Double clicking or pressing the fullscreen button does only change the UI in Gwenview to the fullscreen one but does not go to fullscreen itself on Wayland. STEPS TO REPRODUCE 1. Start Plasma Wayland 2. Open an Image 3. Press fullscreen button SOFTWARE VERSIONS (available in About System) KDE Plasma Version: 5.14.3 KDE Frameworks Version: 5.52.0 Qt Version: 5.11.2 related: https://bugs.kde.org/show_bug.cgi?id=366764
it's a Qt bug. Fullscreen works as expected with gwenview 18.08.2 and Qt 5.12 beta 3 on Arch Linux.