OpenGL-accelerated Skia drawing for Win32/GTK backends

[kekekeks]

Differencies from #1917

• While being platform-agnostic allows calling OpenGL-functions
• Actual implementations for Win32/GTK via EGL/ANGLE
• Proper separation of display, context and surface
• Separate OpenGL-context for UI-thread drawing (RenderTargetBitmap is hw-accelerated)
• No hardcode for stencil size and sample count

[jmacato]

This really is a game-changer! It handles animations with ease

I was testing with RenderDemo & ImmediateRenderer and sometimes it crashes whenever i click on Tabs/Menu. this was the stack trace:

WARNING: failed to attach stencil buffer for clip mask. Clip will be ignored.

Unhandled Exception: System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.NullReferenceException: Object reference not set to an instance of an object.
   at Avalonia.Controls.Platform.DefaultMenuInteractionHandler.PointerReleased(Object sender, PointerReleasedEventArgs e) in {avaloniaDir}/src/Avalonia.Controls/Platform/DefaultMenuInteractionHandler.cs:line 334
   --- End of inner exception stack trace ---
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor, Boolean wrapExceptions)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at System.Delegate.DynamicInvokeImpl(Object[] args)
   at Avalonia.Interactivity.Interactive.RaiseEventImpl(RoutedEventArgs e) in {avaloniaDir}/src/Avalonia.Interactivity/Interactive.cs:line 199
   at Avalonia.Interactivity.Interactive.BubbleEvent(RoutedEventArgs e) in {avaloniaDir}/src/Avalonia.Interactivity/Interactive.cs:line 158
   at Avalonia.Interactivity.Interactive.RaiseEvent(RoutedEventArgs e) in {avaloniaDir}/src/Avalonia.Interactivity/Interactive.cs:line 141
   at Avalonia.Input.MouseDevice.MouseUp(IMouseDevice device, IInputRoot root, Point p, MouseButton button, InputModifiers inputModifiers) in {avaloniaDir}/src/Avalonia.Input/MouseDevice.cs:line 247
   at Avalonia.Input.MouseDevice.ProcessRawEvent(RawMouseEventArgs e) in {avaloniaDir}/src/Avalonia.Input/MouseDevice.cs:line 132
   at Avalonia.Input.MouseDevice.ProcessRawEvent(RawInputEventArgs e) in {avaloniaDir}/src/Avalonia.Input/MouseDevice.cs:line 104
   at Avalonia.Input.InputManager.ProcessInput(RawInputEventArgs e) in {avaloniaDir}/src/Avalonia.Input/InputManager.cs:line 38
   at Avalonia.Controls.TopLevel.HandleInput(RawInputEventArgs e) in {avaloniaDir}/src/Avalonia.Controls/TopLevel.cs:line 350
   at Avalonia.Gtk3.WindowBaseImpl.<>c__DisplayClass94_0.<OnInput>b__0() in {avaloniaDir}/src/Gtk/Avalonia.Gtk3/WindowBaseImpl.cs:line 400
   at Avalonia.Threading.JobRunner.Job.Avalonia.Threading.JobRunner.IJob.Run() in {avaloniaDir}/src/Avalonia.Base/Threading/JobRunner.cs:line 169
   at Avalonia.Threading.JobRunner.RunJobs(Nullable`1 priority) in {avaloniaDir}/src/Avalonia.Base/Threading/JobRunner.cs:line 40
   at Avalonia.Gtk3.Gtk3Platform.<>c__DisplayClass28_0.<Signal>b__0() in {avaloniaDir}/src/Gtk/Avalonia.Gtk3/Gtk3Platform.cs:line 108
   at Avalonia.Gtk3.Interop.GlibTimeout.Handler(IntPtr data) in {avaloniaDir}/src/Gtk/Avalonia.Gtk3/Interop/GlibTimeout.cs:line 12
   at Avalonia.Gtk3.Gtk3Platform.RunLoop(CancellationToken cancellationToken) in {avaloniaDir}/src/Gtk/Avalonia.Gtk3/Gtk3Platform.cs:line 81
   at Avalonia.Threading.Dispatcher.MainLoop(CancellationToken cancellationToken) in {avaloniaDir}/src/Avalonia.Base/Threading/Dispatcher.cs:line 64
   at Avalonia.Application.Run(Window mainWindow) in {avaloniaDir}/src/Avalonia.Controls/Application.cs:line 259
   at Avalonia.Controls.AppBuilderBase`1.Start[TMainWindow](Func`1 dataContextProvider) in {avaloniaDir}/src/Avalonia.Controls/AppBuilderBase.cs:line 128
   at RenderDemo.App.Main(String[] args) in {avaloniaDir}/samples/RenderDemo/App.xaml.cs:line 19

[kekekeks]

I don't think that the crash is related to OpenGL changes. The stencil warning is a bit concerning though.

[jmacato]

@kekekeks yeah, it's repeating that warning over and over when the rotating geometry clipped animation is running

[danwalmsley]

A few nits, let me know if you want me to do the fixes

[danwalmsley]

NIT: 1 class / interface per file

[danwalmsley]

NIT: 1 interface per file

[danwalmsley]

I think the only functional change required now is to make it disabled by default, so that we can add this to 0.7 release and people who want to test it can, but existing code wont potentially be exposed to any issues in gpu rendering we don't yet know about.

[danwalmsley]

LGTM great work :)