Switch to Span<T> or ReadOnlySpan<T>

[mattleibow]

Description

Part of #2615

The SkiaSharp codebase is quite old and existed before the introduction of spans. (See more https://learn.microsoft.com/en-us/dotnet/standard/memory-and-spans/memory-t-usage-guidelines)

Current files in the core binding using arrays:

• Definitions.cs
• GRGlInterface.cs
• GRVkExtensions.cs
• SKBitmap.cs
• SKCanvas.cs
• SKCodec.cs
• SKColorFilter.cs
• SKColorSpace.cs
• SKColorSpaceStructs.cs
• SKData.cs
  • Start using spans instead of arrays #2617
  • public byte[] ToArray () is intentially an array, there is:
    • public ReadOnlySpan<byte> AsSpan ()
    • public Span<byte> Span { get; }
• SKFont.cs
• SKFontManager.cs
• SKFrontBufferedManagedStream.cs
• SKFrontBufferedStream.cs
• SKImage.cs
  • Start using spans instead of arrays #2617
• SKManagedStream.cs
• SKManagedWStream.cs
• SKMaskFilter.cs
• SKMatrix.cs
• SKMatrix44.cs
• SKObject.cs
• SKPMColor.cs
• SKPaint.cs
• SKPath.cs
• SKPathEffect.cs
  • Start using spans instead of arrays #2617
• SKRoundRect.cs
  • Start using spans instead of arrays #2617
  • public SKPoint[] Radii { get; } still exists as it is a convenience and this is accessible using non-arrays by querying each corner individually (which is what this property does)
• SKRuntimeEffect.cs
• SKShader.cs
• SKStream.cs
• SKString.cs
• SKTextBlob.cs
• SKTypeface.cs
• SKVertices.cs
• SkiaApi.generated.cs
• Util.cs

NOTE: not all usages are bad. There are cases where returning an array is acceptable because we have span alternatives, or the data is best contained in an array.

[xoofx]

Hey Matthew, I'm currently prototyping with Avalonia, and there are plenty of places in the code where Avalonia allocates a lot because there are missing Span APIs in SkiaSharp.

Would it be ok If I was making a single PR to bring Span for all existing APIs? I haven't checked how much work it could be but I see that there are some pending PR that did some parts, so wondering why they are not merged? Or I could do all of them in one go.

Let me know. ☺️

[xoofx]

Actually #2669 is maybe covering what is left so I will followup with this issue.