WPF + Skia + OpenGL

A proof-of-concept of a GPU-accelerated surface without using WindowsFormsHost

Idea

Create a GL context manually, render all the compute-intensive stuff on an off-screen surface, and draw the result on a WPF-compatible control (in this case SKElement).

Why

SkiaSharp's examples use a WindowsFormsHost control for GPU-accelerated rendering, which uses OpenTK.

There are however a few issues with WindowsFormsHost:

• A window with AllowsTransparency enabled shows no controls - no transparency possible
• Given we can't do AllowsTransparency, setting WindowStyle to None still shows a border
• Airspace problems - things like context menus or DragMove don't work over a forms host

How

Instead of using OpenTK, we're creating a GL context through native calls on opengl32.dll. This code has already been provided in SkiaSharp's test suite:

_glContext = new WglContext();
_glContext.MakeCurrent();

Then, we initialize an offscreen surface as usual:

_grContext = GRContext.Create(GRBackend.OpenGL);
_surface = SKSurface.Create(_grContext, true, new SKImageInfo(width, height));

After drawing on the surface's canvas, we draw the result back on SKElement' canvas:

canvas.DrawSurface(_surface, new SKPoint(0f, 0f));

The surface is disposed and recreated when the SKElement's size changes.