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