[ios] Summarize places, roads after zooming with VoiceOver

After zooming, MGLMapView’s accessibility value now indicates the number of visible roads and lists out a few places visible in the current viewport, starting with the features at the highest z-index (not necessarily the largest or the closest to the center of the view). Avoid saying that no annotations are visible.

5 files changed, 127 insertions, 20 deletions

diff --git a/platform/darwin/src/MGLStyle.mm b/platform/darwin/src/MGLStyle.mm
index 52efc7a85a..244fb94ef9 100644
--- a/platform/darwin/src/MGLStyle.mm
+++ b/platform/darwin/src/MGLStyle.mm
@@ -638,7 +638,7 @@ static NSURL *MGLStyleURL_trafficNight;
             self.URL ? [NSString stringWithFormat:@"\"%@\"", self.URL] : self.URL];
 }
 
-#pragma mark Style language preferences
+#pragma mark Mapbox Streets source introspection
 
 - (void)setLocalizesLabels:(BOOL)localizesLabels
 {
@@ -749,4 +749,29 @@ static NSURL *MGLStyleURL_trafficNight;
     }
 }
 
+- (NS_SET_OF(MGLVectorSource *) *)mapboxStreetsSources {
+    return [self.sources objectsPassingTest:^BOOL (__kindof MGLVectorSource * _Nonnull source, BOOL * _Nonnull stop) {
+        return [source isKindOfClass:[MGLVectorSource class]] && source.mapboxStreets;
+    }];
+}
+
+- (NS_ARRAY_OF(MGLStyleLayer *) *)placeStyleLayers {
+    NSSet *streetsSourceIdentifiers = [self.mapboxStreetsSources valueForKey:@"identifier"];
+    
+    NSSet *placeSourceLayerIdentifiers = [NSSet setWithObjects:@"marine_label", @"country_label", @"state_label", @"place_label", @"water_label", @"poi_label", @"rail_station_label", @"mountain_peak_label", nil];
+    NSPredicate *isPlacePredicate = [NSPredicate predicateWithBlock:^BOOL (MGLVectorStyleLayer * _Nullable layer, NSDictionary<NSString *, id> * _Nullable bindings) {
+        return [layer isKindOfClass:[MGLVectorStyleLayer class]] && [streetsSourceIdentifiers containsObject:layer.sourceIdentifier] && [placeSourceLayerIdentifiers containsObject:layer.sourceLayerIdentifier];
+    }];
+    return [self.layers filteredArrayUsingPredicate:isPlacePredicate];
+}
+
+- (NS_ARRAY_OF(MGLStyleLayer *) *)roadStyleLayers {
+    NSSet *streetsSourceIdentifiers = [self.mapboxStreetsSources valueForKey:@"identifier"];
+    
+    NSPredicate *isPlacePredicate = [NSPredicate predicateWithBlock:^BOOL (MGLVectorStyleLayer * _Nullable layer, NSDictionary<NSString *, id> * _Nullable bindings) {
+        return [layer isKindOfClass:[MGLVectorStyleLayer class]] && [streetsSourceIdentifiers containsObject:layer.sourceIdentifier] && [layer.sourceLayerIdentifier isEqualToString:@"road_label"];
+    }];
+    return [self.layers filteredArrayUsingPredicate:isPlacePredicate];
+}
+
 @end
diff --git a/platform/darwin/src/MGLStyle_Private.h b/platform/darwin/src/MGLStyle_Private.h
index 92b08e844b..e5bd79dc02 100644
--- a/platform/darwin/src/MGLStyle_Private.h
+++ b/platform/darwin/src/MGLStyle_Private.h
@@ -14,6 +14,8 @@ namespace mbgl {
 @class MGLAttributionInfo;
 @class MGLMapView;
 @class MGLOpenGLStyleLayer;
+@class MGLVectorSource;
+@class MGLVectorStyleLayer;
 
 @interface MGLStyle (Private)
 
@@ -30,4 +32,11 @@ namespace mbgl {
 
 @end
 
+@interface MGLStyle (MGLStreetsAdditions)
+
+@property (nonatomic, readonly, copy) NS_ARRAY_OF(MGLVectorStyleLayer *) *placeStyleLayers;
+@property (nonatomic, readonly, copy) NS_ARRAY_OF(MGLVectorStyleLayer *) *roadStyleLayers;
+
+@end
+
 NS_ASSUME_NONNULL_END
diff --git a/platform/ios/resources/Base.lproj/Localizable.strings b/platform/ios/resources/Base.lproj/Localizable.strings
index 3f59262d71..815f7a3498 100644
--- a/platform/ios/resources/Base.lproj/Localizable.strings
+++ b/platform/ios/resources/Base.lproj/Localizable.strings
@@ -34,6 +34,9 @@
 /* Accessibility label */
 "INFO_A11Y_LABEL" = "About this map";
 
