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Re: [Qemu-devel] Re: [PATCH] Use opaque alpha channel to support Xgl
From: |
Anthony Liguori |
Subject: |
Re: [Qemu-devel] Re: [PATCH] Use opaque alpha channel to support Xgl |
Date: |
Mon, 06 Mar 2006 18:51:32 -0600 |
User-agent: |
Mail/News 1.5 (X11/20060213) |
Christian Walther wrote:
Anthony Liguori wrote:
I really don't like this patch as it seems like a hack but I couldn't
figure out a way to differentiate in SDL between a 24-bit depth with
a 32-bit pixel width (which is a common, non-alpha format) and a true
32 bit depth with an alpha channel.
Check SDL_Surface->format.Amask (see
http://www.libsdl.org/cgi/docwiki.cgi/SDL_5fPixelFormat).
Here's the pixel format under normal X (24 bit depth):
BitsPerPixel 32
BytesPerPixel 4
Rloss Gloss, Bloss, Aloss {0, 0, 0, 8}
Rshift, Gshift, Bshift, Ashift {16, 8, 0, 0}
Rmask, Gmask, Bmask, Amask {ff0000, ff00, ff, 0}
Colorkey: 0
Alpha: 255
Here's the pixel format under Xgl:
BitsPerPixel 32
BytesPerPixel 4
Rloss Gloss, Bloss, Aloss {0, 0, 0, 8}
Rshift, Gshift, Bshift, Ashift {16, 8, 0, 0}
Rmask, Gmask, Bmask, Amask {ff0000, ff00, ff, 0}
Colorkey: 0
Alpha: 255
Notice that they are identical. They probably shouldn't be (what's SDL
doing not setting an Amask when there is an alpha channel...).
Hopefully, this will be fixed in future versions of SDL.
I'm not convinced there's something to fix in SDL rather than Qemu
(but I'm not familiar with the issue), but if there is, please post
this on the SDL mailing list (address@hidden,
http://news.gmane.org/gmane.comp.lib.sdl).
I will.
Regards,
Anthony Liguori
-Christian
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