gtk snaps are properly themed only with light themes and Adwaita

[fcole90]

Try to install the gimp snap. If you use one among Adwaita, Ambiance or Radiance it will be themed correctly, while if you use other themes it will have a Win95-like look.

This happens to me on Artful using the Arc theme. It's a system theme installed using the arc-theme ubuntu package. I also have the same problem using the Adwaita dark theme.

ProblemType: Bug
DistroRelease: Ubuntu 17.10
Package: snapd 2.26.10+17.10
ProcVersionSignature: Ubuntu 4.11.0-10.15-generic 4.11.8
Uname: Linux 4.11.0-10-generic x86_64
NonfreeKernelModules: nvidia_uvm nvidia_drm nvidia_modeset nvidia
ApportVersion: 2.20.5-0ubuntu5
Architecture: amd64
CurrentDesktop: GNOME
Date: Thu Jul 20 18:30:18 2017
InstallationDate: Installed on 2015-03-21 (852 days ago)
InstallationMedia: Ubuntu 15.04 "Vivid Vervet" - Alpha amd64 (20150321)
SourcePackage: snapd
UpgradeStatus: Upgraded to artful on 2017-07-18 (2 days ago)

[Launchpad Janitor (janitor)]

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

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See https://forum.snapcraft.io/t/use-the-system-gtk-theme/496 and https://forum.snapcraft.io/t/desktop-improvements-report-and-plans/3510 for progress on this