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       Prima::X11 - usage guide for X11 environment


       This document describes subtle topics one must be aware when
       programming or using Prima programs under X11.

       The document covers various aspects of the toolkit and their
       implementation details with guidelines of the expected use. Also,
       standard X11 user-level and programming techniques are visited.

Basic command-line switches

           Prints the command-line arguments available and exits.

           Sets X display address in Xlib notation. If not set, standard Xlib
           ( "XOpenDisplay(null)" ) behavior applies.



           Sets X visual, to be used by default. Example:


           Turn off X synchronization

       "--bg", "--fg"
           Set default background and foreground colors. Example:


           Sets default font. Example:


           Runs Prima without X11 display initialized. This switch can be used
           for programs that use only OS-independent parts of Prima, such as
           image subsystem or PostScript generator, in environments where X is
           not present, for example, a CGI script.  Obviously, any attempt to
           create instance of "Prima::Application" or otherwise access
           X-depended code under such conditions causes the program to abort.

           There are alternatives to use the command switch. First, there is
           module "Prima::noX11" for the same purpose but more convenient to
           use as

              perl -MPrima::noX11

           construct. Second, there is a technique to continue execution even
           if connection to a X server failed:

              use Prima::noX11;
              use Prima;

              my $error = Prima::XOpenDisplay();
              if ( defined $error) {
                   print "not connected to display: $error\n";
              } else {
                   print "connected to display\n";

           The Prima::noX11 module exports a single function "XOpenDisplay"
           into "Prima" namespace, to connect to the X display explicitly. The
           display to be connected to is $ENV{DISPLAY}, unless started
           otherwise on command line ( with --display option) or with
           parameter to the "XOpenDisplay" function.

           This technique may be useful to programs that use Prima imaging
           functionality and may or may not use windowing capabilites.

X resources database

       X11 provides XRDB, the X resource database, a keyed list of arbitrary
       string values stored on the X server. Each key is a combination of
       names and classes of widgets, each in string form. The key is
       constructed so the leftmost substring ( name or class ) corresponds to
       the top-level item in the hierarchy, usually the application name or
       class. Although the XRDB can be changed via native X API, it is rarely
       done by applications. Instead, the user creates a file, usually named
       .Xdefaults, which contains the database in the string form.

       The format of .Xdefaults directly reflects XRDB capabilities, one of
       the most important of which is globbing, manifested via * ( star )
       character. Using globbing, the user can set up a property value that
       corresponds to multiple targets:

          *.ListBox.backColor: yellow

       The string above means that all widgets of ListBox class must have
       yellow background.

       The application itself is responsible for parsing the strings and
       querying the XRDB.  Also, both class names and widget names, as well as
       database values are fully defined in terms of the application. There
       are some guidelines though, for example, colors and fonts best
       described in terms, native to the X server.  Also, classes and names
       are distinguished by the case: classes must begin with the upper
       register letter. Also, not every character can be stored in the XRDB
       database ( space, for example, cannot) , and therefore XRDB API
       automatically converts these to _ ( underscore ) characters.

       Prima defines its all set of resources, divided in two parts: general
       toolkit settings and per-widget settings. The general settings
       functionality is partially overloaded by command-line arguments. Per-
       widget settings are fonts and colors, definable for each Prima widget.

       All of the general settings are applicable to the top-level item of
       widget hierarchy, named after the application, and "Prima" class. Some
       of these, though, are needed to be initialized before the application
       instance itself is created, so these can be accessed via "Prima" class
       only, for example, "Prima.Visual".  Some, on the contrary, may
       occasionally overlap with per-widget syntax.  In particular, one must
       vary not to mix

          Prima.font: some-font


          Prima*font: some-font

       The former syntax is a general setting, and sets the default Prima
       font.  The latter is a per-widget assignment, and explicitly sets font
       to all Prima widgets, effectively ruining the toolkit font inheritance
       scheme. The same is valid for an even more oppressive

          *font: some-font


       The allowed per-widget settings are colors and font settings only ( see
       corresponding sections ). It is an arguably useful feature to map all
       widget properties onto XRDB, but Prima does not implement this,
       primarily because no one asked for it, and also because this creates
       unnecessary latency when enumeration of all properties for each widget
       takes place.

