merged upstream develop

@@ -36,6 +36,7 @@
 #import "RMCacheObject.h"
 #import "RMCircle.h"
 #import "RMConfiguration.h"
+#import "RMCompositeSource.h"
 #import "RMCoordinateGridSource.h"
 #import "RMDBMapSource.h"
 #import "RMDatabaseCache.h"

@@ -35,7 +35,7 @@
     RMFractalTileProjection *_tileProjection;
 }
 
-@synthesize minZoom = _minZoom, maxZoom = _maxZoom;
+@synthesize minZoom = _minZoom, maxZoom = _maxZoom, cacheable = _cacheable, opaque = _opaque;
 
 - (id)init
 {
@@ -48,6 +48,9 @@
     self.minZoom = kDefaultMinTileZoom;
     self.maxZoom = kDefaultMaxTileZoom;
 
+    self.cacheable = YES;
+    self.opaque = YES;
+
     return self;
 }
 
@@ -69,6 +72,11 @@
                                  userInfo:nil];
 }    
 
+- (BOOL)tileSourceHasTile:(RMTile)tile
+{
+    return YES;
+}
+
 - (void)cancelAllDownloads
 {
 }

@@ -62,10 +62,19 @@
     __block UIImage *image = nil;
 
 	tile = [[self mercatorToTileProjection] normaliseTile:tile];
-    image = [tileCache cachedImage:tile withCacheKey:[self uniqueTilecacheKey]];
 
-    if (image)
-        return image;
+    // Return NSNull here so that the RMMapTiledLayerView will try to
+    // fetch another tile if missingTilesDepth > 0
+    if ( ! [self tileSourceHasTile:tile])
+        return (UIImage *)[NSNull null];
+
+    if (self.isCacheable)
+    {
+        image = [tileCache cachedImage:tile withCacheKey:[self uniqueTilecacheKey]];
+
+        if (image)
+            return image;
+    }
 
     dispatch_async(dispatch_get_main_queue(), ^(void)
     {
@@ -155,7 +164,7 @@
         }
     }
 
-    if (image)
+    if (image && self.isCacheable)
         [tileCache addImage:image forTile:tile withCacheKey:[self uniqueTilecacheKey]];
 
     [tileCache release];

@@ -70,8 +70,11 @@
 
 - (void)touch
 {
-    [_timestamp autorelease];
-    _timestamp = [NSDate new];
+    @synchronized (self)
+    {
+        [_timestamp autorelease];
+        _timestamp = [NSDate new];
+    }
 }
 
 - (NSString *)description

+//
+//  RMCompositeSource.h
+//  MapView
+//
+// Copyright (c) 2008-2012, Route-Me Contributors
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+//
+// * Redistributions of source code must retain the above copyright notice, this
+//   list of conditions and the following disclaimer.
+// * Redistributions in binary form must reproduce the above copyright notice,
+//   this list of conditions and the following disclaimer in the documentation
+//   and/or other materials provided with the distribution.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+// POSSIBILITY OF SUCH DAMAGE.
+
+#import "RMAbstractMercatorTileSource.h"
+
+@interface RMCompositeSource : RMAbstractMercatorTileSource
+
+- (id)initWithTileSources:(NSArray *)tileSources tileCacheKey:(NSString *)tileCacheKey;
+
+@property (nonatomic, readonly) NSArray *tileSources;
+
+@end

