Hi,
I just committed a patch I have been working on for a while. See bug
report https://savannah.gnu.org/bugs/?27782
This should solve various differences between GNUstep vs Cocoa image
drawing when Cairo is used, especially with -[NSImage
drawInRect:fromRect:operation:fraction:] or similar.
For the Cairo backend, this method should now give the same result
than Cocoa when the destination is flipped, rotated or scaled. The
scaling between the inRect and the fromRect should also work
correctly. Various border cases such as passing NSZeroRect are now
handled in a way that matches Cocoa.
The performance should also be much better when you draw a small
source rect from a big image, since we only manipulate the source rect
area rather than the whole image now. We also do not create an
intermediate image to apply the graphics context transform, we just
delegate that to Cairo, so this should improve performance a bit too.
Cairo also had various issues with -compositeGStateXXX and -
DPSimageXXX. This means NSImage composite/dissolve methods now behave
correctly, NSCopyBits too and -[NSView scrollRect:by:] should work in
non-flipped coordinates unlike previously.
The Cairo backend unlike other backends should now match the Cocoa
image drawing behavior exactly. This should be visible if you play
with NSAffineTransform a lot. For example, in a flipped view, concat a
rotation, a scaling and a manual flip transform, then draw an image
with by scaling it with inRect and fromRect.
Art, Xlib and Winlib backends shouldn't have changed much since they
still use the old code path. This code path is much more complex than
the Cairo code path that delegates as much as possible to the backend
rather than trying to handle things like rotation on the Gui side.
I tested Cairo, Art and Xlib, they work fine for me with GSTest, Gorm
and various Étoilé applications. I haven't tested the Winlib backend,
so I'm interested to know if it still works correctly.
I'll commit the test application I have been using to compare Cocoa vs
GNUstep behavior soon.
Although I tried to simplify the code as much as possible, there are
still some cleaning to do and also things to be worked out. e.g.
NSCopyBits doesn't behave the same on GNUstep and Cocoa when you give
it a view gstate.
Cheers,
Quentin.
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