Mapsui: LineString crashes when zooming out with SKGLSurfaceView on Android

[pauldendulk]

To reproduce,

• Check out branch https://github.com/Mapsui/Mapsui/tree/research/linestring-hang-in-gl.
• Start Mapsui.Samples.Droid.
• Select the 'Many Vertices' sample under 'Special'.
• Pan a bit to see it behaves fair. A bit sluggish bug okay.
• Zoom out and it becomes more sluggish.
• Zoom further out and the map becomes unresponsive.

The same behaves normally when using the SKCanvasView instead of the SKGLSurfaceView.

[pauldendulk]

@charlenni I am going to revert iOS and Android to non GL versions. 😔

We need to submit this at skiasharp.

[charlenni]

@pauldendulk Do you really think, this is the best way? You will loose the speed of the GPU backend (see here) for a use case, that happens one time in a year. And only on Android, because if you use the same sample on UWP, than there are no problems.

I would suggest to leave it as it is and create an issue at SkiaSharp or direct in Skia.

[pauldendulk]

Better performance is seen immediately. Instant gratification, so very attractive. But in this case the downside may be obscure crashes that are sometimes not easy to reproduce and show only up in user logs. This can be a nightmare in a later phase of development where a customer demands stability before they accept the release.

Stuff like this and this could be related to GL instability. Crashes like this are rarely just a simple bug. It usually means they don' t know how to properly management the native resources. This has been a problem for years now, I don't expect it to be fixed soon.

Then again, you did make me think. Perhaps the solution should be to offer both. I was thinking about a MapControlGL version, but in that case we would need maximal code reuse. A better way maybe to add a method to switch render mode, like we have in the WPF MapControl, switching between Xaml and Skia. This way we can just go forward with both implementations. For the user the switch will be very easy.

[pauldendulk]

And we should indeed submit an issue. Preferably with a minimal reproducible sample. But I have two issues open with no response so far. https://github.com/mono/SkiaSharp/issues?q=is%3Aissue+is%3Aopen+pauldendulk

[pauldendulk]

Perhaps we should also start to dig into SkiaSharp more. Get some knowledge of the code. I cloned it only once, many years ago. Perhaps we could contact other users, like the people building Avalonia.

[mattleibow]

This might be a duplicate of #1121

[charlenni]

The above comment belongs to #865.

[pauldendulk]

@mattleibow This report is for Android. I am not completely sure there is no flaw in Mapsui here but when I go back to non-GL there is no crash which does indicate it is a SkiaSharp problem.

[pauldendulk]

@mattleibow Tested with 1.68.2-pr.1180.4 and could not reproduce the problem as reported above. Pushed it to this branch: https://github.com/Mapsui/Mapsui/tree/research/skiasharp-1.68.2-pr.1180.4.

It took a bit longer because 1.68.2-pr.1180.4 is not considered the latest version. I ended up replacing it manually in the csproj. Also we are busy getting the children's homeschooling program up and running. They are 7 and 9 and suddenly have to work on laptops and have a lot of questions :)

[mattleibow]

This is sounding like good news... Let me know as soon as you are sure you have found a problem or solution. I am getting positive vibes from this build.

[pauldendulk]

No further reports. Assumed fixed.