1pod::Prima::X11(3)    User Contributed Perl Documentation   pod::Prima::X11(3)
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NAME

6       Prima::X11 - usage guide for X11 environment
7

DESCRIPTION

9       This document describes subtle topics one must be aware when
10       programming or using Prima programs under X11.
11
12       The document covers various aspects of the toolkit and their
13       implementation details with guidelines of the expected use. Also,
14       standard X11 user-level and programming techniques are visited.
15

Basic command-line switches

17       "--help"
18           Prints the command-line arguments available and exits.
19
20       "--display"
21           Sets X display address in Xlib notation. If not set, standard Xlib
22           ( "XOpenDisplay(null)" ) behavior applies.
23
24           Example:
25
26              --display=:0.1
27
28       "--visual"
29           Sets X visual, to be used by default. Example:
30
31              --visual=0x23
32
33       "--sync"
34           Turn off X synchronization
35
36       "--bg", "--fg"
37           Set default background and foreground colors. Example:
38
39             --bg=BlanchedAlmond
40
41       "--font"
42           Sets default font. Example:
43
44              --font='adobe-helvetica-medium-r-*-*--*-120-*-*-*-*-*-*'
45
46       "--no-x11"
47           Runs Prima without X11 display initialized. This switch can be used
48           for programs that use only OS-independent parts of Prima, such as
49           image subsystem or PostScript generator, in environments where X is
50           not present, for example, a CGI script.  Obviously, any attempt to
51           create instance of "Prima::Application" or otherwise access
52           X-depended code under such conditions causes the program to abort.
53
54           There are alternatives to use the command switch. First, there is
55           module "Prima::noX11" for the same purpose but more convenient to
56           use as
57
58              perl -MPrima::noX11
59
60           construct. Second, there is a technique to continue execution even
61           if connection to a X server failed:
62
63              use Prima::noX11;
64              use Prima;
65
66              my $error = Prima::XOpenDisplay();
67              if ( defined $error) {
68                   print "not connected to display: $error\n";
69              } else {
70                   print "connected to display\n";
71              }
72
73           The Prima::noX11 module exports a single function "XOpenDisplay"
74           into "Prima" namespace, to connect to the X display explicitly. The
75           display to be connected to is $ENV{DISPLAY}, unless started
76           otherwise on command line ( with --display option) or with
77           parameter to the "XOpenDisplay" function.
78
79           This technique may be useful to programs that use Prima imaging
80           functionality and may or may not use windowing capabilites.
81

X resources database

83       X11 provides XRDB, the X resource database, a keyed list of arbitrary
84       string values stored on the X server. Each key is a combination of
85       names and classes of widgets, each in string form. The key is
86       constructed so the leftmost substring ( name or class ) corresponds to
87       the top-level item in the hierarchy, usually the application name or
88       class. Although the XRDB can be changed via native X API, it is rarely
89       done by applications. Instead, the user creates a file, usually named
90       .Xdefaults, which contains the database in the string form.
91
92       The format of .Xdefaults directly reflects XRDB capabilities, one of
93       the most important of which is globbing, manifested via * ( star )
94       character. Using globbing, the user can set up a property value that
95       corresponds to multiple targets:
96
97          *.ListBox.backColor: yellow
98
99       The string above means that all widgets of ListBox class must have
100       yellow background.
101
102       The application itself is responsible for parsing the strings and
103       querying the XRDB.  Also, both class names and widget names, as well as
104       database values are fully defined in terms of the application. There
105       are some guidelines though, for example, colors and fonts best
106       described in terms, native to the X server.  Also, classes and names
107       are distinguished by the case: classes must begin with the upper
108       register letter. Also, not every character can be stored in the XRDB
109       database ( space, for example, cannot) , and therefore XRDB API
110       automatically converts these to _ ( underscore ) characters.
111
112       Prima defines its all set of resources, divided in two parts: general
113       toolkit settings and per-widget settings. The general settings
114       functionality is partially overloaded by command-line arguments. Per-
115       widget settings are fonts and colors, definable for each Prima widget.
116
117       All of the general settings are applicable to the top-level item of
118       widget hierarchy, named after the application, and "Prima" class. Some
119       of these, though, are needed to be initialized before the application
120       instance itself is created, so these can be accessed via "Prima" class
121       only, for example, "Prima.Visual".  Some, on the contrary, may
122       occasionally overlap with per-widget syntax.  In particular, one must
123       vary not to mix
124
125          Prima.font: some-font
126
127       with
128
129          Prima*font: some-font
130
131       The former syntax is a general setting, and sets the default Prima
132       font.  The latter is a per-widget assignment, and explicitly sets font
133       to all Prima widgets, effectively ruining the toolkit font inheritance
134       scheme. The same is valid for an even more oppressive
135
136          *font: some-font
137
138       record.
139
140       The allowed per-widget settings are colors and font settings only ( see
141       corresponding sections ). It is an arguably useful feature to map all
142       widget properties onto XRDB, but Prima does not implement this,
143       primarily because no one asked for it, and also because this creates
144       unnecessary latency when enumeration of all properties for each widget
145       takes place.
146
147       All global settings have identical class and name, varied in the case
148       of the first letter. For example, to set "Submenudelay" value, one can
149       do it either by
150
151          Prima.Submenudelay: 10
152
153       or
154
155          Prima.submenudelay: 10
156
157       syntax. Despite that these calls are different, in a way that one
158       reaches for the whole class and another for the name, for the majority
159       of these properties it does not matter. To avoid confusion, for all
160       properties their names and class are given as
161       "PropetyClass.propertyname" index.
162

