FrameBuffer _currentFrameBuffer;//default = null, system provide frame buffer
internal CanvasGL2d(int canvasW, int canvasH)
{
this.canvasW = canvasW;
this.canvasH = canvasH;
////setup viewport size
int max = Math.Max(canvasW, canvasH);
////square viewport
orthoView = MyMat4.ortho(0, max, 0, max, 0, 1);
//-----------------------------------------------------------------------
shaderRes = new CanvasToShaderSharedResource();
shaderRes.OrthoView = orthoView;
//-----------------------------------------------------------------------
basicFillShader = new BasicFillShader(shaderRes);
smoothLineShader = new SmoothLineShader(shaderRes);
rectFillShader = new RectFillShader(shaderRes);
gdiImgTextureShader = new GdiImageTextureShader(shaderRes);
gdiImgTextureWithWhiteTransparentShader = new GdiImageTextureWithWhiteTransparentShader(shaderRes);
blurShader = new BlurShader(shaderRes);
glesTextureShader = new OpenGLESTextureShader(shaderRes);
invertAlphaFragmentShader = new InvertAlphaLineSmoothShader(shaderRes); //used with stencil ***
// tessListener.Connect(tess,
//Tesselate.Tesselator.WindingRuleType.Odd, true);
conv3x3TextureShader = new Conv3x3TextureShader(shaderRes);
msdfShader = new DrawingGL.MultiChannelSdf(shaderRes);
msdfSubPixelRenderingShader = new DrawingGL.MultiChannelSubPixelRenderingSdf(shaderRes);
sdfShader = new DrawingGL.SingleChannelSdf(shaderRes);
//----
Tesselator tess = new Tesselator();
tess.WindingRule = Tesselator.WindingRuleType.Odd;
tessTool = new TessTool(tess);
//-----------------------------------------------------------------------
//GL.Enable(EnableCap.CullFace);
//GL.FrontFace(FrontFaceDirection.Cw);
//GL.CullFace(CullFaceMode.Back);
GL.Enable(EnableCap.Blend);
GL.BlendFunc(BlendingFactorSrc.SrcAlpha, BlendingFactorDest.OneMinusSrcAlpha);
GL.ClearColor(1, 1, 1, 1);
//-------------------------------------------------------------------------------
GL.Viewport(0, 0, canvasW, canvasH);
}