Too much friction when flicking (short-distance panning) the map

[1ec5]

@lbud showed me today that the way MGLMapView handles panning gestures seems to impede navigation more than MapKit and the Google Maps SDK, as measured by the (very handy!) ease-of-getting-across-town metric. Part of this perception may come from #1258, but we definitely differ from those frameworks in other ways as well.

Here’s the first thing that comes to mind: in Mapbox GL, “flicking” the map doesn’t cause it to travel as far, and it takes a more robust pan gesture to register a flick. Both MapKit and the Google Maps SDK are more sensitive to flicks. The result is that you feel more friction while navigating.

I don’t have a good setup for scientifically comparing our gesture recognition, but in the name of pseudoscience, I positioned an MGLMapView and a MKMapView both so that Twp. Rd. E in Williams Co., OH, is at the bottom at roughly the same zoom level. (This county built roads in a mostly regular grid, numbering north-south roads and lettering east-west roads, surely anticipating this experiment.) In the screen recordings below, 16 downward flicks of roughly the same length and speed sent the MGLMapView north to Co. Rd. I but the MKMapView all the way to SR 34 (which would be J on the grid):

On a device, the same gestures also took the MGLMapView to Co. Rd. I but sent the MKMapView past I-80/90 (roughly O on the grid). Google Maps sped all the way to Co. Rd. S.

It’s important to get this gesture right because it’s probably going to be the most common.

[incanus]

Interesting, I don't use it this way at all, but my gestures are totally influenced by my development!

/cc @mourner, who tweaked our current inertial pan last.

[mourner]

@1ec5 can you try fiddling with the deceleration and ease parameters here? https://github.com/mapbox/mapbox-gl-native/blob/master/platform/ios/MGLMapView.mm#L661 E.g. decreasing deceleration will make it travel further, and changing ease will alter the slowdown curve.

[ljbade]

It would be nice to take the values you end up with here and using them for panning on Android too. Flicking is rather broken on Android currently though.

[1ec5]

I’m continuing to play with the constants, with an eye towards making the map feel as slippery as a UIScrollView. Unfortunately, making the map slipperier exacerbates our low framerate when panning.

[1ec5]

The framerate didn’t turn out to be impacted by 2bc63f7 after all. I was probably seeing minor performance degradation due to increased tile loading from panning farther each time, but it’s pretty smooth overall.