https://stripe.com/relay Look at the moving screenshot on the 'phone'. They don't line up properly with the screen for us but they do for Chrome. It would be nice to investigate why there's a difference in the transform positioning.

[Tracking Requested - why for this release]: This is a regression from bug 1181240 when we changed from gfx3DMatrix to Matrix4x4. This is a regression in 42, about to go to beta. It is worth tracking until we find out how wide spread the problem is.

I imagine the zero crossing code...

I am starting to investigate... It appears that the effect changes if you alter layout.css.devPixelsPerPx

The positioning of the moving screenshot appears to have been corrected with Bug 1204824. Broken on: 43.0a1 (2015-09-17) Good on: 43.0a1 (2015-09-18) I noticed; however, that the moving screenshot turns black when scrolled half-way off the top of the viewport. This occurs in nightly (2015-09-18) but not in 41.0b9. This appears to be a separate issue, and has not yet been confirmed as regressed by bug 1181240.

Did you see the black out / culling issue when finding this bug, BenWa? Shall we close this bug (marked as duplicate to Bug 1204824) and open a new bug to track the screenshot turning black?

(In reply to :kip (Kearwood Gilbert) from comment #5) > Did you see the black out / culling issue when finding this bug, BenWa? > > Shall we close this bug (marked as duplicate to Bug 1204824) and open a new > bug to track the screenshot turning black? Yes, please, open another bug for this issue.

I have added Bug 1207326 to track the issue resulting in the transformed element appearing black.