round rect Corner button rectangular region rounded corners Round Border CreateRoundRectRgn rectangular region rounded corners.

  round rect Corner button rectangular region rounded corners Round Border

The CreateRoundRectRgn function creates a rectangular region with rounded corners.
CreatePolyPolygonRgn
CreatePolygonRgn
CreateRectRgn
CreateRectRgnIndirect
DeleteObject
ExtCreateRegion
GetRegionData
Region Functions
Regions Overview
SelectObject

https://stackoverflow.com/questions/11675374/how-to-make-tframe-with-rounded-corners
https://github.com/pauloalvis/Delphi-PraButtonStyle

https://stackoverflow.com/questions/28486521/rounded-edges-in-button-c-sharp-winforms
https://stackoverflow.com/questions/21121968/how-do-i-create-button-with-rounded-corners-edges-on-winform-c
https://stackoverflow.com/questions/5755719/rounded-and-titled-tpanel-in-delphi-7
https://stackoverflow.com/questions/11675374/how-to-make-tframe-with-rounded-corners
https://stackoverflow.com/questions/42345751/firemonkey-hide-overflow-of-round-corners-using-stylebook
https://stackoverflow.com/questions/61159652/is-there-a-way-to-shape-a-button-around-its-picture-in-delphi

wincontrols round rect Corner CreateRoundRectRgn RoundedRadDropDownButton 

https://github.com/project-jedi/jvcl/blob/master/jvcl/run/JvThemes.pas