Windows 7 - VST3 - Per Monitor DPI is changing the scaling factor of the Host window (Cubase)


We’ve recently had a report of loading our VST3 plugins in Cubase 10 on Windows 7 causing the host window’s scale factor to change

This is reproducible with the demo Gain Plugin as long as JUCE_WIN_PER_MONITOR_DPI_AWARE is set to 1

With that flag set to 0 the plugin window is blurry but the host window is unaffected by loading the plugin

This is what the window looks like before loading the Gain Plugin

After loading the plugin you can see all of the main host’s window title is far larger, as are the toolbar options at the top

Would you suggest trying the ScopedDPIAwarenessDisabler in the VST3 wrapper as well as the VST2 one?

I can’t reproduce this, and I can’t see where in the code this would be happening. We only set the DPI awareness in standalone apps, plug-ins should just use the host’s DPI awareness setting (see this method).

Is this only happening in VST3 versions of the plug-in?

Thanks for getting back to me

I’ve just compiled a VST and yes, it happens there as well
Does the device you’re using have a HiDPI screen? I was able to recreate it on both a Macbook and a Windows Surface running Windows 7 in VMWare

I’ll try and dig around a little more, the process of debugging has been a terror. Any time I try and use Visual Studio in the VM, Windows pops up and tells me its running slow, so it turns Aero off, which in turn means Cubase won’t load…

Let me know if there is any more information you need from me

Yes the device has a hiDPI screen, but AFAIK DPI-aware apps aren’t supported fully on Windows 7. If I open the preferences panel in Cubase 10 the “Enable HiDPI” checkbox isn’t there like it is on 8.1 and 10 so the plug-in should be opened in non DPI-aware mode and therefore shouldn’t interact with the host’s settings at all…

Interesting, is your Windows Text size set to 100% ?
That seems to be where the problem lies, I have it set at 150%, but setting it to 100% means everything works correctly

From the images it looks as though opening the plugin is somehow forcing the host to change its text size to maybe 200%. I remember reading that Cubase doesn’t support non-integer scale factors, but maybe I’m just mentally combining two unrelated things…

That seems a pretty mental thing for the host to do if true!

Interesting, that could be it. I’ll take a look.

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Just tried with 125%, also fine
Seems to just be 150% that causes the problem

OK, this should be fixed here:

Thanks Ed, its a shame it makes the plugin blurry, but I feel that is the nature of the beast

Rather that than messing up the DAWs UI