Make sure GlyphRunImpl.InkBounds are always at a positive location

[Gillibald]

What does the pull request do?

For an unknown reason, Skia reports glyph bounds at a negative x-position which causes some alignment issues for monospace fonts. This PR makes sure glyph bounds are always at a positive position.

What is the current behavior?

What is the updated/expected behavior with this PR?

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

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

Obsoletions / Deprecations

Fixed issues

Fixes: #16555

[avaloniaui-bot]

You can test this PR using the following package version. 11.2.999-cibuild0050990-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[MrJul]

Just a though, aren't the negative bounds returned because of the edging?

Avalonia/src/Skia/Avalonia.Skia/GlyphRunImpl.cs

Lines 54 to 58 in d1cdb29

	// Ideally the requested edging should be passed to the glyph run.
	// Currently the edging is computed dynamically inside the drawing context, so we can't know it in advance.
	// But the bounds depends on the edging: for now, always use SubpixelAntialias so we have consistent values.
	// The resulting bounds may be shifted by 1px on some fonts:
	// "F" text with Inter size 14 has a 0px left bound with SubpixelAntialias but 1px with Antialias.

This comment says that the result could be shifted by 1px, but it could also probably be -1px depending on the font.

---

Since that negative bound might apply to several other characters in the run and not only the first, won't shifting the bounds of the whole run potentially cause other problems, for example with hit testing?

Also, should we add a render test here to avoid future regressions?

[Gillibald]

Y sounds like we need a render test

[Gillibald]

https://issues.skia.org/issues/40036500

[Gillibald]

So ideally glyph bounds should never affect layout. So each glyphs anchor point should be adjusted to the expected glyph advances. In the end this should only matter for the first glyph's bounds because these define the left edge of a run.

[avaloniaui-bot]

You can test this PR using the following package version. 11.2.999-cibuild0051781-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[avaloniaui-bot]

You can test this PR using the following package version. 11.2.999-cibuild0051805-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]