Ok, so VST turned out to be a real drama. A few full days of work and I'm finally at the point I feel comfortable releasing it.
There were several moments where I thought I had a generic solution that supported fully dynamic resizing, even on hosts that don't support it. Alas, that method broke some hosts that
did support it.
The hosts that don't support sizing through dragging the window border can be resized using the sliders under
Code:
Application settings > Graphical settings
I've prepared a little summary of which hosts I've tested and their behavior:
*OBS has some weird bug where the VST window can be closed using the X on its window, but that fails to register in the audio filters window. It requires closing and opening the filters overview to see the
Open Plug-in Interface button again.
About DPI:
Scaling to the correct DPI requires reopening the window in just about any host. The detected DPI can be seen when unfolding the Graphical settings menu.
Note that we can't do anything about the wrong DPI being detected after reopening the window: crappy implementation of MFC seems to be an inherent "feature" of VST hosts.