VST2 editor window size and scaling on Linux is erratic with 200% desktop scaling

When opening and resizing a VST2 plugin editor on Linux the editor content is not scaled and the window seems too small.
Also resizing it using the juce bottom-right drag control will result in jerky movement and often jumping back to very small sizes.

This is with a stock juce 6.1.2 AudioPluginDemo compiled to VST2 target
The host is juce AudioPluginHost 6.1.2
OS is Ubuntu 20.04, on a 4K monitor, with desktop scaling set to 200%

The problem does NOT occur with VST3, nor with Standalone.
Also everything works fine when desktop scaling is set to 100%
Also works fine with MacOS, Win10 even with 200% scaling on

FWIW: seems that a VST opcode “AeCs PreS” is sent during VST2 plugin creation which causes the juce plugin wrapper to set the editor’s scalefactor to 2 when linux desktop is scaled to 200%

Any idea how to fix this?


This appears to be a bug in JUCE, so it will need to be fixed on our side.

OK thanks for looking into it - I’ll wait for the fix then