NSOutlineView Changing disclosure Image

Question

I my outline view, i am adding Custom cell, To drawing custom cell, i am referring example code , present in the Cocoa documentation

http://www.martinkahr.com/2007/05/04/nscell-image-and-text-sample/

I want to change the disclosure image of the cell with my custom image, i have tried following things

- (void)outlineView:(NSOutlineView *)outlineView willDisplayCell:(id)cell forTableColumn:(NSTableColumn *)tableColumn item:(id)item 
    {
        if([item isKindOfClass:[NSValue class]])
        {
            MyData *pDt = (MyData *)[item pointerValue];
            if(pDt->isGroupElement())
            {
                [cell setImage:pGroupImage];
            }
        }
}

but that too not working, Is there any other way to change the disclosure image, also how can i find out in willDisplayCell whether Item is expand or collapse, so i can set the image accordingly,

Is this only the place to change the disclosure image ?

Answer 1

A nice way to change the disclosure image is to use a view based outline view:

In your ViewController with NSOutlineViewDelegate:

- (NSView *)outlineView:(NSOutlineView *)outlineView viewForTableColumn:(NSTableColumn *)tableColumn item:(id)item
{
    CustomNSTableCellView *cell    = [outlineView makeViewWithIdentifier:tableColumn.identifier owner:self];
    cell.item                      = item;

    return cell;
}

You have to subclass your NSOutlineView and overide the method:

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

    if ([identifier isEqualToString:NSOutlineViewDisclosureButtonKey])
    {
        // Do your customization
        // return disclosure button view

        [view setImage:[NSImage imageNamed:@"Disclosure_Categories_Plus"]];
        [view setAlternateImage:[NSImage imageNamed:@"Disclosure_Categories_Minus"]];
        [view setBordered:NO];
        [view setTitle:@""];

        return view;
    }

    return view;
}

//Frame of the disclosure view
- (NSRect)frameOfOutlineCellAtRow:(NSInteger)row
{
    NSRect frame = NSMakeRect(4, (row * 22), 19, 19);
    return frame;
}

Answer 2

After researching this issue myself, and trying some of the answers here, I have found that the other approaches mentioned will work, but will require that you perform a lot more manual intervention in order to avoid screen artifacts and other strange behavior.

The simplest solution I found is the following, which should work in most cases.

This solution has the added benefit of the system automatically handling a great many other cases, such as column movement, etc, without your involvement.

- (void)outlineView:(NSOutlineView *)outlineView willDisplayOutlineCell:(id)cell
     forTableColumn:(NSTableColumn *)tableColumn
               item:(id)item
{
    [cell setImage:[NSImage imageNamed: @"Navigation right 16x16 vWhite_tx"]];
    [cell setAlternateImage:[NSImage imageNamed: @"Navigation down 16x16 vWhite_tx"]];
}

In your case, you would wrap this up with your class detection logic, and set the cell images appropriately for your cases.