       All global settings have identical class and name, varied in the case
       of the first letter. For example, to set "Submenudelay" value, one can
       do it either by

          Prima.Submenudelay: 10


          Prima.submenudelay: 10

       syntax. Despite that these calls are different, in a way that one
       reaches for the whole class and another for the name, for the majority
       of these properties it does not matter. To avoid confusion, for all
       properties their names and class are given as
       "PropetyClass.propertyname" index.


   Default fonts
       Prima::Application defines set of "get_default_XXX_font" functions,
       where each returns some user-selected font, to be displayed
       correspondingly in menu, message, window captions, all other widgets,
       and finally a default font. While in other OS’es these are indeed
       standard configurable user options, raw X11 doesn’t define any.
       Nevertheless, as the high-level code relies on these, corresponding
       resources are defined. These are:

       ·   font - Application::get_default_font

       ·   caption_font - Application::get_caption_font. Used in "Prima::MDI".

       ·   menu_font - Widget::get_default_menu_font. Default font for pull-
           down and pop-up menus.

       ·   msg_font - Application::get_message_font. Used in "Prima::MsgBox".

       ·   widget_font - Widget::get_default_font.

       All of the global font properties can only be set via "Prima" class, no
       application name is recognized. Also, these properties are identical to
       "--font", "--menu-font", "--caption-font", "--msg-font", and
       "--widget-font" command-line arguments.  The per-widget properties are
       "font" and "popupFont", of class "Font", settable via XRDB only:

          Prima*Dialog.font: my-fancy-dialog-font
          Prima.FontDialog.font: some-conservative-font

       By default, Prima font is 12.Helvetica .

   X core fonts
       The values of the font entries are standard XLFD strings, the default
       "*-*-*-*-*-*-*-*-*-*-*-*-*-*-*" pattern, where each star character can
       be replaced by a particular font property, as name, size, charset, and
       so on. To interactively select an appropriate font, use standard
       "xfontsel" program from X11 distribution.

       Note, that encoding part of the font is recommended to left
       unspecified, otherwise it may clash with LANG environment variable,
       which is used by Prima font subsystem to determine which font to select
       when no encoding is given.  This advice, though, is correct only when
       both LANG and encoding part of a desired font match. In order to force
       a particular font encoding, the property "Prima.font" must contain one.

       Alternatively, and/or to reduce X font traffic, one may set
       "IgnoreEncodings.ignoreEncodings" property, which is a semicolon-
       separated list of encodings Prima must not account. This feature has
       limited usability when for example fonts in Asian encodings result in
       large font requests.  Another drastic measure to decrease font traffic
       is a boolean property "Noscaledfonts.noscaledfonts", which, if set to
       1, restricts the choice of fonts to the non-scalable fonts only.

   Xft fonts
       Recently, Prima was made to compile with Xft library, which contrary to
       core X font API, can make use of client-side fonts. Plus, Xft offers
       appealing features as font antialiasing, unicode, and arguably a better
       font syntax. The Xft font syntax is inherited from "fontconfig" library
       and to be consulted from "man fonts-conf", but currently ( November
       2003 ) basic font descriptions can be composed as follows:


       A font with name "Palatino" and size 12.


       A font with name "Arial", size 10, bold, italic. The "fontconfig"
       syntax allows more than that, for example, arbitrary matrix
       transformations, but Prima can make use only of font name, size, and
       style flags.

           "--no-xft" command-line argument, and boolean "UseXFT.usexft" XRDB
           property can be used to disable use of the Xft library.

           Disables all X11 core fonts, except "fixed" fonts. The "fixed" font
           is selected for the same reasons that X server is designed to
           provide at least one font, which usually is "fixed".

           It is valid to combine "--no-core-fonts" and "--no-xft". Moreover,
           adding "--noscaled" to these gives Prima programs a ’classic’ X

           Can be set to either "xft" or "core", to select a font provider
           mechanism to match unknown or incompletely specified fonts against.

           Default value: "xft" ( if compiled in ), "core" otherwise.

           If set, turns off Xft antialiasing.


   XRDB conventions
       X traditionally contains a color names database, usually a text file
       named rgb.txt.  Check your X manual where exactly this file resides and
       what is its format.  The idea behind it is that users can benefit from
       portable literal color names, with color values transparently
       adjustable to displays capabilities.  Thus, it is customary to write

          color: green

       for many applications, and these in turn call "XParseColor" to convert
       strings into RGB values.

