987121 - Auto-scroll doesn't stop anymore in center position (autoscroll)

Status: VERIFIED FIXED

(Firefox :: General, defect)

Description

[Thomas Stache]

Autoscroll used to stop moving when the mouse cursor is placed in a "neutral" position, e.g. on a position with the same y-coordinate as the auto-scroll indicator for vertical scrolling.

Maybe related to/caused by bug 938359?

Comment 1

[Thomas Stache]

(In reply to Thomas Stache from comment #0)
> Autoscroll used to stop moving when the mouse cursor is placed in a
> "neutral" position, e.g. on a position with the same y-coordinate as the
> auto-scroll indicator for vertical scrolling.

Sigh... Missed to say that it keeps scrolling slowly now!

Comment 2

[Thomas Stache]

This is also reproducible on Aurora 30.0a2 (2014-03-23).

Comment 3

[Alice0775 White]

Regression window:
http://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=a2ec4ab256e8&tochange=7d192442dfca

Comment 4

[Thomas Stache]

Being more specific: the scrolling doesn't stop when the mouse is over the auto-scroll symbol.(In reply to Thomas Stache from comment #0)
> Autoscroll used to stop moving when the mouse cursor is placed in a
> "neutral" position, e.g. on a position with the same y-coordinate as the
> auto-scroll indicator for vertical scrolling.

Being more specific: the scrolling doesn't stop when the mouse is over the auto-scroll symbol. Next to it (offset to the side for the vertical case) it stops.

Comment 5

[Bill McCloskey [inactive unless it's an emergency] (:billm)]

I can reproduce this. It looks like as long as the cursor is within the autoscroll circle its position is ignored.

Comment 6

[Bill McCloskey [inactive unless it's an emergency] (:billm)]

Attachment: fix-autoscroll

It looks like the problem is that the content script doesn't get mousemove events when the cursor is over the autoscroll circle. The XUL window does get mousemove events in that case, which is why this worked before.

The only way I can see around this is to forward the mousemove events from the parent to the child. That's what this patch does.

Comment 7

[:Felipe Gomes (needinfo for replies!)]

Wow, the irony...  Alternatively, we could set up auto-forwarding from the circle too by modifying 
nsEventStateManager::IsRemoteTarget (and/or HandleCrossProcessEvent). What do you think makes most sense from an implementation point of view?

Comment 8

[Bill McCloskey [inactive unless it's an emergency] (:billm)]

(In reply to :Felipe Gomes from comment #7)
> Wow, the irony...  Alternatively, we could set up auto-forwarding from the
> circle too by modifying 
> nsEventStateManager::IsRemoteTarget (and/or HandleCrossProcessEvent). What
> do you think makes most sense from an implementation point of view?

Err, I don't know. I guess we could add a special attribute to the autoscroll circle's DOM node. I still think I prefer forwarding though. If the same problem occurs in other circumstances, then we could consider modifying IsRemoteTarget.

Comment 9

[:Felipe Gomes (needinfo for replies!)]

Oh, or I guess much simpler: we could just add pointer-events: none on the circle's DOM node, and it should just work. Can you see if that works? If not we will go with your patch

Comment 10

[Bill McCloskey [inactive unless it's an emergency] (:billm)]

(In reply to :Felipe Gomes from comment #9)
> Oh, or I guess much simpler: we could just add pointer-events: none on the
> circle's DOM node, and it should just work. Can you see if that works? If
> not we will go with your patch

That doesn't seem to help, although I'm not sure why. I'm having a hard time tracing through how the code handles the pointer-events property.

Comment 11

[Bill McCloskey [inactive unless it's an emergency] (:billm)]

Attachment: pointer-events-none

On IRC, Felipe suggested using the mousethrough="always" attribute on the autoscroller XUL node. That worked. I looked into the code a little more to figure out why the one works and the other doesn't. I found this special handling of mousethrough here:

http://mxr.mozilla.org/mozilla-central/source/layout/xul/nsMenuPopupFrame.cpp#249

Apparently the autoscroller gets its own widget, and so we need to tell the widget code to handle mouse events specially. If I comment out this code, the mousethrough="always" attribute no longer fixes the problem in this bug.

I guess we might be able to change nsMenuPopupFrame to deal with pointer-events: none, but I'm probably not the best person to do that.

Comment 12

[Bill McCloskey [inactive unless it's an emergency] (:billm)]

https://hg.mozilla.org/integration/mozilla-inbound/rev/0e01c0304046

Comment 13

[Neil Deakin]

(In reply to Bill McCloskey (:billm) from comment #11)
> I guess we might be able to change nsMenuPopupFrame to deal with
> pointer-events: none, but I'm probably not the best person to do that.

pointer-events: none will cause the mouse events to be ignored entirely, as it only deals within the same window. mousethrough="always" will forward the event to another window that is underneath the popup using OS layer mechanisms, so your use of mousethrough is correct here.

Comment 14

[Phil Ringnalda (:philor)]

https://hg.mozilla.org/mozilla-central/rev/0e01c0304046

Comment 15

[Benjamin Kerensa [:bkerensa]]

We would be interested in an uplift request for this!

Comment 16

[Bill McCloskey [inactive unless it's an emergency] (:billm)]

Bug 938359 was backed out on aurora so 31 is now the only affected release.

Comment 17

[Chandan Kumar Baba]

status-firefox 30 : fixed -> disabled

Comment 18

[u279076]

I think this should get some QA attention since it was a regression.

Comment 19

[[SV Manager] Florin Mezei, QA (:FlorinMezei)]

Reproduced the issue using Nightly from 2014-03-16 (BuildID: 20140316030202).

Verified as fixed on Win 7 x64, Mac OS X 10.9.3, Ubuntu 13.04 x64, with latest Firefox 31 Beta 6 (BuildID: 20140630185627). Scrolling now stops as expected when the cursor is anywhere inside the autoscroll circle.