Ubuntu 20.04: Buttons/icons at the edge of the touchscreen don't respond to taps if they are very small

[Kai-Chuan Hsieh]

[ Impact ]

Touchscreen touches at the left or bottom edges (within 20px) of the screen are not treated as mouse clicks. Icons only get highlighted, not launched.

[ Test Plan ]

0. Find a touchscreen.
1. Set Ubuntu Dock in Panel mode (the default mode) if not already.
2. Touch as close to the edge of the screen as possible. Aim for the gap between the icon and the edge of the screen.

Expect: The app launch animation occurs for each tap. Icons aren't just highlighted.

[ Where problems could occur ]

Anywhere in touchscreen gesture tracking or even regular touchscreen usage. As this bug demonstrates, the former is able to interfere with even simple touchscreen actions.

[ Workaround ]

Size the Ubuntu Dock adequately large so it is unlikely the user will touch less than 20 pixels from the edge of the screen.

[ Original description ]

On Dell OptiPlex 7400 AIO, go to gnome-control-center > appearance, adjust the dock icon-size to 24. It is hard to launch corner app like firefox, or trigger the launcher. The app icon gets focus but not clicked.

1. Ubuntu version 20.04.6
2. gnome-shell 3.36.9-0ubuntu0.20.04.2
3. The app or launcher is launched after a click
4. Only see focus but no app launched

[Kai-Chuan Hsieh (kchsieh)]

Upload video when encountering the issue

[loukangzhen (kangzhen)]

This is customer report issue.
Understand we need time to investigate the root cause, can we have issue summary ( the suspect RC, fix plan and outlook) for customer to understand in the first place by 11/30?

[Artur Pak (artur-at-work)]

Added debug log messages in appIcons.js and dash.js in directory /<email address hidden>/.
Attaching debug logs below.

In summary, I can observe the following:
When it works with large icon, then "appIcon.connect('clicked', (actor)" is successfully triggered.
After making small icon, "clicked" is not triggered and "launchNewWindow()" is not called anymore.
After long press on icon (don't have to press "Open in a New Windows" or any other buttons, just press elsewhere to make the dialog disappear), it triggers "appIcon.connect('key-focus-in', (actor)" after which "launchNewWindow()" can be called successfully on icon pressing.

[Daniel van Vugt (vanvugt)]

20.04: FAIL
20.10: FAIL
21.04: FAIL (69ubuntu1)
21.10: PASS (70~ubuntu3)
22.04: PASS
23.10: PASS
24.04: PASS

[Daniel van Vugt (vanvugt)]

My current theory is that when icons are sufficiently small or close to the edge of the screen, it's too easy for the touch "gesture" to start outside of the icon area (e.g. finger touching the display bezel). The pressure then increases and the touch moves into the icon area. But that's much the same as dragging your finger onto an icon. Try it in the app grid and you'll get the same behaviour (icon thinks you're hovering, not clicking).

Such touches may work more often in later Ubuntu releases just by virtue of the actor/theme padding in ubuntu-dock. But I can reproduce the same issue even in newer Ubuntu releases by sliding a finger onto an icon. So I think that's probably the issue -- not really a bug but it feels like a bug if you don't know the touch started outside the icon's sensitive area.

Short term I just suggest good UI design - if it's a touch UI then make sure the icons and buttons are big. Longer term we'll see what we can do about making 20.04 more reliable, but we're busy supporting a lot of different releases.

[Daniel van Vugt (vanvugt)]

Fix Released → Invalid for newer releases, to clarify that we haven't yet found evidence for a fix that was released and can be backported. Just that the bug doesn't happen in newer releases.

[Daniel van Vugt (vanvugt)]

Reported upstream what seems to be the issue:
https://gitlab.gnome.org/GNOME/mutter/-/issues/3183

But I might be wrong and there might be multiple issues.

[Daniel van Vugt (vanvugt)]

In review: https://salsa.debian.org/gnome-team/gnome-shell/-/merge_requests/76

[Artur Pak (artur-at-work)]

hi @Loukang,
 Thanks to Daniel's help in identifying the patch.
 I have built a ppa package to test the fix.

 Could you install the gnome-shell from my personal PPA?
 https://launchpad.net/~artur-at-work/+archive/ubuntu/verification

 And let us know if problem was resolved.

Thank you.

[loukangzhen (kangzhen)]

Many thanks for all the working. The install command is below?

sudo add-apt-repository ppa:artur-at-work/verification
sudo apt install gnome-shell

[Artur Pak (artur-at-work)]

Yes, that's correct.
You may also need "sudo apt update" after adding the repository

[loukangzhen (kangzhen)]

Test PPA in #13 at both Dell and ODM side, the issue is gone, it works!

[Daniel van Vugt (vanvugt)]

https://warthogs.atlassian.net/browse/UDENG-1937 will need to be solved before this can progress.

[Andreas Hasenack (ahasenack)]

Hello Kai-Chuan, or anyone else affected,

Accepted gnome-shell into focal-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/gnome-shell/3.36.9-0ubuntu0.20.04.3 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how to enable and use -proposed. Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested, what testing has been performed on the package and change the tag from verification-needed-focal to verification-done-focal. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-focal. In either case, without details of your testing we will not be able to proceed.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance for helping!

N.B. The updated package will be released to -updates after the bug(s) fixed by this package have been verified and the package has been in -proposed for a minimum of 7 days.

[Kai-Chuan Hsieh (kchsieh)]

Tested by ODM.

1. install oem ISO on Dell OptiPlex 7400
2. Enable Proposed channel (Pre-released updates (focal-proposed))
3. $sudo apt update
4. $sudo apt upgrade
5. Reboot system to make updates take effect
6. Four corners of the touch screen are sensitive, touch response speed is prompt

[Daniel van Vugt (vanvugt)]

This is currently blocked by bug 1915929.

[Launchpad Janitor (janitor)]

This bug was fixed in the package gnome-shell - 3.36.9-0ubuntu0.20.04.3

---------------
gnome-shell (3.36.9-0ubuntu0.20.04.3) focal; urgency=medium

  [ Marco Trevisan (Treviño) ]
  * debian/patches: Cherry-pick upstream calendar-server crash fix
    (LP: #1915929)
  * debian/patches: Refresh indexes

  [ Daniel van Vugt ]
  * Add edgeDragAction-Change-edge-trigger-threshold-to-AFTER.patch
    (LP: #2042796)

 -- Marco Trevisan (Treviño) <email address hidden> Mon, 11 Dec 2023 20:08:17 +0100

[Łukasz Zemczak (sil2100)]

The verification of the Stable Release Update for gnome-shell has completed successfully and the package is now being released to -updates. Subsequently, the Ubuntu Stable Release Updates Team is being unsubscribed and will not receive messages about this bug report. In the event that you encounter a regression using the package from -updates please report a new bug using ubuntu-bug and tag the bug report regression-update so we can easily find any regressions.