[NodeLeading] TreeView row spacing collapses when NodeLeading is set between 0.0 and 1.0

[Olina-Zhang]

.NET version

.NET 11.0.100-preview.7.26365.114 + Private dlls built from Net11/Integration-3 branch of https://github.com/KlausLoeffelmann/winforms repo

Did it work in .NET Framework?

Not tested/verified

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

Not support, new feature of #14768

Issue description

When TreeView.NodeLeading is set to a floating-point value between 0.0 and 1.0 (for example, 0.2, 0.5, or 0.8), the spacing between TreeView nodes becomes noticeably compressed, making the nodes appear crowded.

Interestingly, this issue does not occur when NodeLeading is exactly 0.0 (legacy behavior) or exactly 1.0 (honest row-height). The unexpected behavior only occurs for values strictly between 0.0 and 1.0.

Steps to reproduce

1. Create a WinForms application targeting .NET 11.
2. Add several TreeViews with multiple nodes.
3. Set TreeView.NodeLeading to different values:

• 0.0
• 0.5
• 1.0
• 2.0

4. Compare the spacing between adjacent nodes.

[KlausLoeffelmann]

That's by design.

Even if it does not seem to make sense for "normal" Font rendering, when it comes to custom rendering, then by having half or even quarter lines, we can "emulate" lines with variable height.