[ios] Made annotation views accessible

Annotation views now serve as their own accessibility elements. The developer’s own subclass of MGLAnnotationView can customize the view’s accessibility frame and/or path to more accurately reflect the visual hit target.

4 files changed, 85 insertions, 19 deletions

diff --git a/platform/ios/src/MGLAnnotationContainerView.m b/platform/ios/src/MGLAnnotationContainerView.m
index cd9c990ef0..9a823c839c 100644
--- a/platform/ios/src/MGLAnnotationContainerView.m
+++ b/platform/ios/src/MGLAnnotationContainerView.m
@@ -35,4 +35,18 @@
     }
 }
 
+#pragma mark UIAccessibility methods
+
+- (UIAccessibilityTraits)accessibilityTraits {
+    return UIAccessibilityTraitAdjustable;
+}
+
+- (void)accessibilityIncrement {
+    [self.superview.superview accessibilityIncrement];
+}
+
+- (void)accessibilityDecrement {
+    [self.superview.superview accessibilityDecrement];
+}
+
 @end
diff --git a/platform/ios/src/MGLAnnotationView.mm b/platform/ios/src/MGLAnnotationView.mm
index 6f1d94c3e7..31657dbf4e 100644
--- a/platform/ios/src/MGLAnnotationView.mm
+++ b/platform/ios/src/MGLAnnotationView.mm
@@ -1,6 +1,8 @@
 #import "MGLAnnotationView.h"
 #import "MGLAnnotationView_Private.h"
-#import "MGLMapView.h"
+#import "MGLMapView_Internal.h"
+
+#import "NSBundle+MGLAdditions.h"
 
 #include <mbgl/util/constants.hpp>
 
@@ -103,4 +105,43 @@
     return [super actionForLayer:layer forKey:event];
 }
 
+#pragma mark UIAccessibility methods
+
+- (BOOL)isAccessibilityElement {
+    return !self.hidden;
+}
+
+- (UIAccessibilityTraits)accessibilityTraits {
+    return UIAccessibilityTraitButton | UIAccessibilityTraitAdjustable;
+}
+
+- (NSString *)accessibilityLabel {
+    return [self.annotation respondsToSelector:@selector(title)] ? self.annotation.title : super.accessibilityLabel;
+}
+
+- (NSString *)accessibilityValue {
+    return [self.annotation respondsToSelector:@selector(subtitle)] ? self.annotation.subtitle : super.accessibilityValue;
+}
+
+- (NSString *)accessibilityHint {
+    return NSLocalizedStringWithDefaultValue(@"ANNOTATION_A11Y_HINT", nil, nil, @"Shows more info", @"Accessibility hint");
+}
+
+- (CGRect)accessibilityFrame {
+    CGRect accessibilityFrame = self.frame;
+    CGRect minimumFrame = CGRectInset({ self.center, CGSizeZero },
+                                      -MGLAnnotationAccessibilityElementMinimumSize.width / 2,
+                                      -MGLAnnotationAccessibilityElementMinimumSize.height / 2);
+    accessibilityFrame = CGRectUnion(accessibilityFrame, minimumFrame);
+    return accessibilityFrame;
+}
+
+- (void)accessibilityIncrement {
+    [self.superview accessibilityIncrement];
+}
+
+- (void)accessibilityDecrement {
+    [self.superview accessibilityDecrement];
+}
+
 @end
\ No newline at end of file
diff --git a/platform/ios/src/MGLMapView.mm b/platform/ios/src/MGLMapView.mm
index ee4346f27b..1ad758dc77 100644
--- a/platform/ios/src/MGLMapView.mm
+++ b/platform/ios/src/MGLMapView.mm
@@ -98,7 +98,6 @@ const CGFloat MGLAnnotationImagePaddingForHitTest = 5;
 /// Distance from the callout’s anchor point to the annotation it points to.
 const CGFloat MGLAnnotationImagePaddingForCallout = 1;
 
-/// Minimum size of an annotation’s accessibility element.
 const CGSize MGLAnnotationAccessibilityElementMinimumSize = CGSizeMake(10, 10);
 
