mindsnacks/MSCachedAsyncViewDrawing — pull request #6 by jacobjennings (2012-12-06 01:40:37+00:00)
Title: Keep track of in-progress tasks; avoid crash with CGSizeZero

Keep track of in-progress render tasks to avoid duplication of effort for identical cache keys. This optimizes for cases where multiple events for the same cache key might be generated in quick succession before the first render is finished and written to the cache.

A nil image can result from someone sending in CGSizeZero. I think calling completion with the nil image without crashing is a good expected result for that case.