deleting many pages with many scraps quickly will crash in [JotGLContext presentRenderBuffer:]

[adamwulf]

Found another issue while working on #939

1. load up the 100 pages of small data set
2. launch + list view
3. delete pages one after another quickly.
4. after ~10 or 20 pages => crash

currently testing on iOS7, not sure about ios8

[adamwulf]

@heatherwong can you repro this?

related/dup of #940, #524, and others

[adamwulf]

seems to happen when presenting a render buffer of one context while another is loading stroke/texture data. especially when loading texture during CGContextClearRect() in JotGLTexture.m. i'll keep reproving to double check

[heatherwong]

I have seen that before, but not always reproducible.

[adamwulf]

just happened in same JotGLTexture file, but at glTexImage2D instead of CGContextClearRect.

it's never been easily reproduced for me in the past, but the above AT is doing the trick for me tonight

[heatherwong]

I was able to repro. I think it's more consistent to repro when you start each row with page with many scraps and delete them quickly. page with less scrap not as easy to crash app.

[adamwulf]

current research suggests its the JotGLTextureBackedFrameBuffer not cleaning up the context properly after use. still working on it...

[adamwulf]

got it narrowed down to how the texture backed frame buffer clears its contents when loading state on a background thread. gotta head to bed though, i'll tackle tomorrow (*today)

[adamwulf]

still tracking, looks like its how the backing texture frame buffer is used in drawBackingTexture:atP1:...

[adamwulf]

BOOM.

this bug was a killer. i'm 99.9% sure i've got it fixed. AT:

1. load up 100 small scrapped pages
2. list view
3. delete over and over and over
4. no more crash from [JotView presentRenderBuffer]

however, now i'm getting a crash from running out of memory, there's a leak somewhere when deleting all the pages. opened up a new issue for that one: #953

[heatherwong]

verify block by #956

[heatherwong]

verified in RC8