General Application Compositing

[Maskawanian]

I am interested in creating a Mac OS X dock like application for fun to learn compositing. I am a former Mac OS X developer but am finding that Linux could soon replace most of the reasons I liked Mac OS X. I digress, Does anyone know how in GTK to create a window that is transparent, but a child widget is not, for example having an image full opacity. with nothing behind it?

Any pointers would be much appreciated.

-- Dan

[lagorgy]

Maybe you should take a look at avant-window-navigator, its a dock like the one you're trying to develop. You can talk to the main dev and maybe help him instead of duplicating efforts, what do u think?

http://code.google.com/p/avant-window-navigator/

[rememo]

Hi,

seeing that you already asked at the awn forums, I thought I would give you a direct reply. This is how it is done in gnome-terminal:

static void
initialize_alpha_mode (TerminalWindow *window)
{
GdkScreen *screen;
GdkColormap *colormap;

screen = gtk_widget_get_screen (GTK_WIDGET (window));
colormap = gdk_screen_get_rgba_colormap (screen);
if (colormap != NULL && gdk_screen_is_composited (screen))
{
/* Set RGBA colormap if possible so VTE can use real alpha
* channels for transparency. */

gtk_widget_set_colormap(GTK_WIDGET (window), colormap);
window->priv->have_argb_visual = TRUE;
}
else
{
window->priv->have_argb_visual = FALSE;
}
}


So you have to check if compositing (i.e. through compiz) is available first, before setting the rgba colormap. You can take a closer look at the code of gnome-terminal here:
http://cvs.gnome.org/viewcvs/gnome-terminal/src/terminal-window.c?rev=1.139&view=markup

However, as lagorgy said: I strongly recommend to help neil with his avant-window-navigator dock or the authors of the other docks (mainly kiba-dock and gnome-dock, although they already have zoom support).

[FunkyM]

Another example in C# here (http://macslow.thepimp.net/?p=46) (in general faster to understand the overall basics). Also checkout other posts in that blog with loads of examples of different stuff. Then either checkout AWN as suggested or check gnome-dock's sources here (http://www.gnome-dock.org).

[Maskawanian]

Hi,

seeing that you already asked at the awn forums, I thought I would give you a direct reply. This is how it is done in gnome-terminal:

static void
initialize_alpha_mode (TerminalWindow *window)
{
GdkScreen *screen;
GdkColormap *colormap;

screen = gtk_widget_get_screen (GTK_WIDGET (window));
colormap = gdk_screen_get_rgba_colormap (screen);
if (colormap != NULL && gdk_screen_is_composited (screen))
{
/* Set RGBA colormap if possible so VTE can use real alpha
* channels for transparency. */

gtk_widget_set_colormap(GTK_WIDGET (window), colormap);
window->priv->have_argb_visual = TRUE;
}
else
{
window->priv->have_argb_visual = FALSE;
}
}


So you have to check if compositing (i.e. through compiz) is available first, before setting the rgba colormap. You can take a closer look at the code of gnome-terminal here:
http://cvs.gnome.org/viewcvs/gnome-terminal/src/terminal-window.c?rev=1.139&view=markup

However, as lagorgy said: I strongly recommend to help neil with his avant-window-navigator dock or the authors of the other docks (mainly kiba-dock and gnome-dock, although they already have zoom support).

Don't get me wrong I just want to learn myself duplicating the efforts of others so that I can submit quality patches rather then poor code.

But thanks I really appreciate it.

[Maskawanian]

In fact I did more research and found this example for anyone who is interested:

http://plan99.net/%7Emike/blog/?p=38

If you want transparency with XShape:

http://macslow.thepimp.net/?p=26

[RYX]

For the python-approach to XShape/compositing you could also have a look at the screenlets base classes.

:)