Introduced a way to lease the underlying platform graphics context from Skia context (#14652)

* Introduced a way to lease the underlying platform graphics context from Skia context

* API suppression

api/Avalonia.Skia.nupkg.xml

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- https://learn.microsoft.com/en-us/dotnet/fundamentals/package-validation/diagnostic-ids -->
+<Suppressions xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
+  <Suppression>
+    <DiagnosticId>CP0006</DiagnosticId>
+    <Target>M:Avalonia.Skia.ISkiaSharpApiLease.TryLeasePlatformGraphicsApi</Target>
+    <Left>baseline/netstandard2.0/Avalonia.Skia.dll</Left>
+    <Right>target/netstandard2.0/Avalonia.Skia.dll</Right>
+  </Suppression>
+</Suppressions>

src/Skia/Avalonia.Skia/DrawingContextImpl.cs

@@ -99,6 +99,7 @@ namespace Avalonia.Skia
                 private readonly DrawingContextImpl _context;
                 private readonly SKMatrix _revertTransform;
                 private bool _isDisposed;
+                private bool _leased;
 
                 public ApiLease(DrawingContextImpl context)
                 {
@@ -107,11 +108,26 @@ namespace Avalonia.Skia
                     _context._leased = true;
                 }
 
-                public SKCanvas SkCanvas => _context.Canvas;
+                void CheckLease()
+                {
+                    if (_leased)
+                        throw new InvalidOperationException("The underlying graphics API is currently leased");
+                }
+
+                T CheckLease<T>(T rv)
+                {
+                    CheckLease();
+                    return rv;
+                }
+
+                public SKCanvas SkCanvas => CheckLease(_context.Canvas);
+                // GrContext is accessible during the lease since one might want to wrap native resources
+                // Into Skia ones
                 public GRContext? GrContext => _context.GrContext;
-                public SKSurface? SkSurface => _context.Surface;
-                public double CurrentOpacity => _context._currentOpacity;
-                
+                public SKSurface? SkSurface => CheckLease(_context.Surface);
+                public double CurrentOpacity => CheckLease(_context._currentOpacity);
+
+
                 public void Dispose()
                 {
                     if (!_isDisposed)
@@ -121,6 +137,36 @@ namespace Avalonia.Skia
                         _isDisposed = true;
                     }
                 }
+
+                class PlatformApiLease : ISkiaSharpPlatformGraphicsApiLease
+                {
+                    private readonly ApiLease _parent;
+
+                    public PlatformApiLease(ApiLease parent, IPlatformGraphicsContext context)
+                    {
+                        _parent = parent;
+                        _parent.GrContext?.Flush();
+                        Context = context;
+                        _parent._leased = true;
+                    }
+                    
+                    public void Dispose()
+                    {
+                        _parent._leased = false;
+                        _parent.GrContext?.ResetContext();
+                    }
+
+                    public IPlatformGraphicsContext Context { get; }
+                }
+                
+                public ISkiaSharpPlatformGraphicsApiLease? TryLeasePlatformGraphicsApi()
+                {
+                    CheckLease();
+                    if (_context._gpu is ISkiaGpuWithPlatformGraphicsContext gpu &&
+                        gpu.PlatformGraphicsContext is { } context)
+                        return new PlatformApiLease(this, context);
+                    return null;
+                }
             }
         }
         

src/Skia/Avalonia.Skia/Gpu/ISkiaGpu.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using Avalonia.Metadata;
 using Avalonia.Platform;
 using SkiaSharp;
 
@@ -24,6 +25,13 @@ namespace Avalonia.Skia
         /// <param name="session">An optional custom render session.</param>
         ISkiaSurface? TryCreateSurface(PixelSize size, ISkiaGpuRenderSession? session);
     }
+
+    //TODO12: Merge into ISkiaGpu
+    [Unstable]
+    public interface ISkiaGpuWithPlatformGraphicsContext : ISkiaGpu
+    {
+        IPlatformGraphicsContext? PlatformGraphicsContext { get; }
+    }
     
     public interface ISkiaSurface : IDisposable
     {

src/Skia/Avalonia.Skia/Gpu/Metal/SkiaMetalGpu.cs

@@ -2,11 +2,12 @@ using System;
 using System.Collections.Generic;
 using System.Runtime.InteropServices;
 using Avalonia.Metal;
+using Avalonia.Platform;
 using SkiaSharp;
 
 namespace Avalonia.Skia.Metal;
 
-internal class SkiaMetalGpu : ISkiaGpu
+internal class SkiaMetalGpu : ISkiaGpu, ISkiaGpuWithPlatformGraphicsContext
 {
     private SkiaMetalApi _api = new();
     private GRContext? _context;
@@ -31,6 +32,7 @@ internal class SkiaMetalGpu : ISkiaGpu
 
     public bool IsLost => false;
     public IDisposable EnsureCurrent() => _device.EnsureCurrent();
+    public IPlatformGraphicsContext? PlatformGraphicsContext => _device;
 
     public ISkiaGpuRenderTarget? TryCreateRenderTarget(IEnumerable<object> surfaces)
     {

src/Skia/Avalonia.Skia/Gpu/OpenGl/GlSkiaGpu.cs

@@ -10,7 +10,8 @@ using static Avalonia.OpenGL.GlConsts;
 
 namespace Avalonia.Skia
 {
-    internal class GlSkiaGpu : ISkiaGpu, IOpenGlTextureSharingRenderInterfaceContextFeature
+    internal class GlSkiaGpu : ISkiaGpu, IOpenGlTextureSharingRenderInterfaceContextFeature,
+        ISkiaGpuWithPlatformGraphicsContext
     {
         private readonly GRContext _grContext;
         private readonly IGlContext _glContext;
@@ -152,6 +153,7 @@ namespace Avalonia.Skia
 
         public bool IsLost => _glContext.IsLost;
         public IDisposable EnsureCurrent() => _glContext.EnsureCurrent();
+        public IPlatformGraphicsContext? PlatformGraphicsContext => _glContext;
 
         public object? TryGetFeature(Type featureType)
         {

src/Skia/Avalonia.Skia/ISkiaSharpApiLeaseFeature.cs

@@ -1,5 +1,6 @@
 using System;
 using Avalonia.Metadata;
+using Avalonia.Platform;
 using SkiaSharp;
 
 namespace Avalonia.Skia;
@@ -17,4 +18,11 @@ public interface ISkiaSharpApiLease : IDisposable
     GRContext? GrContext { get; }
     SKSurface? SkSurface { get; }
     double CurrentOpacity { get; }
+    ISkiaSharpPlatformGraphicsApiLease? TryLeasePlatformGraphicsApi();
+}
+
+[Unstable]
+public interface ISkiaSharpPlatformGraphicsApiLease : IDisposable
+{
+    IPlatformGraphicsContext Context { get; }
 }