Disable gallery cell alpha animation - it was distracting
Refactor GalleryCollectionViewDataSource to a simpler base class, and derive GalleryOverviewCollectionViewDataSource from it
More refactoring - make filterPredicate and sortDescriptors vars on base data source which can be assigned at runtime
Rename GalleryCollectionViewDataSource to BasicGalleryCollectionViewDataSource
Use transparency layers for stroke rendering
Got rid of transparency layer stroke rendering because it didn't fix any problems, and was potentially a performance killer.
Simplified drawing path to use a single bezier curve

does not improve anything, but scratches an itch I had about drawing complexity.
Implement a basic gallery detail view