PropertyGrid: Splitter bar out of position when resizing the help pane at the bottom of a PropertyGrid

[tvidvei]

.NET version

.NET version: 10.0.0-preview.4.25258.110 (Currently the latest publicly available preview version)

Did it work in .NET Framework?

No

Did it work in any of the earlier releases of .NET Core or .NET 5+?

Testing with the latest .NET versions (net60, net70, net80) give the same error. Same for .NET Framework 4.8.1

Issue description

When trying to resize the HelpPane at the bottom of a PropertyGrid, a splitter bar appears to indicate the new position of the split. But it displays a wrong position.

The error seems to be related to the handling of hight DPI, which is controlled by the ApplicationHighDpiMode property in the project settings. Changing this setting in WinFormsControlsTest from SystemAware to PerMonitorV2 reduces the deviation slightly, but it is still significant.

dotnet/winforms commit tested: 1e15c51 25.04.2025 4:25 CET
.NET version: 10.0.0-preview.4.25258.110
OS: Windows 11 Pro, version: 24H2
Hardware:
Lenovo Yoga Slim 7 14Q8X9 (Laptop)

• Display on Laptop: Resolution=2944x1840, Scale=200%
• External monitor: Resolution=1920x1080, Scale=100%

Steps to reproduce

This error can easily be reproduced by running the WinFormsControlsTests (in dotnet/winforms), open a PropertyGrid and try to resize the HelpPane at the bottom. The same error can be seen e.g. in the Property pane in VS2022 and anywhere where PropertyGrid is used

[tvidvei]

This issue appears to be the same as issue #13459, as the splitter bar is drawn by DrawReversibleLine. As mentioned, in the description, the error occurs also on .NET Framework 4.8.1, and in the property pane in VS2022.

I just tested with single monitor on my laptop: Then everything is fine.

It seems as the error is related to the adjustments for High DPI or scaling in cases with multiple monitors. But not the scaling in itself. My laptops scaling is 200%

It is also remarkable that the SplitContainer works properly in the cases when the DrawReverseLine error occurs. That can be verified by using the WinFormsControlsTest's Splitter test.

(Similar comment left in #13459)

[tvidvei]

Closing this issue as it is the same as #13459