TextLayout: TextStyleOverrides aren't applied correctly

[solveEM]

What does the pull request do?

This PR ensures that all TextStyleOverrides are applied correctly.

What is the current behavior?

Currently, the first TextRun is generated too long.
For example, we have the following text

Hello World\r\n
Hello

... and TextStyleOverrides to highlight the first two "He" at the beginning of each line:

IReadOnlyList<ValueSpan> textStyleOverrides = new List<ValueSpan>()
{
new ValueSpan(0, 2, new GenericTextRunProperties(typeface, backgroundBrush: Brushes.Aqua)),
new ValueSpan(13, 2, new GenericTextRunProperties(typeface, backgroundBrush: Brushes.Aqua)),
};

-> the first TextRun is generated too long:

What is the updated/expected behavior with this PR?

The first TextRun has the expected length:

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

The FormattedTextSource->CreateTextStyleRun method was iterating through all the TextStyleOverrides (TextModifiers) and applying them to the TextRun until the last one was in scope. I changed it to apply the first TextStyleOverride in scope to the TextRun and return it immediately, as it makes no sense to apply more than one override to one TextRun? This makes the hasOverride flag obsolete.

[avaloniaui-bot]

You can test this PR using the following package version. 11.3.999-cibuild0054143-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[cla-avalonia]

• All contributors have signed the CLA.

[solveEM]

@cla-avalonia agree