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Update information about visuals

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Based on a patch by Jasper St. Pierre,
https://bugzilla.gnome.org/show_bug.cgi?id=639520
This commit is contained in:
Matthias Clasen 2011-01-14 20:45:53 -05:00
parent 8f6a8441a2
commit d790fd4fdd
1 changed files with 14 additions and 13 deletions
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27
docs/reference/gtk/question_index.sgml
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@ -547,23 +547,24 @@ How do I create a transparent toplevel window ?
<answer> <answer>
<para> <para>
To make a window transparent, it needs to use a visual which supports that. To make a window transparent, it needs to use a visual which supports that.
This is done by getting the RGBA colormap of the screen with This is done by getting the RGBA visual of the screen with
gdk_screen_get_rgba_colormap() and setting it on the window. Note that gdk_screen_get_rgba_visual() and setting it on the window. Note that
gdk_screen_get_rgba_colormap() will return %NULL if transparent windows gdk_screen_get_rgba_visual() will return %NULL if transparent windows
are not supported on the screen; also note that this may change from are not supported on the screen, you should fall back to
screen to screen, so it needs to be repeated whenever the window is moved gdk_screen_get_system_visual() in that case. Additionally, note that this
to a different screen. will change from screen to screen, so it needs to be repeated whenever the
window is moved to a different screen.
<informalexample><programlisting> <informalexample><programlisting>
GdkColormap *colormap; GdkVisual *visual;
colormap = gdk_screen_get_rgba_colormap (screen); visual = gdk_screen_get_rgba_visual (screen);
if (!colormap) if (visual == NULL)
colormap = gdk_screen_get_rgb_colormap (screen); visual = gdk_screen_get_system_visual (screen);
gtk_widget_set_colormap (widget, colormap); gtk_widget_set_visual (GTK_WIDGET (window), visual);
</programlisting></informalexample> </programlisting></informalexample>
One possibility to fill the alpha channel on the window is to use To fill the alpha channel on the window simply use cairos
gdk_draw_rgb_32_image(). RGBA drawing capabilities.
</para> </para>
<para> <para>
Note that the presence of an RGBA visual is no guarantee that the Note that the presence of an RGBA visual is no guarantee that the