       Prima is no exception to the scheme. Each widget can be assigned eight
       color properties: "color", "hiliteBackColor", "disabledColor",
       "dark3DColor" "backColor", "hiliteColor", "disabledBackColor",
       "light3DColor" by their name:

          Prima.backColor: #cccccc

       Additionally, set of command-line arguments allows overriding default
       values for these:

       ·   "--fg" - color

       ·   "--bg" - backColor

       ·   "--hilite-fg" - hiliteColor

       ·   "--hilite-bg" - hiliteBackColor

       ·   "--disabled-fg" - disabledColor

       ·   "--disabled-bg" - disabledBackColor

       ·   "--light" - light3DColor

       ·   "--dark" - dark3DColor

       X protocol works with explicitly defined pixel values only.  A pixel
       value, maximum 32-bit value, represents a color in a display. There are
       two different color coding schemes - direct color and indexed color.
       The direct color-coded pixel value can unambiguously be converted into
       a RGB-value, without any external information.  The indexed-color
       scheme represents pixel value as an index in a palette, which resided
       on X server. Depending on the color cell value of the palette, RGB
       color representation can be computed. A X display can contain more than
       one palette, and allow ( or disallow ) modification of palette color
       cells depending on a visual, the palette is attributed to.

       A visual is a X server resource, containing representation of color
       coding scheme, color bit depth, and modificability of the palette. X
       server can ( and usually does ) provide more than one visual, as well
       as different bit depths.  There are six classes of visuals in X
       paradigm. In each, Prima behaves differently, also depending on display
       bit depth available.  In particular, color dithering can be used on
       displays with less than 12-bit color depth. On displays with modifiable
       color palette, Prima can install its own values in palettes, which may
       result in an effect known as display flashing. To switch to a non-
       default visual, use "Prima.Visual" XRDB property or "--visual" command-
       line argument.  List of visuals can be produced interactively by
       standard "xdpyinfo" command from X distribution, where each class of
       visual corresponds to one of six visual classes:

           All color cells are read-only, and contain monochrome values only.
           A typical example is a two-color, black-and-white monochrome
           display.  This visual is extremely rarely met.

           Contains modifiable color palette, and capable of displaying
           monochrome values only. Theoretically, any paletted display on a
           monochrome monitor can be treated as a GrayScale visual. For both
           GrayScale and StaticGray visuals Prima resorts to dithering if it
           cannot get at least 32 evenly spaced gray values from black to

           All color cells are read-only.  A typical example is a PC display
           in a 16-color EGA mode.  This visual is rarely met.

           All color cells are modifiable. Typically, 8-bit displays define
           this class for a default visual. For both StaticColor and
           PseudoColor visuals dithering is always used, although for
           "PseudoColor" Prima resorts to that only if X server cannot
           allocate another color.

           On "PseudoColor" and "GrayScale" Prima allocates a small set of
           colors, not used in palette modifications. When a bitmap is to be
           exported via clipboard, or displayed in menu, or sent to a window
           manager as an icon to be displayed, it is downgraded to using these
           colors only, which are though guaranteedly to stay permanent
           through life of the application.

           Each pixel value is explicitly coded as RGB. Typical example are
           16, 24, or 32-bit display modes. This visual class is the best in
           terms of visual quality.

           Same as TrueColor, but additionally each pixel value can be
           reprogrammed.  Not all hardware support this visual, and usually by
           default it is not set.  Prima supports this mode in exactly same
           way as TrueColor without additional features. During testing, it
           appeared that non-default DirectColor visuals require explicit
           assignment of each pixel used, which is inappropriate for color-
           rich images, and therefore Prima refuses to work on a non-default
           DirectColor visual.


       As described in the previous section, X does not standardize pixel
       memory format for TrueColor and "DirectColor" visuals, so there is a
       chance that Prima wouldn’t work on some bizarre hardware. Currently,
       Prima knows how to compose pixels of 15, 16, 24, and 32 bit depth, of
       contiguous ( not interspersed ) red-green-blue memory layout. Any other
       pixel memory layout causes Prima to fail.

       Prima supports shared memory image X extension, which speeds up image
       display for X servers and clients running on same machine. The price
       for this is that if Prima program aborts, the shared memory will never
       be returned to the OS.  To remove the leftover segments, use your OS
       facilities, for example, "ipcrm" on *BSD.

