Calling setNeedsDisplay:YES on layer-hosting view does not redraw the view

After further research in Apple's sample code of a kiosk-style menu I found out that if you are using a layer-hosting view, you have to take care of the screen updates which are neccessary due to model changes yourself. Calling setNeedsDisplay:YES on the NSView will not do anything.

So what one has to do if one has to update a view one should write a method like reloadData and in it one should call setNeedsDisplayon each CALayer that needs a refresh. I am still not sure if a call to this method on the root layer will propagate through all the children layers but I do not think so.

I solved the problem now by calling setNeedsDisplay on the individual CALayers that needed recaching. It works without problems.

There is also an oft-used practice of having an empty "drawrect", a la -(void) drawRect:(NSRect)dirtyRect {} to help coerce things into drawing, i believe via good ole view.needsDisplay = YES;.

and it should be noted.. that what is indeed happening is that - by saying your NSView *view; is layer.delegate = view; causes the layer to be drawn when [layer setNeedsDisplay]; is called.... via - (void) drawLayer:(CALayer *)layer inContext:(CGContextRef)ctx {...}..

along the same vein... when saying layer.layoutManager = view... subsequent demands that [layer setNeedsLayout]; will be fulfilled only when the - (void) layoutSublayersOfLayer:(CALayer *)layer {..} method is implemented..

These vital concepts are glossed over / strewn about in Apple's docs... and they are really so pivotal to making absolutely anything work at all.