+//
+//  RMCompositeSource.m
+//  MapView
+//
+// Copyright (c) 2008-2012, Route-Me Contributors
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+//
+// * Redistributions of source code must retain the above copyright notice, this
+//   list of conditions and the following disclaimer.
+// * Redistributions in binary form must reproduce the above copyright notice,
+//   this list of conditions and the following disclaimer in the documentation
+//   and/or other materials provided with the distribution.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+// POSSIBILITY OF SUCH DAMAGE.
+
+#import "RMCompositeSource.h"
+#import "RMTileCache.h"
+
+@implementation RMCompositeSource
+{
+    NSArray *_tileSources;
+    NSString *_uniqueTilecacheKey;
+}
+
+- (id)initWithTileSources:(NSArray *)tileSources tileCacheKey:(NSString *)tileCacheKey
+{
+    if (!(self = [super init]))
+        return nil;
+
+    NSAssert(tileSources != nil && [tileSources count], @"Empty host parameter not allowed");
+
+    _tileSources = [tileSources copy];
+
+    if (tileCacheKey)
+    {
+        _uniqueTilecacheKey = [tileCacheKey retain];
+    }
+    else
+    {
+        self.cacheable = NO;
+        _uniqueTilecacheKey = nil;
+    }
+
+    float tileSourcesMinZoom = FLT_MAX, tileSourcesMaxZoom = FLT_MIN;
+    BOOL tileSourcesAreOpaque = YES;
+
+    for (id <RMTileSource> currentTileSource in _tileSources)
+    {
+        tileSourcesMinZoom = MIN(tileSourcesMinZoom, currentTileSource.minZoom);
+        tileSourcesMaxZoom = MAX(tileSourcesMaxZoom, currentTileSource.maxZoom);
+
+        if ( ! currentTileSource.isOpaque)
+            tileSourcesAreOpaque = NO;
+    }
+
+    self.minZoom = tileSourcesMinZoom;
+    self.maxZoom = tileSourcesMaxZoom;
+    self.opaque  = tileSourcesAreOpaque;
+
+    return self;
+}
+
+- (void)dealloc
+{
+    [_uniqueTilecacheKey release]; _uniqueTilecacheKey = nil;
+    [_tileSources release]; _tileSources = nil;
+    [super dealloc];
+}
+
+- (NSArray *)tileSources
+{
+    return [[_tileSources copy] autorelease];
+}
+
+- (NSString *)uniqueTilecacheKey
+{
+    return _uniqueTilecacheKey;
+}
+
+- (NSString *)shortName
+{
+	return @"Generic Map Source";
+}
+
+- (NSString *)longDescription
+{
+	return @"Generic Map Source";
+}
+
+- (NSString *)shortAttribution
+{
+	return @"n/a";
+}
+
+- (NSString *)longAttribution
+{
+	return @"n/a";
+}
+
+- (UIImage *)imageForTile:(RMTile)tile inCache:(RMTileCache *)tileCache
+{
+    UIImage *image = nil;
+
+	tile = [[self mercatorToTileProjection] normaliseTile:tile];
+
+    if (self.isCacheable)
+    {
+        image = [tileCache cachedImage:tile withCacheKey:[self uniqueTilecacheKey]];
+
+        if (image)
+            return image;
+    }
+
+    dispatch_async(dispatch_get_main_queue(), ^(void)
+    {
+        [[NSNotificationCenter defaultCenter] postNotificationName:RMTileRequested object:[NSNumber numberWithUnsignedLongLong:RMTileKey(tile)]];
+    });
+
+    [tileCache retain];
+
+    NSMutableArray *tileImages = [NSMutableArray arrayWithCapacity:[_tileSources count]];
+
+    for (NSUInteger p = 0; p < [_tileSources count]; ++p)
+        [tileImages addObject:[NSNull null]];
+
+    for (NSInteger u = [_tileSources count]-1; u >=0 ; --u)
+    {
+        id <RMTileSource> tileSource = [_tileSources objectAtIndex:u];
+
+        if (tile.zoom < tileSource.minZoom || tile.zoom > tileSource.maxZoom || ![tileSource tileSourceHasTile:tile])
+            continue;
+
+        UIImage *tileImage = [tileSource imageForTile:tile inCache:tileCache];
+
+        if (tileImage)
+        {
+            [tileImages replaceObjectAtIndex:u withObject:tileImage];
+
+            if (tileSource.isOpaque)
+                break;
+        }
+    }
+
+    // composite the collected images together
+    //
+    for (UIImage *tileImage in tileImages)
+    {
+        if ( ! [tileImage isKindOfClass:[UIImage class]])
+            continue;
+
+        if (image != nil)
+        {
+            UIGraphicsBeginImageContext(image.size);
+            [image drawAtPoint:CGPointMake(0,0)];
+            [tileImage drawAtPoint:CGPointMake(0,0)];
+
+            image = UIGraphicsGetImageFromCurrentImageContext();
+            UIGraphicsEndImageContext();
+        }
+        else
+        {
+            image = tileImage;
+        }
+    }
+
+    if (image && self.isCacheable)
+        [tileCache addImage:image forTile:tile withCacheKey:[self uniqueTilecacheKey]];
+
+    [tileCache release];
+
+    dispatch_async(dispatch_get_main_queue(), ^(void)
+    {
+        [[NSNotificationCenter defaultCenter] postNotificationName:RMTileRetrieved object:[NSNumber numberWithUnsignedLongLong:RMTileKey(tile)]];
+    });
+
+    return image;
+}
+
+@end

