1315250 - Multi-touch has considerable lag when Pointer Events is preffed on

Status: NEW

(Core :: DOM: UI Events & Focus Handling, defect, P2)

Description

[Alexandru Simonca [:asimonca], Release Desktop QA]

Attachment: pointer events touch.mp4

[Affected versions]:
- Firefox Nightly 52.0a1

[Affected platforms]:
- Windows 10 x64

[Steps to reproduce]:
Make sure that the build has e10s enabled. If not, go to about:config and right-click -> new -> boolean to add the pref "browser.tabs.remote.force-enable" and set it to "true".

1. Go to about:config and set the "dom.w3c_pointer_events.enabled" preff to "true"
2. Go to https://patrickhlauke.github.io/touch/tracker/multi-touch-tracker-pointer-hud.html.
3. First use one finger to drag across the canvas and then try with more.

[Expected result]:
- The tracker should run smoothly.

[Actual result]:
- The tracker experiences lag when Pointer Events is preffed on.

[Regression range]:
- This is not a regression since this feature is new.

[Additional notes]:
- This only happens when the pref "dom.w3c_pointer_events.enabled" is set to "true". The tracker does not lag if the preff is set to "false"

Comment 1

[Julien Cristau [:jcristau]]

Mass wontfix for bugs affecting firefox 52.

Comment 2

[Edgar Chen [:edgar]]

I intended to take bug 1323400, not this one :p.
bug 1323400 could be one of the lag sources I would suspect.

Comment 3

[Olli Pettay [:smaug]]

A performance profile would be nice here, with IPC logging.