Fix leaking brushes

[NikolayXHD]

Fixes #9429

Proposed changes

1. Return brush wrapper in situations when brush consumer is not certain whether it should dispose the brush.
   wrapper.Dispose method will not touch the underlying brush if it is system brush.
2. Cache the native brushes returned by Win32 GetSysColorBrush override
3. Render text input backround explicitly, because 2. somehow breaks default system rendering.

Test methodology

• run GitExtensions
• scroll revision grid back and forth, click on different revisions
• observe GDI objects count using GDIView (thank you @pmiossec)

Test environment(s)

Windows 10

Merge strategy

• Rebase merge

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✒️ I contribute this code under The Developer Certificate of Origin.

[gerhardol]

+1
Seem fine to me, I have only briefly run this.

[pmiossec]

Return brush wrapper in situations when brush consumer is not certain whether it should dispose the brush.
wrapper.Dispose method will not touch the underlying brush if it is system brush.

Clever idea. I have checked with the portable version and from what I see with GdiView, it is working great and fix the issue.

Code seems good. I will give it another look later.

I was just wondering. On the project, do we prefer:

using(var foo = new Brush())
{}

or

using var foo = new Brush();

[gerhardol]

I was just wondering. On the project, do we prefer:

using(var foo = new Brush())
{}

or

using var foo = new Brush();

The latter generally, but the case I checked here the first was still required (null check).

[RussKie]

I've started to review, but got caught up with work. Will complete this week.

[RussKie]

👍 with some comments

[RussKie]

@NikolayXHD I've made few tweaks, please have a look.

[NikolayXHD]

@NikolayXHD I've made few tweaks, please have a look.

Ok, meged the changes changes to respective commits, thank you.

[RussKie]

Thank you!

[gerhardol]

Thanks!
Will this be merged to master too, even if themes are not possible yet with .NET5?
How should we remember this otherwise?

[NikolayXHD]

Will this be merged to master too, even if themes are not possible yet with .NET5?

Sure thing :)