+/* List separator */
+"LIST_SEPARATOR" = ", ";
+
 /* User-friendly error description */
 "LOAD_MAP_FAILED_DESC" = "The map failed to load because an unknown error occurred.";
 
@@ -46,8 +49,17 @@
 /* Accessibility label */
 "MAP_A11Y_LABEL" = "Map";
 
-/* Map accessibility value */
-"MAP_A11Y_VALUE" = "Zoom %1$dx\n%2$ld annotation(s) visible";
+/* Map accessibility value; {number of visible annotations} */
+"MAP_A11Y_VALUE_ANNOTATIONS" = "%ld annotation(s) visible.";
+
+/* Map accessibility value; {list of visible places} */
+"MAP_A11Y_VALUE_PLACES" = "Places visible: %@.";
+
+/* Map accessibility value; {number of visible roads} */
+"MAP_A11Y_VALUE_ROADS" = "%ld road(s) visible.";
+
+/* Map accessibility value; {zoom level} */
+"MAP_A11Y_VALUE_ZOOM" = "Zoom %dx.";
 
 /* User-friendly error description */
 "PARSE_STYLE_FAILED_DESC" = "The map failed to load because the style is corrupted.";
diff --git a/platform/ios/resources/en.lproj/Localizable.stringsdict b/platform/ios/resources/en.lproj/Localizable.stringsdict
index e849318fe5..435b7bdfe8 100644
--- a/platform/ios/resources/en.lproj/Localizable.stringsdict
+++ b/platform/ios/resources/en.lproj/Localizable.stringsdict
@@ -2,22 +2,26 @@
 <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
 <plist version="1.0">
 <dict>
-	<key>MAP_A11Y_VALUE</key>
+	<key>MAP_A11Y_VALUE_ANNOTATIONS</key>
 	<dict>
 		<key>NSStringLocalizedFormatKey</key>
-		<string>%#@level@
-%#@count@</string>
-		<key>level</key>
+		<string>%#@count@</string>
+		<key>count</key>
 		<dict>
 			<key>NSStringFormatSpecTypeKey</key>
 			<string>NSStringPluralRuleType</string>
 			<key>NSStringFormatValueTypeKey</key>
-			<string>d</string>
+			<string>ld</string>
 			<key>one</key>
-			<string>Zoom %dx</string>
+			<string>%d annotation visible</string>
 			<key>other</key>
-			<string>Zoom %dx</string>
+			<string>%d annotations visible</string>
 		</dict>
+	</dict>
+	<key>MAP_A11Y_VALUE_ROADS</key>
+	<dict>
+		<key>NSStringLocalizedFormatKey</key>
+		<string>%#@count@</string>
 		<key>count</key>
 		<dict>
 			<key>NSStringFormatSpecTypeKey</key>
@@ -25,9 +29,25 @@
 			<key>NSStringFormatValueTypeKey</key>
 			<string>ld</string>
 			<key>one</key>
-			<string>%d annotation visible</string>
+			<string>%d road visible</string>
 			<key>other</key>
-			<string>%d annotations visible</string>
+			<string>%d roads visible</string>
+		</dict>
+	</dict>
+	<key>MAP_A11Y_VALUE_ZOOM</key>
+	<dict>
+		<key>NSStringLocalizedFormatKey</key>
+		<string>%#@level@</string>
+		<key>level</key>
+		<dict>
+			<key>NSStringFormatSpecTypeKey</key>
+			<string>NSStringPluralRuleType</string>
+			<key>NSStringFormatValueTypeKey</key>
+			<string>d</string>
+			<key>one</key>
+			<string>Zoom %dx</string>
+			<key>other</key>
+			<string>Zoom %dx</string>
 		</dict>
 	</dict>
 </dict>
diff --git a/platform/ios/src/MGLMapView.mm b/platform/ios/src/MGLMapView.mm
index ed51754b0a..630688f05a 100644
--- a/platform/ios/src/MGLMapView.mm
+++ b/platform/ios/src/MGLMapView.mm
@@ -43,6 +43,7 @@
 #import "MGLFoundation_Private.h"
 #import "MGLRendererFrontend.h"
 
+#import "MGLVectorSource+MGLAdditions.h"
 #import "NSBundle+MGLAdditions.h"
 #import "NSDate+MGLAdditions.h"
 #import "NSException+MGLAdditions.h"
@@ -2355,8 +2356,53 @@ public:
 
