[Bug 1572331] [NEW] GtkPlug scaled to half the expected size on HiDPI screens

[Launchpad Bug Tracker]

You have been subscribed to a public bug by Francesco Fumanti (frafu):

Hi,

Marmuta wrote a patch for this issue, that I applied to the gtk+3.0
package shipping currently in the development version of Ubuntu zesty.
You will find the corresponding debdiff attached to this bug thread.

Marmuta performed tests with org.gnome.desktop.interface scaling-factor
= 2 , where few issues are left for Onboard on hidpi screens, that are
not related to gtk, but rather to unity-greeter or gnome-screensaver. He
did not notice any issue with scaling-factor = 1.

Can a sponsor please review the debdiff?

Thanks in advance.

Francesco

=============================================================================
Original description:

See attached screen shot. Blue is a GtkPlug, black is a GtkSocket.
Source code below.

What I expect to happen is that the GtkPlug has the same size as the GtkSocket.
What actually happens is that GtkPlug only covers a quarter of the area of the GtkSocket.

Impact: Onboard on HiDPI displays is near unusable at login and lock
screen, aka unity-greeter and gnome-screensaver. Original bug report
here: https://bugs.launchpad.net/bugs/1562734.

Steps to reproduce:
- build plug and socket samples from below
- set display scaling factor to 2
  System Settings -> Display -> Scale for menu and title bars = 2
- run  ./socket $(head -1 <(./plug))
-> blue GtkPlug is too small, it should cover all the black

- resize the window
-> at smaller sizes the scaling suddenly corrects itself, at larger ones it's wrong again

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: libgtk-3-0 3.18.9-1ubuntu3
ProcVersionSignature: Ubuntu 4.4.0-18.34-generic 4.4.6
Uname: Linux 4.4.0-18-generic x86_64
ApportVersion: 2.20.1-0ubuntu2
Architecture: amd64
CurrentDesktop: Unity
Date: Wed Apr 20 01:48:50 2016
SourcePackage: gtk+3.0
UpgradeStatus: No upgrade log present (probably fresh install)

** Affects: gtk
     Importance: Medium
         Status: Confirmed

** Affects: gtk+3.0 (Ubuntu)
     Importance: Low
         Status: Triaged


** Tags: amd64 apport-bug xenial
-- 
GtkPlug scaled to half the expected size on HiDPI screens
https://bugs.launchpad.net/bugs/1572331
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