On-the-fly DPI changes support?

[sjoerdk-of]

Hi!

Playing around with reaper I found that system dpi settings are only applied when the plugin gui is first opened.
That matches the description over here https://github.com/free-audio/clap/blob/main/include/clap/ext/gui.h,
so i guess that's the way it's supposed to work.

The way vst3 does it is to notify the plugin each time the system DPI changes. For single monitor setups that's not a big deal,
but for multiple monitors with different DPI scaling on each one I think it's definately valuable. Prevents the user from
having the close and reopen the plugin gui when dragging between monitors. Would it be possible to add this feature?

[geraintluff]

Shouldn't this be handled by calling set_scale() again, when the window API changes the underlying resolution of its canvas/whatever?

APIs like Cocoa shouldn't use .set_scale() anyway (since they work in logical pixels), and I'd expect those to have some way for you to listen yourself (e.g. I found NSViewLayerContentScaleDelegate, although it's not immediately obvious how you'd hook it up)

[baconpaul]

I agree with @geraintluff - hosts should call set_scale whenever they need.

[geraintluff]

Vote to close, since if hosts aren't calling .set_scale(), that's not a CLAP standard issue?

[baconpaul]

I would close it once we add to the comments that hosts can call set scale on running plugins again if dpi changes hrs