Optimize icon rendering: simplify logic and eliminate redundant calculations

[DJm00n]

• Replaced HDC with Graphics in DrawIcon() for smoother GDI+ integration
• Optimized Rectangle management – removed unnecessary variables, directly adjusting sizes
• Simplified stretch logic (Inflate) – replaced complex calculations with a concise method call
• Unified Draw() and DrawUnstretched() – now both directly call DrawIcon() without intermediate processing
• Eliminated duplicate Matrix.Offset calculations, ensuring targetRect is adjusted directly
• No functional changes, just cleaner, more maintainable code 🚀

Regression?

• No

Microsoft Reviewers: Open in CodeFlow

[codecov]

Codecov Report

Attention: Patch coverage is 73.33333% with 4 lines in your changes missing coverage. Please review.

Project coverage is 76.60189%. Comparing base (5821493) to head (28c65ed).
Report is 29 commits behind head on main.

Additional details and impacted files

@@                 Coverage Diff                  @@
##                main      #13449          +/-   ##
====================================================
+ Coverage   62.21083%   76.60189%   +14.39105%     
====================================================
  Files           3213        3230          +17     
  Lines         638302      639043         +741     
  Branches       47201       47287          +86     
====================================================
+ Hits          397093      489519       +92426     
+ Misses        234153      145951       -88202     
+ Partials        7056        3573        -3483     

Flag	Coverage Δ
Debug	76.60189% <73.33333%> (+14.39105%)	⬆️
integration	18.79058% <0.00000%> (+0.00179%)	⬆️
production	51.00214% <73.33333%> (+32.21335%)	⬆️
test	97.40411% <ø> (ø)
unit	48.40830% <73.33333%> (?)

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[DJm00n]

@JeremyKuhne can you please take a look at this PR?

[JeremyKuhne]

Looking, also letting CoPilot have a look.

[Copilot]

Pull Request Overview

This PR refactors Icon.DrawIcon to use Graphics instead of raw HDC, simplifies rectangle handling, and unifies the two Draw methods.

• Replaced HDC-based drawing with Graphics and DeviceContextHdcScope
• Collapsed manual width/height calculations into Rectangle operations (Inflate, Offset, Intersect)
• Streamlined Draw and DrawUnstretched to forward directly to DrawIcon

Reviewed Changes

Copilot reviewed 1 out of 1 changed files in this pull request and generated 2 comments.

File	Description
src/System.Drawing.Common/src/System/Drawing/Icon.cs	Refactored DrawIcon signature/logic, simplified rectangle math
src/System.Drawing.Common/src/System/Drawing/Icon.cs (Draw overloads)	Removed manual transform offset and copy, now calls DrawIcon directly

[Copilot]

Using Rectangle.Inflate with a scale factor (targetRect.Width / imageRect.Width) inflates the rectangle by pixel amounts rather than resizing it to the desired dimensions. This misuses Inflate for stretching logic and leads to incorrect sizing. Consider directly assigning imageRect.Size = targetRect.Size when stretch is true, or apply a proper scaling transformation.

Suggested change

	imageRect.Inflate(stretch
	? new Size(targetRect.Width / imageRect.Width, targetRect.Height / imageRect.Height)
	: new Size(0, 0));
	if (stretch)
	{
	imageRect.Size = targetRect.Size;
	}

[Copilot]

[nitpick] Switching from truncating the graphics transform offset (previously via integer cast) to rounding may shift drawing by one pixel. If precise alignment is critical, use consistent rounding or truncation to match existing behavior or clearly document this change.

Suggested change

	targetRect.Offset(Point.Round(graphics.Transform.Offset));
	targetRect.Offset(Point.Truncate(graphics.Transform.Offset));

[JeremyKuhne]

Love the cleanup here! If you can do this in steps where you move the calculations into a private helper first and create some good unit tests, I'd be happy to work with you to take this. (We're extremely resource bound for a while.)

Once the helper methods are collapsed to a single line there is no need to keep them.

Ultimately this helper code should really live in the Graphics class. It could also be further optimized by avoiding creating the Matrix object by using TransformElements.

[DJm00n]

@JeremyKuhne I also wanted to do the same changes in the System.Windows.Forms.Cursor class. How can I properly share code between them?

[JeremyKuhne]

@DJm00n Presumably by putting the code in Graphics as they share the need for it to render?