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Re: GNUstep on Cygwin

From: Alexander Malmberg
Subject: Re: GNUstep on Cygwin
Date: Wed, 17 Dec 2003 19:18:21 +0100

Fred Kiefer wrote:
> - I found a way to wrok around the image drawing bug in winlib. What I
> did is just copy some complicated lines over from XGGState and now it
> works. I will submit this when CVS is available again. Still I would
> like to understand why this is needed. My feeling is that these
> complicated operations are not needed and are an artefact of incorrect
> flipped view handling further up.

Flipped view handling shouldn't affect you here (unless you try to use
viewIsFlipped or something, but those are deprecated; we really should
remove them soon). All you "really" need to do is handle arbitrary
transforms by looking at the ctm and the matrix passed to -DPSImage:....

Depending on what kind of image drawing/compositing primitives you have
(or are willing to write), it might be easier (for the backend
developer) to just special-case the two ctm:s that -gui uses most
(identify and vertically flipped). However, IIRC, just about all of the
problems back-xlib has had with images and flipping have been caused by
not supporting arbitrary transforms, and from trying to hack around this
by checking for certain specific cases. Handling transforms properly is
conceptually a lot cleaner, and is the only way of getting correct
results when someone actually uses a non-trivial transform.

- Alexander Malmberg

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