README
1README for GDK-DirectFB
2------------------------
3
4This is the GDK backend that allows GTK to work on top of DirectFB.
5
6Important:
7The current code does not pass through directfb passed on the gtk
8apps command line on to directfb you need to set the environment variable
9DFBARGS.
10Example:
11export DFBARGS=system=sdl
12
13DirectFB is a hardware abstraction layer on top of the Linux
14frame buffer that provides drawing functions, a window stack and
15support for input devices. The code you find here is a backend for
16GDK, the drawing kit used by GTK+.
17
18
19As DirectFB provides drawing functions, a windowing stack and manages
20input devices, this is a lightweight GDK port. Some parts of GDK
21require higher level drawing functions that are supported by
22cairo on DirectFB.
23GDK also uses some feature like bitmaps that do not map well to
24modern graphics hardware and are for that reason not yet supported in
25this snapshot. See the file TODO for a list of missing features.
26
27
28If you want GTK+ to draw window decorations for you, edit the file
29gtk/gtkwindow-decorate.c and uncomment the line that says
30#define DECORATE_WINDOWS.
31
32
33GTK+ application compiled with this version of GTK+ understand some
34additional command-line options special to the DirectFB GDK backend:
35
36 --transparent-unfocused Makes unfocused windows translucent.
37
38 --argb-font Use ARGB surfaces for fonts, needed for some
39 broken hardware.
40
41 --glyph-surface-cache Lets you tune the size of the glyph cache,
42 the default is to cache glyphs from 8 faces.
43
44 --enable-color-keying This option turns on a hack that does the
45 following:
46
47 (1) It overrides the color used to draw the window background to
48 gdk_directfb_bg_color as defined in gdkprivate-directfb.h.
49 Note that the alpha value only takes effect if the window has
50 an alpha channel.
51 (2) It also draws all rectangles that are drawn in
52 gdk_directfb_bg_color_key in this color (gdk_directfb_bg_color).
53
54 This feature can be used to create windows with translucent background.
55
56Additionally all DirectFB command-line options as described in the
57directfbrc man-page are supported.
58
59
60This version of GTK+ also introduces two new functions that are special
61to the DirectFB version. You need to include gdk/gdkdirectfb.h to be
62able to use them.
63
64 gdk_directfb_window_set_opacity (GdkWindow *window, guchar opacity));
65
66 This function sets the overall opacity for toplevel GDK windows.
67
68 gdk_directfb_visual_by_format (DFBSurfacePixelFormat pixel_format);
69
70 This function returns a GdkVisual for a DirectFB pixelformat and
71 thus gives you control over the window surface. If for example
72 you want to create a window with alpha channel you can use some
73 code like the following:
74
75 visual = gdk_directfb_visual_by_format (DSPF_ARGB);
76 cmap = gdk_colormap_new (visual, FALSE);
77 gtk_widget_push_colormap (cmap);
78 window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
79 gtk_widget_pop_colormap ();
80 g_object_unref (cmap);
81
82Don't use these functions if you want to be able to compile your
83application against GTK+-X11 or other GTK+ versions.
84
85
86If you are developing a GTK+ application for GTK+-DirectFB make sure
87you use the gtk+-directfb-2.0.pc file when calling pkg-config to get
88the correct compiler and linker flags for GTK+-DirectFB:
89
90 pkg-config --cflags gtk+-directfb-2.0
91 pkg-config --libs gtk+-directfb-2.0
92
93
94See the file TODO for a list of unimplemented features.
95
96
97Detailed and up-to-date instructions on how to build a complete
98set of GTK-DFB libraries is avalable in the WIKI of the DirectFB project
99at the address
100http://www.directfb.org/wiki/index.php/Projects:GTK_on_DirectFB
101
102
103This library is free software; you can redistribute it and/or modify it
104under the terms of the GNU Lesser General Public License as published
105by the Free Software Foundation; either version 2 of the License, or
106(at your option) any later version.
107