[Question] Issue with IntPtr versus Safehandles in Gdi32.BitBlt

[josdemmers]

I was wondering if I was missing some overload functions or I'm implementing this wrong.
Will first post the relevant code:

public Bitmap GetScreenCapture(IntPtr handle)
{
      Bitmap bitmap;

      PInvoke.RECT region;
      PInvoke.User32.GetWindowRect(handle, out region);
      
      var desktopWindowHandle = PInvoke.User32.GetDesktopWindow();
      var windowDCHandle = PInvoke.User32.GetWindowDC(desktopWindowHandle);
      var memoryDCHandle = PInvoke.Gdi32.CreateCompatibleDC(windowDCHandle);
      var bitmapHandle = PInvoke.Gdi32.CreateCompatibleBitmap(windowDCHandle, region.right - region.left, region.bottom - region.top);
      var bitmapOldHandle = PInvoke.Gdi32.SelectObject(memoryDCHandle, bitmapHandle);

      bool success = PInvoke.Gdi32.BitBlt(memoryDCHandle, 0, 0, region.right - region.left, region.bottom - region.top, windowDCHandle, region.left, region.top, SRCCOPY | CAPTUREBLT);

      try
      {
        bitmap = Image.FromHbitmap(bitmapHandle);
      }
      finally
      {
        PInvoke.Gdi32.SelectObject(memoryDCHandle, bitmapOldHandle);
        PInvoke.Gdi32.DeleteObject(bitmapHandle);
        PInvoke.Gdi32.DeleteDC(memoryDCHandle);
        PInvoke.User32.ReleaseDC(desktopWindowHandle, windowDCHandle);
      }

      return bitmap;
}

The issue is the function BitBlt wants IntPtr as input while the functions GetWindowDC and CreateCompatibleDC both return a SafeDCHandle.
Is there an overload for GetWindowDC and CreateCompatibleDC that return an IntPtr instead? Or can I make BitBlt to somehow accept the SafeDCHandles?

Before using this package I would use the code below. But this package sound really great. Safes a lot of time defining all the windows library functions you want to use.

[DllImport("gdi32.dll")]
public static extern IntPtr CreateCompatibleDC(IntPtr hdc);

[AArnott]

I suspect BitBlt should take SafeDCHandle as well. I'll send a PR to do this.
In the meantime you can always get the IntPtr from a SafeHandle using DangerousGetHandle(). Check the documentation on SafeHandle to learn how to use it safely for this.