@@ -81,7 +81,7 @@ static double coordinateGridSpacingDecimal[19] = {
 @synthesize gridColor = _gridColor;
 @synthesize gridLineWidth = _gridLineWidth;
 @synthesize gridLabelInterval = _gridLabelInterval;
-@synthesize gridMode = _labelingMode;
+@synthesize gridMode = _gridMode;
 @synthesize minorLabelColor = _minorLabelColor;
 @synthesize minorLabelFont = _minorLabelFont;
 @synthesize majorLabelColor = _majorLabelColor;
@@ -93,14 +93,16 @@ static double coordinateGridSpacingDecimal[19] = {
         return nil;
 
     self.minZoom = 5;
-    self.maxZoom = 18;
+    self.maxZoom = 17;
+
+    self.opaque = NO;
 
     self.gridColor = [UIColor colorWithWhite:0.1 alpha:0.6];
     self.gridLineWidth = 2.0;
     self.gridLabelInterval = 1;
 
     self.gridMode = GridModeGeographicDecimal;
-    self.minorLabelColor = self.majorLabelColor = [UIColor colorWithWhite:0.1 alpha:0.6];
+    self.minorLabelColor = self.majorLabelColor = [UIColor colorWithWhite:0.1 alpha:0.7];
     self.minorLabelFont = [UIFont boldSystemFontOfSize:14.0];
     self.majorLabelFont = [UIFont boldSystemFontOfSize:11.0];
 
@@ -314,7 +316,29 @@ static double coordinateGridSpacingDecimal[19] = {
 
 - (NSString *)uniqueTilecacheKey
 {
-    return @"RMCoordinateGrid";
+    NSString *tileCacheKey = nil;
+
+    switch (self.gridMode)
+    {
+        case GridModeGeographic: {
+            tileCacheKey = @"RMCoordinateGridGeographic";
+            break;
+        }
+        case GridModeGeographicDecimal:
+        {
+            tileCacheKey = @"RMCoordinateGridDecimal";
+            break;
+        }
+        case GridModeUTM: {
+            tileCacheKey = @"RMCoordinateGridUTM";
+            break;
+        }
+    }
+
+    if ( ! tileCacheKey)
+        tileCacheKey = @"RMCoordinateGrid";
+
+    return tileCacheKey;
 }
 
 - (NSString *)shortName

@@ -203,10 +203,14 @@
     __block UIImage *image = nil;
 
 	tile = [[self mercatorToTileProjection] normaliseTile:tile];
-    image = [tileCache cachedImage:tile withCacheKey:[self uniqueTilecacheKey]];
 
-    if (image)
-        return image;
+    if (self.isCacheable)
+    {
+        image = [tileCache cachedImage:tile withCacheKey:[self uniqueTilecacheKey]];
+
+        if (image)
+            return image;
+    }
 
     // get the unique key for the tile
     NSNumber *key = [NSNumber numberWithLongLong:RMTileKey(tile)];
@@ -227,7 +231,7 @@
         [result close];
     }];
 
-    if (image)
+    if (image && self.isCacheable)
         [tileCache addImage:image forTile:tile withCacheKey:[self uniqueTilecacheKey]];
 
 	return image;

@@ -360,6 +360,27 @@
     }];
 }
 
+- (void)removeAllCachedImagesForCacheKey:(NSString *)cacheKey
+{
+    RMLog(@"removing tiles for key '%@' from the db cache", cacheKey);
+
+    [_writeQueue addOperationWithBlock:^{
+        [_writeQueueLock lock];
+
+        [_queue inDatabase:^(FMDatabase *db)
+         {
+             BOOL result = [db executeUpdate:@"DELETE FROM ZCACHE WHERE cache_key = ?", cacheKey];
+
+             if (result == NO)
+                 RMLog(@"Error purging cache");
+         }];
+
+        [_writeQueueLock unlock];
+
+        _tileCount = [self countTiles];
+    }];
+}
+
 - (void)touchTile:(RMTile)tile withKey:(NSString *)cacheKey
 {
     [_writeQueue addOperationWithBlock:^{

@@ -15,6 +15,8 @@
 #import "RMMBTilesSource.h"
 #import "RMDBMapSource.h"
 
