Doug Sherk (:drs) (inactive) Reporter
	Description • 10 years ago

Reduced test case: http://people.mozilla.org/~dsherk/wc.html

This bug only occurs on B2G. It also occurs on Geckos for both v2.2 and v3.0.

On desktop, the scrollable region containing "aaa ... [x100]" is scrollable and behaves as expected.

On v3.0 from today, the scrollable region is completely unscrollable.

On v2.2, the scrollable region is scrollable, but is clipped after a few hundred px and events such as "click"'s are always from the origin, {0, 0}. For example, if I scroll down 100px and then tap at the top left of the scrollable region, my event should be somewhere around {0, 100}, but instead, it's at {0, 0}.

William, could you take a look at this? Kartikaya (:kats) says that this is unlikely to be an issue with APZ.

As a side note, we have fixed this in one of our apps improperly this way:
https://github.com/gaia-components/gaia-dom-tree/commit/509e6b61d8c618f43066a5bd544c56feea36c227

	William Chen [:wchen] Assignee
	Comment 1 • 10 years ago

Here is a work around that lets scrolling work but likely causes a bug somewhere else. It seems like the ScrollableLayerGuid for stuff in shadow DOM isn't getting the right PresShellId which is causing it to fail a comparison in APZCTreeManager::FindTargetNode.

	Kartikaya Gupta (email:kats@mozilla.staktrace.com)
	Comment 2 • 10 years ago

I'm surprised that failure to set the zoom constraints would result in failure to scroll. At most it should allow zooming when it shouldn't.

Does the shadow DOM stuff get a separate presShell or something? I know nothing about how it works.

	Doug Sherk (:drs) (inactive) Reporter
	Comment 3 • 10 years ago

Comment on attachment 8566947 [details] [diff] [review]
work around

This doesn't seem to fix the issue for me, even in the reduced test case. On m-c from today both with and without this patch, the region containing "aaa [...]" is unscrollable.

	Doug Sherk (:drs) (inactive) Reporter
	Comment 4 • 10 years ago

This workaround in addition to attachment 8566947 [details] [diff] [review] seems to fix the issue for now.

	Doug Sherk (:drs) (inactive) Reporter
	Comment 5 • 10 years ago

Both landed on cypress:

https://hg.mozilla.org/projects/cypress/rev/319654fb4d8e
https://hg.mozilla.org/projects/cypress/rev/56d627560621

	William Chen [:wchen] Assignee
	Comment 6 • 10 years ago

I uploaded the wrong patch, I meant to upload the changes in Doug's patch with changes to GetTargetAPZC instead of UpdateZoomConstraints. The changes to UpdateZoomConstraints are unnecessary.

(In reply to Kartikaya Gupta (email:kats@mozilla.com) from comment #2)
> Does the shadow DOM stuff get a separate presShell or something? I know
> nothing about how it works.

No, it doesn't. My guess is that wherever we are getting the doc shell, we are doing it in a way that doesn't work for shadow DOM content (e.g. GetCurrentDoc()->GetDocShell(), nodes in a shadow DOM don't have a current doc).

	Kartikaya Gupta (email:kats@mozilla.staktrace.com)
	Comment 7 • 10 years ago

I think the main places we obtain the presShellId are at [1] and [2]. I can't recall offhand if we go through the doc to get that anywhere.

[1] http://mxr.mozilla.org/mozilla-central/source/layout/base/nsDisplayList.cpp?rev=5ef8e549a1d9#893
[2] http://mxr.mozilla.org/mozilla-central/source/gfx/layers/apz/util/APZCCallbackHelper.cpp#264

	Kartikaya Gupta (email:kats@mozilla.staktrace.com)
	Comment 8 • 10 years ago

Oh I guess it might be http://mxr.mozilla.org/mozilla-central/source/gfx/layers/apz/util/APZCCallbackHelper.cpp?rev=abe8b4e23df0#247 - is it possible to get a domwindowutils for shadow dom content?

	William Chen [:wchen] Assignee
	Comment 9 • 10 years ago

(In reply to Kartikaya Gupta (email:kats@mozilla.com) from comment #8)
> Oh I guess it might be
> http://mxr.mozilla.org/mozilla-central/source/gfx/layers/apz/util/
> APZCCallbackHelper.cpp?rev=abe8b4e23df0#247 - is it possible to get a
> domwindowutils for shadow dom content?

Yeah, it looks like that was it.

	William Chen [:wchen] Assignee
	Comment 10 • 10 years ago

https://hg.mozilla.org/integration/mozilla-inbound/rev/0f97b9f85516

	Wes Kocher (:KWierso) (Not reading bugmail; email directly if needed)
	Comment 11 • 10 years ago

https://hg.mozilla.org/mozilla-central/rev/0f97b9f85516