Feature querying ignores antimeridian (was: MGLAnnotationView flickers if annotations are around the antimeridian)

[captainbarbosa]

Platform: iOS
Mapbox SDK version: 3.6.4, 3.7.0-rc.1

When placing MGLAnnotationViews on a map that closely straddle both sides of the antimeridian, the annotations flicker when zooming/panning.

• The issue is not seen if MGLAnnotationViews are replaced with MGLAnnotationImage.
• The issue is not seen if the MGLAnnotationViews reside on one side of the antimeridian.

Steps to trigger behavior

1. Create annotations that straddle the antimeridian on both sides

Coordinates used for annotations:

let coordinates = [CLLocationCoordinate2D(latitude: 28, longitude: -177),
          CLLocationCoordinate2D(latitude: 30.0, longitude: -178.0),
          CLLocationCoordinate2D(latitude: 35.0, longitude: 180.0),
          CLLocationCoordinate2D(latitude: 40.0, longitude: 175.0),
          CLLocationCoordinate2D(latitude: 45.0, longitude: 170.0),
          CLLocationCoordinate2D(latitude: 46.0, longitude: 170.0),
          CLLocationCoordinate2D(latitude: 51, longitude: 175),
          CLLocationCoordinate2D(latitude: 52, longitude: 174)]

2. Zoom/pan map

3. Observe flickering

Expected behavior

MGLAnnotationView should not flicker when zooming and panning on the map.

Actual behavior

MGLAnnotationView flickers when zooming and panning on the map.

[ericdeveloper]

I tested this in 3.7 using a circle and symbol layer to see if we could provide a workaround. While the individual annotations didn't flicker, the entire tiles appeared to flicker at the antimeridian. Trying the same with just the base map displays the same behavior.

[1ec5]

entire tiles appeared to flicker at the antimeridian

@ericdeveloper, I would imagine that’s a separate issue, since it occurs even in the absence of annotations.

[1ec5]

I believe the root cause of the original issue above is that, in mbgl, the assumption is that a bbox straddling the antimeridian would have one side beyond ±180° longitude. But mbgl::TilePyramid::queryRenderedFeatures independently converts each screen coordinate in the query’s bounding polygon to a geographic coordinate:

mapbox-gl-native/src/mbgl/renderer/renderer.cpp

Lines 45 to 54 in 9ed3aea

	return impl->queryRenderedFeatures(
	{
	box.min,
	{box.max.x, box.min.y},
	box.max,
	{box.min.x, box.max.y},
	box.min
	},
	options
	);

mapbox-gl-native/src/mbgl/renderer/tile_pyramid.cpp

Lines 217 to 229 in 9ed3aea

	for (const auto& p : geometry) {
	queryGeometry.push_back(TileCoordinate::fromScreenCoordinate(
	transformState, 0, { p.x, transformState.getSize().height - p.y }).p);
	}
	mapbox::geometry::box<double> box = mapbox::geometry::envelope(queryGeometry);
	std::vector<std::reference_wrapper<const RenderTile>> sortedTiles{ renderTiles.begin(),
	renderTiles.end() };
	std::sort(sortedTiles.begin(), sortedTiles.end(), [](const RenderTile& a, const RenderTile& b) {
	return std::tie(a.id.canonical.z, a.id.canonical.y, a.id.wrap, a.id.canonical.x) <
	std::tie(b.id.canonical.z, b.id.canonical.y, b.id.wrap, b.id.canonical.x);
	});

mbgl::TilePyramid::queryRenderedFeatures needs to add 180° to any converted coordinate that’s on a different hemisphere (has a differently signed longitude) than the first coordinate.

The reason this only affects annotation views is that non-view-backed annotations (MGLAnnotationImage) and symbol layers don’t rely on feature querying to determine whether to show a given marker. But if you were to use feature querying on a symbol layer, for example to implement interactivity, you’d run into the same problem of symbols becoming non-interactive near the antimeridian.

/ref #4664 #9731 mapbox/mapbox-gl-js#2321
/cc @kkaefer

[stale]

This issue has been automatically detected as stale because it has not had recent activity and will be archived. Thank you for your contributions.

[stale]

This issue has been automatically detected as stale because it has not had recent activity and will be archived. Thank you for your contributions.