1270165 - APZC::ResetTouchInputState assumes CurrentTouchBlock can return null, but it can't

Status: RESOLVED FIXED

(Core :: Panning and Zooming, defect)

Description

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

The code at http://mxr.mozilla.org/mozilla-central/source/gfx/layers/apz/src/AsyncPanZoomController.cpp?rev=f15a963b5d4e#3763 has a typo. It's an if condition, meaning it allows for the possibility that CurrentTouchBlock() returns null. However, that function is never supposed to be called in such a case; internally it asserts that there the current block exists and is a touch block.

This call site does, however, need to deal with being called without a touch block being active, and so needs to do CurrentBlock()->AsTouchBlock() which will return null if the current block is not a touch block. The code should be safe to assume that there is a CurrentBlock().

Comment 1

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

Attachment: MozReview Request: Bug 1270165 - Allow ResetTouchInputState to be called while a non-touch block is the current block. r?botond

Review commit: https://reviewboard.mozilla.org/r/50489/diff/#index_header
See other reviews: https://reviewboard.mozilla.org/r/50489/

Comment 2

[Botond Ballo [:botond]]

Comment on attachment 8748710 [details]
MozReview Request: Bug 1270165 - Allow ResetTouchInputState to be called while a non-touch block is the current block. r?botond

https://reviewboard.mozilla.org/r/50489/#review47255

Comment 3

[Pulsebot]

https://hg.mozilla.org/integration/mozilla-inbound/rev/4c87fb10e5f0

Comment 4

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/4c87fb10e5f0

Comment 5

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

Comment on attachment 8748710 [details]
MozReview Request: Bug 1270165 - Allow ResetTouchInputState to be called while a non-touch block is the current block. r?botond

Approval Request Comment
[Feature/regressing bug #]: bug 1240202
[User impact if declined]: none; this code triggers a debug-only assertion in some cases but in production there is no bad effect. would like to uplift this as a prerequisite for uplifting bug 1231570.
[Describe test coverage new/current, TreeHerder]: covered by the tests in bug 1231570
[Risks and why]: zero risk, it's just a small typo
[String/UUID change made/needed]: none

Comment 6

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

Comment on attachment 8748710 [details]
MozReview Request: Bug 1270165 - Allow ResetTouchInputState to be called while a non-touch block is the current block. r?botond

APZ fix, has test coverage, let's bring it to aurora.

Comment 7

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

https://hg.mozilla.org/releases/mozilla-aurora/rev/dc14ef255927