The NSWindow content view has a supervisor that is an instance of NSThemeFrame. This class is responsible for drawing the title text, background texture of the window / toolbar and contains routines for everything else (close button, full-screen button, NSDocument icon, etc.).
Objective-C NSThemeFrame drawRect: , , .
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: https://github.com/abhibeckert/Dux/blob/master/Dux/DuxProjectWindow.m ( : , DUX_DARK_MODE == 1)
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