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Bug in DDOVER_ALPHACONSTOVERRIDE
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snowholgi
Sep 28, 2007, 9:20:00 AM9/28/07
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Hello,
My hardware supports constant alpha blitting. After implementing the code in
the display driver and returning the correct caps it still doesn't work.
Because I don't have source for ddoverlay i have stepped through the
assembler code and found, that there must be a mistake in source code.
Assembly code does the following:
r1 = 1 << dwAlphaConstBitDepth;
r1 = ~r1;
r2 = dwAlphaConst;
TST r1, r2
BEQ error
My hardware supports constant alpha blitting. After implementing the code in
the display driver and returning the correct caps it still doesn't work.
Because I don't have source for ddoverlay i have stepped through the
assembler code and found, that there must be a mistake in source code.
Assembly code does the following:
r1 = 1 << dwAlphaConstBitDepth;
r1 = ~r1;
r2 = dwAlphaConst;
TST r1, r2
BEQ error
In my case, I set dwAlphaConstBitDepth to 4 and dwAlphaConst to a value
between 0 and 0x0F.
r1 = 1 << 4 = 0x10;
r1 = ~r1 = 0xFFFFFFEF;
r2 = dwAlphaConst;
TST r1, r2
BEQ error
But then, I always jump to error. Only when i set dwAlphaConst to 0x10, the
function works. So this must be an error and possibly MS can fix it.
Can anybody confirm this bug ?
Regards
Holger
and...@microsoft.com
Sep 30, 2007, 2:48:38 PM9/30/07
to
On Sep 28, 6:20 am, snowholgi <snowho...@discussions.microsoft.com>
wrote:
wrote:
Yes, I'm sorry, but this is a bug in Microsoft code that we recently
became aware of. Please request a fix if it is blocking your
development.
-Andy
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