[ios, macos] Document setting visible coordinates that cross antimeridian #9804

fabian-guerra · 2017-08-18T14:26:42Z

Adds documentation to clarify how to use coordinate bounds that cross the anti-meridian.

1ec5

I think it would be best if we fix this issue in mbgl so that the Android and macOS SDKs also benefit from the fix. mbgl already allows features and shape annotations to straddle the antimeridian by specifying vertices with longitudes beyond ±180°. Can you investigate how that works and adapt Transform to do likewise?

1ec5 · 2017-08-18T17:43:49Z

platform/ios/src/MGLMapView.mm


    mbgl::CameraOptions cameraOptions = _mbglMap->cameraForLatLngs(latLngs, padding);
+
+    if (boundariesCrossDateTime) {


This code base calls it the “antimeridian”, not the “date time”.

1ec5 · 2017-08-18T17:46:05Z

platform/darwin/src/MGLGeometry_Private.h

+
+ @return A coordinate at given fraction. */
+// Ported from http://www.movable-type.co.uk/scripts/latlong.html
+NS_INLINE CLLocationCoordinate2D MGLCLCoordinateAtFraction(CLLocationCoordinate2D origin, CLLocationCoordinate2D destination, double fraction) {


This is a lot of code to inline. Move the body of the function to MGLGeometry.mm.

1ec5 · 2017-08-18T18:07:34Z

Can you investigate how that works and adapt Transform to do likewise?

Actually, it looks like the method affected by this PR uses -cameraForCameraOptions:, so I’d look into whether mbgl::Map::cameraForLatLngs() needs to know how to straddle the antimeridian.

friedbunny · 2017-08-30T18:43:28Z

This seems like good candidate for testing; perhaps in MGLGeometryTests.

fabian-guerra · 2017-09-06T23:22:44Z

@1ec5 I changed the implementation to follow this https://github.com/mapbox/mapbox-gl-native/blob/release-ios-v3.6.0-android-v5.1.0/platform/darwin/src/MGLPolyline.h#L36 that led me to avoid adding new functions.

1ec5 · 2017-09-08T01:48:21Z

platform/ios/src/MGLMapView.mm

@@ -2667,6 +2667,11 @@ - (void)_setVisibleCoordinates:(const CLLocationCoordinate2D *)coordinates count
    {
        latLngs.push_back({coordinates[i].latitude, coordinates[i].longitude});
    }
+
+    if (count == 4 && coordinates[1].longitude > 0 && coordinates[3].longitude < 0) {


This public method is intended to work for an arbitrary number of coordinates.

1ec5 · 2017-09-08T01:51:42Z

platform/ios/src/MGLMapView.mm

@@ -2707,6 +2712,19 @@ - (void)_setVisibleCoordinates:(const CLLocationCoordinate2D *)coordinates count
    [self didChangeValueForKey:@"visibleCoordinateBounds"];
 }

+- (std::vector<mbgl::LatLng>)normalizeCoordinatesForAntimeridianSW:(CLLocationCoordinate2D)sw ne:(CLLocationCoordinate2D)ne
+{
+    CLLocationDegrees longitude = (180 + (180 - fabs(sw.longitude))) * -1;


If I’m not mistaken, the mbgl::LatLngBounds class can handle spanning the antimeridian – that’s how the existing shape annotation functionality is able to handle the antimeridian gracefully. See the mbgl::LatLngBounds::extend() and mbgl::LatLng::unwrapForShortestPath() methods in particular.

fabian-guerra · 2017-09-11T19:17:57Z

@1ec5 Giving a second thought I'm thinking the best solution for this is keep the consistency across our API by adding the proper documentation to setVisibleCoordinateBounds just like https://github.com/mapbox/mapbox-gl-native/blob/release-ios-v3.6.0-android-v5.1.0/platform/darwin/src/MGLPolyline.h#L36 in Polyline we are not responsible for extending the coordinates. Thoughts?

/cc @boundsj

1ec5 · 2017-09-12T01:35:49Z

I’m not sure I follow. That documentation states that MGLPolyline correctly handles straddling the antimeridian on the map as long as you specify some coordinates beyond ±180° longitude. #9731 is about -[MGLMapView setVisibleCoordinateBounds:] fails to straddle the antimeridian and instead shows “the other side” of the world.

fabian-guerra · 2017-09-12T01:53:24Z

What I mean is if devs also set setVisibleCoordinateBounds beyond ±180º it will work.