Fonts

164   Default fonts
165       Prima::Application defines set of "get_default_XXX_font" functions,
166       where each returns some user-selected font, to be displayed
167       correspondingly in menu, message, window captions, all other widgets,
168       and finally a default font. While in other OS'es these are indeed
169       standard configurable user options, raw X11 doesn't define any.
170       Nevertheless, as the high-level code relies on these, corresponding
171       resources are defined. These are:
172
173       ·   font - Application::get_default_font
174
175       ·   caption_font - Application::get_caption_font. Used in "Prima::MDI".
176
177       ·   menu_font - Widget::get_default_menu_font. Default font for pull-
178           down and pop-up menus.
179
180       ·   msg_font - Application::get_message_font. Used in "Prima::MsgBox".
181
182       ·   widget_font - Widget::get_default_font.
183
184       All of the global font properties can only be set via "Prima" class, no
185       application name is recognized. Also, these properties are identical to
186       "--font", "--menu-font", "--caption-font", "--msg-font", and
187       "--widget-font" command-line arguments.  The per-widget properties are
188       "font" and "popupFont", of class "Font", settable via XRDB only:
189
190          Prima*Dialog.font: my-fancy-dialog-font
191          Prima.FontDialog.font: some-conservative-font
192
193       By default, Prima font is 12.Helvetica .
194
195   X core fonts
196       The values of the font entries are standard XLFD strings, the default
197       "*-*-*-*-*-*-*-*-*-*-*-*-*-*-*" pattern, where each star character can
198       be replaced by a particular font property, as name, size, charset, and
199       so on. To interactively select an appropriate font, use standard
200       "xfontsel" program from X11 distribution.
201
202       Note, that encoding part of the font is recommended to left
203       unspecified, otherwise it may clash with LANG environment variable,
204       which is used by Prima font subsystem to determine which font to select
205       when no encoding is given.  This advice, though, is correct only when
206       both LANG and encoding part of a desired font match. In order to force
207       a particular font encoding, the property "Prima.font" must contain one.
208
209       Alternatively, and/or to reduce X font traffic, one may set
210       "IgnoreEncodings.ignoreEncodings" property, which is a semicolon-
211       separated list of encodings Prima must not account. This feature has
212       limited usability when for example fonts in Asian encodings result in
213       large font requests.  Another drastic measure to decrease font traffic
214       is a boolean property "Noscaledfonts.noscaledfonts", which, if set to
215       1, restricts the choice of fonts to the non-scalable fonts only.
216
217   Xft fonts
218       Recently, Prima was made to compile with Xft library, which contrary to
219       core X font API, can make use of client-side fonts. Plus, Xft offers
220       appealing features as font antialiasing, unicode, and arguably a better
221       font syntax. The Xft font syntax is inherited from "fontconfig" library
222       and to be consulted from "man fonts-conf", but currently ( November
223       2003 ) basic font descriptions can be composed as follows:
224
225          Palatino-12
226
227       A font with name "Palatino" and size 12.
228
229          Arial-10:BI
230
231       A font with name "Arial", size 10, bold, italic. The "fontconfig"
232       syntax allows more than that, for example, arbitrary matrix
233       transformations, but Prima can make use only of font name, size, and
234       style flags.
235
236       "--no-xft"
237           "--no-xft" command-line argument, and boolean "UseXFT.usexft" XRDB
238           property can be used to disable use of the Xft library.
239
240       "--no-core-fonts"
241           Disables all X11 core fonts, except "fixed" fonts. The "fixed" font
242           is selected for the same reasons that X server is designed to
243           provide at least one font, which usually is "fixed".
244
245           It is valid to combine "--no-core-fonts" and "--no-xft". Moreover,
246           adding "--noscaled" to these gives Prima programs a 'classic' X
247           look.
248
249       "--font-priority"
250           Can be set to either "xft" or "core", to select a font provider
251           mechanism to match unknown or incompletely specified fonts against.
252
253           Default value: "xft" ( if compiled in ), "core" otherwise.
254
255       "--no-aa"
256           If set, turns off Xft antialiasing.
257

