Re: gdiplus: Use StretchBlt instead of GdiAlphaBlend if device doesn't support alpha blending. Resend.

[Vincent Povirk]

I ran some of my drawing tests with GdipSetCompositingMode(graphics,
CompositingModeSourceCopy), and it looks like native in that mode does
roughly what your patch does, except that pixels that would be 100%
transparent are not drawn. If a printer device behaves differently
then that would be very strange.

If it is the same, it probably makes sense to use (and maybe set at
graphics creation time if it's appropriate for the HDC) the
compositing mode flag.

So I guess this is an acceptable approach, and could probably be
committed as is and refined later, but it'd be nice if you could look
into compositing modes and drawing with 100% transparent colors, since
you have a test program set up for printing and I don't.