cocoa - CGEventPost - hold a key (shift) -

i'm looking way design little panel modifier keys on (shift, command example) , have possibility click on virtual keyboard.

i'd have behavior :

• click on virtual key (shift).
• the shift button holds, , keeps being pressed.
• type standard keyboard.
• click time on virtual shift key release it.

here code i'm using :

cgeventsourceref source = cgeventsourcecreate(kcgeventsourcestatehidsystemstate); cgeventref shiftkeydown = cgeventcreatekeyboardevent(source, (cgkeycode)56, yes); cgeventref shiftkeyup = cgeventcreatekeyboardevent(source, (cgkeycode)56, no);  cgeventpost(kcgannotatedsessioneventtap, shiftkeydown); cgeventpost(kcgannotatedsessioneventtap, shiftkeyup);  cfrelease(shiftkeyup); cfrelease(shiftkeydown); cfrelease(source); 

i can't find way keep pressed until click on time. though "push on push off" button cell type key unfortunately no. :-)

any ?

thanks in advance.

a shift key virtually pressed way, released automatically when followed event doesn't contain shift flag. seems limitation, or possibly bug, considering documentation sort of indicates otherwise: https://developer.apple.com/reference/coregraphics/cgevent/1456564-init#discussion

the way found achieve looking for, setup event listener, , add shift flag every event should modified shift key.

example on how listen keyboard events: https://stackoverflow.com/a/31898592/1445812 (swift)

example on how had shift flag intercepted events:

event?.flags.insert(.maskshift) 

hope helps. if knows how same without having add flags every event, please tell.