Graphics Windows GDI Region framergn FillRgn FrameRgn InvertRgn

 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/