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[Shawn Rutledge <shawn.t.rutledge@xxxxxxxxx>]

Public bug reported:

I'm reporting this on behalf of a coworker who has a 4K monitor, which
disconnects whenever it sleeps.  Older monitors didn't do that; but Qt
5.5 tries to be honest about it: the QScreen is destroyed whenever its
corresponding monitor is disconnected, QGuiApplication::primaryScreen()
returns null, and so on.  KDE developers have been complaining.  So in
Qt 5.6 we made it keep the last-remaining QScreen as a fake instance,
whenever the last monitor is disconnected.  The main patch is here

https://codereview.qt-project.org/#/c/138201/

You might need to cherry-pick that
(a094af001795c9651b299d700a992150d1aba33a in qtbase) for as long as you
are shipping Qt 5.5, to get Kubuntu behaving decently.  It's relevant on
Ubuntu 16.04.  Too bad that Ubuntu LTS is not shipping the LTS Qt 5.6
release, but I know we are behind on our release schedule.

Some users have also reported that their laptop's screen disconnects
when it sleeps.  And I have often experienced 5.5-based builds of
Creator crashing or disappearing when I switch machines on my KVM.  So,
sorry that we didn't fix it sooner.  It was my mistake for believing
that modeling disappearing screens "correctly" was a good idea: it
turned out to be a platform inconsistency which developers were not
ready for.

** Affects: qtbase-opensource-src (Ubuntu)
     Importance: Undecided
         Status: New

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Ubuntu.
https://bugs.launchpad.net/bugs/1548766

Title:
  KDE crashes when the monitor is disconnected (when it sleeps, in some
  cases)

Status in qtbase-opensource-src package in Ubuntu:
  New

Bug description:
  I'm reporting this on behalf of a coworker who has a 4K monitor, which
  disconnects whenever it sleeps.  Older monitors didn't do that; but Qt
  5.5 tries to be honest about it: the QScreen is destroyed whenever its
  corresponding monitor is disconnected,
  QGuiApplication::primaryScreen() returns null, and so on.  KDE
  developers have been complaining.  So in Qt 5.6 we made it keep the
  last-remaining QScreen as a fake instance, whenever the last monitor
  is disconnected.  The main patch is here

  https://codereview.qt-project.org/#/c/138201/

  You might need to cherry-pick that
  (a094af001795c9651b299d700a992150d1aba33a in qtbase) for as long as
  you are shipping Qt 5.5, to get Kubuntu behaving decently.  It's
  relevant on Ubuntu 16.04.  Too bad that Ubuntu LTS is not shipping the
  LTS Qt 5.6 release, but I know we are behind on our release schedule.

  Some users have also reported that their laptop's screen disconnects
  when it sleeps.  And I have often experienced 5.5-based builds of
  Creator crashing or disappearing when I switch machines on my KVM.
  So, sorry that we didn't fix it sooner.  It was my mistake for
  believing that modeling disappearing screens "correctly" was a good
  idea: it turned out to be a platform inconsistency which developers
  were not ready for.

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