I am trying to develop a plug in for motion in Objective-c using the FxPlug template and so far I have been having issues with getting "NSOpenPanel" to be called from a push button in order to get a file dialog window, similar to the "File" generator present in Motion. [paramAPI addPushButtonWithName: @"MIDI file" parameterID: 1 selector: @selector(MIDI_func) parameterFlags: kFxParameterFlag_DEFAULT] I have tried to call NSOpenPanel through "dispatch_async" so that it would run on the main thread and thus not crash but when I press the button it appears not to work - (void)MIDI_func {     NSLog(@"Button pressed");     dispatch_async(dispatch_get_main_queue(), ^{         NSOpenPanel* openDlg = [NSOpenPanel openPanel];         [openDlg setCanChooseFiles:YES];         [openDlg setAllowsMultipleSelection:NO];         [openDlg setCanChooseDirectories:NO];         if ([openDlg runModal] == NSModalResponseOK) {             NSArray* urls = [openDlg URLs];             for(NSInteger i = 0; i < [urls count]; i++ ) {                 NSString* url = [urls objectAtIndex:i];                 NSLog(@"Url: %@", url);             }         }     }); } How can I achieve this or is there a function in the FxPlug SDK that will let me open a file dialog from the host application?