Made lat/lon/zoom inspectable

Declared these IB-specific inspectables in a separate category that developers are not expected to import. Currently these inspectables are order-dependent due to #1181.

Ref #929

gyp/platform-ios.gypi

@@ -20,6 +20,7 @@
         '../include/mbgl/ios/MGLMapboxEvents.h',
         '../platform/ios/MGLMapboxEvents.m',
         '../include/mbgl/ios/MGLMapView.h',
+        '../include/mbgl/ios/MGLMapView+IBAdditions.h',
         '../platform/ios/MGLMapView.mm',
         '../include/mbgl/ios/MGLAnnotation.h',
         '../include/mbgl/ios/MGLUserLocation.h',

include/mbgl/ios/MGLMapView+IBAdditions.h

@@ -0,0 +1,29 @@
+#import "MGLMapView.h"
+
+@interface MGLMapView (IBAdditions)
+
+// Core properties that can be manipulated in the Attributes inspector in
+// Interface Builder. These redeclarations merely add the IBInspectable keyword.
+// They appear here to ensure that they appear above the convenience properties;
+// inspectables declared in MGLMapView.h are always sorted before those in
+// MGLMapView+IBAdditions.h, due to ASCII sort order.
+
+@property (nonatomic) IBInspectable NSString *accessToken;
+@property (nonatomic) IBInspectable NSString *mapID;
+
+// Some convenience properties related to the initial viewport. These properties
+// are not meant to be used outside of Interface Builder. latitude and longitude
+// are backed by properties of type CLLocationDegrees, but these declarations
+// must use the type double because Interface Builder is unaware that
+// CLLocationDegrees is a typedef for double.
+
+/// Initial latitude at which the receiver is centered.
+@property (nonatomic) IBInspectable double latitude;
+
+/// Initial longitude at which the receiver is centered.
+@property (nonatomic) IBInspectable double longitude;
+
+/// Initial zoom level of the receiver.
+@property (nonatomic) IBInspectable double zoomLevel;
+
+@end

include/mbgl/ios/MGLMapView.h

@@ -39,9 +39,8 @@ IB_DESIGNABLE
 
 /** @name Authorizing Access */
 
-/** Sets a Mapbox API access token for the map view. 
-*   @param accessToken A Mapbox API token. */
-@property (nonatomic) IBInspectable NSString *accessToken;
+/** Mapbox API access token for the map view. */
+@property (nonatomic) NSString *accessToken;
 
 #pragma mark - Managing Constraints
 
@@ -166,10 +165,11 @@ IB_DESIGNABLE
 /** @name Styling the Map */
 
 /** Mapbox map ID of the style currently displayed in the receiver, or `nil` if the style does not have a map ID.
- 
-    The style may lack a map ID if it is located at an HTTP, HTTPS, or asset: URL. Use -styleURL to get the URL in these cases.
- */
-@property (nonatomic) IBInspectable NSString *mapID;
+*
+*   The style may lack a map ID if it is located at an HTTP, HTTPS, or local file URL. Use `styleURL` to get the URL in these cases. 
+*
+*   To display the default style, set this property to `nil`. */
+@property (nonatomic) NSString *mapID;
 
 /** Returns the URLs to the styles bundled with the library. */
 - (NSArray *)bundledStyleURLs;

platform/ios/MGLMapView.mm

@@ -1,4 +1,5 @@
 #import "MGLMapView.h"
+#import "MGLMapView+IBAdditions.h"
 
 #import <mbgl/platform/log.hpp>
 #import <mbgl/platform/gl.hpp>
@@ -92,6 +93,8 @@ @interface MGLMapView () <UIGestureRecognizerDelegate, GLKViewDelegate, CLLocati
 
 @implementation MGLMapView {
     BOOL _isTargetingInterfaceBuilder;
+    CLLocationDegrees _pendingLatitude;
+    CLLocationDegrees _pendingLongitude;
 }
 
 #pragma mark - Setup & Teardown -
@@ -365,6 +368,8 @@ - (BOOL)commonInit
     // set initial position
     //
     mbglMap->setLatLngZoom(mbgl::LatLng(0, 0), mbglMap->getMinZoom());
+    _pendingLatitude = NAN;
+    _pendingLongitude = NAN;
 
     // setup change delegate queue
     //
@@ -1126,6 +1131,11 @@ - (void)toggleDebug
 
 #pragma mark - Geography -
 
++ (NSSet *)keyPathsForValuesAffectingCenterCoordinate
+{
+    return [NSSet setWithObjects:@"latitude", @"longitude", nil];
+}
+
 - (void)setCenterCoordinate:(CLLocationCoordinate2D)coordinate animated:(BOOL)animated preservingTracking:(BOOL)tracking
 {
     self.userTrackingMode = (tracking ? self.userTrackingMode : MGLUserTrackingModeNone);
@@ -2388,3 +2398,59 @@ void invalidate() override
 };
 
 @end
+
+@implementation MGLMapView (IBAdditions)
+
++ (NSSet *)keyPathsForValuesAffectingLatitude
+{
+    return [NSSet setWithObject:@"centerCoordinate"];
+}
+
+- (double)latitude
+{
+    return self.centerCoordinate.latitude;
+}
+
+- (void)setLatitude:(double)latitude
+{
+    if ( ! isnan(_pendingLongitude))
+    {
+        self.centerCoordinate = CLLocationCoordinate2DMake(latitude, _pendingLongitude);
+        _pendingLatitude = NAN;
+        _pendingLongitude = NAN;
+    }
+    else
+    {
+        // Not enough info to make a valid center coordinate yet. Stash this
+        // latitude away until the longitude is set too.
+        _pendingLatitude = latitude;
+    }
+}
+
++ (NSSet *)keyPathsForValuesAffectingLongitude
+{
+    return [NSSet setWithObject:@"centerCoordinate"];
+}
+
+- (double)longitude
+{
+    return self.centerCoordinate.longitude;
+}
+
+- (void)setLongitude:(double)longitude
+{
+    if ( ! isnan(_pendingLatitude))
+    {
+        self.centerCoordinate = CLLocationCoordinate2DMake(_pendingLatitude, longitude);
+        _pendingLatitude = NAN;
+        _pendingLongitude = NAN;
+    }
+    else
+    {
+        // Not enough info to make a valid center coordinate yet. Stash this
+        // longitude away until the latitude is set too.
+        _pendingLongitude = longitude;
+    }
+}
+
+@end