initial featuresAt implementation

include/mbgl/ios/MGLMapView.h

@@ -82,6 +82,13 @@ IB_DESIGNABLE
 /** The button shown in the lower-right of the map which when pressed displays the map attribution information. */
 @property (nonatomic, readonly) UIButton *attributionButton;
 
+/** Query the visible map for features at a given point. 
+*
+*   @param point A point on screen, for example at a user gesture.
+*   @param radius A distance in which to query features around the point.
+*   @return An array of `NSDictionary` objects representing features near the point. Keys and values provided include `MGLFeatureLayerNameKey` for the feature layer name in the active style, `MGLFeatureSourceNameKey` for the feature source name in the active style, and `MGLFeaturePropertiesKey` containing a dictionary of properties of the feature from the source data as `NSString` keys and values. */
+- (NS_ARRAY_OF(NSDictionary *) *)featureDescriptionsAtPoint:(CGPoint)point radius:(CGFloat)radius;
+
 #pragma mark - Accessing the Delegate
 
 /** @name Accessing the Delegate */

include/mbgl/ios/MGLTypes.h

@@ -26,6 +26,15 @@ typedef NS_ENUM(NSUInteger, MGLUserTrackingMode) {
     MGLUserTrackingModeFollowWithCourse,
 };
 
+/** The style layer name for a queried map feature. */
+extern NSString * const MGLFeatureLayerNameKey;
+
+/** The style source name for a queried map feature. */
+extern NSString * const MGLFeatureSourceNameKey;
+
+/** The properties from the source data for a queried map feature. */
+extern NSString * const MGLFeaturePropertiesKey;
+
 NS_ASSUME_NONNULL_END
 
 #pragma clang diagnostic push

include/mbgl/map/map.hpp

@@ -7,6 +7,7 @@
 #include <mbgl/util/geo.hpp>
 #include <mbgl/util/noncopyable.hpp>
 #include <mbgl/util/vec.hpp>
+#include <mbgl/util/interactive_features.hpp>
 #include <mbgl/annotation/annotation.hpp>
 
 #include <cstdint>
@@ -159,6 +160,9 @@ class Map : private util::noncopyable {
     LatLngBounds getBoundsForAnnotations(const AnnotationIDs&);
     double getTopOffsetPixelsForAnnotationSymbol(const std::string&);
 
+    // Features
+    std::vector<FeatureDescription> featureDescriptionsAt(const PrecisionPoint, const uint16_t radius = 0) const;
+
     // Sprites
     void setSprite(const std::string&, std::shared_ptr<const SpriteImage>);
     void removeSprite(const std::string&);

include/mbgl/util/interactive_features.hpp

@@ -0,0 +1,20 @@
+#ifndef MBGL_UTIL_INTERACTIVE_FEATURES
+#define MBGL_UTIL_INTERACTIVE_FEATURES
+
+#include <map>
+#include <string>
+
+namespace mbgl {
+
+struct FeatureDescription {
+    inline explicit FeatureDescription(std::string layer_, std::string source_, std::map<std::string, std::string>properties_)
+    : layer(layer_), source(source_), properties(properties_) {}
+
+    std::string layer;
+    std::string source;
+    std::map<std::string, std::string> properties;
+};
+
+}
+
+#endif

ios/app/MBXViewController.mm

@@ -11,6 +11,8 @@ @interface MBXViewController () <UIActionSheetDelegate, MGLMapViewDelegate>
 
 @property (nonatomic) MGLMapView *mapView;
 @property (nonatomic) NSUInteger styleIndex;
+@property (nonatomic) UIView *interactiveShield;
+@property (nonatomic) UITextView *featuresView;
 
 @end
 
@@ -139,6 +141,7 @@ - (void)showSettings
                                                                 @"Add 10,000 Points",
                                                                 @"Add Test Shapes",
                                                                 @"Remove Annotations",
+                                                                @"Enable Interactivity",
                                                                 nil];
 
