Memory leak when working with an external font

[kkmserver]

Describe the bug

Hello

My program needs to display machine coordinates 30 times per second.
The form has a simple TextBlock:

The Feed field is of type double
Updating the field on the screen via:
OnPropertyChanged(nameof(Feed));

I encountered a memory leak (screenshots 1 and 2).


330 MB is leaked in 200 seconds.

Memory leaks occur even in idle apps, but very slowly and barely noticeably. You only notice it when elements are frequently updated.

I noticed that in the profiler, these strings are in objects somehow related to Font.
I started experimenting.
I came to the conclusion that the memory leak occurs every time the TextBlock is drawn via OnPropertyChanged(nameof(Feed)) – regardless of whether the data has changed or not.

And then I noticed that these TextBlocks had a style with an external font:

<Style Selector="Canvas.Big > TextBlock"> </Style>

Where WhiteRabbit is an external font declared in App.axaml like this:
avares://JupiterCNC/Assets/Fonts/White Rabbit#White Rabbit

I disabled this font in the style, and the memory leak did not stop - but it decreased 100 times!

I tried rolling back to Avalonia 11.3.8 and the memory leak stopped.

AvaloniaUI 11.3.9
Net.core 10.0
Windows

To Reproduce

1. Add an external font to App.axaml:
   <FontFamily x:Key="WhiteRabbit">avares://JupiterCNC/Assets/Fonts/White Rabbit#White Rabbit</FontFamily>

2. Add this font to the TextBlock:

<Style Selector="Canvas.Big > TextBlock">
        <Setter Property="FontFamily" Value="{StaticResource WhiteRabbit}"/>
</Style>

3. Frequently refresh the Text in the TextBlock while working.

Expected behavior

No response

Avalonia version

11.3.9

OS

Windows

Additional context

No response

[Gillibald]

Please test with: 12.0.999-cibuild0060475-alpha

[kkmserver]

On 12.0.999-cibuild0060475-alpha, everything is exactly the same.

[Gillibald]

Please provide a minimal sample that reproduces the issue. I can't reproduce this in the Sandbox.

[kkmserver]

I've compiled an example:
https://drive.google.com/file/d/1MMejE0UKprY_cNsrE7goPem4w7sVXw_a/view?usp=sharing

If you migrate the example to AvaloniaUI 11.3.8, the leak will stop.
Just remember to force a rebuild of the app after migrating to 11.3.8 (I always forget to do this :) )