Performance regression from pre-3 to pre-8

[parrots]

Pre-3 fixed the flickering issue for adding/removing annotations on iOS, and the performance was stellar. A matter of milliseconds to make annotation changes and see them in the UI.

Using pre-8 (may have happened earlier, haven't updated since pre-3) annotation changes now take ~1 second to reflect in the UI. There is no flickering or main-thread hanging, that's still all good, but the redraw now takes over a second to complete async.

[parrots]

From @incanus via email conversations: I bet it’s related to 656cb4c

[1ec5]

A rebase will say for sure, but #2951 is also a possibility.

[incanus]

I'm definitely seeing this in @parrots's app using 3.0.0-pre.8. Working on profiling now.

[incanus]

And definitely still not seeing the problem with 3.0.0-pre.3 on the same codebase.

[incanus]

Simply moving 656cb4c back to enableSetNeedsDisplay = YES and having invalidate call setNeedsDisplay again is enough to make this go away, so it does seem to be related to 656cb4c / CADisplayLink.

Trying to figure out what update case we're missing here and how to fix it.

/cc @adam-mapbox

[incanus]

Ah! The CADisplayLink is only added to NSDefaultRunLoopMode, but scrolling animations and such by Apple block that run loop so that normal activities suspend and scrolls are performant.

[incanus]

We need UITrackingRunLoopMode as well.

http://stackoverflow.com/questions/7551411/uiscrollview-blocks-run-loop
http://stackoverflow.com/questions/12622800/why-does-uiscrollview-pause-my-cadisplaylink

[incanus]

NAILED IT

👉 #3072

[incanus]

Merged #3072 into release branch & cherry-picked to master.