1194811 - ZoomConstraintsClient probably doesn't update the double-tap-to-zoom flag properly

Status: RESOLVED FIXED

(Core :: Panning and Zooming, defect)

Description

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

The ZoomConstraintsClient class decides whether or not double-tap-to-zoom is allowed based in part by whether or not the CSS viewport is <= the screen size [1]. Therefore, if either the CSS viewport or the screen size changes (such as on device rotation) this flag should be updated. However I don't believe ZoomConstraintClient does so, since it probably doesn't get triggered on a rotation. I haven't confirmed this yet.

[1] http://mxr.mozilla.org/mozilla-central/source/layout/base/ZoomConstraintsClient.cpp?rev=e7c3406ce2c6#185

Comment 1

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

Confirmed using linked test case in the B2G browser on an Aries device.

Comment 2

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

Attachment: Patch

Pretty simple fix, just recompute the zoom constraints on resize.

Comment 3

[Botond Ballo [:botond]]

Comment on attachment 8651907 [details] [diff] [review]
Patch

Review of attachment 8651907 [details] [diff] [review]:
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Is there a reason MobileViewportManager and ZoomConstraintsClient get notified by resizes in different ways (PresShell::ResizeReflow() vs. listening to a resize event)?

Comment 4

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

Comment on attachment 8651907 [details] [diff] [review]
Patch

Hm, that's a good point. For some reason I was thinking that we want to run the ZCC after the MVM has recomputed the new CSS viewport but since the ZCC just uses nsViewportInfo directly that doesn't make much sense. Also it looks like the ZCC is using CalculateCompositionSizeForFrame intead of GetContentViewerSize like MVM does, so that should probably be updated as well. Let me rework the patch.

Comment 5

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

Attachment: Part 1 - Trigger ZCC recompute on screen size change

Comment 6

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

Attachment: Part 2 - Make ZCC screen size computation consistent with MVM

Comment 7

[Botond Ballo [:botond]]

Comment on attachment 8652477 [details] [diff] [review]
Part 2 - Make ZCC screen size computation consistent with MVM

Review of attachment 8652477 [details] [diff] [review]:
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Nice catch!

Comment 8

[Pulsebot]

https://hg.mozilla.org/integration/mozilla-inbound/rev/f796042daff0
https://hg.mozilla.org/integration/mozilla-inbound/rev/84ff0f8456e7

Comment 9

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/f796042daff0
https://hg.mozilla.org/mozilla-central/rev/84ff0f8456e7