CanvasEffect property source generator

[Sergio0694]

Description

This issue tracks adding a new source generator for CanvasEffect properties.
It will be conceptually similar to the MVVM Toolkit observable property generator.

Proposed API

In ComputeSharp.D2D1.WinUI:

namespace ComputeSharp.D2D1.WinUI;

[AttributeUsage(AttributeTargets.Property, AllowMultiple = false)]
public sealed class GeneratedCanvasEffectPropertyAttribute(CanvasEffectInvalidationType invalidationType = CanvasEffectInvalidationType.Update) : Attribute
{
    public CanvasEffectInvalidationType InvalidationType { get; }
}

Example use

User code:

public sealed partial class MyEffect : CanvasEffect
{
    [GeneratedCanvasEffectProperty]
    public partial int BlurAmount { get; set; }
}

Generated code:

partial class MyEffect : CanvasEffect
{
    public partial int BlurAmount
    {
        get => field;
        set
        {
            if (EqualityComparer<int>.Default.Equals(field, value))
            {
                return;
            }

            int oldValue = field;
    
            OnBlurAmountChanging(value);
            OnBlurAmountChanging(oldValue, value);

            field = value;

            OnBlurAmountChanged(value);
            OnBlurAmountChanged(oldValue, value);
    
            InvalidateEffectGraph(invalidationType);
        }
    }

    partial void OnBlurAmountChanging(int newValue);
    partial void OnBlurAmountChanging(int oldValue, int newValue);
    partial void OnBlurAmountChanged(int newValue);
    partial void OnBlurAmountChanged(int oldValue, int newValue);
}

This should contain any drawbacks for the proposal
that came up during the discussions.

Alternatives

Just do nothing.

Work items

• Refactor existing APIs to be top-level and accessible
• Add attribute type
• Implement generator
• Implement analyzers