       The clipboard exchange of images is incompletely implemented, since
       Prima does not accompany ( and neither reads ) COLORMAP, FOREGROUND,
       and BACKGROUND clipboard data, which contains pixel RGB values for a
       paletted image. As a palliative, the clipboard-bound images are
       downgraded to a safe set of colors, locked immutable either by X server
       or Prima core.

       On images in the clipboard: contrary to the text in the clipboard,
       which can be used several times, images seemingly cannot. The Bitmap or
       Pixmap descriptor, stored in the clipboard, is rendered invalid after
       it has been read once.

Window managers

       The original design of X protocol did not include the notion of a
       window manager, and latter is was implemented as an ad-hoc patch, which
       results in race conditions when configuring widgets. The extreme
       situation may well happen when even a non-top level widget may be
       influenced by a window manager, when for example a top-level widget was
       reparented into another widget, but the window manager is not aware or
       this yet.

       The consequences of this, as well as programming guidances are
       described in "Prima::Window". Here, we describe other aspects of
       interactions with WMs, as WM protocols, hints, and properties.

       Prima was tested with alternating success under the following window
       managers: mwm, kwin, wmaker, fvwm, fvwm2, enlightment, sawfish,
       blackbox, 9wm, olvm, twm, and in no-WM environment.

       Prima makes use of "WM_DELETE_WINDOW" and "WM_TAKE_FOCUS" protocols.
       While "WM_DELETE_WINDOW" use is straightforward and needs no further
       attention, "WM_TAKE_FOCUS" can be tricky, since X defines several of
       input modes for a widget, which behave differently for each WM.  In
       particular, ’focus follows pointer’ gives pains under twm and mwm,
       where navigation of drop-down combo boxes is greatly hindered by window
       manager. The drop-down list is programmed so it is dismissed as soon
       its focus is gone; these window managers withdraw focus even if the
       pointer is over the focused widget’s border.

       Size, position, icons, and other standard X hints are passed to WM in a
       standard way, and, as inter-client communication manual ( ICCCM )
       allows, repeatedly misinterpreted by window managers. Many ( wmaker,
       for example ) apply the coordinates given from the program not to the
       top-level widget itself, but to its decoration.  mwm defines list of
       accepted icon sizes so these can be absurdly high, which adds confusion
       to a client who can create icon of any size, but unable to determine
       the best one.

   Non-standard properties
       Prima tries to use WM-specific hints, known for two window managers:
       mwm and kwin.  For mwm ( Motif window manager ) Prima sets hints of
       decoration border width and icons only. For kwin ( and probably to
       others, who wish to conform to specifications of ) Prima uses "NET_WM_STATE" property, in
       particular its maximization and task-bar visibility hints.

       Use of these explicitly contradicts ICCCM, and definitely may lead to
       bugs in future ( at least with "NET_WM_STATE", since Motif interface
       can hardly expected to be changed ).  To disable the use of non-
       standard WM properties, "--icccm" command-line argument can be set.


       X does not support unicode, and number of patches were applied to X
       servers and clients to make the situation change. Currently ( 2003 )
       standard unicode practices are not emerged yet, so Prima copes up with
       what ( in author’s opinion ) is most promising: Xft and iconv

       X11 supports 8-bit and 16-bit text string display, and neither can be
       used effectively to display unicode strings. A "XCreateFontSet"
       technique, which combines several fonts under one descriptor, or a
       similarly implemented technique is the only way to provide correct
       unicode display.

       Also, core font transfer protocol suffers from ineffective memory
       representation, which creates latency when fonts with large span of
       glyphs is loaded. Such fonts, in still uncommon though standard
       iso10646 encoding, are the only media to display multi-encoding text
       without falling back to hacks similar to "XCreateFontSet".

       These, and some other problems are efficiently solved by Xft library, a
       superset of X core font functionality. Xft features Level 1 ( November
       2003 ) unicode display and supports 32-bit text strings as well as
       UTF8-coded strings.  Xft does not operate with charset encodings, and
       these are implemented in Prima using iconv charset convertor library.

       Prima does not support extended input methods ( XIM etc ), primarily
       because the authors are not acquainted with CIJK problem domain.
       Volunteers are welcome.

