[robloo]

What does the pull request do?

Fixes the issues discussed in:

• GeometryBuilder.DrawRoundedCornersRectangle passes corner-arc rotation in radians; only renders correctly because the Skia backend treats it as degrees #21445

What is the current behavior?

1. RectangleGeometry (and Rectangle) drawing specifically with RadiusX or RadiusY has a small 1.57 degree rotation on each corner radius arc..
   • Rectangle drawing without any corner radius was never broken (is uses a fast path without a stream geometry context). This also explains why it was unnoticed for so long since RadiusX or RadiusY support came later in 11.x and probably still isn't widely used.
2. ArcTo method comments have incorrect units and are not clearly worded.

What is the updated/expected behavior with this PR?

RectangleGeometry with corner radius drawing is fixed. ArcTo method comments are now more clearly worded.

How was the solution implemented (if it's not obvious)?

Obvious and now documented better.

Checklist

• Added unit tests (if possible)?
• Added XML documentation to any related classes?
• Consider submitting a PR to https://github.com/AvaloniaUI/avalonia-docs with user documentation

Breaking changes

None

Obsoletions / Deprecations

None

Fixed issues

Fixes #21445

[robloo]

Leaving draft because more code review is required for related methods. The Arc shape has suspect code using radians. The PreciseArcTo() method is also suspect.

[avaloniaui-bot]

You can test this PR using the following package version. 12.1.999-cibuild0065949-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[grokys]

Hey @robloo any news on this PR? Is it still a draft?

[robloo]

@grokys It was still a draft because I suspected the issue was endemic to more APIs. The plan was to review them.

If the team wants to get this in I'll mark as ready. This PR does fix the actual issue ticket. Additional work can be done in follow-up PRs as time permits.

[avaloniaui-bot]

You can test this PR using the following package version. 12.2.999-cibuild0068728-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[Copilot]

Pull request overview

Fixes incorrect corner-arc rotation when building rounded rectangles from a Rect + (radiusX, radiusY) by ensuring the emitted elliptical corner arcs are axis-aligned (rotation angle 0). Also clarifies IGeometryContext.ArcTo XML documentation to state rotationAngle is specified in degrees.

Changes:

• Set rotationAngle: 0.0 for all four ArcTo calls in GeometryBuilder.DrawRoundedCornersRectangle(StreamGeometryContext, Rect, double, double) and remove the unused PiOver2 constant.
• Update IGeometryContext.ArcTo XML docs to describe rotationAngle as degrees and improve parameter wording/punctuation.

Reviewed changes

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

File	Description
src/Avalonia.Base/Platform/IGeometryContext.cs	Updates ArcTo XML documentation (degrees, clearer wording).
src/Avalonia.Base/Media/GeometryBuilder.cs	Fixes rounded-rectangle corner arc rotation by using rotationAngle: 0.0.

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[grokys]

LGTM!

[avaloniaui-bot]

You can test this PR using the following package version. 12.2.999-cibuild0068877-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]