[ios] snap to north if interaction ends within ±7°

[friedbunny]

If a user pinch-rotates and the gesture ends within ±7° of north, reset to north (0°).

This behavior is the same as in MapKit.

First proposed in #938, implemented in #1059, reverted in #1064. (Closes #1064.)

/cc @1ec5

[friedbunny]

Going to leave this convenient iosapp debug code here:

- (void)mapViewRegionIsChanging:(__unused MGLMapView *)mapView
{
    [self updateDirectionDebug];
}
- (void)mapView:(__unused MGLMapView *)mapView regionDidChangeAnimated:(__unused BOOL)animated
{
    [self updateDirectionDebug];
}

- (void)updateDirectionDebug
{
    if (! _directionDebug)
    {
        _directionDebug = [[UILabel alloc] initWithFrame:CGRectMake(250, 100, 100, 50)];
        [self.view addSubview:_directionDebug];
    }

    _directionDebug.text = [NSString stringWithFormat:@"%.2f", self.mapView.direction];
}

[1ec5]

Could this be done as part of -unrotateIfNeededAnimated:?

[friedbunny]

I'm looking into integrating it in -unrotateIfNeededAnimated:. That does get called rather frequently...

[friedbunny]

I went ahead and integrated the snapping with -unrotateIfNeededAnimated:. This will cover more cases and be called more frequently.

I've not copied the delayed animations and disabled user interaction that exists just above in -unrotateIfNeededAnimated: because it does not appear to be necessary.

[1ec5]

What if the developer hides the compass view? Shouldn’t the map view snap to north regardless?

[friedbunny]

Good point, will look at changing this.

[friedbunny]

Ergh, accidentally included iosapp debug code. Will back that out.

[friedbunny]

Rebased and squashed.