+#define IS_VALID_TILE_IMAGE(image) (image != nil && [image isKindOfClass:[UIImage class]])
+
 @implementation RMMapTiledLayerView
 {
     RMMapView *_mapView;
@@ -47,8 +49,8 @@
     self.useSnapshotRenderer = NO;
 
     CATiledLayer *tiledLayer = [self tiledLayer];
-    size_t levelsOf2xMagnification = _mapView.tileSourcesContainer.maxZoom;
-    if (_mapView.adjustTilesForRetinaDisplay) levelsOf2xMagnification += 1;
+    size_t levelsOf2xMagnification = _mapView.tileSourcesMaxZoom;
+    if (_mapView.adjustTilesForRetinaDisplay && _mapView.screenScale > 1.0) levelsOf2xMagnification += 1;
     tiledLayer.levelsOfDetail = levelsOf2xMagnification;
     tiledLayer.levelsOfDetailBias = levelsOf2xMagnification;
 
@@ -100,7 +102,9 @@
                 for (int y=y1; y<=y2; ++y)
                 {
                     UIImage *tileImage = [_tileSource imageForTile:RMTileMake(x, y, zoom) inCache:[_mapView tileCache]];
-                    [tileImage drawInRect:CGRectMake(x * rectSize, y * rectSize, rectSize, rectSize)];
+
+                    if (IS_VALID_TILE_IMAGE(tileImage))
+                        [tileImage drawInRect:CGRectMake(x * rectSize, y * rectSize, rectSize, rectSize)];
                 }
             }
 
@@ -112,6 +116,13 @@
         int x = floor(rect.origin.x / rect.size.width),
             y = floor(fabs(rect.origin.y / rect.size.height));
 
+        if (_mapView.adjustTilesForRetinaDisplay && _mapView.screenScale > 1.0)
+        {
+            zoom--;
+            x >>= 1;
+            y >>= 1;
+        }
+
 //        NSLog(@"Tile @ x:%d, y:%d, zoom:%d", x, y, zoom);
 
         UIGraphicsPushContext(context);
@@ -168,7 +179,7 @@
 
                     tileImage = [_tileSource imageForTile:RMTileMake((int)nextTileX, (int)nextTileY, currentZoom) inCache:[_mapView tileCache]];
 
-                    if (tileImage)
+                    if (IS_VALID_TILE_IMAGE(tileImage))
                     {
                         // crop
                         float cropSize = 1.0 / powf(2.0, (float)currentTileDepth);
@@ -184,6 +195,10 @@
 
                         break;
                     }
+                    else
+                    {
+                        tileImage = nil;
+                    }
 
                     currentTileDepth++;
                     currentZoom = zoom - currentTileDepth;
@@ -191,40 +206,63 @@
             }
         }
 
-        if (_mapView.debugTiles)
+        if (IS_VALID_TILE_IMAGE(tileImage))
         {
-            UIGraphicsBeginImageContext(tileImage.size);
+            if (_mapView.adjustTilesForRetinaDisplay && _mapView.screenScale > 1.0)
+            {
+                // Crop the image
+                float xCrop = (floor(rect.origin.x / rect.size.width) / 2.0) - x;
+                float yCrop = (floor(rect.origin.y / rect.size.height) / 2.0) - y;
+
+                CGRect cropBounds = CGRectMake(tileImage.size.width * xCrop,
+                                               tileImage.size.height * yCrop,
+                                               tileImage.size.width * 0.5,
+                                               tileImage.size.height * 0.5);
+
+                CGImageRef imageRef = CGImageCreateWithImageInRect([tileImage CGImage], cropBounds);
+                tileImage = [UIImage imageWithCGImage:imageRef];
+                CGImageRelease(imageRef);
+            }
+
+            if (_mapView.debugTiles)
+            {
+                UIGraphicsBeginImageContext(tileImage.size);
 
-            CGContextRef debugContext = UIGraphicsGetCurrentContext();
+                CGContextRef debugContext = UIGraphicsGetCurrentContext();
 
-            CGRect debugRect = CGRectMake(0, 0, tileImage.size.width, tileImage.size.height);
+                CGRect debugRect = CGRectMake(0, 0, tileImage.size.width, tileImage.size.height);
 
-            [tileImage drawInRect:debugRect];
+                [tileImage drawInRect:debugRect];
 
-            UIFont *font = [UIFont systemFontOfSize:32.0];
+                UIFont *font = [UIFont systemFontOfSize:32.0];
 
