Thanks Keith. This makes a lot more sense to me now.  Say if I go ahead
modifying the driver to expose depth 32 windows, do you think the current
XFree86 server is capable of handling this or some additional work is
required?

Jonathan Bian

-----Original Message-----
From: Keith Packard [mailto:[EMAIL PROTECTED]]
Sent: Tuesday, June 04, 2002 12:54 PM
To: [EMAIL PROTECTED]
Cc: Keith Packard
Subject: Re: [Render] Destination alpha? 



Around 11 o'clock on Jun 4, "Bian, Jonathan" wrote:

> Hi, I am trying to find out whether I can use Render to modify the alpha
> channel in a frame buffer that's in ARGB 8888 format.   I modified Keith's
> sample code slightly to render a red rectangle into the frame buffer with
> the destination alpha set to 0x80.  But I get 0x00FF0000 in the frame
buffer
> instead of the desired 0x80FF0000.

You'll need to create a window of depth 32 instead of depth 24 -- depth 24 
windows don't have any place to store the alpha value.  That requires that 
the driver expose depth 32 windows, which is probably not the case 
currently.

You can try the rest of the code by using a depth 32 pixmap to make sure 
your understanding of the rendering operations is accurate; we do need to 
go whack the server to expose depth 32 windows where possible.

Keith Packard        XFree86 Core Team        HP Cambridge Research Lab


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