[lazarus] Bitmap transparency?

Andrew Johnson acjgenius at earthlink.net
Sat Nov 8 11:38:41 EST 2003

On Sat, 2003-11-08 at 10:56, Micha Nelissen wrote:
> Big *sigh*. Turns out that StretchBlt is implemented with transparency 
> support in gtk. Really, these extensions need to be documented in 
> TInterfaceObject. How else can we EVER expect to get other (like qt) 
> interfaces working? The win32 api is at least documented in msdn.

oh. hum. this is not an extension to the routine.

that is because of pixmaps. pixmaps natively have a mask, bi-level
bitmask. Win32 on the other hand uses bitmap which has no such thing.
Thus native format on windows has no need for transparency in the
stretch routine, which is why in Delphi they have to have special
functions etc to handle it.

AKA this is because in gtk+ the alpha support is in the backend level,
in win32 it must be on the LCL/App level, or with a special function in
the backend.

This isn't a matter of what the function does so much as what the format
is. If pixmap didn't natively support alpha via a bitmask, then the
routine wouldn't handle it. :)


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