODE> 2288<DD> Scroll horizontally one half field width forward. 2289<DT> <CODE>REQ_SCR_HBHALF</CODE> 2290<DD> Scroll horizontally one half field width backward. 2291</DL> 2292 2293For scrolling purposes, a <EM>page</EM> of a field is the height 2294of its visible part. 2295 2296<H3><A NAME="fedit">Editing Requests</A></H3> 2297 2298When you pass the forms driver an ASCII character, it is treated as a 2299request to add the character to the field's data buffer. Whether this 2300is an insertion or a replacement depends on the field's edit mode 2301(insertion is the default. <P> 2302 2303The following requests support editing the field and changing the edit 2304mode: 2305 2306<DL> 2307<DT> <CODE>REQ_INS_MODE</CODE> 2308<DD> Set insertion mode. 2309<DT> <CODE>REQ_OVL_MODE</CODE> 2310<DD> Set overlay mode. 2311<DT> <CODE>REQ_NEW_LINE</CODE> 2312<DD> New line request (see below for explanation). 2313<DT> <CODE>REQ_INS_CHAR</CODE> 2314<DD> Insert space at character location. 2315<DT> <CODE>REQ_INS_LINE</CODE> 2316<DD> Insert blank line at character location. 2317<DT> <CODE>REQ_DEL_CHAR</CODE> 2318<DD> Delete character at cursor. 2319<DT> <CODE>REQ_DEL_PREV</CODE> 2320<DD> Delete previous word at cursor. 2321<DT> <CODE>REQ_DEL_LINE</CODE> 2322<DD> Delete line at cursor. 2323<DT> <CODE>REQ_DEL_WORD</CODE> 2324<DD> Delete word at cursor. 2325<DT> <CODE>REQ_CLR_EOL</CODE> 2326<DD> Clear to end of line. 2327<DT> <CODE>REQ_CLR_EOF</CODE> 2328<DD> Clear to end of field. 2329<DT> <CODE>REQ_CLEAR_FIELD</CODE> 2330<DD> Clear entire field. 2331</DL> 2332 2333The behavior of the <CODE>REQ_NEW_LINE</CODE> and <CODE>REQ_DEL_PREV</CODE> requests 2334is complicated and partly controlled by a pair of forms options. 2335The special cases are triggered when the cursor is at the beginning of 2336a field, or on the last line of the field. <P> 2337 2338First, we consider <CODE>REQ_NEW_LINE</CODE>: <P> 2339 2340The normal behavior of <CODE>REQ_NEW_LINE</CODE> in insert mode is to break the 2341current line at the position of the edit cursor, inserting the portion of 2342the current line after the cursor as a new line following the current 2343and moving the cursor to the beginning of that new line (you may think 2344of this as inserting a newline in the field buffer). <P> 2345 2346The normal behavior of <CODE>REQ_NEW_LINE</CODE> in overlay mode is to clear the 2347current line from the position of the edit cursor to end of line. 2348The cursor is then moved to the beginning of the next line. <P> 2349 2350However, <CODE>REQ_NEW_LINE</CODE> at the beginning of a field, or on the 2351last line of a field, instead does a <CODE>REQ_NEXT_FIELD</CODE>. 2352<CODE>O_NL_OVERLOAD</CODE> option is off, this special action is 2353disabled. <P> 2354 2355Now, let us consider <CODE>REQ_DEL_PREV</CODE>: <P> 2356 2357The normal behavior of <CODE>REQ_DEL_PREV</CODE> is to delete the previous 2358character. If insert mode is on, and the cursor is at the start of a 2359line, and the text on that line will fit on the previous one, it 2360instead appends the contents of the current line to the previous one 2361and deletes the current line (you may think of this as deleting a 2362newline from the field buffer). <P> 2363 2364However, <CODE>REQ_DEL_PREV</CODE> at the beginning of a field is instead 2365treated as a <CODE>REQ_PREV_FIELD</CODE>. <P> If the 2366<CODE>O_BS_OVERLOAD</CODE> option is off, this special action is 2367disabled and the forms driver just returns <CODE>E_REQUEST_DENIED</CODE>. <P> 2368 2369See <A HREF="#frmoptions">Form Options</A> for discussion of how to set 2370and clear the overload options. 2371 2372<H3><A NAME="forder">Order Requests</A></H3> 2373 2374If the type of your field is ordered, and has associated functions 2375for getting the next and previous values of the type from a given value, 2376there are requests that can fetch that value into the field buffer: 2377 2378<DL> 2379<DT> <CODE>REQ_NEXT_CHOICE</CODE> 2380<DD> Place the successor value of the current value in the buffer. 2381<DT> <CODE>REQ_PREV_CHOICE</CODE> 2382<DD> Place the predecessor value of the current value in the buffer. 2383</DL> 2384 2385Of the built-in field types, only <CODE>TYPE_ENUM</CODE> has built-in successor 2386and predecessor functions. When you define a field type of your own 2387(see <A HREF="#fcustom">Custom Validation Types</A>), you can associate 2388our own ordering functions. 