1ec5 · 2017-09-12T02:09:16Z

Oh, I see what you mean. If setting a coordinate bounds that goes beyond ±180° already works, then that’s great. The remaining issue is whether the developer should get the same behavior by setting a “backwards” coordinate bounds in which sw.longitude > ne.longitude. As long as the ±180° approach works, it isn’t as important to address the remaining issue, at least not while #4664 is still open.

fabian-guerra · 2017-12-14T22:18:01Z

I added the documentation comments to clarify how to use bounds that cross the anti-meridian. We already support extending longitudes beyond ±180°.

1ec5

This is a good change to make, but I don’t think we can say that it fixes #9731 or #4664 per se. Rather, those issues would be addressed like this: the setter would add 360 to ne.longitude if sw.longitude > ne.longitude.

1ec5 · 2017-12-15T05:48:47Z

platform/ios/src/MGLMapView.h

@@ -668,12 +668,24 @@ MGL_EXPORT IB_DESIGNABLE
 Changing the value of this property updates the receiver immediately. If you
 want to animate the change, call `-setVisibleCoordinateBounds:animated:`
 instead.
+
+ To make the visible bounds go across the antimeridian or international date line,
+ specify some longitudes less than −180 degrees or greater than 180 degrees.


This documentation is for a getter, not a setter, so it should talk about what it means to see a longitude beyond ±180°:

If a longitude is less than −180 degrees or greater than 180 degrees, the visible bounds straddles the antimeridian or international date line.

…n usage.

fabian-guerra · 2017-12-15T22:07:35Z

@1ec5 you are right. This PR does not fix #9731 or #4664 per se. Attempts only to clarify how to handle this use case.

fabian-guerra added this to the ios-v3.6.2 milestone Aug 18, 2017

fabian-guerra self-assigned this Aug 18, 2017

fabian-guerra requested review from jfirebaugh and 1ec5 August 18, 2017 14:26

1ec5 reviewed Aug 18, 2017

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kkaefer added the iOS Mapbox Maps SDK for iOS label Aug 21, 2017

fabian-guerra mentioned this pull request Aug 21, 2017

setVisibleCoordinates won't set viewport crossing international dateline #9731

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fabian-guerra modified the milestones: ios-v3.6.3, ios-v3.6.2 Aug 24, 2017

fabian-guerra force-pushed the fabian-visible-coordinates-9731 branch from a01bddc to f76cf3a Compare September 6, 2017 23:19

fabian-guerra changed the title ~~[ios] Fix visible coordinates when boundaries cross international datelline~~ [ios, macos] Fix visible coordinates when boundaries cross international datelline Sep 6, 2017

1ec5 reviewed Sep 8, 2017

View reviewed changes

boundsj removed this from the ios-v3.6.3 milestone Sep 18, 2017

fabian-guerra force-pushed the fabian-visible-coordinates-9731 branch from f76cf3a to 3997c68 Compare October 10, 2017 20:53

fabian-guerra changed the base branch from release-ios-v3.6.0-android-v5.1.0 to release-agua October 10, 2017 20:53

fabian-guerra force-pushed the fabian-visible-coordinates-9731 branch from 3997c68 to ae76552 Compare December 14, 2017 22:12

1ec5 approved these changes Dec 15, 2017

View reviewed changes

[ios] Update visible coordinates documentation to reflect antimeridia…

773b145

…n usage.

fabian-guerra force-pushed the fabian-visible-coordinates-9731 branch from ae76552 to 773b145 Compare December 15, 2017 22:03

fabian-guerra merged commit ff62fa9 into release-agua Dec 21, 2017

fabian-guerra deleted the fabian-visible-coordinates-9731 branch December 21, 2017 20:04

fabian-guerra mentioned this pull request Dec 21, 2017

[macos] Update visible coordinates documentation #10783

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1ec5 changed the title ~~[ios, macos] Fix visible coordinates when boundaries cross international datelline~~ [ios, macos] Document setting visible coordinates that cross international datelline Feb 20, 2018

1ec5 changed the title ~~[ios, macos] Document setting visible coordinates that cross international datelline~~ [ios, macos] Document setting visible coordinates that cross antimeridian Feb 20, 2018

1ec5 mentioned this pull request Feb 20, 2018

[iOS] visibleCoordinateBounds inaccurate when longitude discontinuity around +/-180 is visible on screen #4664

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[ios, macos] Document setting visible coordinates that cross antimeridian #9804

[ios, macos] Document setting visible coordinates that cross antimeridian #9804

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		mbgl::CameraOptions cameraOptions = _mbglMap->cameraForLatLngs(latLngs, padding);

		if (boundariesCrossDateTime) {

[ios, macos] Document setting visible coordinates that cross antimeridian #9804

[ios, macos] Document setting visible coordinates that cross antimeridian #9804

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