Colors

259   XRDB conventions
260       X traditionally contains a color names database, usually a text file
261       named rgb.txt.  Check your X manual where exactly this file resides and
262       what is its format.  The idea behind it is that users can benefit from
263       portable literal color names, with color values transparently
264       adjustable to displays capabilities.  Thus, it is customary to write
265
266          color: green
267
268       for many applications, and these in turn call "XParseColor" to convert
269       strings into RGB values.
270
271       Prima is no exception to the scheme. Each widget can be assigned eight
272       color properties: "color", "hiliteBackColor", "disabledColor",
273       "dark3DColor" "backColor", "hiliteColor", "disabledBackColor",
274       "light3DColor" by their name:
275
276          Prima.backColor: #cccccc
277
278       Additionally, set of command-line arguments allows overriding default
279       values for these:
280
281       ·   "--fg" - color
282
283       ·   "--bg" - backColor
284
285       ·   "--hilite-fg" - hiliteColor
286
287       ·   "--hilite-bg" - hiliteBackColor
288
289       ·   "--disabled-fg" - disabledColor
290
291       ·   "--disabled-bg" - disabledBackColor
292
293       ·   "--light" - light3DColor
294
295       ·   "--dark" - dark3DColor
296
297   Visuals
298       X protocol works with explicitly defined pixel values only.  A pixel
299       value, maximum 32-bit value, represents a color in a display. There are
300       two different color coding schemes - direct color and indexed color.
301       The direct color-coded pixel value can unambiguously be converted into
302       a RGB-value, without any external information.  The indexed-color
303       scheme represents pixel value as an index in a palette, which resided
304       on X server. Depending on the color cell value of the palette, RGB
305       color representation can be computed. A X display can contain more than
306       one palette, and allow ( or disallow ) modification of palette color
307       cells depending on a visual, the palette is attributed to.
308
309       A visual is a X server resource, containing representation of color
310       coding scheme, color bit depth, and modificability of the palette. X
311       server can ( and usually does ) provide more than one visual, as well
312       as different bit depths.  There are six classes of visuals in X
313       paradigm. In each, Prima behaves differently, also depending on display
314       bit depth available.  In particular, color dithering can be used on
315       displays with less than 12-bit color depth. On displays with modifiable
316       color palette, Prima can install its own values in palettes, which may
317       result in an effect known as display flashing. To switch to a non-
318       default visual, use "Prima.Visual" XRDB property or "--visual" command-
319       line argument.  List of visuals can be produced interactively by
320       standard "xdpyinfo" command from X distribution, where each class of
321       visual corresponds to one of six visual classes:
322
323       StaticGray
324           All color cells are read-only, and contain monochrome values only.
325           A typical example is a two-color, black-and-white monochrome
326           display.  This visual is extremely rarely met.
327
328       GrayScale
329           Contains modifiable color palette, and capable of displaying
330           monochrome values only. Theoretically, any paletted display on a
331           monochrome monitor can be treated as a GrayScale visual. For both
332           GrayScale and StaticGray visuals Prima resorts to dithering if it
333           cannot get at least 32 evenly spaced gray values from black to
334           white.
335
336       StaticColor
337           All color cells are read-only.  A typical example is a PC display
338           in a 16-color EGA mode.  This visual is rarely met.
339
340       PseudoColor
341           All color cells are modifiable. Typically, 8-bit displays define
342           this class for a default visual. For both StaticColor and
343           PseudoColor visuals dithering is always used, although for
344           "PseudoColor" Prima resorts to that only if X server cannot
345           allocate another color.
346
347           On "PseudoColor" and "GrayScale" Prima allocates a small set of
348           colors, not used in palette modifications. When a bitmap is to be
349           exported via clipboard, or displayed in menu, or sent to a window
350           manager as an icon to be displayed, it is downgraded to using these
351           colors only, which are though guaranteedly to stay permanent
352           through life of the application.
353
354       TrueColor
355           Each pixel value is explicitly coded as RGB. Typical example are
356           16, 24, or 32-bit display modes. This visual class is the best in
357           terms of visual quality.
358
359       DirectColor
360           Same as TrueColor, but additionally each pixel value can be
361           reprogrammed.  Not all hardware support this visual, and usually by
362           default it is not set.  Prima supports this mode in exactly same
363           way as TrueColor without additional features.
364

