Ability to configure font features

[HermanKirshin]

What does the pull request do?

Added ability to configure font features.

What is the current behavior?

Default font configuration is used. For example in case of Inter by default it will automatically replace -> with arrow, 'x' between numbers to mathematical multiply sign and numbers are not tabular (this makes tables hardly readable).
See attached screenshot - current behavior is under 'Default'. Actual text specified in TextBlock.Text is

111111 x64 ->
999999 x64 ->

What is the updated/expected behavior with this PR?

Text elements now have property FontFeatures that allow to specify comma-separated feature values that configures the font (feature syntax is for example here). Property can be specified either on Run, or on TextBlock or on TextBox or on container (as attached), absolutely same as other font-related properties like size etc:

      <TextBlock Text="111111 x64 ->" FontFeatures="-calt,+tnum"></TextBlock> 

      <TextBlock>
        <Run FontFeatures="-calt,+tnum">111111 x64 -></Run>
      </TextBlock>

      <TextBox Text="111111 x64 ->" FontFeatures="-calt,+tnum"></TextBox>

      <StackPanel TextElement.FontFeatures="-calt,+tnum">
        <TextBlock Text="111111 x64 ->" />
      </StackPanel>

[avaloniaui-bot]

You can test this PR using the following package version. 11.1.999-cibuild0043462-beta. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[Gillibald]

Thanks for your contribution. I have added some comments.

In general, we should try to let Harfbuzz parse features/tags or just copy the parsing logic from HarfBuzzSharp

Something like this should be possible:

<TextElement.FontFeatures>
    <FontFeatureCollection>
        <FontFeature Tag="liga" Value="0"/>
    <FontFeatureCollection>
</TextElement.FontFeatures>

[Gillibald]

@HermanKirshin Are you able to continue working on this or should I take over?

[HermanKirshin]

@HermanKirshin Are you able to continue working on this or should I take over?

@Gillibald Hi! Thanks for the review. Sorry for the delay, I'm a bit overwhelmed by work tasks currently, but assume that will be able to fix this PR on the weekend. But if you prefer to take over I wont mind either.

[Gillibald]

I just wanted to make sure this is still being worked on take your time

[avaloniaui-bot]

You can test this PR using the following package version. 11.1.999-cibuild0043981-beta. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[HermanKirshin]

@Gillibald Here are the fixes. I squashed commits for cleaner history.

[avaloniaui-bot]

You can test this PR using the following package version. 11.1.999-cibuild0044012-beta. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[Gillibald]

I have made some adjustments myself but I am not able to push to your fork

Here are the changes: https://github.com/AvaloniaUI/Avalonia/tree/pull/14157

[Gillibald]

FontFeature is no longer mutable to avoid unexpected behavior. If someone wanted to animate text by altering font features one has to replace the whole collection.

[HermanKirshin]

Merged pull/14157 into the fork

[avaloniaui-bot]

You can test this PR using the following package version. 11.1.999-cibuild0044042-beta. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[avaloniaui-bot]

You can test this PR using the following package version. 11.1.999-cibuild0044175-beta. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[Gillibald]

Thank you for your contribution