Revert changes in PR11529 and PR11761

[LeafShi1]

Fixes #12590

Root Cause

In order to fix the flickering issue#2053861, I modified the drawing logic of ComboBox in #11529, this leads to the current issue and issue #11760.

Proposed changes

• Revert the changes on PR Issue 2053861 fix combo box flickering issue #11529 and PR Issue 11760 fix tool strip combo box display #11761

Customer Impact

• ComboBox dropdown button can be shown normally when switching RightToLeft property, or recreating the combobox for any other reason.

Regression?

• Yes

Risk

• Minimal

Before

When change the RightToLeft property after expanding the Popup FlatStyle comboBox, the dropdown button on the comboBox disappeared

After

The dropdown button on the comboBox can be show normally

Test methodology

• Manually

Test environment(s)

• .net 10.0.0-alpha.1.24605.1

Microsoft Reviewers: Open in CodeFlow

[codecov]

Codecov Report

Attention: Patch coverage is 62.50000% with 9 lines in your changes missing coverage. Please review.

Project coverage is 76.15371%. Comparing base (a54a4a9) to head (bbe67a5).
Report is 8 commits behind head on main.

Additional details and impacted files

@@                 Coverage Diff                 @@
##                main      #12737         +/-   ##
===================================================
+ Coverage   76.12836%   76.15371%   +0.02535%     
===================================================
  Files           3188        3191          +3     
  Lines         640086      640087          +1     
  Branches       47233       47230          -3     
===================================================
+ Hits          487287      487450        +163     
+ Misses        149269      149120        -149     
+ Partials        3530        3517         -13     

Flag	Coverage Δ
Debug	76.15371% <62.50000%> (+0.02535%)	⬆️
integration	18.16891% <0.00000%> (+0.00183%)	⬆️
production	50.06555% <62.50000%> (+0.05324%)	⬆️
test	97.02819% <ø> (-0.00009%)	⬇️
unit	47.27376% <62.50000%> (+0.03053%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

[Tanya-Solyanik]

Thank you! Please re-activate the associated bug and investigate an alternative fix. We'll service this fix if we receive customer reports.

[ricardobossan]

/backport to release/9.0

[github-actions]

Started backporting to release/9.0: https://github.com/dotnet/winforms/actions/runs/12768052150

[github-actions]

@ricardobossan backporting to release/9.0 failed, the patch most likely resulted in conflicts:

$ git am --3way --ignore-whitespace --keep-non-patch changes.patch

Applying: Revert 11761
Using index info to reconstruct a base tree...
M	src/System.Windows.Forms/src/System/Windows/Forms/Controls/ComboBox/ComboBox.FlatComboAdapter.cs
M	src/System.Windows.Forms/src/System/Windows/Forms/Controls/ComboBox/ComboBox.cs
M	src/System.Windows.Forms/src/System/Windows/Forms/Controls/ToolStrips/ToolStripComboBox.ToolStripComboBoxControl.ToolStripComboBoxFlatComboAdapter.cs
Falling back to patching base and 3-way merge...
Auto-merging src/System.Windows.Forms/src/System/Windows/Forms/Controls/ToolStrips/ToolStripComboBox.ToolStripComboBoxControl.ToolStripComboBoxFlatComboAdapter.cs
Auto-merging src/System.Windows.Forms/src/System/Windows/Forms/Controls/ComboBox/ComboBox.cs
Auto-merging src/System.Windows.Forms/src/System/Windows/Forms/Controls/ComboBox/ComboBox.FlatComboAdapter.cs
Applying: Revert PR 11529
Using index info to reconstruct a base tree...
M	src/System.Windows.Forms/src/System/Windows/Forms/Controls/ComboBox/ComboBox.FlatComboAdapter.cs
M	src/System.Windows.Forms/src/System/Windows/Forms/Controls/ComboBox/ComboBox.cs
Falling back to patching base and 3-way merge...
Auto-merging src/System.Windows.Forms/src/System/Windows/Forms/Controls/ComboBox/ComboBox.cs
Auto-merging src/System.Windows.Forms/src/System/Windows/Forms/Controls/ComboBox/ComboBox.FlatComboAdapter.cs
CONFLICT (content): Merge conflict in src/System.Windows.Forms/src/System/Windows/Forms/Controls/ComboBox/ComboBox.FlatComboAdapter.cs
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
hint: When you have resolved this problem, run "git am --continue".
hint: If you prefer to skip this patch, run "git am --skip" instead.
hint: To restore the original branch and stop patching, run "git am --abort".
hint: Disable this message with "git config advice.mergeConflict false"
Patch failed at 0002 Revert PR 11529
Error: The process '/usr/bin/git' failed with exit code 128

Please backport manually!