796705 - Implement empty transactions for non-translation transform changes

Status: NEW

(Core :: Layout, defect)

Description

[Chris Jones [:cjones] inactive; ni?/f?/r? if you need me]

Followup to bug 790505.  What makes this difficult is that we need recompute the rendering resolution for the transformed frame, and then see whether that would have changed in the new transform.  We don't have all that information available in nsFrame.cpp, and it would be very expensive to build in general.

Another potential solution is to just not bother with the rendering resolution when we're able to optimize transform changes to empty transactions.  This is on the speed side of the speed/quality tradeoff.

Comment 1

[Chris Jones [:cjones] inactive; ni?/f?/r? if you need me]

Need to do some testing, but I think we'll want this for competitive parity, and it optimizes an important content use case in e.g. b2g gallery.