beginModalSession(for:)
Sets up a modal session with the given window and returns a pointer to the NSModalSession structure representing the session.
Declaration
func beginModalSession(for window: NSWindow) -> NSApplication.ModalSessionParameters
- window:
The window for the session.
Return Value
A pointer to the NSModalSession structure that represents the session.
Discussion
In a modal session, the app receives mouse events only if they occur in aWindow. The window is made key, and if not already visible is placed onscreen using the NSWindow method center().
The beginModalSession(for:) method only sets up the modal session. To actually run the session, use runModalSession(_:). beginModalSession(for:) should be balanced by endModalSession(_:). Make sure these two messages are sent within the same exception-handling scope. That is, if you send beginModalSession(for:) inside an NS_DURING construct, you must send endModalSession(_:) before NS_ENDHANDLER.
If an exception is raised, beginModalSession(for:) arranges for proper cleanup. Do not use NS_DURING constructs to send an endModalSession(_:) message in the event of an exception.
A loop using these methods is similar to a modal event loop run with runModal(for:), except the app can continue processing between method invocations.