Fix non-HiDPI mode on HiDPI displays on macOS Catalina.

[bruvzg]

Fixes #32805

On macOS 10.15 HiDPI support is on by default, we need to directly specify we do not need scaling if HiDPI is not allowed by project settings.

[AlexRixhardson]

Tested on MacBook Pro (Retina, Mid 2012) and it works perfectly. Thanks!

[AlexRixhardson]

I recommend this patch to be put into the 3.2 milestone.

[akien-mga]

Thanks!

[akien-mga]

Cherry-picked for 3.1.2.

[akien-mga]

Cherry-picked for 3.0.7.

[akien-mga]

@bruvzg For the 2.1 branch only half of the patch applies properly (the added else branch). Do you think it's sufficient or are more changes needed there?

[bruvzg]

Do you think it's sufficient or are more changes needed there?

• First part is to change scale on moving from one screen to another (having retina MacBook with non-retina secondary display is pretty common).

It's better to add whole if-else for the first part os_osx.mm#L340-L344 and the change in this line os_osx.mm#L348 (cherrypick #11718 changes).

• Second part is for the new window creation and should apply as is.

[akien-mga]

Thanks for the details! I wouldn't be able to test the changes myself beyond ensuring that it compiles, so if you're able to do and test the relevant cherry-picks for 2.1, that would be very helpful.
We don't necessarily need to backport full blown HiDPI support if it was lacking in the 2.1 branch, as long as we keep the current state working (so satisfying Catalina's new requirements).