-            CGContextSetStrokeColorWithColor(debugContext, [UIColor whiteColor].CGColor);
-            CGContextSetLineWidth(debugContext, 2.0);
-            CGContextSetShadowWithColor(debugContext, CGSizeMake(0.0, 0.0), 5.0, [UIColor blackColor].CGColor);
+                CGContextSetStrokeColorWithColor(debugContext, [UIColor whiteColor].CGColor);
+                CGContextSetLineWidth(debugContext, 2.0);
+                CGContextSetShadowWithColor(debugContext, CGSizeMake(0.0, 0.0), 5.0, [UIColor blackColor].CGColor);
 
-            CGContextStrokeRect(debugContext, debugRect);
+                CGContextStrokeRect(debugContext, debugRect);
 
-            CGContextSetFillColorWithColor(debugContext, [UIColor whiteColor].CGColor);
+                CGContextSetFillColorWithColor(debugContext, [UIColor whiteColor].CGColor);
 
-            NSString *debugString = [NSString stringWithFormat:@"Zoom %d", zoom];
-            CGSize debugSize1 = [debugString sizeWithFont:font];
-            [debugString drawInRect:CGRectMake(5.0, 5.0, debugSize1.width, debugSize1.height) withFont:font];
+                NSString *debugString = [NSString stringWithFormat:@"Zoom %d", zoom];
+                CGSize debugSize1 = [debugString sizeWithFont:font];
+                [debugString drawInRect:CGRectMake(5.0, 5.0, debugSize1.width, debugSize1.height) withFont:font];
 
-            debugString = [NSString stringWithFormat:@"(%d, %d)", x, y];
-            CGSize debugSize2 = [debugString sizeWithFont:font];
-            [debugString drawInRect:CGRectMake(5.0, 5.0 + debugSize1.height + 5.0, debugSize2.width, debugSize2.height) withFont:font];
+                debugString = [NSString stringWithFormat:@"(%d, %d)", x, y];
+                CGSize debugSize2 = [debugString sizeWithFont:font];
+                [debugString drawInRect:CGRectMake(5.0, 5.0 + debugSize1.height + 5.0, debugSize2.width, debugSize2.height) withFont:font];
 
-            tileImage = UIGraphicsGetImageFromCurrentImageContext();
+                tileImage = UIGraphicsGetImageFromCurrentImageContext();
 
-            UIGraphicsEndImageContext();
-        }
+                UIGraphicsEndImageContext();
+            }
 
-        [tileImage drawInRect:rect];
+            [tileImage drawInRect:rect];
+        }
+        else
+        {
+//            NSLog(@"Invalid image for {%d,%d} @ %d", x, y, zoom);
+        }
 
         UIGraphicsPopContext();
     }

@@ -168,9 +168,9 @@ typedef enum : NSUInteger {
 - (id)initWithFrame:(CGRect)frame
       andTilesource:(id <RMTileSource>)newTilesource
    centerCoordinate:(CLLocationCoordinate2D)initialCenterCoordinate
-          zoomLevel:(float)initialZoomLevel
-       maxZoomLevel:(float)maxZoomLevel
-       minZoomLevel:(float)minZoomLevel
+          zoomLevel:(float)initialTileSourceZoomLevel
+       maxZoomLevel:(float)initialTileSourceMaxZoomLevel
+       minZoomLevel:(float)initialTileSourceMinZoomLevel
     backgroundImage:(UIImage *)backgroundImage;
 
 - (void)setFrame:(CGRect)frame;
@@ -214,6 +214,10 @@ typedef enum : NSUInteger {
 /** The maximum zoom level of the map, clamped to the range supported by the tile source(s). */
 @property (nonatomic, assign) float maxZoom;
 
+@property (nonatomic, assign) float tileSourcesZoom;
+@property (nonatomic, assign) float tileSourcesMinZoom;
+@property (nonatomic, assign) float tileSourcesMaxZoom;
+
 @property (nonatomic, assign) RMProjectedRect projectedBounds;
 @property (nonatomic, readonly) RMProjectedPoint projectedOrigin;
 @property (nonatomic, readonly) RMProjectedSize projectedViewSize;

