Repository: flutter
Issue: Rendering of COLRv1 fonts is broken
Labels: engine,a: typography,c: rendering,has reproducible steps,P2,team-engine,triaged-engine,found in release: 3.13,found in release: 3.14

Flutter already supports rendering of COLRv0 font, the request here is to fix rendering of COLRv1 fonts,

### Steps to reproduce

1. Download a CORLv1 font from https://github.com/simoncozens/lottie2vf/raw/main/examples/fire.ttf and put it in `fonts/fire.ttf`
2. Add the following to you `pubspec.yaml`:
```
    - family: fire
      fonts:
        - asset: fonts/fire.ttf
```
3. Show the following somewhere in your screen,
`const Text('a', style: TextStyle(fontFamily: 'fire', fontSize: 40))`



### Expected results

As you _already_ can see the expected result when html is passed to `--web-renderer` using `flutter run -d chrome --web-renderer html`:

<img width="143" alt="image" src="https://github.com/flutter/flutter/assets/833473/7bfea1f2-1dbb-44c8-b0c3-41f63d512ac4">


### Actual results

Everywhere else, say with `flutter run -d chrome --web-renderer canvaskit` or with `flutter run -d macos` and `flutter run -d macos --enable-impeller`, you'll get just a blank screen.

### Code sample

The complete demo is here https://github.com/ebraminio/flutter_variable_font_animation_demo which shows COLRv0 [and it's animation] is already supported and it just lacks the newer COLRv1 support.

<img width="797" alt="image" src="https://github.com/flutter/flutter/assets/833473/a2bf5437-42bc-42c0-b8be-eae4e9a68d57">

The big picture here is to turn animations to COLRv1 font files using https://github.com/simoncozens/lottie2vf so no need for shipping an extra runtime just for the sake of animated icons. Flutter already uses icon fonts so animations packed in a font will be the most natural thing for it rather than yet another file format for it. COLRv1 even supports font subsetting as the support is added to harfbuzz-subset.

See http://simoncozens.github.io/colrv1-rocks/ for the context

Compare https://ebraminio.github.io/flutter_variable_font_animation_demo/build-web-html/ and https://ebraminio.github.io/flutter_variable_font_animation_demo/build-web-canvaskit/ in Chrome

And it would be nice if any arbitrary variation can be applied to fonts inside `Icon()` object but that's https://github.com/flutter/flutter/issues/134902 and different from this bug.

CCing @jonahwilliams and @dnfield from https://github.com/flutter/flutter/issues/111599 as this issue continue to happen both in Impeller and Skia renderer.

As the file is closed I like to response the following here:

> Those funcs with SVG in the name look to be in CoreText somewhere...

COLRv1, just like the already supported COLRv0 doesn't have anything to do with XML, that font probably itself contained SVG which isn't the case with fonts we like to use that specifically are created to leverage COLRv1.

### Flutter Doctor output

<details><summary>Doctor output</summary>

```console
Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, 3.13.4, on macOS 13.4.1 22F770820d darwin-arm64, locale en-US)
[✓] Android toolchain - develop for Android devices (Android SDK version 34.0.0)
[✓] Xcode - develop for iOS and macOS (Xcode 14.3.1)
[✓] Chrome - develop for the web
[✓] Android Studio (version 2022.3)
[✓] VS Code (version 1.82.0)
[✓] Proxy Configuration
[✓] Connected device (2 available)
[✓] Network resources

• No issues found!
```

</details>