RawImage_FromDevice fails with negative coordinates

• Lazarus/FPC Version: 2.2.4
• Operating System: Windows XP, 7 and 10
• CPU / Bitness: probably both
• BGRABitmap: 11.5.4

Note: this issue was copied from bgrabitmap issue #200. As such it requires BGRABitmap though it could be easily adapter to call RawImage_FromDevice directly. I don't have myself multiple monitors so I can't check. I've notified the original author of the bugreport that a project depending only on LCL would be preferable.

What happens

When trying to get a screenshot of multiple monitors, RawImage_FromDevice fails.

program ScreenshotFailsDemo;
var
  Bitmap: TBGRABitmap;
  ScreenDC: Windows.HDC;
  Rect: TRect;
begin
  Rect.Left   := GetSystemMetrics(SM_XVIRTUALSCREEN);
  Rect.Top    := GetSystemMetrics(SM_YVIRTUALSCREEN);
  Rect.Width  := GetSystemMetrics(SM_CXVIRTUALSCREEN);
  Rect.Height := GetSystemMetrics(SM_CYVIRTUALSCREEN);
  DebugLn('Region: ', DbgS(Rect));

  Bitmap := TBGRABitmap.Create(Rect.Width, Rect.Height, BGRABlack);

  try
    try
      ScreenDC := GetDC(HWND_DESKTOP); // Get DC for all monitors
      DebugLn('Start taking screenshot...');
      Bitmap.LoadFromDevice(ScreenDC, Rect);
      ReleaseDC(0, ScreenDC);
      Bitmap.SaveToFile('screenshot.png');
      DebugLn('Screenshot saved');
    except
      on E: exception do DebugLn('Error: ', e.tostring);
    end;
  finally
    Bitmap.Free;
    ReadLn;
  end;
end.  

It throws Cannot get raw image from device exception when some of Rects values is negative. For example on this display configuration where primary display number 1 located to the right of the number 2:

Program output:

Region: l=-640,t=0,r=1736,b=752
Start taking screenshot...
Error: Exception: Cannot get raw image from device

Another example without error:

Program output:

Region: l=0,t=0,r=2376,b=752
Start taking screenshot...
Screenshot saved

Demo project: ScreenshotFailsDemo.zip

What did you expect

That the whole desktop would be captured.

A workaround was found in AutoScreenshot project.

Steps to reproduce

Run the test project.