1120400 - Elements with position:fixed are not fixed to the bottom of content window

Status: RESOLVED FIXED

(Core :: Panning and Zooming, defect)

Description

[Teodora Vermesan (:TeoVermesan)]

Attachment: Screenshot from 2015-01-12 15:06:55.png

Tested with:
Device: Samsung Galaxy Nexus (Android 4.2.1), Nexus 4 (Android 4.4)

Steps to reproduce:
1. Open https://bug705506.bugzilla.mozilla.org/attachment.cgi?id=577122

Expected results:
- Fixed elements should stay fixed to the viewport.

Actual results: 
- The fixed footer from the bottom of screen is displayed in the middle of the page.

Please see the attached screenshot.

Comment 1

[Teodora Vermesan (:TeoVermesan)]

Regression window-wanted:
1. mozilla-central:
good build: 07-01-2015
bad build: 08-01-2015

pushlog: http://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=33781a3a5201&tochange=70de2960aa87

2. inbound:
good build: 1420648378
bad build: 1420648560

pushlog: http://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=6399ee520bcc&tochange=a4c67bb878ff

Comment 2

[Botond Ballo [:botond]]

I can repro this. Will investigate.

Comment 3

[Botond Ballo [:botond]]

This is broken on B2G as well.

Based on my investigation so far, I believe the problem is that the calculation of the |aPreviousTransformForRoot| argument for |AsyncCompositionManager::AlignFixedAndStickyLayers| [1] needs to be updated to reflect the changes in bug 1076241.

[1] http://mxr.mozilla.org/mozilla-central/source/gfx/layers/composite/AsyncCompositionManager.cpp?rev=15a1d3459835#265

Comment 4

[Botond Ballo [:botond]]

Attachment: bug1120400.patch

It's nice when a fix to a bug consists of removing a piece of code that was arbitrary-seeming to begin with :)

Comment 5

[Kartikaya Gupta (email:[e-mail])]

Comment on attachment 8547784 [details] [diff] [review]
bug1120400.patch

Review of attachment 8547784 [details] [diff] [review]:
-----------------------------------------------------------------

I don't understand this code, but having less of it is good :)

Comment 6

[Botond Ballo [:botond]]

Try push that includes this patch: https://treeherder.mozilla.org/ui/#/jobs?repo=try&revision=8f40f1b579f6

Comment 7

[Botond Ballo [:botond]]

(In reply to Botond Ballo [:botond] from comment #6)
> Try push that includes this patch:
> https://treeherder.mozilla.org/ui/#/jobs?repo=try&revision=8f40f1b579f6

Had to cancel that one due to a mistake an a different patch it included. Here's a new Try push, and it's green:

https://treeherder.mozilla.org/ui/#/jobs?repo=try&revision=f5237502df73

Comment 8

[Botond Ballo [:botond]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/a59f566ddd0f

Comment 10

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/a59f566ddd0f

Comment 11

[Botond Ballo [:botond]]

Comment on attachment 8547784 [details] [diff] [review]
bug1120400.patch

Approval Request Comment
[Feature/regressing bug #]: Bug 1076241.
[User impact if declined]: Fixed-position layers are mispositioned.
[Describe test coverage new/current, TBPL]: Tested locally, and landed on m-c.
[Risks and why]:  Low; it's a small, straightforward, and isolated change.
[String/UUID change made/needed]: None.

Comment 12

[Botond Ballo [:botond]]

(In reply to Botond Ballo [:botond] from comment #11)
> Comment on attachment 8547784 [details] [diff] [review]
> bug1120400.patch
> 
> Approval Request Comment
> [Feature/regressing bug #]: Bug 1076241.
> [User impact if declined]: Fixed-position layers are mispositioned.
> [Describe test coverage new/current, TBPL]: Tested locally, and landed on
> m-c.
> [Risks and why]:  Low; it's a small, straightforward, and isolated change.
> [String/UUID change made/needed]: None.

Note that the regression and the fix only affect APZ platforms (by default, just B2G) and Fennec.

Comment 13

[Teodora Vermesan (:TeoVermesan)]

The fixed footer from the bottom of the screen is displayed correctly at the bottom of the page, so:
Verified as fixed on:
Device: Samsung Galaxy Nexus (Android 4.1.2) and Nexus 4 (Android 4.4)
Build: Firefox for Android 38.0a1 (2015-01-15)

Comment 14

[Lawrence Mandel [:lmandel] (use needinfo)]

Comment on attachment 8547784 [details] [diff] [review]
bug1120400.patch

Aurora+

Comment 15

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/releases/mozilla-aurora/rev/41b26cb119e2

Comment 16

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/releases/mozilla-b2g37_v2_2/rev/41b26cb119e2