Graphics Windows GDI Region framergn FillRgn FrameRgn InvertRgn
https://learn.microsoft.com/en-us/windows/win32/gdi/region-functions
https://github.com/wuxc/pywin32doc/blob/master/md/win32gui.md
framergn regions setcapture windowfrompoint ptinregion offsetrgn
https://www.codeproject.com/Articles/1944/Guide-to-WIN32-Regions
https://learn.microsoft.com/en-us/windows/win32/gdi/combining-regions
https://www.codeproject.com/Articles/291/Creating-Holes-in-a-Window
https://www.flipcode.com/archives/Win32_Window_Skinning.shtml
WindowPicker - Pick any window using mouse and highlight window region
https://binaryworld.net/Main/CodeDetail.aspx?CodeId=3753
https://www.codeproject.com/Tips/127813/Using-SetCapture-and-ReleaseCapture-correctly-usua
http://www.flounder.com/setwindowrgn.htm
Custom VCL Control for getting window handles. (Spy++ style reticle) – Chapman World
https://chapmanworld.com/2018/10/04/custom-vcl-control-for-getting-window-handles-spy-style-reticle/