2389 2390<H3><A NAME="fappcmds">Application Commands</A></H3> 2391 2392Form requests are represented as integers above the <CODE>curses</CODE> value 2393greater than <CODE>KEY_MAX</CODE> and less than or equal to the constant 2394<CODE>MAX_COMMAND</CODE>. If your input-virtualization routine returns a 2395value above <CODE>MAX_COMMAND</CODE>, the forms driver will ignore it. 2396 2397<H2><A NAME="fhooks">Field Change Hooks</A></H2> 2398 2399It is possible to set function hooks to be executed whenever the 2400current field or form changes. Here are the functions that support this: 2401 2402<PRE> 2403typedef void (*HOOK)(); /* pointer to function returning void */ 2404 2405int set_form_init(FORM *form, /* form to alter */ 2406 HOOK hook); /* initialization hook */ 2407 2408HOOK form_init(FORM *form); /* form to query */ 2409 2410int set_form_term(FORM *form, /* form to alter */ 2411 HOOK hook); /* termination hook */ 2412 2413HOOK form_term(FORM *form); /* form to query */ 2414 2415int set_field_init(FORM *form, /* form to alter */ 2416 HOOK hook); /* initialization hook */ 2417 2418HOOK field_init(FORM *form); /* form to query */ 2419 2420int set_field_term(FORM *form, /* form to alter */ 2421 HOOK hook); /* termination hook */ 2422 2423HOOK field_term(FORM *form); /* form to query */ 2424</PRE> 2425 2426These functions allow you to either set or query four different hooks. 2427In each of the set functions, the second argument should be the 2428address of a hook function. These functions differ only in the timing 2429of the hook call. 2430 2431<DL> 2432<DT> form_init 2433<DD> This hook is called when the form is posted; also, just after 2434each page change operation. 2435<DT> field_init 2436<DD> This hook is called when the form is posted; also, just after 2437each field change 2438<DT> field_term 2439<DD> This hook is called just after field validation; that is, just before 2440the field is altered. It is also called when the form is unposted. 2441<DT> form_term 2442<DD> This hook is called when the form is unposted; also, just before 2443each page change operation. 2444</DL> 2445 2446Calls to these hooks may be triggered 2447<OL> 2448<LI>When user editing requests are processed by the forms driver 2449<LI>When the current page is changed by <CODE>set_current_field()</CODE> call 2450<LI>When the current field is changed by a <CODE>set_form_page()</CODE> call 2451</OL> 2452 2453See <A NAME="ffocus">Field Change Commands</A> for discussion of the latter 2454two cases. <P> 2455 2456You can set a default hook for all fields by passing one of the set functions 2457a NULL first argument. <P> 2458 2459You can disable any of these hooks by (re)setting them to NULL, the default 2460value. 2461 2462<H2><A HREF="#ffocus">Field Change Commands</A></H2> 2463 2464Normally, navigation through the form will be driven by the user's 2465input requests. But sometimes it is useful to be able to move the 2466focus for editing and viewing under control of your application, or 2467ask which field it currently is in. The following functions help you 2468accomplish this: 2469 2470<PRE> 2471int set_current_field(FORM *form, /* form to alter */ 2472 FIELD *field); /* field to shift to */ 2473 2474FIELD *current_field(FORM *form); /* form to query */ 2475 2476int field_index(FORM *form, /* form to query */ 2477 FIELD *field); /* field to get index of */ 2478</PRE> 2479 2480The function <CODE>field_index()</CODE> returns the index of the given field 2481in the given form's field array (the array passed to <CODE>new_form()</CODE> or 2482<CODE>set_form_fields()</CODE>). <P> 2483 2484The initial current field of a form is the first active field on the 2485first page. The function <CODE>set_form_fields()</CODE> resets this.<P> 2486 2487It is also possible to move around by pages. 