protected override void OnPointerPressed(PointerRoutedEventArgs args)
{
uint id = args.Pointer.PointerId;
Point pt = args.GetCurrentPoint(referencePanel).Position;
if (fingerTouches.ContainsKey(id))
{
fingerTouches.Remove(id);
}
FingerInfo fingerInfo = new FingerInfo
{
LastPosition = new Point(Double.PositiveInfinity, Double.PositiveInfinity),
ThisPosition = pt,
};
fingerTouches.Add(id, fingerInfo);
CapturePointer(args.Pointer);
base.OnPointerPressed(args);
}
// Every 1/60th second, update bitmap with user drawings
bool OnTimerTick()
{
if (bitmap == null)
{
return(true);
}
// Determine the current color.
float tColor = stopwatch.ElapsedMilliseconds % 10000 / 10000f;
fingerPaint.Color = SKColor.FromHsl(360 * tColor, 100, 50);
titleLabel.TextColor = fingerPaint.Color.ToFormsColor();
// Determine the rotation angle.
float tAngle = stopwatch.ElapsedMilliseconds % 5000 / 5000f;
angle = 360 * tAngle;
SKMatrix matrix = SKMatrix.MakeRotationDegrees(-angle, bitmap.Width / 2, bitmap.Height / 2);
// Loop trough the fingers touching the screen.
foreach (long id in idDictionary.Keys)
{
FingerInfo fingerInfo = idDictionary[id];
// Get the canvas size in pixels. It's square so it's only one number.
float canvasSize = 0;
if (canvasView is SKCanvasView)
{
canvasSize = (canvasView as SKCanvasView).CanvasSize.Width;
}
else
{
canvasSize = (canvasView as SKGLView).CanvasSize.Width;
}
// Convert Xamarin.Forms coordinates to pixels for drawing on the bitmap.
// Also, make an offset factor if there's been resizing and the bitmap
// is now larger than the canvas. (It's never smaller.)
float factor = canvasSize / (float)canvasView.Width; // scaling factor
float offset = (bitmapSize - canvasSize) / 2; // bitmap always >= canvas
SKPoint convertedPoint = new SKPoint(factor * (float)fingerInfo.ThisPosition.X + offset,
factor * (float)fingerInfo.ThisPosition.Y + offset);
// Now rotate the point based on the rotation angle
SKPoint pt0 = matrix.MapPoint(convertedPoint);
if (!float.IsPositiveInfinity(fingerInfo.LastPosition.X))
{
// Draw four lines in four quadrants.
SKPoint pt1 = fingerInfo.LastPosition;
bitmapCanvas.DrawLine(pt0.X, pt0.Y, pt1.X, pt1.Y, fingerPaint);
float x0Flip = bitmap.Width - pt0.X;
float y0Flip = bitmap.Height - pt0.Y;
float x1Flip = bitmap.Width - pt1.X;
float y1Flip = bitmap.Height - pt1.Y;
bitmapCanvas.DrawLine(x0Flip, pt0.Y, x1Flip, pt1.Y, fingerPaint);
bitmapCanvas.DrawLine(pt0.X, y0Flip, pt1.X, y1Flip, fingerPaint);
bitmapCanvas.DrawLine(x0Flip, y0Flip, x1Flip, y1Flip, fingerPaint);
}
// Save the current point for next time through.
fingerInfo.LastPosition = pt0;
}
// Redraw the canvas.
if (canvasView is SKCanvasView)
{
(canvasView as SKCanvasView).InvalidateSurface();
}
else
{
(canvasView as SKGLView).InvalidateSurface();
}
return(true);
}
