Simplify revision grid repainting

[MaxKoll]

Proposed changes

Repaint by invoking Update() at the end of each BackgroundUpdater operation instead of using a quasi-periodic approach.

Before

Repaints are triggered periodically by the Scroll event and do not coincidence with the asynchronous revision graph updates.

After

• Repaint after every revision graph update.
• Simpler code.

Test methodology

• Observing WM_PAINT messages via WndProc() override.
• Lots of scrolling the revision grid.

Test environment(s)

• Git 2.38.1.windows.1
• Microsoft Windows NT 10.0.19045.0
• .NET 6.0.16
• DPI 134dpi (140% scaling)

Merge strategy

I agree that the maintainer squash merge this PR (if the commit message is clear).

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

[mstv]

Occasionally, only one graph lane is shown on refresh after an operation - for long time or until a manual refresh. It might be related to some background git commands which can take very long on the affected (private) repos. I need to observe it longer.

[gerhardol]

Seem OK, have not used it

[MaxKoll]

Occasionally, only one graph lane is shown on refresh after an operation - for long time or until a manual refresh. It might be related to some background git commands which can take very long on the affected (private) repos. I need to observe it longer.

I must admit I have not tested it intensely outside the context of scrolling. I'm unsure how this could affect anything other than repaints during scrolling, as the only thing gone is the periodic call to Update() in OnScroll(). Every other line is just overhead.

I would therefore assume that the added await this.InvokeAsync(Update); inside UpdateVisibleRowRangeInternalAsync() is causing problems, but how?

[RussKie]

The rebase operation is notorious for leaving the graph incomplete and undrawn (e.g., #9223). Perhaps, this could provide more testing opportunities.

[mstv]

It is different from #9223 where no graph is displayed at all.

[mstv]

Thank you for bringing this up. Included in and superseded by #11719.