[Windows] GDI resource leaks when using the software renderer code path

[sevenstars]

GDI resource (Device Context) leaks when using the software renderer code path.

This only happens when the app is using software rasterization, i.e., if the embedder explicitly specifies FlutterRendererType::kSoftware or AngleSurfaceManager::Create() somehow fails.

The leak happens in every frame, so after a while, number of leaks will soon reach the default per-process limit of GDI handles and then the app UI will not be responsive.

[danagbemava-nc]

Hi @sevenstars, would it be possible for you to provide a complete minimal reproducible code sample as well as steps to reproduce?

Please also provide the output of flutter doctor -v.

Thank you

[sevenstars]

Hi @sevenstars, would it be possible for you to provide a complete minimal reproducible code sample as well as steps to reproduce?

Please also provide the output of flutter doctor -v.

Thank you

The leak can be reproduced when the app is using software rasterization on Windows, i.e., in one of scenarios as follows:

1. The embedder explicitly specifies kSoftware as the FlutterRendererType when calling embedder API FlutterEngineRun(), or
2. AngleSurfaceManager::Create() somehow fails

I've created a PR to fix this: flutter/engine#34574

[danagbemava-nc]

Hi @sevenstars, I'm not familiar with the scenarios you described above.

Can you provide a small sample app that has any of the scenarios described above?

[sevenstars]

The leak can be reproduced with any flutter app using the software fallback path. The flutter engine will try to use hardware accelerated rendering if possible, and I found AngleSurfaceManager::Create() somehow fails on some Windows 7 machines, so in this case the flutter engine will use the software fallback path.

You can reproduce the leak on any Windows 10 machine, using the following steps:

1. Use the DirectX Control Panel (DXCpl.exe) to apply Direct3D debug settings for the flutter app.
2. Run the image_list example app.
3. Use the GDIView tool to see the resource leaks.

The result:
After running the app for a few minutes, you will see the number of leaks reaches 10000, and the app will stop updating.

Use the DirectX Control Panel (DXCpl.exe) to apply Direct3D debug settings for the flutter app

Run the image_list example app

Use the GDIView tool to see the resource leaks

cc @danagbemava-nc

[danagbemava-nc]

Thanks for the repro info. I am unable to repro this at the moment so I will label for further insight and update when I am able to repro.

Sample for testing https://github.com/flutter/flutter/tree/master/examples/image_list