How to customize disclosure cell in view-based NSOutlineView

Question

I'm trying to customize the disclosure arrow appearance in my view-based NSOutlineView. I saw that it's recommended to use

- (void)outlineView:(NSOutlineView *)outlineView willDisplayOutlineCell:(id)cell forTableColumn:(NSTableColumn *)tableColumn item:(id)item

delegate method to achieve it. The problem is that this method is not called for some reason. I have 2 custom cell views - one for item and second for header item. May be this method is not called for view-based outline views? May be something became broken in Lion?

Please shed some light.

Answer 1

Solution 1:

Subclass NSOutlineView and override makeViewWithIdentifier:owner:

- (id)makeViewWithIdentifier:(NSString *)identifier owner:(id)owner {
    id view = [super makeViewWithIdentifier:identifier owner:owner];

    if ([identifier isEqualToString:NSOutlineViewDisclosureButtonKey]) {
        // Do your customization
    }

    return view;
}

For Source Lists use NSOutlineViewShowHideButtonKey.

Solution 2:

Interface Builder

The button is added to the column and the identifier set to NSOutlineViewDisclosureButtonKey.

Official documentation from NSOutlineView.h

/* The following NSOutlineView*Keys are used by the View Based NSOutlineView to create the "disclosure button" used to collapse and expand items. The NSOutlineView creates these buttons by calling [self makeViewWithIdentifier:owner:] passing in the key as the identifier and the delegate as the owner. Custom NSButtons (or subclasses thereof) can be provided for NSOutlineView to use in the following two ways:
 1. makeViewWithIdentifier:owner: can be overridden, and if the identifier is (for instance) NSOutlineViewDisclosureButtonKey, a custom NSButton can be configured and returned. Be sure to set the button.identifier to be NSOutlineViewDisclosureButtonKey.
 2. At design time, a button can be added to the outlineview which has this identifier, and it will be unarchived and used as needed.
 
 When a custom button is used, it is important to properly set up the target/action to do something (probably expand or collapse the rowForView: that the sender is located in). Or, one can call super to get the default button, and copy its target/action to get the normal default behavior.
 
 NOTE: These keys are backwards compatible to 10.7, however, the symbol is not exported prior to 10.9 and the regular string value must be used (i.e.: @"NSOutlineViewDisclosureButtonKey").
 */
APPKIT_EXTERN NSString *const NSOutlineViewDisclosureButtonKey NS_AVAILABLE_MAC(10_9); // The normal triangle disclosure button
APPKIT_EXTERN NSString *const NSOutlineViewShowHideButtonKey NS_AVAILABLE_MAC(10_9); // The show/hide button used in "Source Lists"