CGEventPostToPSN不适用于cgkeycode（56）

CGEventRef e1 = CGEventCreateKeyboardEvent(NULL, (CGKeyCode)55, YES);
CGEventRef e4 = CGEventCreateKeyboardEvent(NULL, (CGKeyCode)0, YES);

CGEventPostToPSN(&spotPSN, e1);
CGEventPostToPSN(&spotPSN, e4);

// virtual key code for letter 'a'
CGKeyCode keycode = 0;

// keyboard event for letter 'a'
CGEventRef event = CGEventCreateKeyboardEvent(NULL, keycode, true);

// modify keyboard event so that it becomes 'command-a'
CGEventSetFlags(event, kCGEventFlagMaskCommand);