What is CGContextSetBaseCTM(CGContextRef c, CGAffineTransform afftransform)?

I am interested in knowing that what this private API do CGContextSetBaseCTM(CGContextRef c, CGAffineTransform afftransform) ?

Does it has any relation with the fact that various context synced properly on screen by setting there Base CTM?

I mean I have always wondered开发者_如何学运维, how does the applications/os sync various context to display the various controls on right locations?

Thank you for your time.

CGContextSetBaseCTM(CGContextRef c, CGAffineTransform afftransform) just sets your Base of Current transformation matrix. This is with respect to context. Has no role in other contexts. Window Manager syncs all contents to right location on screen.