Currently, we only support opaque surfaces for the OGL pipeline
(although we will eventually support translucent VolatileImages, see 5002129).
However, sometimes we select an FBConfig (or PixelFormat, on Windows) that contains
an alpha channel. Our opaque surfaces should still work properly even if the
GraphicsConfig has an alpha channel. However, this is currently not the case.
For example, if a compositing operation results in an alpha value of 0.5,
and the destination surface is considered opaque (e.g. a window) but the associated
visual has an alpha channel, then we will actually store the non-opaque alpha
value in the destination. This is obviously incorrect, because future compositing
operations will take that non-opaque alpha value into account, even though it
should be treated as opaque.
###@###.### 2005-05-30 21:06:22 GMT