Expose SKBlender

[mattleibow]

Description of Change

SKBlender represents a custom blend function in the Skia pipeline.

When a blender is present in a paint, the BlendMode property is ignored. A blender combines a source color (the result of our paint) and destination color (from the canvas) into a final color.

Bugs Fixed

None.

API Changes

// NEW TYPES

public unsafe class SKBlender : SKObject, ISKReferenceCounted
{
    public static SKBlender CreateBlendMode (SKBlendMode mode);
    public static SKBlender CreateArithmetic (float k1, float k2, float k3, float k4, bool enforcePMColor);
}

public class SKRuntimeBlenderBuilder : SKRuntimeEffectBuilder
{
    public SKRuntimeBlenderBuilder (SKRuntimeEffect effect);
    public SKBlender Build ();
}

// NEW MEMBERS

class SKImageFilter
{
    public static SKImageFilter CreateBlendMode (SKBlender blender, SKImageFilter? background);
    public static SKImageFilter CreateBlendMode (SKBlender blender, SKImageFilter? background, SKImageFilter? foreground);
    public static SKImageFilter CreateBlendMode (SKBlender blender, SKImageFilter? background, SKImageFilter? foreground, SKRect cropRect);
}

class SKPaint
{
    public SKBlender Blender { get; set; }
}

class SKRuntimeEffect
{
    public SKBlender ToBlender ();
    public SKBlender ToBlender (SKRuntimeEffectUniforms uniforms);
    public SKBlender ToBlender (SKRuntimeEffectUniforms uniforms, SKRuntimeEffectChildren children);
}

struct SKRuntimeEffectChild
{
    public SKRuntimeEffectChild (SKBlender blender);
    public SKBlender Blender { get; }
    public static implicit operator SKRuntimeEffectChild (SKBlender blender);
}

class SKShader
{
    public static SKShader CreateBlend (SKBlendMode mode, SKShader shaderA, SKShader shaderB);
    public static SKShader CreateBlend (SKBlender blender, SKShader shaderA, SKShader shaderB);
}

Behavioral Changes

None.

Required skia PR

mono/skia#123

PR Checklist

• Has tests (if omitted, state reason in description)
• Rebased on top of main at time of PR
• Merged related skia PRs
• Changes adhere to coding standard
• Updated documentation

[mattleibow]

/azp run

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