SkiaSharp could dispose objects too early

[laurenceSaes]

Skia objects, like SkiaSharp.SKPaint, have disposable Skia properties that are retrieved based on their underlying C++ objects. The C# owner class does not have any reference to the C# equivalent of this property. This could result in too early garbage collection of dependent objects. This dispose action will call the C# destructor and free all allocated memory while the property is still in use.

See for example the following scenario:

• A new SkiaSharp.SKPaint instance is created
• A Shader is set onto the SKPaint object
• Garbage collection is triggered
• The C# Shader class is garbage collected since it is not referenced anymore. All C++ shader resources are freed
• A fatal crash will occur since the SKPaint is making use of the freed memory

An alternative fault situation:

• A new SkiaSharp.SKPaint instance is created
• A Shader is set onto the SKPaint object
• The SKPaint instance is used
• Garbage collection is triggered
• The C# Shader class is garbage collected since it is not referenced anymore. All C++ shader resources are freed
• The SKPaint object is disposed
• A fatal crash occurs when the SKPaint instance tried to destruct the shader.

The SKPaint.Shader property:

public SKShader Shader
{
  get => SKShader.GetObject(SkiaApi.sk_paint_get_shader(this.Handle));
  set => SkiaApi.sk_paint_set_shader(this.Handle, value == null ? IntPtr.Zero : value.Handle);
}

The SkiaSharp.SKPaint class should hold a reference to the C# Shader to prevent garbage collection.

An example of the alternative situation, this results in the following fatal crash:

Version information:

• SkiaSharp version 2.80.3

[DamianSuess]

I too am getting the same error with .NET MAUI on WinUI/UWP.

• v2.88.3.0
• net6.0-windows10.0.19041.0\win10-x64\AppX\SkiaSharp.Views.Windows.dll