protected override void OnPaint(PaintEventArgs e)
{
if (designMode)
{
e.Graphics.Clear(BackColor);
return;
}
base.OnPaint(e);
MakeCurrent();
// create the contexts if not done already
if (grContext == null)
{
var glInterface = GRGlInterface.CreateDefaultInterface();
grContext = GRContext.CreateGl(glInterface);
}
// get the new surface size
var newSize = new SKSizeI(Width, Height);
// manage the drawing surface
if (renderTarget == null || lastSize != newSize || !renderTarget.IsValid)
{
// create or update the dimensions
lastSize = newSize;
GL.GetInteger(GetPName.FramebufferBinding, out var framebuffer);
GL.GetInteger(GetPName.StencilBits, out var stencil);
GL.GetInteger(GetPName.Samples, out var samples);
var maxSamples = grContext.GetMaxSurfaceSampleCount(colorType);
if (samples > maxSamples)
{
samples = maxSamples;
}
glInfo = new GRGlFramebufferInfo((uint)framebuffer, colorType.ToGlSizedFormat());
// destroy the old surface
surface?.Dispose();
surface = null;
canvas = null;
// re-create the render target
renderTarget?.Dispose();
renderTarget = new GRBackendRenderTarget(newSize.Width, newSize.Height, samples, stencil, glInfo);
}
// create the surface
if (surface == null)
{
surface = SKSurface.Create(grContext, renderTarget, surfaceOrigin, colorType);
canvas = surface.Canvas;
}
using (new SKAutoCanvasRestore(canvas, true))
{
// start drawing
OnPaintSurface(new SKPaintGLSurfaceEventArgs(surface, renderTarget, surfaceOrigin, colorType));
}
// update the control
canvas.Flush();
SwapBuffers();
}