unity8 stops processing touch input events after holding the palm for a few seconds on the screen

[Jean-Baptiste Lallement]

current build number: 403
device name: arale
channel: ubuntu-touch/rc-proposed/meizu.en

Test Case:
1. Boot the phone and unlock it
2. hold your palm on the border of the screen for several seconds (I'm on the application scope by default)
3. Scroll the page up and down

Expected result
Scrolling works as expected, page goes up/down

Actual result
The dash is like frozen. A right edge swipe works and clears the problem up.

The following records are logged in unity8.log

[...]
[2016-08-17:18:18:37.829] qtmir.sensor: Screen::onOrientationReadingChanged
[2016-08-17:18:18:37.832] qtmir.sensor: Screen::customEvent - new orientation 8 handled
[2016-08-17:18:18:39.119] qtmir.sensor: Screen::onOrientationReadingChanged
[2016-08-17:18:18:39.122] qtmir.sensor: Screen::customEvent - new orientation 1 handled
[2016-08-17:18:18:54.957] qtmir.surfaces: MirSurfaceItem(unity8-dash) - Got a QEvent::TouchBegin while there's still an active/unfinished touch sequence.
[2016-08-17:18:20:42.033] qtmir.sensor: Screen::onOrientationReadingChanged
[2016-08-17:18:20:42.036] qtmir.sensor: Screen::customEvent - new orientation 8 handled
[2016-08-17:18:20:42.849] qtmir.sensor: Screen::onOrientationReadingChanged
[2016-08-17:18:20:42.853] qtmir.sensor: Screen::customEvent - new orientation 1 handled

<Here I do a right edge swipe>

[2016-08-17:18:20:45.100] qtmir.surfaces: MirSurface[0x1670f10,"unity8-dash"]::updateActiveFocus() unfocused
[2016-08-17:18:20:45.217] [PERFORMANCE]: Last frame took 89 ms to render.
[2016-08-17:18:20:45.295] [PERFORMANCE]: Last frame took 35 ms to render.
[2016-08-17:18:20:46.037] [PERFORMANCE]: Last frame took 88 ms to render.
[2016-08-17:18:20:46.271] qtmir.surfaces: MirSurface[0x1670f10,"unity8-dash"]::updateActiveFocus() focused
[2016-08-17:18:20:46.298] qtmir.clipboard: D-Bus GetContents - returning 0 bytes

[Dave Morley (davmor2)]

Confirmed for me it opened the section I clicked on but it took an age

[Michał Sawicz (saviq)]

These look suspicious:
> qtmir.surfaces: MirSurfaceItem(unity8-dash) - Got a QEvent::TouchBegin while there's still an active/unfinished touch sequence.

[Michał Sawicz (saviq)]

I can't reproduce on krillin here, though.

[Michał Sawicz (saviq)]

Can you try and make sure you're not touching the screen when reproducing this? We're thinking this might be a input issue rather than the shaking itself.

[Jean-Baptiste Lallement (jibel)]

You're right, if freezes by just holding your palm on the border of the screen. I updated the description.