avoid altering annotation view transforms set by user

[incanus]

I unearthed a bug where trying to set an annotation view transform of your own gets rapidly reset nearly every frame while annotation view center is changing due to the CATransform3DIdentity that is repeatedly set in our setCenter: override.

One case this doesn't cover is when you do have draggable views but still want to set a transform. Perhaps we could create an alternate setter called setCenterDuringAnnotationUpdate: which is called by -[MGLMapView updateAnnotationViews] to bypass any of this drag-related transform setting entirely?

@1ec5 @friedbunny @boundsj

[mention-bot]

@incanus, thanks for your PR! By analyzing this pull request, we identified @boundsj, @1ec5 and @friedbunny to be potential reviewers.

[1ec5]

-updateTransform isn’t about dragging (and is already a no-op while dragging). It’s about scalesWithViewingDistance, which is on by default and which this PR breaks. The method is also set to get more complex once #5245 lands.

[1ec5]

If resetting to CATransform3DIdentity is a problem, one solution would be:

1. Keep track of the CATransform3D that we apply within -updateTransform.
2. Every time we call -updateTransform, reverse the previously-applied transform and apply the new one, without ever resetting to CATransform3DIdentity.

[incanus]

Yeah I am thinking the manual bookkeeping might be necessary. Will keep on this.

[incanus]

I think I fixed things in c0edb62. However @1ec5 I would also appreciate an eye on 51aeb89 to make sure that I didn't lose some intended effect by simply getting rid of the unconditional identify transform there.

[1ec5]

I think that should be OK. Incidentally, CALayer.sublayerTransform seems purpose-made for our intended effect, but it’s iOS 8+ API.

[1ec5]

Also, would you do the honors and update the changelog?

[incanus]

Not sure why Android test is failing, but going to rebase on master and merge this.