When touching and holding a long press, mapControl becomes blank

[zimuyanghua]

Mapsui Version
Mapsui 4.1

Mapsui Platform
Avalonia

Device
Linux

Describe the bug
I load a map in mbtiles format, and when I touch and hold the screen, the map becomes blank. However, I don't encounter this issue when I long-press with a mouse. It seems to trigger the system's long-press for right-click gesture.

I haven't added any additional code, just loaded the map, and no exceptions were thrown.

QQ202418-14468.mp4

I'm not sure if this is a bug or not.

[zimuyanghua]

I added the log
Mapsui.Logging.Logger.LogDelegate += (level, message, ex) =>
{
Console.WriteLine(message); // <-- Put a break point here, most UI platforms do not show the console logging.
// todo: Forward to your own logger
};
output:

Unexpected error in skia renderer

[zimuyanghua]

more detail about the error：

[pauldendulk]

Given the number of things on my plate this is not something I will try to reproduce. I don't have a touch screen and don't work default on Linux.

The bug could be related to extreme values (near zero or maximum double) in the unitsPerPixel, or something weird in the resolutions. It is probably a real bug in Mapsui or BruTile. It could also be a bug in Avalonia.

What you could do it try to reproduce it with the Avalonia sample that is part of this git repository.

git clone git@github.com:Mapsui/Mapsui.git

And run the Avalonia sample.

This is the method in BruTile that is involved.

public static int GetNearestLevel(IDictionary<int, Resolution> resolutions, double unitsPerPixel)
{
    if (resolutions.Count == 0)
    {
        throw new ArgumentException("No tile resolutions");
    }

    var orderedResolutions = resolutions.OrderByDescending(r => r.Value.UnitsPerPixel).ToList();

    //smaller than smallest
    if (orderedResolutions.Last().Value.UnitsPerPixel > unitsPerPixel) return orderedResolutions.Last().Key;

    //bigger than biggest
    if (orderedResolutions.First().Value.UnitsPerPixel < unitsPerPixel) return orderedResolutions.First().Key;

    var result = -1;
    var resultDistance = double.MaxValue;
    foreach (var current in orderedResolutions)
    {
        var distance = Math.Abs(current.Value.UnitsPerPixel - unitsPerPixel);
        if (distance < resultDistance)
        {
            result = current.Key;
            resultDistance = distance;
        }
    }
    if (result < 0) throw new Exception("Unexpected error when calculating nearest level");
    return result;
}

[pauldendulk]

oh and I forgot. Thanks for the bug report! The movie really helps.

[zimuyanghua]

I tried the Avalonia demo and this issue also occurs. Since the test environment can only be offline, I only tested the mbtiles format. I'll try again with a map in a different offline format

[pauldendulk]

I tried the Avalonia demo and this issue also occurs.

But that means you could retrieve can see what is happening in the debugger when result is smaller than zero. What are argument values for the resolutions and the unitsPerPixel.