Comment 24 for bug 263661

I think there is a way to get consistent cross-platform rendering without sacrificing too much performance. The common case is that images are not scaled, and post-bug 296818, we don't even keep them around in memory in uncompressed form. So that says to me that we could treat images in display memory as a pure cache, and in particular, we could do all the scaling on the client side before copying to display memory. That would mean that it's our copy of pixman doing all the work, so we know it's correct, but there wouldn't be any need to pull the image data off the X server, rescale it, and put it back, like what happens now if you enable EXTEND_PAD on Linux.

We *would* create offscreen bitmap surfaces for the scaled images so that as long as the nsThebesImage object sticks around, repaint doesn't have to repeat the scaling work. I think this might even make scrolling of a scaled document faster, because right now we're scaling everything on every draw operation.

I'm reluctant to implement this before joedrew!'s rumored image layer cleanups land, because right now it's such a horrible mess in there, but I'm willing to make an attempt at it if those are not happening anytime soon.