Images

366       As described in the previous section, X does not standardize pixel
367       memory format for TrueColor and DirectColor visuals, so there is a
368       chance that Prima wouldn't work on some bizarre hardware. Currently,
369       Prima knows how to compose pixels of 15, 16, 24, and 32 bit depth, of
370       contiguous ( not interspersed ) red-green-blue memory layout. Any other
371       pixel memory layout causes Prima to fail.
372
373       Prima supports shared memory image X extension, which speeds up image
374       display for X servers and clients running on same machine. The price
375       for this is that if Prima program aborts, the shared memory will never
376       be returned to the OS.  To remove the leftover segments, use your OS
377       facilities, for example, "ipcrm" on *BSD.
378
379       To disable shared memory with images, use "--no-shmem" switch in
380       command-line arguments.
381
382       The clipboard exchange of images is incompletely implemented, since
383       Prima does not accompany ( and neither reads ) COLORMAP, FOREGROUND,
384       and BACKGROUND clipboard data, which contains pixel RGB values for a
385       paletted image. As a palliative, the clipboard-bound images are
386       downgraded to a safe set of colors, locked immutable either by X server
387       or Prima core.
388
389       On images in the clipboard: contrary to the text in the clipboard,
390       which can be used several times, images seemingly cannot. The Bitmap or
391       Pixmap descriptor, stored in the clipboard, is rendered invalid after
392       it has been read once.
393

Window managers

395       The original design of X protocol did not include the notion of a
396       window manager, and latter is was implemented as an ad-hoc patch, which
397       results in race conditions when configuring widgets. The extreme
398       situation may well happen when even a non-top level widget may be
399       influenced by a window manager, when for example a top-level widget was
400       reparented into another widget, but the window manager is not aware or
401       this yet.
402
403       The consequences of this, as well as programming guidances are
404       described in "Prima::Window". Here, we describe other aspects of
405       interactions with WMs, as WM protocols, hints, and properties.
406
407       Prima was tested with alternating success under the following window
408       managers: mwm, kwin, wmaker, fvwm, fvwm2, enlightment, sawfish,
409       blackbox, 9wm, olvm, twm, and in no-WM environment.
410
411   Protocols
412       Prima makes use of "WM_DELETE_WINDOW" and "WM_TAKE_FOCUS" protocols.
413       While "WM_DELETE_WINDOW" use is straightforward and needs no further
414       attention, "WM_TAKE_FOCUS" can be tricky, since X defines several of
415       input modes for a widget, which behave differently for each WM.  In
416       particular, 'focus follows pointer' gives pains under twm and mwm,
417       where navigation of drop-down combo boxes is greatly hindered by window
418       manager. The drop-down list is programmed so it is dismissed as soon
419       its focus is gone; these window managers withdraw focus even if the
420       pointer is over the focused widget's border.
421
422   Hints
423       Size, position, icons, and other standard X hints are passed to WM in a
424       standard way, and, as inter-client communication manual ( ICCCM )
425       allows, repeatedly misinterpreted by window managers. Many ( wmaker,
426       for example ) apply the coordinates given from the program not to the
427       top-level widget itself, but to its decoration.  mwm defines list of
428       accepted icon sizes so these can be absurdly high, which adds confusion
429       to a client who can create icon of any size, but unable to determine
430       the best one.
431
432   Non-standard properties
433       Prima tries to use WM-specific hints, known for two window managers:
434       mwm and kwin.  For mwm ( Motif window manager ) Prima sets hints of
435       decoration border width and icons only. For kwin ( and probably to
436       others, who wish to conform to specifications of
437       http://www.freedesktop.org/ ) Prima uses "NET_WM_STATE" property, in
438       particular its maximization and task-bar visibility hints.
439
440       Use of these explicitly contradicts ICCCM, and definitely may lead to
441       bugs in future ( at least with "NET_WM_STATE", since Motif interface
442       can hardly expected to be changed ).  To disable the use of non-
443       standard WM properties, "--icccm" command-line argument can be set.
444

