[core] Fix querying for annotations near tile boundaries at high zoom.

Fixes issue #12472.
This commit doesn't address the underlying issues that come from symbolAnnotationTree using a slightly lower precision coordinate system than the annotations themselves.
Instead, it just puts a small padding around each tile when it queries for tile data, so that symbols right at the tile boundary will be included in both tiles.
The rendering/querying code will take care of only displaying one instance.
The padding is in global coordinates, so at higher zoom the padding will be larger in tile units -- this is consistent with precision loss also being greater at higher zoom.

6 files changed, 24 insertions, 1 deletions

diff --git a/platform/android/CHANGELOG.md b/platform/android/CHANGELOG.md
index a7113546b5..daef4095f9 100644
--- a/platform/android/CHANGELOG.md
+++ b/platform/android/CHANGELOG.md
@@ -4,6 +4,7 @@ Mapbox welcomes participation and contributions from everyone.  If you'd like to
 
 ## master
 - Don't default-show text/icons that depend on the placement of a paired icon/text [#12483](https://github.com/mapbox/mapbox-gl-native/issues/12483)
+- Fix symbol querying for markers near tile boundaries at high zoom. ([#12472](https://github.com/mapbox/mapbox-gl-native/issues/12472))
 
 ## 6.4.0-beta.1 - August 9, 2018
  - Don't prefetch tiles for geojson sources [#12529](https://github.com/mapbox/mapbox-gl-native/pull/12529)
diff --git a/platform/ios/CHANGELOG.md b/platform/ios/CHANGELOG.md
index cf03852328..e3ad4d5b3e 100644
--- a/platform/ios/CHANGELOG.md
+++ b/platform/ios/CHANGELOG.md
@@ -7,6 +7,7 @@ Mapbox welcomes participation and contributions from everyone. Please read [CONT
 * Improved the Swift interface for `MGLMapView.decelerationRate`. ([#12584](https://github.com/mapbox/mapbox-gl-native/issues/12584))
 * Fixed inconsistencies in exception naming. ([#12583](https://github.com/mapbox/mapbox-gl-native/issues/12583))
 * Don't default-show text/icons that depend on the placement of a paired icon/text [#12483](https://github.com/mapbox/mapbox-gl-native/issues/12483)
+* Fix the behavior of `-[MGLMapView visibleFeaturesAtPoint:]` near tile boundaries at high zoom. ([#12472](https://github.com/mapbox/mapbox-gl-native/issues/12472))
 
 ## 4.3.0
 
diff --git a/platform/macos/CHANGELOG.md b/platform/macos/CHANGELOG.md
index c0266aff5a..1c1454de4d 100644
--- a/platform/macos/CHANGELOG.md
+++ b/platform/macos/CHANGELOG.md
@@ -3,6 +3,7 @@
 # master
 
 - Don't default-show text/icons that depend on the placement of a paired icon/text [#12483](https://github.com/mapbox/mapbox-gl-native/issues/12483)
+- Fix the `-[MGLMapView annotationAtPoint:]` method near tile boundaries at high zoom. ([#12472](https://github.com/mapbox/mapbox-gl-native/issues/12472))
 
 ## Styles and rendering
 
diff --git a/platform/node/CHANGELOG.md b/platform/node/CHANGELOG.md
index 81210ab153..cfb86f4dbf 100644
--- a/platform/node/CHANGELOG.md
+++ b/platform/node/CHANGELOG.md
@@ -1,5 +1,6 @@
 # master
 - Don't default-show text/icons that depend on the placement of a paired icon/text [#12483](https://github.com/mapbox/mapbox-gl-native/issues/12483)
+- Fix symbol querying for annotations near tile boundaries at high zoom. ([#12472](https://github.com/mapbox/mapbox-gl-native/issues/12472))
 - The `Map` constructor now accepts a `mode` option which can be either `"static"` (default) or `"tile"`. It must be set to `"tile"` when rendering individual tiles in order for the symbols to match across tiles.
 - Remove unnecessary memory use when collision debug mode is not enabled ([#12294](https://github.com/mapbox/mapbox-gl-native/issues/12294))
 - Added support for rendering `symbol-placement: line-center` ([#12337](https://github.com/mapbox/mapbox-gl-native/pull/12337))
diff --git a/src/mbgl/annotation/annotation_manager.cpp b/src/mbgl/annotation/annotation_manager.cpp
index 41eedf17dc..1baf83179e 100644
--- a/src/mbgl/annotation/annotation_manager.cpp
+++ b/src/mbgl/annotation/annotation_manager.cpp
@@ -140,7 +140,13 @@ std::unique_ptr<AnnotationTileData> AnnotationManager::getTileData(const Canonic
     auto pointLayer = tileData->addLayer(PointLayerID);
 
     LatLngBounds tileBounds(tileID);
-
+    // Hack for https://github.com/mapbox/mapbox-gl-native/issues/12472
+    // To handle precision issues, query a slightly larger area than the tile bounds
+    // Symbols at a border can be included in vector data for both tiles
+    // The rendering/querying logic will make sure the symbols show up in only one of the tiles
+    tileBounds.extend(LatLng(tileBounds.south() - 0.000000001, tileBounds.west() - 0.000000001));
+    tileBounds.extend(LatLng(tileBounds.north() + 0.000000001, tileBounds.east() + 0.000000001));
+    
     symbolTree.query(boost::geometry::index::intersects(tileBounds),
         boost::make_function_output_iterator([&](const auto& val){
             val->updateLayer(tileID, *pointLayer);
diff --git a/test/api/annotations.test.cpp b/test/api/annotations.test.cpp
index 07257851ac..fea1f87106 100644
--- a/test/api/annotations.test.cpp
+++ b/test/api/annotations.test.cpp
@@ -59,6 +59,18 @@ TEST(Annotations, SymbolAnnotation) {
 //    }
 }
 
+TEST(Annotations, SymbolAnnotationTileBoundary) {
+    // Almost exactly the same as SymbolAnnotation test above, but offset my fractions of a degree
+    // tests precision issue from https://github.com/mapbox/mapbox-gl-native/issues/12472
+    AnnotationTest test;
+    
+    test.map.getStyle().loadJSON(util::read_file("test/fixtures/api/empty.json"));
+    test.map.addAnnotationImage(namedMarker("default_marker"));
+    test.map.addAnnotation(SymbolAnnotation { Point<double>(0.000000000000001, 0.00000000000001), "default_marker" });
+    test.map.setZoom(10);
+    test.checkRendering("point_annotation");
+}
+
 TEST(Annotations, LineAnnotation) {
     AnnotationTest test;
 
@@ -475,3 +487,4 @@ TEST(Annotations, ChangeMaxZoom) {
     test.map.setZoom(test.map.getMaxZoom());
     test.checkRendering("line_annotation_max_zoom");
 }
+