1064055 - Make all code that changes DrawTarget transforms use the Moz2D API directly

Status: NEW

(Core :: Graphics, defect)

Description

[Jonathan Watt [:jwatt]]

We should make all code that changes DrawTarget transforms use the Moz2D API directly instead of using gfxContext or nsRenderingContext API.

Comment 1

[Jonathan Watt [:jwatt]]

Attachment: kill gfxContext::Multiply()

Comment 2

[Bas Schouten (:bas.schouten)]

Comment on attachment 8487856 [details] [diff] [review]
kill gfxContext::Multiply()

Review of attachment 8487856 [details] [diff] [review]:
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So much awesome that I missed to review.

Comment 3

[Nicholas Nethercote [inactive]]

jwatt: is this still worth landing?

Comment 4

[Jonathan Watt [:jwatt]]

It's worth landing if it's not buggy. I'm trying to remember why I didn't land this though.

To be safe, we need to be sure that there will not be any save-restore of gfxContext::mTransform (e.g. via gfxContextMatrixAutoSaveRestore) between any points where we set and restore a DrawTarget::mTransform. This is because the code that restores gfxContext::mTransform has no knowledge of changes that are made directly to DrawTarget::mTransform, yet it restores the state on both the gfxContext and DrawTarget. If that happens between a save-restore of DrawTarget::mTransform then the wrong state will be temporarily set on the DrawTarget.

I don't think I'd noticed this issue at the time of writing this patch, and I think some of the changes in this patch may potentially be buggy as a result despite the patch passing Try. I'll dig into the code at some point when I have time.