@@ -210,9 +210,9 @@
 
 - (void)performInitializationWithTilesource:(id <RMTileSource>)newTilesource
                            centerCoordinate:(CLLocationCoordinate2D)initialCenterCoordinate
-                                  zoomLevel:(float)initialZoomLevel
-                               maxZoomLevel:(float)maxZoomLevel
-                               minZoomLevel:(float)minZoomLevel
+                                  zoomLevel:(float)initialTileSourceZoomLevel
+                               maxZoomLevel:(float)initialTileSourceMaxZoomLevel
+                               minZoomLevel:(float)initialTileSourceMinZoomLevel
                             backgroundImage:(UIImage *)backgroundImage
 {
     _constrainMovement = _enableBouncing = _zoomingInPivotsAroundCenter = NO;
@@ -266,11 +266,11 @@
         [self setBackgroundView:_loadingTileView];
     }
 
-    if (minZoomLevel < newTilesource.minZoom) minZoomLevel = newTilesource.minZoom;
-    if (maxZoomLevel > newTilesource.maxZoom) maxZoomLevel = newTilesource.maxZoom;
-    [self setMinZoom:minZoomLevel];
-    [self setMaxZoom:maxZoomLevel];
-    [self setZoom:initialZoomLevel];
+    if (initialTileSourceMinZoomLevel < newTilesource.minZoom) initialTileSourceMinZoomLevel = newTilesource.minZoom;
+    if (initialTileSourceMaxZoomLevel > newTilesource.maxZoom) initialTileSourceMaxZoomLevel = newTilesource.maxZoom;
+    [self setTileSourcesMinZoom:initialTileSourceMinZoomLevel];
+    [self setTileSourcesMaxZoom:initialTileSourceMaxZoomLevel];
+    [self setTileSourcesZoom:initialTileSourceZoomLevel];
 
     [self setTileSource:newTilesource];
     [self setCenterCoordinate:initialCenterCoordinate animated:NO];
@@ -995,16 +995,13 @@
         self.userTrackingMode = RMUserTrackingModeNone;
     
     // Calculate rounded zoom
-    float newZoom = fmin(ceilf([self zoom]) + 0.99, [self maxZoom]);
-
-    if (newZoom == self.zoom)
-        return;
+    float newZoom = fmin(ceilf([self zoom]) + 1.0, [self maxZoom]);
 
     float factor = exp2f(newZoom - [self zoom]);
 
     if (factor > 2.25)
     {
-        newZoom = fmin(ceilf([self zoom]) - 0.01, [self maxZoom]);
+        newZoom = fmin(ceilf([self zoom]), [self maxZoom]);
         factor = exp2f(newZoom - [self zoom]);
     }
 
@@ -1020,16 +1017,13 @@
 - (void)zoomOutToNextNativeZoomAt:(CGPoint)pivot animated:(BOOL) animated
 {
     // Calculate rounded zoom
-    float newZoom = fmax(floorf([self zoom]) - 0.01, [self minZoom]);
-
-    if (newZoom == self.zoom)
-        return;
+    float newZoom = fmax(floorf([self zoom]), [self minZoom]);
 
     float factor = exp2f(newZoom - [self zoom]);
 
     if (factor > 0.75)
     {
-        newZoom = fmax(floorf([self zoom]) - 1.01, [self minZoom]);
+        newZoom = fmax(floorf([self zoom]) - 1.0, [self minZoom]);
         factor = exp2f(newZoom - [self zoom]);
     }
 
@@ -1160,10 +1154,7 @@
     {
         RMMapTiledLayerView *tiledLayerView = [[RMMapTiledLayerView alloc] initWithFrame:CGRectMake(0.0, 0.0, contentSize.width, contentSize.height) mapView:self forTileSource:tileSource];
 
-        if (self.adjustTilesForRetinaDisplay && _screenScale > 1.0)
-            ((CATiledLayer *)tiledLayerView.layer).tileSize = CGSizeMake(tileSideLength * 2.0, tileSideLength * 2.0);
-        else
-            ((CATiledLayer *)tiledLayerView.layer).tileSize = CGSizeMake(tileSideLength, tileSideLength);
+        ((CATiledLayer *)tiledLayerView.layer).tileSize = CGSizeMake(tileSideLength, tileSideLength);
 
         [_tiledLayersSuperview addSubview:tiledLayerView];
     }
@@ -1801,8 +1792,8 @@
     else
         _constrainingProjectedBounds = _projection.planetBounds;
 
