Nested CCLayouts

[haligalaph]

When there are several levels of nested CCLayouts, and the lowest one needs layout, it takes several frames to update the whole hierarchy. The lowest CCLayout will be updated at the first frame, its parent will be updated next frame and so on. Cause of this there are noticeable flickers, that looks bad.
It could be overcome by adding this code into the needsLayout method:

if ([_parent isKindOfClass:[CCLayout class]])
{
    CCLayout* layout = (CCLayout*)_parent;
    [layout needsLayout];
}

But it results in layout method being called two times at one frame for all layouts in hierarchy except the lowest one. To fix this additional member variable called _layoutGuard could be added like this:

// CCLayout.m

- (void) needsLayout
{
    if(!_layoutGuard)
    {
        if ([_parent isKindOfClass:[CCLayout class]])
        {
            CCLayout* layout = (CCLayout*)_parent;
            [layout needsLayout];
        }
        _needsLayout = YES;
    }
}

- (void) layout
{
    _layoutGuard = YES;
    _needsLayout = NO;
}

- (void) layoutDone
{
    _layoutGuard = NO;
}

// CCLayoutBox.m

- (void) layout
{
    [super layout];
   ...
    [self layoutDone];
}

But this is not very good solution in my opinion. Maybe there is a better one.