func canvasContext(c jquery.JQuery) (x *canvas.Context) { x = canvas.GetContext(c) h := float64(c.Width()) w := float64(c.Height()) x.PixelsPerPoint = screenPixelsPerPoint x.PointsPerPixel = 1 / screenPixelsPerPoint x.Size = r2.XY(h*x.PointsPerPixel, w*x.PointsPerPixel) // Always work in points not pixels. x.Scale(r2.XY1(screenPixelsPerPoint)) return }