With occlusion detection, apps stop responding when switching from another app.

[Nick Dedekind]

If you switch from one app to the next, and start scrolling around (eg in dash) very soon after switching, the app will sometimes stop rendering.

Reproduce:
1) Start an app (eg dialer) from dash
2) wait a few seconds in dialer.
3) Do a quick switch back to dash, and immediately start scrolling/swiping around.

Expected:
app behaves normally and responds to user input.

Actual:
sometimes the dash will stop responding for an undetermined amount of time, or until you interact with another part of the shell.

[Launchpad Janitor (janitor)]

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

[Pat McGowan (pat-mcgowan)]

regression from last qtmir landing

[Nick Dedekind (nick-dedekind)]

Testing in Ubuntu 15.04 (r168):

This problem seems to be related to mir dropping old buffers when the visibility changes from occluded->exposed.
If I remove the "drop old buffers" code from mir::scene::BasicSurface::set_visibility, then it seems to come right.

There have been some changes in mir related to the buffer stream and arbiter which I'm testing if might make a difference. It may also be that we're not handling the dropped buffers correctly in qtmir?

[Launchpad Janitor (janitor)]

This bug was fixed in the package qtubuntu - 0.62+16.04.20151109-0ubuntu1

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qtubuntu (0.62+16.04.20151109-0ubuntu1) xenial; urgency=medium

  [ Nick Dedekind ]
  * Reverted occlusion detection (lp#1514556) (LP: #1514556)

 -- Gerry Boland <email address hidden> Mon, 09 Nov 2015 22:43:18 +0000

[Launchpad Janitor (janitor)]

This bug was fixed in the package qtmir - 0.4.6+16.04.20151113-0ubuntu1

---------------
qtmir (0.4.6+16.04.20151113-0ubuntu1) xenial; urgency=medium

  [ Nick Dedekind ]
  * Update surface textures when dropping frames. (LP: #1515356)

 -- Gerry Boland <email address hidden> Fri, 13 Nov 2015 16:42:38 +0000