2488 2489<PRE> 2490int set_form_page(FORM *form, /* form to alter */ 2491 int page); /* page to go to (0-origin) */ 2492 2493int form_page(FORM *form); /* return form's current page */ 2494</PRE> 2495 2496The initial page of a newly-created form is 0. The function 2497<CODE>set_form_fields()</CODE> resets this. 2498 2499<H2><A NAME="frmoptions">Form Options</A></H2> 2500 2501Like fields, forms may have control option bits. They can be changed 2502or queried with these functions: 2503 2504<PRE> 2505int set_form_opts(FORM *form, /* form to alter */ 2506 int attr); /* attribute to set */ 2507 2508int form_opts_on(FORM *form, /* form to alter */ 2509 int attr); /* attributes to turn on */ 2510 2511int form_opts_off(FORM *form, /* form to alter */ 2512 int attr); /* attributes to turn off */ 2513 2514int form_opts(FORM *form); /* form to query */ 2515</PRE> 2516 2517By default, all options are on. Here are the available option bits: 2518 2519<DL> 2520<DT> O_NL_OVERLOAD 2521<DD> Enable overloading of <CODE>REQ_NEW_LINE</CODE> as described in <A 2522NAME="fedit">Editing Requests</A>. The value of this option is 2523ignored on dynamic fields that have not reached their size limit; 2524these have no last line, so the circumstances for triggering a 2525<CODE>REQ_NEXT_FIELD</CODE> never arise. 2526<DT> O_BS_OVERLOAD 2527<DD> Enable overloading of <CODE>REQ_DEL_PREV</CODE> as described in 2528<A NAME="fedit">Editing Requests</A>. 2529</DL> 2530 2531The option values are bit-masks and can be composed with logical-or in 2532the obvious way. 2533 2534<H2><A NAME="fcustom">Custom Validation Types</A></H2> 2535 2536The <CODE>form</CODE> library gives you the capability to define custom 2537validation types of your own. Further, the optional additional arguments 2538of <CODE>set_field_type</CODE> effectively allow you to parameterize validation 2539types. Most of the complications in the validation-type interface have to 2540do with the handling of the additional arguments within custom validation 2541functions. 2542 2543<H3><A NAME="flinktypes">Union Types</A></H3> 2544 2545The simplest way to create a custom data type is to compose it from two 2546preexisting ones: 2547 2548<PRE> 2549FIELD *link_fieldtype(FIELDTYPE *type1, 2550 FIELDTYPE *type2); 2551</PRE> 2552 2553This function creates a field type that will accept any of the values 2554legal for either of its argument field types (which may be either 2555predefined or programmer-defined). 2556 2557If a <CODE>set_field_type()</CODE> call later requires arguments, the new 2558composite type expects all arguments for the first type, than all arguments 2559for the second. Order functions (see <A HREF="#forder">Order Requests</A>) 2560associated with the component types will work on the composite; what it does 2561is check the validation function for the first type, then for the second, to 2562figure what type the buffer contents should be treated as. 2563 2564<H3><A NAME="fnewtypes">New Field Types</A></H3> 2565 2566To create a field type from scratch, you need to specify one or both of the 2567following things: 2568 2569<UL> 2570<LI>A character-validation function, to check each character as it is entered. 2571<LI>A field-validation function to be applied on exit from the field. 2572</UL> 2573 2574Here's how you do that: 2575<PRE> 2576typedef int (*HOOK)(); /* pointer to function returning int */ 2577 2578FIELDTYPE *new_fieldtype(HOOK f_validate, /* field validator */ 2579 HOOK c_validate) /* character validator */ 2580 2581 2582int free_fieldtype(FIELDTYPE *ftype); /* type to free */ 2583</PRE> 2584 2585At least one of the arguments of <CODE>new_fieldtype()</CODE> must be 2586non-NULL. The forms driver will automatically call the new type's 2587validation functions at appropriate points in processing a field of 2588the new type. <P> 2589 2590The function <CODE>free_fieldtype()</CODE> deallocates the argument 2591fieldtype, freeing all storage associated with it. <P> 2592 2593Normally, a field validator is called when the user attempts to 2594leave the field. Its first argument is a field pointer, from which it 2595can get to field buffer 0 and test it. If the function returns TRUE, 2596the operation succeeds; if it returns FALSE, the edit cursor stays in 2597the field. <P> 2598 2599A character validator gets the character passed in as a first argument. 2600It too should return TRUE if the character is valid, FALSE otherwise. 