Optimize OnDrawItem to prevent GDI resource exhaustion by caching scaled icon size

[LeafShi1]

Fixes #14122

Root Cause

The exception: An object could not be created, possibly due to a lack of memory, but most likely due to invalid input
was triggered because of how OnDrawItem handled icon creation in a high-frequency drawing path:

Repeated GDI object creation in hot path
Each call to OnDrawItem executed:

• Icon.FromHandle(cursor.Handle)
• Clone()
• ScaleSmallIconToDpi(...)

This pattern allocates multiple unmanaged GDI resources per draw cycle. Under heavy redraw (scrolling, hover, DPI changes), these allocations accumulate quickly, exhausting GDI handles.

Proposed changes

• Introduced a caching mechanism for scaled icon width based on (Cursor, DPI) to minimize redundant object creation.
• Ensured ScaleSmallIconToDpi is still called as required, but only during cache population rather than every draw.
• Added proper disposal of temporary Icon objects during cache initialization.
• Cleared the cache in the End method to release resources when the control lifecycle ends.

Customer Impact

• Eliminates random crashes caused by GDI handle exhaustion in owner-drawn controls.

Regression?

• Yes

Risk

• Minimal

Screenshots

Before

When using a PropertyGrid to edit properties of type Cursor, resizing the Cursor UITypeEditor drop-down window causes the application to stop responding or crash.

ResizeCursorEdiorIssue.mp4

After

AfterChanges.mp4

Test methodology

• Manual testing

Test environment(s)

• .net 10.0.0-rc.3.25603.106

Microsoft Reviewers: Open in CodeFlow

[codecov]

Codecov Report

❌ Patch coverage is 13.33333% with 13 lines in your changes missing coverage. Please review.
✅ Project coverage is 77.15542%. Comparing base (5d64bba) to head (2c380b6).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@                 Coverage Diff                 @@
##                main      #14123         +/-   ##
===================================================
+ Coverage   76.01271%   77.15542%   +1.14271%     
===================================================
  Files           3279        3279                 
  Lines         645325      645339         +14     
  Branches       47720       47721          +1     
===================================================
+ Hits          490529      497914       +7385     
+ Misses        145491      143737       -1754     
+ Partials        9305        3688       -5617     

Flag	Coverage Δ
Debug	77.15542% <13.33333%> (+1.14271%)	⬆️
integration	18.99480% <0.00000%> (?)
production	52.02161% <13.33333%> (+2.56216%)	⬆️
test	97.40749% <ø> (ø)
unit	49.46226% <13.33333%> (+0.00281%)	⬆️

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Pull request overview

This PR addresses a critical GDI resource exhaustion issue that causes crashes in owner-drawn controls during high-frequency drawing operations. The fix introduces intelligent caching of scaled icon widths to prevent repeated GDI object creation in hot code paths.

Key Changes:

• Implemented a dictionary-based cache using (Cursor, DPI) tuples to store computed icon widths
• Refactored OnDrawItem to use the cached values instead of repeatedly creating Icon objects
• Added proper cache cleanup in the End() method to prevent memory leaks

[ricardobossan]

All LGTM!