 - (NSString *)accessibilityValue
 {
+    NSMutableArray *facts = [NSMutableArray array];
+    
     double zoomLevel = round(self.zoomLevel + 1);
-    return [NSString stringWithFormat:NSLocalizedStringWithDefaultValue(@"MAP_A11Y_VALUE", nil, nil, @"Zoom %dx\n%ld annotation(s) visible", @"Map accessibility value"), (int)zoomLevel, (long)self.accessibilityAnnotationCount];
+    [facts addObject:[NSString stringWithFormat:NSLocalizedStringWithDefaultValue(@"MAP_A11Y_VALUE_ZOOM", nil, nil, @"Zoom %dx.", @"Map accessibility value; {zoom level}"), (int)zoomLevel]];
+    
+    NSInteger annotationCount = self.accessibilityAnnotationCount;
+    if (annotationCount) {
+        [facts addObject:[NSString stringWithFormat:NSLocalizedStringWithDefaultValue(@"MAP_A11Y_VALUE_ANNOTATIONS", nil, nil, @"%ld annotation(s) visible.", @"Map accessibility value; {number of visible annotations}"), (long)self.accessibilityAnnotationCount]];
+    }
+    
+    NSArray *placeFeatures = self.visiblePlaceFeatures;
+    if (placeFeatures.count) {
+        NSMutableArray *placesArray = [NSMutableArray arrayWithCapacity:placeFeatures.count];
+        NSMutableSet *placesSet = [NSMutableSet setWithCapacity:placeFeatures.count];
+        for (id <MGLFeature> placeFeature in placeFeatures.reverseObjectEnumerator) {
+            NSString *name = [placeFeature attributeForKey:@"name"];
+            if (![placesSet containsObject:name]) {
+                [placesArray addObject:name];
+                [placesSet addObject:name];
+            }
+            if (placesArray.count >= 3) {
+                break;
+            }
+        }
+        NSString *placesString = [placesArray componentsJoinedByString:NSLocalizedStringWithDefaultValue(@"LIST_SEPARATOR", nil, nil, @", ", @"List separator")];
+        [facts addObject:[NSString stringWithFormat:NSLocalizedStringWithDefaultValue(@"MAP_A11Y_VALUE_PLACES", nil, nil, @"Places visible: %@.", @"Map accessibility value; {list of visible places}"), placesString]];
+    }
+    
+    NSArray *roadFeatures = self.visibleRoadFeatures;
+    if (roadFeatures.count) {
+        [facts addObject:[NSString stringWithFormat:NSLocalizedStringWithDefaultValue(@"MAP_A11Y_VALUE_ROADS", nil, nil, @"%ld road(s) visible.", @"Map accessibility value; {number of visible roads}"), roadFeatures.count]];
+    }
+    
+    NSString *value = [facts componentsJoinedByString:@" "];
+    return value;
+}
+
+- (NS_ARRAY_OF(id <MGLFeature>) *)visiblePlaceFeatures
+{
+    NSArray *placeStyleLayerIdentifiers = [self.style.placeStyleLayers valueForKey:@"identifier"];
+    return [self visibleFeaturesInRect:self.bounds inStyleLayersWithIdentifiers:[NSSet setWithArray:placeStyleLayerIdentifiers]];
+}
+
+- (NS_ARRAY_OF(id <MGLFeature>) *)visibleRoadFeatures
+{
+    NSArray *roadStyleLayerIdentifiers = [self.style.roadStyleLayers valueForKey:@"identifier"];
+    return [self visibleFeaturesInRect:self.bounds inStyleLayersWithIdentifiers:[NSSet setWithArray:roadStyleLayerIdentifiers]];
 }
 
 - (CGRect)accessibilityFrame
@@ -2390,14 +2436,9 @@ public:
 {
     if (self.calloutViewForSelectedAnnotation)
     {
-        return 2 /* selectedAnnotationCalloutView, mapViewProxyAccessibilityElement */;
-    }
-    NSInteger count = self.accessibilityAnnotationCount + 2 /* compass, attributionButton */;
-    if (self.userLocationAnnotationView)
-    {
-        count++;
+        return 2 /* calloutViewForSelectedAnnotation, mapViewProxyAccessibilityElement */;
     }
-    return count;
+    return !!self.userLocationAnnotationView + self.accessibilityAnnotationCount + self.visiblePlaceFeatures.count + 2 /* compass, attributionButton */;
 }
 
 - (NSInteger)accessibilityAnnotationCount