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:(NSOutlineVi         


        

Answer 1

This answer is written with OS X 10.7 in mind, for newer versions of OS X/macOS, refer to WetFish's answer

That method does not get called because it is only relevant for cell based outline views.

In a view based outline view, the disclosure triangle is a regular button in the row view of expandable rows. I don't know where it gets added, but it does, and NSView's didAddSubview: method handles exactly that situation of a view being added somewhere else.

Hence, subclass NSTableRowView, and override didAddSubview:, like this:

-(void)didAddSubview:(NSView *)subview
{
    // As noted in the comments, don't forget to call super:
    [super didAddSubview:subview];

    if ( [subview isKindOfClass:[NSButton class]] ) {
        // This is (presumably) the button holding the 
        // outline triangle button.
        // We set our own images here.
        [(NSButton *)subview setImage:[NSImage imageNamed:@"disclosure-closed"]];
        [(NSButton *)subview setAlternateImage:[NSImage imageNamed:@"disclosure-open"]];
    }
}

Of course, your outline view's delegate will have to implement outlineView:rowViewForItem: to return the new row view.

Despite the name, frameOfOutlineCellAtRow: of NSOutlineView still gets called for view based outline views, so for the positioning of your triangle, you might want to subclass the outline view and override that method, too.