     [sheet showFromBarButtonItem:self.navigationItem.leftBarButtonItem animated:YES];
@@ -245,6 +248,35 @@ - (void)actionSheet:(UIActionSheet *)actionSheet didDismissWithButtonIndex:(NSIn
     {
         [self.mapView removeAnnotations:self.mapView.annotations];
     }
+    else if (buttonIndex == actionSheet.firstOtherButtonIndex + 9)
+    {
+        if ([self.mapView.styleURL.scheme isEqualToString:@"mapbox"])
+        {
+            self.mapView.userInteractionEnabled = NO;
+
+            self.interactiveShield = [[UIView alloc] initWithFrame:self.mapView.frame];
+            self.interactiveShield.backgroundColor = [UIColor clearColor];
+            self.interactiveShield.userInteractionEnabled = YES;
+            [self.view insertSubview:self.interactiveShield aboveSubview:self.mapView];
+
+            UIPanGestureRecognizer *pan = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handleInteractivityPan:)];
+            [self.interactiveShield addGestureRecognizer:pan];
+
+            self.featuresView = [[UITextView alloc] initWithFrame:CGRectMake(20, self.topLayoutGuide.length + 20,
+                self.view.bounds.size.width / 2 - 40, self.view.bounds.size.height * 2 / 3)];
+            self.featuresView.font = [UIFont systemFontOfSize:10];
+            self.featuresView.backgroundColor = [UIColor whiteColor];
+            self.featuresView.alpha = 0.75;
+            self.featuresView.text = @"Moving the map is now disabled until you change the style. Pan with your finger to query for features.";
+
+            [self.view addSubview:self.featuresView];
+
+            self.mapView.styleURL = [NSURL URLWithString:@"asset://streets-interactive-poi-v8.json"];
+
+            [(UIButton *)self.navigationItem.titleView setTitle:@"Interactive Streets" forState:UIControlStateNormal];
+        }
+
+    }
 }
 
 - (void)parseFeaturesAddingCount:(NSUInteger)featuresCount
@@ -306,8 +338,71 @@ - (void)handleLongPress:(UILongPressGestureRecognizer *)longPress
     }
 }
 
+- (void)handleInteractivityPan:(UIPanGestureRecognizer *)pan
+{
+    if (pan.state == UIGestureRecognizerStateBegan || pan.state == UIGestureRecognizerStateChanged)
+    {
+        self.featuresView.userInteractionEnabled = NO;
+
+        CGPoint point = [pan locationInView:pan.view];
+
+        NSArray *features = [self.mapView featureDescriptionsAtPoint:point radius:50];
+
+        if ([features count])
+        {
+            NSMutableString *output = [NSMutableString string];
+
+            for (NSDictionary *feature in features)
+            {
+                [output appendString:@"Layer: "];
+                [output appendString:[feature objectForKey:MGLFeatureLayerNameKey]];
+                [output appendString:@"\n"];
+
+                [output appendString:@"Source: "];
+                [output appendString:[feature objectForKey:MGLFeatureSourceNameKey]];
+                [output appendString:@"\n"];
+
+                NSDictionary *properties = [feature objectForKey:MGLFeaturePropertiesKey];
+
+                for (NSString *key in [properties allKeys])
+                {
+                    [output appendString:@"{"];
+                    [output appendString:key];
+                    [output appendString:@"}: "];
+                    [output appendString:properties[key]];
+                    [output appendString:@"\n"];
+                }
+
+                [output appendString:@"\n"];
+            }
+
+            self.featuresView.text = output;
+            self.featuresView.contentOffset = CGPointZero;
+        }
+        else
+        {
+            self.featuresView.text = nil;
+        }
+    }
+    else
+    {
+        self.featuresView.userInteractionEnabled = YES;
+    }
+}
+
 - (void)cycleStyles
 {
+    if (self.interactiveShield)
+    {
+        [self.interactiveShield removeFromSuperview];
+        self.interactiveShield = nil;
+
+        [self.featuresView removeFromSuperview];
+        self.featuresView = nil;
+
+        self.mapView.userInteractionEnabled = YES;
+    }
+
     UIButton *titleButton = (UIButton *)self.navigationItem.titleView;
 
     self.styleIndex = (self.styleIndex + 1) % mbgl::util::default_styles::numOrderedStyles;

ios/app/mapboxgl-app.gypi

@@ -14,7 +14,8 @@
         './polyline.geojson',
         './threestates.geojson',
         './Settings.bundle/',
-        './app-info.plist'
+        './app-info.plist',
+        './streets-interactive-poi-v8.json'
       ],
 
       'dependencies': [