1204824 - Transform perspective is dependent on devicePixelRatio

Status: RESOLVED FIXED

(Core :: Layout, defect)

Description

[Christian Sonne [:cers]]

Attachment: transformperspective.html

In Firefox (but not in Chrome or Safari) the transform perspective is dependent on devicePixelRatio.

Steps to reproduce:
1) load attached test case on non-retina screen
2) compare rendering to reference included in test case
3) move tab/window to retina screen
4) repeat 2)

Result:
In Firefox on a retina screen, elements to not line up. They do on non-retina screen.

Expected result:
Rendering should be the same on both screens.

Note: for elements to line up on retina in Firefox (but only Firefox), the perspective needs to be doubled (in this case to 500px) which matches the devicePixelRatio of 2 on a retina screen.

Comment 1

[Boris Zbarsky [:bzbarsky]]

Timothy, is this something you'd know about, or someone else?

Comment 2

[Timothy Nikkel (:tnikkel)]

This was caused by bug 1181240 exposing a bug in Matrix4x4. Specifically Matrix4x4::PreScale should be scaling all values in the first three rows, not just the first three columns. That code came from bug 825928 (the layers refactoring). Patch coming up.

Comment 3

[Timothy Nikkel (:tnikkel)]

Attachment: Patch

Comment 4

[Pulsebot]

https://hg.mozilla.org/integration/mozilla-inbound/rev/e14ce8302fd7

Comment 5

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/mozilla-central/rev/e14ce8302fd7

Comment 6

[Milan Sreckovic [:milan] (needinfo for best results)]

[Tracking Requested - why for this release]:
A regression in 42, effecting matrix computation on devices with different than 1 pixel ratio.  This is across the board on CSS computations and would have far reaching effects.

Comment 7

[Milan Sreckovic [:milan] (needinfo for best results)]

Comment on attachment 8661957 [details] [diff] [review]
Patch

Approval Request Comment
[Feature/regressing bug #]: 1181240
[User impact if declined]: Wrong CSS transformations.
[Describe test coverage new/current, TreeHerder]: none
[Risks and why]: low, there was a bug in the matrix computation.
[String/UUID change made/needed]:

The Aurora request is assuming 42 is still in Aurora

Comment 10

[Liz Henry (:lizzard) (relman/hg->git project)]

Comment on attachment 8661957 [details] [diff] [review]
Patch

This missed aurora 42. Moving the flag for beta approval instead.

Comment 11

[Sylvestre Ledru [:Sylvestre]]

Regression, tracking.

Comment 12

[Sylvestre Ledru [:Sylvestre]]

Comment on attachment 8661957 [details] [diff] [review]
Patch

Regression, taking it. Should be in 42 beta 2.

Comment 13

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/releases/mozilla-beta/rev/e38d436d1739