Re: Alpha-composition of two pixmaps

["Dmitry M. Shatrov" <erdizz rambler ru>]

Olexiy Avramchenko wrote:

> Dmitry M. Shatrov wrote:
>
> > Hello.
> >
> > As I know, XRender extension allows to compose two X drawables.
> > Coldn't find a wrapper in GDK, though (except one 'non-public' 
> > function in a CVS version,
> > that draws a filled alpha blended rectangle). Is there any?
> >
> > And, if not, what is ther reason of complete Render support being not 
> > here yet?
>
>
> Hi
> You can draw gdk-pixbuf with alpha-channel to any gdk drawable. Under 
> X GDK *use* XRender for this. Look at "gdk/x11/gdkdrawable-x11.c" for 
> details.
> I dont know about complete XRender support in X11 GDK backend, but you 
> always can code all you need with foreign pixmaps.
>
>    Olexiy
GdkPixbuf is not what I need, cus it is by definition slow. I guess, 
drawing pixbufs is optimized for Render just because it is frequently 
used (all icons, for example), and alpha-drawable-to-drawable is too 
special to even bother about it.

I use GdkPixbuf to draw a marker, then render it to a server-side 
pixmap. That pixmap is used in fast animation (unfortunately non-alpha 
at the moment), so it must be drawn as quick as possible - that's a 
common XRender's task

Looks like it worths adding a pair of calls to gdk-x11 and post it to 
gtk-devel..

Dmitry