At the moment I have a strong feeling that it’s a bug in JUCE regarding the general handling of VST3 in highdpi environments. I’ll try to test more highdpi capable VST3 hosts today and let you know about my findings.
I observed that within the JUCE VST3 wrapper, there are explicit “workarounds” for Cubase 10. The process of instantiating and opening a VST3 plugin leads to a lot of calls of the related functions, not so easy to find out what’s actually happening and in what order, so I haven’t been able to figure it all out within the JUCE code yet. I’ll keep trying though.
Probably related: Cubase 10 HiDPI, Windows and OpenGL
High DPI is getting more popular on Windows, general support has become better, and more hosts start supporting it as well as VST3. I’m beginning to get complaints from customers (at the moment recommending to use the VST2 versions instead), so this is getting more and more critical…