2601 2602<H3><A NAME="fcheckargs">Validation Function Arguments</A></H3> 2603 2604Your field- and character- validation functions will be passed a 2605second argument as well. This second argument is the address of a 2606structure (which we'll call a <EM>pile</EM>) built from any of the 2607field-type-specific arguments passed to <CODE>set_field_type()</CODE>. If 2608no such arguments are defined for the field type, this pile pointer 2609argument will be NULL. <P> 2610 2611In order to arrange for such arguments to be passed to your validation 2612functions, you must associate a small set of storage-management functions 2613with the type. The forms driver will use these to synthesize a pile 2614from the trailing arguments of each <CODE>set_field_type()</CODE> argument, and 2615a pointer to the pile will be passed to the validation functions. <P> 2616 2617Here is how you make the association: 2618 2619<PRE> 2620typedef char *(*PTRHOOK)(); /* pointer to function returning (char *) */ 2621typedef void (*VOIDHOOK)(); /* pointer to function returning void */ 2622 2623int set_fieldtype_arg(FIELDTYPE *type, /* type to alter */ 2624 PTRHOOK make_str, /* make structure from args */ 2625 PTRHOOK copy_str, /* make copy of structure */ 2626 VOIDHOOK free_str); /* free structure storage */ 2627</PRE> 2628 2629Here is how the storage-management hooks are used: 2630 2631<DL> 2632<DT> <CODE>make_str</CODE> 2633<DD> This function is called by <CODE>set_field_type()</CODE>. It gets one 2634argument, a <CODE>va_list</CODE> of the type-specific arguments passed to 2635<CODE>set_field_type()</CODE>. It is expected to return a pile pointer to a data 2636structure that encapsulates those arguments. 2637<DT> <CODE>copy_str</CODE> 2638<DD> This function is called by form library functions that allocate new 2639field instances. It is expected to take a pile pointer, copy the pile 2640to allocated storage, and return the address of the pile copy. 2641<DT> <CODE>free_str</CODE> 2642<DD> This function is called by field- and type-deallocation routines in the 2643library. It takes a pile pointer argument, and is expected to free the 2644storage of that pile. 2645</DL> 2646 2647The <CODE>make_str</CODE> and <CODE>copy_str</CODE> functions may return NULL to 2648signal allocation failure. The library routines will that call them will 2649return error indication when this happens. Thus, your validation functions 2650should never see a NULL file pointer and need not check specially for it. 2651 2652<H3><A NAME="fcustorder">Order Functions For Custom Types</A></H3> 2653 2654Some custom field types are simply ordered in the same well-defined way 2655that <CODE>TYPE_ENUM</CODE> is. For such types, it is possible to define 2656successor and predecessor functions to support the <CODE>REQ_NEXT_CHOICE</CODE> 2657and <CODE>REQ_PREV_CHOICE</CODE> requests. Here's how: 2658 2659<PRE> 2660typedef int (*INTHOOK)(); /* pointer to function returning int */ 2661 2662int set_fieldtype_arg(FIELDTYPE *type, /* type to alter */ 2663 INTHOOK succ, /* get successor value */ 2664 INTHOOK pred); /* get predecessor value */ 2665</PRE> 2666 2667The successor and predecessor arguments will each be passed two arguments; 2668a field pointer, and a pile pointer (as for the validation functions). They 2669are expected to use the function <CODE>field_buffer()</CODE> to read the 2670current value, and <CODE>set_field_buffer()</CODE> on buffer 0 to set the next 2671or previous value. Either hook may return TRUE to indicate success (a 2672legal next or previous value was set) or FALSE to indicate failure. 2673 2674<H3><A NAME="fcustprobs">Avoiding Problems</A></H3> 2675 2676The interface for defining custom types is complicated and tricky. 2677Rather than attempting to create a custom type entirely from scratch, 2678you should start by studying the library source code for whichever of 2679the pre-defined types seems to be closest to what you want. <P> 2680 2681Use that code as a model, and evolve it towards what you really want. 2682You will avoid many problems and annoyances that way. The code 2683in the <CODE>ncurses</CODE> library has been specifically exempted from 2684the package copyright to support this. <P> 2685 2686If your custom type defines order functions, have do something intuitive 2687with a blank field. A useful convention is to make the successor of a 2688blank field the types minimum value, and its predecessor the maximum. 2689</BODY> 2690</HTML> 2691