GNOME Flashback is unusable on computers with a touchscreen.

[Gary Hasson]

[Impact]
GNOME Flashback is unusable on computers with a touchscreen. It crashes every time I try to login.

[Test Case]
Only crashes on computers with a touchscreen.
Fresh install Ubuntu 17.04 Desktop 64bit. (Same for Ubuntu GNOME.)
sudo apt-get install gnome-session-flashback gnome-flashback gnome-flashback-common
Select "GNOME Flashback (Metacity)" at login prompt.
First login to GNOME Flashback works, but all subsequent logins crash back to login.

[Regression Potential]
Low, currently GNOME Flashback is completely unusable on computers with a touchscreen.

The first of two commits (see below) just assigns a variable that would otherwise be always 0, the only thing it changes is that the signal will be disconnected in clear_monitor_manager(), which is the right thing to do.

The second commit makes sure the settings->monitor_manager pointer is checked for nullptr to avoid segfault when dereferencing it. It does not change anything on systems where the crash currently does not occur (because monitor_manager is not nullptr there). It also calls monitors_changed_cb which should be always safe.

[Other Info]
This bug has been fixed upstream:
  https://git.gnome.org/browse/gnome-flashback/commit/?h=gnome-3-22&id=1bf871ada5826ba0058cf109522a9151391224d9
  https://git.gnome.org/browse/gnome-flashback/commit/?h=gnome-3-22&id=b6d1bddcabbf187c45af0d8f05f721930266d270

A test PPA was created for this bug:
  https://launchpad.net/~muktupavels/+archive/ubuntu/bug785227

sudo add-apt-repository ppa:muktupavels/bug785227 && sudo apt-get update && sudo apt-get upgrade
With this test PPA installed on two different brands of computers with touchscreens, GNOME Flashback works correctly without any crashes, both on Ubuntu 17.04 and Ubuntu GNOME 17.04.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Launchpad Janitor (janitor)]

This bug was fixed in the package gnome-flashback - 3.24.0-1ubuntu1

---------------
gnome-flashback (3.24.0-1ubuntu1) artful; urgency=medium

  * Merge with Debian experimental, remaining changes:
    - debian/rules:
      + Add an epoch number to gnome-session-flashback package.
    - debian/gnome-flashback-common.gsettings-override:
      + Disable some not needed gnome-flashback components.
    - debian/gnome-session-flashback.target:
      + The target file for systemd, based on ubuntu-session.target.
      + Install this file into /usr/lib/systemd/user/ directory.
    - debian/control.in:
      + Bump gnome-session-bin dependency to 3.18.1.2-1ubuntu5, to be able
        to use run-systemd-session.
      + Add dependencies on systemd, dbus-user-session and indicator-common.
      + Use Ubuntu VCS fields.
    - debian/patches/run-systemd-session.diff:
      + Use run-systemd-session script for running the session.
    - debian/patches/support-indicator-keyboard.diff:
      + Support “org.gnome.desktop.input-sources current” key, to make
        indicator-keyboard working.
  * Backport upstream commits to fix crashes on computers with touchscreens
    (fix-touchscreen-crashes.diff; LP: #1706572).

 -- Dmitry Shachnev <email address hidden> Thu, 27 Jul 2017 11:19:25 +0300

[Robie Basak (racb)]

> [Regression Potential]
> Low, currently GNOME Flashback is completely unusable on computers with a touchscreen.

Is there any possibility that this fix will impact behaviour for users on computers without a touchscreen? Please could you consider this before performing SRU verification?

For example, the patch says:

++ if (!settings->monitor_manager)
++ return NULL;

Is there any case that settings->monitor_manager might evaluate to false on systems without touchscreens?

[Alberts Muktupāvels (muktupavels)]

On Wed, Aug 9, 2017 at 4:58 PM, Robie Basak <email address hidden>
wrote:

> > [Regression Potential]
> > Low, currently GNOME Flashback is completely unusable on computers with
> a touchscreen.
>
> Is there any possibility that this fix will impact behaviour for users
> on computers without a touchscreen? Please could you consider this
> before performing SRU verification?
>

No, otherwise it would crash for everyone.

For example, the patch says:
>
> ++ if (!settings->monitor_manager)
> ++ return NULL;
>
> Is there any case that settings->monitor_manager might evaluate to false
> on systems without touchscreens?
>

Yes. There is no monitor_manager when object is constructed.

--
Alberts Muktupāvels

[Robie Basak (racb)]

Please could you amend the Regression Potential section in the bug description accordingly? See https://wiki.ubuntu.com/StableReleaseUpdates#Procedure for what we expect to see in there and why we want it.

[Steve Langasek (vorlon)]

Hello Gary, or anyone else affected,

Accepted gnome-flashback into zesty-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/gnome-flashback/3.22.1-0ubuntu1.1 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 and change the tag from verification-needed-zesty to verification-done-zesty. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-zesty. In either case, details of your testing will help us make a better decision.

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

[Gary Hasson (gary-oax)]

Tested GNOME Flashback on a Laptop with a working TouchScreen, running Ubuntu Desktop 64bit 17.04, using instructions provided in the above post by Steve Langasek, dated 2017-10-21.

Test confirmed successful fix, using gnome-flashback 3.22.1-0ubuntu1.1, gnome-flashback-common 3.22.1-0ubuntu1.1 and gnome-session-flashback 3.22.1-0ubuntu1.1.

[Dmitry Shachnev (mitya57)]

Gary, thanks for testing! Marking the fix as verified.

[Launchpad Janitor (janitor)]

This bug was fixed in the package gnome-flashback - 3.22.1-0ubuntu1.1

---------------
gnome-flashback (3.22.1-0ubuntu1.1) zesty; urgency=medium

  * Backport upstream commits to fix crashes on computers with touchscreens
    (fix-touchscreen-crashes.diff; LP: #1706572).
  * Backport upstream commit to fix the disabled Authenticate button in the
    Authentication Agent dialog (polkit-password-entry.diff; LP: #1698994).

 -- Dmitry Shachnev <email address hidden> Thu, 03 Aug 2017 23:06:07 +0300

[Robie Basak (racb)]

The verification of the Stable Release Update for gnome-flashback has completed successfully and the package has now been 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.