 /// Unique identifier representing a single annotation in mbgl.
@@ -2021,6 +2020,13 @@ mbgl::Duration MGLDurationInSeconds(NSTimeInterval duration)
     MGLAnnotationContext &annotationContext = _annotationContextsByAnnotationTag.at(annotationTag);
     id <MGLAnnotation> annotation = annotationContext.annotation;
     
+    // Let the annotation view serve as its own accessibility element.
+    MGLAnnotationView *annotationView = annotationContext.annotationView;
+    if (annotationView && annotationView.superview)
+    {
+        return annotationView;
+    }
+    
     // Lazily create an accessibility element for the found annotation.
     if ( ! annotationContext.accessibilityElement)
     {
@@ -2028,17 +2034,8 @@ mbgl::Duration MGLDurationInSeconds(NSTimeInterval duration)
     }
     
     // Update the accessibility element.
-    MGLAnnotationView *annotationView = annotationContext.annotationView;
-    CGRect annotationFrame;
-    if (annotationView && annotationView.superview)
-    {
-        annotationFrame = [self convertRect:annotationView.bounds fromView:annotationView];
-    }
-    else
-    {
-        MGLAnnotationImage *annotationImage = [self imageOfAnnotationWithTag:annotationTag];
-        annotationFrame = [self frameOfImage:annotationImage.image centeredAtCoordinate:annotation.coordinate];
-    }
+    MGLAnnotationImage *annotationImage = [self imageOfAnnotationWithTag:annotationTag];
+    CGRect annotationFrame = [self frameOfImage:annotationImage.image centeredAtCoordinate:annotation.coordinate];
     CGPoint annotationFrameCenter = CGPointMake(CGRectGetMidX(annotationFrame), CGRectGetMidY(annotationFrame));
     CGRect minimumFrame = CGRectInset({ annotationFrameCenter, CGSizeZero },
                                       -MGLAnnotationAccessibilityElementMinimumSize.width / 2,
@@ -2075,17 +2072,28 @@ mbgl::Duration MGLDurationInSeconds(NSTimeInterval duration)
     {
         return 1;
     }
-    if ( ! [element isKindOfClass:[MGLAnnotationAccessibilityElement class]] &&
-        element != self.attributionButton)
-    {
-        return NSNotFound;
-    }
     
     std::vector<MGLAnnotationTag> visibleAnnotations = [self annotationTagsInRect:self.bounds];
-    if (element == self.attributionButton)
+    
+    MGLAnnotationTag tag = MGLAnnotationTagNotFound;
+    if ([element isKindOfClass:[MGLAnnotationView class]])
+    {
+        id <MGLAnnotation> annotation = [(MGLAnnotationView *)element annotation];
+        tag = [self annotationTagForAnnotation:annotation];
+    }
+    else if ([element isKindOfClass:[MGLAnnotationAccessibilityElement class]])
+    {
+        tag = [(MGLAnnotationAccessibilityElement *)element tag];
+    }
+    else if (element == self.attributionButton)
     {
         return !!self.userLocationAnnotationView + visibleAnnotations.size();
     }
+    else
+    {
+        return NSNotFound;
+    }
+    
     std::sort(visibleAnnotations.begin(), visibleAnnotations.end());
     auto foundElement = std::find(visibleAnnotations.begin(), visibleAnnotations.end(),
                                   ((MGLAnnotationAccessibilityElement *)element).tag);
diff --git a/platform/ios/src/MGLMapView_Internal.h b/platform/ios/src/MGLMapView_Internal.h
index 0538dd0392..6225e11749 100644
--- a/platform/ios/src/MGLMapView_Internal.h
+++ b/platform/ios/src/MGLMapView_Internal.h
@@ -1,5 +1,8 @@
 #import <Mapbox/Mapbox.h>
 
+/// Minimum size of an annotation’s accessibility element.
+extern const CGSize MGLAnnotationAccessibilityElementMinimumSize;
+
 @interface MGLMapView (Internal)
 
 /** Triggers another render pass even when it is not necessary. */