Unicode

446       X does not support unicode, and number of patches were applied to X
447       servers and clients to make the situation change. Currently ( 2003 )
448       standard unicode practices are not emerged yet, so Prima copes up with
449       what ( in author's opinion ) is most promising: Xft and iconv
450       libraries.
451
452   Fonts
453       X11 supports 8-bit and 16-bit text string display, and neither can be
454       used effectively to display unicode strings. A "XCreateFontSet"
455       technique, which combines several fonts under one descriptor, or a
456       similarly implemented technique is the only way to provide correct
457       unicode display.
458
459       Also, core font transfer protocol suffers from ineffective memory
460       representation, which creates latency when fonts with large span of
461       glyphs is loaded. Such fonts, in still uncommon though standard
462       iso10646 encoding, are the only media to display multi-encoding text
463       without falling back to hacks similar to "XCreateFontSet".
464
465       These, and some other problems are efficiently solved by Xft library, a
466       superset of X core font functionality. Xft features Level 1 ( November
467       2003 ) unicode display and supports 32-bit text strings as well as
468       UTF8-coded strings.  Xft does not operate with charset encodings, and
469       these are implemented in Prima using iconv charset convertor library.
470
471   Input
472       Prima does not support extended input methods ( XIM etc ), primarily
473       because the authors are not acquainted with CIJK problem domain.
474       Volunteers are welcome.
475
476   Clipboard
477       Prima supports UTF8 text in clipboard via "UTF8_STRING" transparently,
478       although not by default.
479
480          Prima::Application-> wantUnicodeInput(1)
481
482       is the easiest ( see Prima::Application ) way to initiate UTF8
483       clipboard text exchange.
484
485       Due to the fact that any application can take ownership over the
486       clipboard at any time, "open"/"close" brackets are not strictly
487       respected in X11 implementation. Practically, this means that when
488       modern X11 clipboard daemons ( KDE klipper, for example ) interfere
489       with Prima clipboard, the results may not be consistent from the
490       programmer's view, for example, clipboard contains data after "clear"
491       call, and the like. It must be noted though that this behavior is
492       expected by the users.
493

