Monitor DPI transition on latest Windows 10 causes infinite window growth

[SDLBugzilla]

This bug report was migrated from our old Bugzilla tracker.

These attachments are available in the static archive:

• before (ideal resolution, on 150% dpi monitor) (Screenshot 2019-06-17 13.58.45.png, image/png, 2019-06-17 21:04:10 +0000, 260028 bytes)
• After a few mousemove events on the 100% dpi monitor (Screenshot 2019-06-17 13.58.50.png, image/png, 2019-06-17 21:04:28 +0000, 259863 bytes)

Reported in version: HG 2.1
Reported for operating system, platform: Windows 10, x86

Comments on the original bug report:

On 2019-06-17 21:04:10 +0000, Katelyn Gadd wrote:

Created attachment 3827
before (ideal resolution, on 150% dpi monitor)

If you enable the new 'permonitorv2' DPI awareness mode using an app manifest (app.manifest) in recent versions of Windows 10, SDL windows will grow infinitely on mousemove once they transition to a monitor with lower DPI. I'll attach two comparison screenshots.

I wasn't able to build a reduced repro yet, but from what I can tell the problem is that V2 scales non-client portions of the window and SDL appears to use integer pixels for non client and client size calculations. If the base windows DPI is say 150% (like my 4k monitor) and the window transitions to a 100% DPI window, the values are no longer integral pixel counts and as a result SDL produces rounding errors. When that happens every mouse move causes large vertical growth (because the titlebar is big) and slow horizontal growth. Moving back to the original monitor stops the growth but leaves the size incorrect.

Set component to events since it happens during mousemove event processing.

On 2019-06-17 21:04:28 +0000, Katelyn Gadd wrote:

Created attachment 3828
After a few mousemove events on the 100% dpi monitor

On 2019-06-17 21:44:17 +0000, Sam Lantinga wrote:

Do you have a patch to fix this that we can include in SDL 2.0.10?

Thanks!

On 2019-06-18 06:17:52 +0000, Katelyn Gadd wrote:

I honestly don't know SDL well enough to fix this. I could look into it some. Is there a particular SDL sample or testcase I should use to verify all the DPI-related stuff? I don't want to just end up fixing it for my scenario and breaking it for others.

[slouken]

It looks like this has either been fixed in Windows or in SDL since this bug was reported. I'm testing on Windows 11 Version 10.0.22000 Build 22000, and I am not able to reproduce it.

If this is still active, please add a link to a project I can download and steps to repro.

Thanks!