A unexpected white line in StatusStrip compoent in dotnet 9

[hmisaki]

Description

If a dialog with a dark background and used StatusStrip. Then move the code from dotnet 8 to dotnet 9. There are many unexpected white lines in our dialog.

but if we build our project with dotnet 8. there will be good:

Reproduction Steps

1. create a Winform app with dotnet 9.
2. add componts StatusStrip and ToolStripStatusLabel
3. set the dialog and StatusStrip back color to a grey color, for example:

this.BackColor = Color.FromArgb(255,59,68,83);
statusStrip1.BackColor = BackColor;

4. build the project and run the test app.

Expected behavior

Get a grey dialog and a grey StatusStrip
for example:

Actual behavior

a white line in the dialog

Regression?

It's fine in dotnet 8.

Known Workarounds

no

Configuration

No response

Other information

No response

[Zheng-Li01]

The issue can reproduce on 9.0 & 10.0. For StatusStrip control, the white line not appeared on .NET 8.0; For toolStrip control, the white line appeared on 8.0/9.0/10.0 & .NET Framework as below screenshot.

[JeremyKuhne]

This is due to #11502. We changed the default RenderMode from System to ManagerRenderMode. This should have been marked as a breaking change but was missed.

@hmisaki you should be able to get your old behavior by explicitly setting the RenderMode to System.

@Tanya-Solyanik, @lonitra leaving to you to resolve this the rest of the way.

[Tanya-Solyanik]

@LeafShi1 - please condition fix in #11502 on an AppContext switch System.Windows.Forms.StatusStrip.UseSystemRenderingModeAsDefault. It would be set to false by default. We would want to service this change to NET9

[hmisaki]

Great, It resolved my issue. Thank you @JeremyKuhne

[LeafShi1]

@LeafShi1 - please condition fix in #11502 on an AppContext switch System.Windows.Forms.StatusStrip.UseSystemRenderingModeAsDefault. It would be set to false by default. We would want to service this change to NET9

@Tanya-Solyanik If the default value is set to false, the current issue will not be resolved and customers will have to enable the switch, does this make sense? Or should we use System as the default value, that is, set the default value of the switch to true

[merriemcgaw]

We'll go with an opt-in quirk so that the default behavior is accessible. Thanks for the quick turnaround @LeafShi1!

[LeafShi1]

We'll go with an opt-in quirk so that the default behavior is accessible. Thanks for the quick turnaround @LeafShi1!

So setting the default value of a switch to false is fine, right?

[Tanya-Solyanik]

@LeafShi1 - by default the behavior should be accessible. The AppContext is provided to get compatibility with .NET Framework and simplify migration.