Other XRDB resources

495   Timeouts
496       Raw X11 provides no such GUI helpers as double-click event, cursor, or
497       menu.  Neither does it provide the related time how often, for example,
498       a cursor would blink. Therefore Prima emulates these, but allows the
499       user to reprogram the corresponding timeouts. Prima recognizes the
500       following properties, accessible either via application name or Prima
501       class key. All timeouts are integer values, representing number of
502       milliseconds for the corresponding timeout property.
503
504       Blinkinvisibletime.blinkinvisibletime: MSEC
505           Cursor stays invisible MSEC milliseconds.
506
507           Default value: 500
508
509       Blinkvisibletime.blinkvisibletime: MSEC
510           Cursor stays visible MSEC milliseconds.
511
512           Default value: 500
513
514       Clicktimeframe.clicktimeframe MSEC
515           If 'mouse down' and 'mouse up' events are follow in MSEC, 'mouse
516           click' event is synthesized.
517
518           Default value: 200
519
520       Doubleclicktimeframe.doubleclicktimeframe MSEC
521           If 'mouse click' and 'mouse down' events are follow in MSEC, 'mouse
522           double click' event is synthesized.
523
524           Default value: 200
525
526       Submenudelay.submenudelay MSEC
527           When the used clicks on a menu item, which points to a lower-level
528           menu window, the latter is displayed after MSEC milliseconds.
529
530           Default value: 200
531
532       Scrollfirst.scrollfirst MSEC
533           When an auto-repetitive action, similar to keystroke events
534           resulting from a long key press on the keyboard, is to be
535           simulated, two timeout values are used - 'first' and 'next' delay.
536           These actions are not simulated within Prima core, and the
537           corresponding timeouts are merely advisable to the programmer.
538           Prima widgets use it for automatic scrolling, either by a scrollbar
539           or by any other means.  Also, "Prima::Button" in "autoRepeat" mode
540           uses these timeouts for emulation of a key press.
541
542           "Scrollfirst" is a 'first' timeout.
543
544           Default value: 200
545
546       Scrollnext.scrollnext MSEC
547           A timeout used for same reasons as "Scrollfirst", but after it is
548           expired.
549
550           Default value: 50
551
552   Miscellaneous
553       Visual.visual: VISUAL_ID
554           Selects display visual by VISUAL_ID, which is usually has a form of
555           "0x??".  Various visuals provide different color depth and access
556           scheme. Some X stations have badly chosen default visuals (for
557           example, default IRIX workstation setup has 8-bit default visual
558           selected), so this property can be used to fix things. List of
559           visuals, supported by a X display can be produced interactively by
560           standard "xdpyinfo" command from X distribution.
561
562           Identical to "--visual" command-line argument.
563
564           See Color for more information.
565
566       Wheeldown.wheeldown BUTTON
567           BUTTON is a number of X mouse button event, treated as 'mouse wheel
568           down' event.
569
570           Default value: 5 ( default values for wheeldown and wheelup are
571           current de-facto most popular settings ).
572
573       Wheelup.wheelup BUTTON
574           BUTTON is a number of X mouse button event, treated as 'mouse wheel
575           up' event.
576
577           Default value: 4
578

Debugging

580       The famous 'use the source' call is highly actual with Prima. However,
581       some debug information comes compiled in, and can be activated by
582       "--debug" command-line key. Combination of letters to the key activates
583       debug printouts of different subsystems:
584
585       ·   C - clipboard
586
587       ·   E - events subsystem
588
589       ·   F - fonts
590
591       ·   M - miscellaneous debug info
592
593       ·   P - palettes and colors
594
595       ·   X - XRDB
596
597       ·   A - all of the above
598
599       Example:
600
601          --debug=xf
602
603       Also, the built-in X API "XSynchronize" call, which enables X protocol
604       synchronization ( at expense of operation slowdown though ) is
605       activated with "--sync" command-line argument, and can be used to ease
606       the debugging.
607
608   GTK
609       Prima can be compiled with GTK, and can use its colos and font scheme,
610       and GTK file dialogs. This can be disabled with "--no-gtk" command line
611       switch.
612
613       On MacOSX, GTK usually comes with Quartz implementation, which means
614       that Prima will get into problems with remote X11 connections. Prima
615       tries to detect this condition, but if trouble persists, please use
616       "--no-gtk" switch (and please file a bug report so this can be fixed,
617       too).
618
619   Quartz
620       Prima can be compiled with Cocoa library on MacOSX, that gives access
621       to screen scraping functionality of Application.get_image, that is
622       otherwise is non-functional with XQuartz. To disable it, use
623       "--no-quartz" runtime switch.
624

AUTHOR

626       Dmitry Karasik, <dmitry@karasik.eu.org>.
627

SEE ALSO

629       Prima, Prima::gp-problems, Prima::Widget, Nye A, Xlib programming
630       manual. O'Reilly & Associates, 1995.
631
632
633
634perl v5.32.0                      2020-07-28                pod::Prima::X11(3)
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