Identifiers for touch points are not constant in multi touch

[gebausim]

Propably the best way to showcase this is via https://people.igalia.com/clopez/wkbug/pointer-events/paint.html page. Reproduced by simultaneously doing the snake move with one finger on the right and multiple lines with the other hand. What is expected is the first touch not to be influenced by the other ones and remain the same color/id (red) all the way.

Got:

Expected:

Same issue can also be observed in https://patrickhlauke.github.io/touch/tracker/multi-touch-tracker-index.html page. Where the identifier numbers rapidly change between all the currently active touch ids.

Can be reproduced on cog 0.18 and master with the wayland backend with WPEWebKit 2.42.5. It does not occur with WPEWebKit 2.40.5 or 2.38.6.

The effects of this are that any javascript pan or zoom gestures don't work properly, can be tested on https://elmarquis.github.io/Leaflet.GestureHandling/examples/. Zooming on the map is just very funky. Basically any online maps don't work.

[gebausim]

WebKit issue: https://bugs.webkit.org/show_bug.cgi?id=270516

[psaavedra]

This is interesting. I wonder if you could try again with main/master but reverting WPE - Make TouchPoint ID unique - commit 057b735cbf912f620273106541f2196191c5aa53 and reporting back the results.

[psaavedra]

This is interesting. I wonder if you could try again with main/master but reverting WPE - Make TouchPoint ID unique - commit 057b735cbf912f620273106541f2196191c5aa53 and reporting back the results.

update: From the https://bugs.webkit.org/show_bug.cgi?id=270516 link I see @gebausim you are pointing to the same direction. 🙏🏼

[clopez]

This two patches fix this issue for me:

• patch for WPE: https://github.com/WebKit/WebKit/pull/30926
• patch for Cog: https://github.com/Igalia/cog/pull/720

[gebausim]

Just tested with the patches applied and everything seems to work as expected, thanks!