fixes #494: bring back v4 tiles including 512px for retina

@@ -2498,7 +2498,7 @@
 {
     tileSourcesMinZoom = ceilf(tileSourcesMinZoom) - 0.99;
 
-    if ( ! self.adjustTilesForRetinaDisplay && _screenScale > 1.0)
+    if ( ! self.adjustTilesForRetinaDisplay && _screenScale > 1.0 && ! [RMMapboxSource isUsingLargeTiles])
         tileSourcesMinZoom -= 1.0;
 
     [self setMinZoom:tileSourcesMinZoom];
@@ -2525,7 +2525,7 @@
 {
     tileSourcesMaxZoom = floorf(tileSourcesMaxZoom);
 
-    if ( ! self.adjustTilesForRetinaDisplay && _screenScale > 1.0)
+    if ( ! self.adjustTilesForRetinaDisplay && _screenScale > 1.0 && ! [RMMapboxSource isUsingLargeTiles])
         tileSourcesMaxZoom -= 1.0;
 
     [self setMaxZoom:tileSourcesMaxZoom];
@@ -2558,7 +2558,7 @@
 {
     float zoom = ceilf(_zoom);
 
-    if ( ! self.adjustTilesForRetinaDisplay && _screenScale > 1.0)
+    if ( ! self.adjustTilesForRetinaDisplay && _screenScale > 1.0 && ! [RMMapboxSource isUsingLargeTiles])
         zoom += 1.0;
 
     return zoom;
@@ -2568,7 +2568,7 @@
 {
     tileSourcesZoom = floorf(tileSourcesZoom);
 
-    if ( ! self.adjustTilesForRetinaDisplay && _screenScale > 1.0)
+    if ( ! self.adjustTilesForRetinaDisplay && _screenScale > 1.0 && ! [RMMapboxSource isUsingLargeTiles])
         tileSourcesZoom -= 1.0;
 
     [self setZoom:tileSourcesZoom];
@@ -2634,7 +2634,7 @@
 
 - (float)adjustedZoomForRetinaDisplay
 {
-    if (!self.adjustTilesForRetinaDisplay && _screenScale > 1.0)
+    if (!self.adjustTilesForRetinaDisplay && _screenScale > 1.0 && ! [RMMapboxSource isUsingLargeTiles])
         return [self zoom] + 1.0;
 
     return [self zoom];

@@ -139,6 +139,8 @@ typedef enum : NSUInteger {
 *   Note that you may want to clear the tile cache after changing this value in order to provide a consistent experience. */
 @property (nonatomic, assign) RMMapboxSourceQuality imageQuality;
 
++ (BOOL)isUsingLargeTiles;
+
 #if OS_OBJECT_USE_OBJC
 @property (nonatomic, readonly, strong) dispatch_queue_t dataQueue;
 #else

@@ -83,7 +83,8 @@
         if ([_infoDictionary[@"id"] hasPrefix:@"examples."])
             RMLog(@"Using watermarked example map ID %@. Please go to https://mapbox.com and create your own map style.", _infoDictionary[@"id"]);
 
-        _uniqueTilecacheKey = [NSString stringWithFormat:@"Mapbox-%@%@", _infoDictionary[@"id"], (_infoDictionary[@"version"] ? [@"-" stringByAppendingString:_infoDictionary[@"version"]] : @"")];
+        _uniqueTilecacheKey = [NSString stringWithFormat:@"Mapbox-%@%@%@", _infoDictionary[@"id"], (_infoDictionary[@"version"] ? [@"-" stringByAppendingString:_infoDictionary[@"version"]] : @""),
+            ([RMMapboxSource isUsingLargeTiles] ? @"-512" : @"")];
 
         id dataObject = nil;
         
@@ -355,11 +356,21 @@
     return roundf(([self maxZoom] + [self minZoom]) / 2);
 }
 
++ (BOOL)isUsingLargeTiles
+{
+    return ([[RMConfiguration configuration] accessToken] && [[UIScreen mainScreen] scale] > 1.0);
+}
+
 - (NSString *)uniqueTilecacheKey
 {
     return _uniqueTilecacheKey;
 }
 
+- (NSUInteger)tileSideLength
+{
+    return ([RMMapboxSource isUsingLargeTiles] ? 512 : kMapboxDefaultTileSize);
+}
+
 - (NSString *)shortName
 {
 	return self.infoDictionary[@"name"];