Re: Alpha-composition of two pixmaps

[Michael L Torrie <torriem chem byu edu>]

On Thu, 2004-10-28 at 18:18 +0400, Dmitry M. Shatrov wrote:
> 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.

It's not slow by definition.  Anyway it does use render directly.  So if
you have an accelerated render driver in the X server, it will be plenty
fast.  If not, then it will be slow even if you called render directly.

> 
> 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

Actually, unless you have accelerated render support (like the
experimental render stuff in the NVIDIA driver), I doubt you'll notice a
significate speed improvement using RENDER as opposed to other forms of
drawing.  Hopefully we'll see accelerated render support soon.  By then,
though, you won't even want to use it directly because we'll have good
support for alpha-channel in all aspects of the X server.  That means
your old animation code will still work fine, only this time you can add
an alpha channel to your images as you draw them and the X server will
magically make it all work.

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

I don't think Render should be exposed in gdk.  For one it's just a
backend method, and is not available on all platforms nor is it
available on all X servers.

> 
> Dmitry
> 
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