c# - Rotating Cursor According to Rotated TextBox

Question

I have a TextBox that I allow my users to rotate. But what I would LOVE for my users is to have their Cursor rotate to the same angle that the TextBox was rotated at. For example, if they rotated the TextBox to 28°, then when the Cursor enters that TextBox the Cursor should also rotate itself to 28°.

Any help at all will be greatly appreciated.

Thank you :)

Answer 1

You can rotate your cursor using the System.Drawing.Icon class from WinForms in combination with WPF's bitmap rotation ability.

The way to do this is to load the icon, convert it to a BitmapSource, use Image and RenderTargetBitmap to rotate it, convert it back to an Icon, save it, and finally update bytes 2, 10, and 11 that make it a .cur instead of a .ico.

Here's what the code looks like:

public Cursor GetRotatedCursor(byte[] curFileBytes, double rotationAngle)
{
  // Load as Bitmap, convert to BitmapSource
  var origStream = new MemoryStream(curFileBytes);
  var origBitmap = new System.Drawing.Icon(origStream).ToBitmap();
  var origSource = System.Windows.Interop.Imaging.CreateBitmapSourceFromHBitmap(origBitmap.GetHBitmap());

  // Construct rotated image
  var image = new Image
  {
    BitmapSource = origSource,
    RenderTransform = new RotateTransform(rotationAngle)
  };

  // Render rotated image to RenderTargetBitmap
  var width = origBitmap.Width;
  var height = origBitmap.Height;
  var resultSource = new RenderTargetBitmap(width, height, 96, 96, PixelFormats.Pbgra32);
  resultSource.Render(image);

  // Convert to System.Drawing.Bitmap
  var pixels = new int[width*height];
  resultSource.CopyPixels(pixels, width, 0);
  var resultBitmap = new System.Drawing.Bitmap(width, height, System.Drawing.Imaging.PixelFormat.Format32bppPargb);
  for(int y=0; y<height; y++)
    for(int x=0; x<width; x++)
      resultBitmap.SetPixel(x, y, Color.FromArgb(pixels[y*width+x]));

  // Save to .ico format
  var resultStream = new MemoryStream();
  new System.Drawing.Icon(resultBitmap.GetHIcon()).Save(resultStream);

  // Convert saved file into .cur format
  resultStream.Seek(2); resultStream.WriteByte(curFileBytes, 2, 1);
  resultStream.Seek(10); resultStream.WriteByte(curFileBytes, 10, 2);
  resultStream.Seek(0);

  // Construct Cursor
  return new Cursor(resultStream);
}

If you want to avoid the loop, you can replace it with a small bit of usafe code to call the System.Drawing.Bitmap constructor that takes initialization data:

  fixed(int* bits = pixels)
  {
    resultBitmap = new System.Drawing.Bitmap(width, height, width, System.Drawing.Imaging.PixelFormat.Format32bppPargb, new IntPtr(bits));
  }

You'll need to call this every time your TextBox rotation changes. This can be done either from the code that rotates your TextBox, or from a PropertyChangedCallback on a value that is bound to the TextBox's rotation.