Validating fonts and colors NSToolbarItem items

Using Cocoa with latest SDK on OSX 10.6.6

I have an NSToolbar with custom toolbar items and also the built in fonts and colors NSToolbarItem items (NSToolbarShowFontsItem and NSToolbarShowColorsItem identifiers).

I need to be able to enable/disable those in various situations. Problem is validateToolbarItem: is never called for these items (it is being called for my other toolbar items).

The documentation is not very clear about this:

The toolbar automatically takes care of dark开发者_开发技巧ening an image item when it is clicked and fading it when it is disabled. All your code has to do is validate the item. If an image item has a valid target/action pair, then the toolbar will call NSToolbarItemValidation’s validateToolbarItem: on target if the target implements it; otherwise the item is enabled by default.

I don't explicitly set target/action for these two toolbar items, I want to use their default behavior. Does it mean I can't validate these items? Or is there any other way I can do this?

Thanks.

After some trial and error, I think I was able to figure this out and find a reasonable workaround. I will post a quick answer here for future reference for others facing the same problem.

This is just one more of Cocoa's design flaws. NSToolbar has a hardcoded behavior to set the target/action for NSToolbarShowFontsItem and NSToolbarShowColorsItem to NSApplication so as the documentation hints it will never invoke validateToolbarItem: for these NSToolbarItem items.

If you need those toolbar items validated, the trivial thing to do is not to use the default fonts/colors toolbar items but to roll your own, calling the same NSApplication actions (see below).

If using the default ones, it is possible to redirect the target/action of them to your object and then invoke the original actions

- (void) toolbarWillAddItem:(NSNotification *)notification {
  NSToolbarItem *addedItem = [[notification userInfo] objectForKey: @"item"];
  if([[addedItem itemIdentifier] isEqual: NSToolbarShowFontsItemIdentifier]) {                
    [addedItem setTarget:self];
    [addedItem setAction:@selector(toolbarOpenFontPanel:)];
  } else if ([[addedItem itemIdentifier] isEqual: NSToolbarShowColorsItemIdentifier]) {
    [addedItem setTarget:self];
    [addedItem setAction:@selector(toolbarOpenColorPanel:)];
  }
} 

Now validateToolbarItem: will be called:

- (BOOL)validateToolbarItem:(NSToolbarItem *)theItem {
  //validate item here
}

And here are the actions that will be invoked:

-(IBAction)toolbarOpenFontPanel:(id)sender {
  [NSApp orderFrontFontPanel:sender];
}

-(IBAction)toolbarOpenColorPanel:(id)sender {
  [NSApp orderFrontColorPanel:sender];
}

I guess the engineers who designed this never thought one would want to validate fonts/colors toolbar items. Go figure.