       Prima supports UTF8 text in clipboard via "UTF8_STRING" transparently,
       although not by default.

          Prima::Application-> wantUnicodeInput(1)

       is the easiest ( see Prima::Application ) way to initiate UTF8
       clipboard text exchange.

       Due to the fact that any application can take ownership over the
       clipboard at any time, "open"/"close" brackets are not strictly
       respected in X11 implementation. Practically, this means that when
       modern X11 clipboard daemons ( KDE klipper, for example ) interfere
       with Prima clipboard, the results may not be consistent from the
       programmer’s view, for example, clipboard contains data after "clear"
       call, and the like. It must be noted though that this behavior is
       expected by the users.

Other XRDB resources

       Raw X11 provides no such GUI helpers as double-click event, cursor, or
       menu.  Neither does it provide the related time how often, for example,
       a cursor would blink. Therefore Prima emulates these, but allows the
       user to reprogram the corresponding timeouts. Prima recognizes the
       following properties, accessible either via application name or Prima
       class key. All timeouts are integer values, representing number of
       milliseconds for the corresponding timeout property.

       Blinkinvisibletime.blinkinvisibletime: MSEC
           Cursor stays invisible MSEC milliseconds.

           Default value: 500

       Blinkvisibletime.blinkvisibletime: MSEC
           Cursor stays visible MSEC milliseconds.

           Default value: 500

       Clicktimeframe.clicktimeframe MSEC
           If ’mouse down’ and ’mouse up’ events are follow in MSEC, ’mouse
           click’ event is synthesized.

           Default value: 200

       Doubleclicktimeframe.doubleclicktimeframe MSEC
           If ’mouse click’ and ’mouse down’ events are follow in MSEC, ’mouse
           double click’ event is synthesized.

           Default value: 200

       Submenudelay.submenudelay MSEC
           When the used clicks on a menu item, which points to a lower-level
           menu window, the latter is displayed after MSEC milliseconds.

           Default value: 200

       Scrollfirst.scrollfirst MSEC
           When an auto-repetitive action, similar to keystroke events
           resulting from a long key press on the keyboard, is to be
           simulated, two timeout values are used - ’first’ and ’next’ delay.
           These actions are not simulated within Prima core, and the
           corresponding timeouts are merely advisable to the programmer.
           Prima widgets use it for automatic scrolling, either by a scrollbar
           or by any other means.  Also, "Prima::Button" in "autoRepeat" mode
           uses these timeouts for emulation of a key press.

           "Scrollfirst" is a ’first’ timeout.

           Default value: 200

       Scrollnext.scrollnext MSEC
           A timeout used for same reasons as "Scrollfirst", but after it is

           Default value: 50

       Visual.visual: VISUAL_ID
           Selects display visual by VISUAL_ID, which is usually has a form of
           "0x??".  Various visuals provide different color depth and access
           scheme. Some X stations have badly chosen default visuals (for
           example, default IRIX workstation setup has 8-bit default visual
           selected), so this property can be used to fix things. List of
           visuals, supported by a X display can be produced interactively by
           standard "xdpyinfo" command from X distribution.

           Identical to "--visual" command-line argument.

           See Color for more information.

       Wheeldown.wheeldown BUTTON
           BUTTON is a number of X mouse button event, treated as ’mouse wheel
           down’ event.

           Default value: 5 ( default values for wheeldown and wheelup are
           current de-facto most popular settings ).

       Wheelup.wheelup BUTTON
           BUTTON is a number of X mouse button event, treated as ’mouse wheel
           up’ event.

           Default value: 4


       The famous ’use the source’ call is highly actual with Prima. However,
       some debug information comes compiled in, and can be activated by
       "--debug" command-line key. Combination of letters to the key activates
       debug printouts of different subsystems:

       ·   C - clipboard

       ·   E - events subsystem

       ·   F - fonts

       ·   M - miscellaneous debug info

       ·   P - palettes and colors

       ·   X - XRDB

       ·   A - all of the above



       Also, the built-in X API "XSynchronize" call, which enables X protocol
       synchronization ( at expense of operation slowdown though ) is
       activated with "--sync" command-line argument, and can be used to ease
       the debugging.


       Dmitry Karasik, <>.


       Prima, Prima::gp-problems, Prima::Widget, Nye A, Xlib programming
       manual. O’Reilly & Associates, 1995.