/* GrandPerspective, Version 2.5.4 
 *   A utility for Mac OS X that graphically shows disk usage. 
 * Copyright (C) 2005-2020, Erwin Bonsma 
 * 
 * This program is free software; you can redistribute it and/or modify it 
 * under the terms of the GNU General Public License as published by the Free 
 * Software Foundation; either version 2 of the License, or (at your option) 
 * any later version. 
 * 
 * This program is distributed in the hope that it will be useful, but WITHOUT 
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for 
 * more details. 
 * 
 * You should have received a copy of the GNU General Public License along 
 * with this program; if not, write to the Free Software Foundation, Inc., 
 * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA. 
 */

#import "NotifyingPanel.h"


NSString  *FirstResponderChangedEvent = @"firstResponderChanged";


@interface NotifyingPanel (PrivateMethods) 

- (void) windowFirstResponderChanged_:(NSNotification *)notification;

@end


@implementation NotifyingPanel

// Overrides designated initialiser
- (instancetype)initWithContentRect:(NSRect)contentRect
                          styleMask:(NSWindowStyleMask)styleMask
                            backing:(NSBackingStoreType)backingType
                              defer:(BOOL)flag {
  if (self = [super initWithContentRect: contentRect
                              styleMask: styleMask
                                backing: backingType
                                  defer: flag]) {
    [[NSNotificationCenter defaultCenter] addObserver: self
                                             selector: @selector(windowFirstResponderChanged_:)
                                                 name: FirstResponderChangedEvent
                                               object: self];
  }
  return self;
}


- (BOOL) makeFirstResponder:(NSResponder *)aResponder {
  BOOL  retVal = [super makeFirstResponder: aResponder];

  // Note: Using notification queue here to exploit coalescing behaviour. Sometimes a single click
  // can trigger multiple calls to makeFirstResponder. This is for instance the case when clicking
  // on an instance of NSBrowser. In this case it's nice to only call the delegate once, instead of
  // multiple times.
  //
  // Note: We should never call the delegate directly from here. The OS should be given time to
  // finish changing the first responder; there's still more to do after -makeFirstResponder: gets
  // called. So we should either post the notification via the notification queue with a posting
  // style of NSPostASAP (as is done here). Or alternatively, call the delegate method with
  // -performSelector:withObject:afterDelay:0. [Source: post on Apple Mailing list by Dustin Voss,
  // dd. 30 Mar 2004].

  NSNotification  *notification = [NSNotification notificationWithName: FirstResponderChangedEvent
                                                                object: self];

  [[NSNotificationQueue defaultQueue] enqueueNotification: notification
                                             postingStyle: NSPostASAP
                                             coalesceMask: (NSNotificationCoalescingOnName |
                                                            NSNotificationCoalescingOnSender)
                                                 forModes: nil];

  return retVal;
}


- (void) windowFirstResponderChanged:(NSNotification *)notification {
  // void - can be overridden.
}

@end


@implementation NotifyingPanel (PrivateMethods)

- (void) windowFirstResponderChanged_:(NSNotification *)notification {
  SEL  sel = @selector(windowFirstResponderChanged:);
  id  target = [self.delegate respondsToSelector: sel] ? self.delegate : self;

  // Notify the delegate (if it exists and has implemented the method). 
  // Otherwise just call own method, which can then be overriden if need be.
  [target performSelector: sel withObject: notification];
}

@end
