NSOutlineView indentation issue

Question

I'm using an NSOutlineView object to represent a file structure and am finding that it will not correctly indent any children which are expandable, though it will indent children that aren't.

Here's a picture to show what I mean:

In this example, "AnotherFolder" is a child of "Folder2" yet it does not indent in line with the other indented files. Curiously enough, the child "AnotherFile.java" of "AnotherFolder" does indent correctly (2 levels in).

I have tried setting properties such as "indentationFollowsCells" to no avail. This seems as though it should be very simple but I can't solve it.

Thanks!

Edit: Some extra information upon request:

I am using the NSOutlineViewDataSource protocol for the implementation, here is the code related to that:

- (id)outlineView:(NSOutlineView *)outlineView objectValueForTableColumn:(NSTableColumn *)tableColumn byItem:(id)item {
    return item;
}

- (id)outlineView:(NSOutlineView *)outlineView child:(NSInteger)index ofItem:(id)item {
    NSMutableDictionary* dict;
    if(item == nil) {
        dict = fileTree;
    } else {
        dict = [((MyFile*) item) children];
    }

    NSArray* keys = [dict allKeys];
    NSArray* sorted = [keys sortedArrayUsingSelector:@selector(compare:)];
    NSString* key = [sorted objectAtIndex:index];
    return [dict objectForKey:key];
}

- (BOOL)outlineView:(NSOutlineView *)outlineView isItemExpandable:(id)item {
    return [[item children] count] > 0;
}

- (NSInteger)outlineView:(NSOutlineView *)outlineView numberOfChildrenOfItem:(id)item {
    if(item == nil) {
        return [fileTree count];
    }
    return [[item children] count];
}

Answer 1

Try changing your outline view from a Source outline view to a normal one.