-    [self setMinZoom:_tileSourcesContainer.minZoom];
-    [self setMaxZoom:_tileSourcesContainer.maxZoom];
+    [self setTileSourcesMinZoom:_tileSourcesContainer.minZoom];
+    [self setTileSourcesMaxZoom:_tileSourcesContainer.maxZoom];
     [self setZoom:[self zoom]]; // setZoom clamps zoom level to min/max limits
 
     // Recreate the map layer
@@ -1841,8 +1832,8 @@
     else
         _constrainingProjectedBounds = _projection.planetBounds;
 
-    [self setMinZoom:_tileSourcesContainer.minZoom];
-    [self setMaxZoom:_tileSourcesContainer.maxZoom];
+    [self setTileSourcesMinZoom:_tileSourcesContainer.minZoom];
+    [self setTileSourcesMaxZoom:_tileSourcesContainer.maxZoom];
     [self setZoom:[self zoom]]; // setZoom clamps zoom level to min/max limits
 
     // Recreate the map layer
@@ -1859,10 +1850,7 @@
 
         RMMapTiledLayerView *tiledLayerView = [[RMMapTiledLayerView alloc] initWithFrame:CGRectMake(0.0, 0.0, contentSize.width, contentSize.height) mapView:self forTileSource:newTileSource];
 
-        if (self.adjustTilesForRetinaDisplay && _screenScale > 1.0)
-            ((CATiledLayer *)tiledLayerView.layer).tileSize = CGSizeMake(tileSideLength * 2.0, tileSideLength * 2.0);
-        else
-            ((CATiledLayer *)tiledLayerView.layer).tileSize = CGSizeMake(tileSideLength, tileSideLength);
+        ((CATiledLayer *)tiledLayerView.layer).tileSize = CGSizeMake(tileSideLength, tileSideLength);
 
         if (index >= [[_tileSourcesContainer tileSources] count])
             [_tiledLayersSuperview addSubview:tiledLayerView];
@@ -2064,6 +2052,9 @@
 
 - (void)setMinZoom:(float)newMinZoom
 {
+    if (newMinZoom < 0.0)
+        newMinZoom = 0.0;
+
     _minZoom = newMinZoom;
 
 //    RMLog(@"New minZoom:%f", newMinZoom);
@@ -2073,8 +2064,26 @@
     [self correctMinZoomScaleForBoundingMask];
 }
 
+- (float)tileSourcesMinZoom
+{
+    return self.tileSourcesContainer.minZoom;
+}
+
+- (void)setTileSourcesMinZoom:(float)tileSourcesMinZoom
+{
+    tileSourcesMinZoom = ceilf(tileSourcesMinZoom) - 0.99;
+
+    if ( ! self.adjustTilesForRetinaDisplay && _screenScale > 1.0)
+        tileSourcesMinZoom -= 1.0;
+
+    [self setMinZoom:tileSourcesMinZoom];
+}
+
 - (void)setMaxZoom:(float)newMaxZoom
 {
+    if (newMaxZoom < 0.0)
+        newMaxZoom = 0.0;
+
     _maxZoom = newMaxZoom;
 
 //    RMLog(@"New maxZoom:%f", newMaxZoom);
@@ -2082,6 +2091,21 @@
     _mapScrollView.maximumZoomScale = exp2f(newMaxZoom);
 }
 
+- (float)tileSourcesMaxZoom
+{
+    return self.tileSourcesContainer.maxZoom;
+}
+
+- (void)setTileSourcesMaxZoom:(float)tileSourcesMaxZoom
+{
+    tileSourcesMaxZoom = floorf(tileSourcesMaxZoom);
+
+    if ( ! self.adjustTilesForRetinaDisplay && _screenScale > 1.0)
+        tileSourcesMaxZoom -= 1.0;
+
+    [self setMaxZoom:tileSourcesMaxZoom];
+}
+
 - (float)zoom
 {
     return _zoom;
@@ -2093,11 +2117,31 @@
     _zoom = (newZoom > _maxZoom) ? _maxZoom : newZoom;
     _zoom = (_zoom < _minZoom) ? _minZoom : _zoom;
 
-//    RMLog(@"New zoom:%f", zoom);
+//    RMLog(@"New zoom:%f", _zoom);
 
     _mapScrollView.zoomScale = exp2f(_zoom);
 }
 
+- (float)tileSourcesZoom
+{
+    float zoom = ceilf(_zoom);
+
+    if ( ! self.adjustTilesForRetinaDisplay && _screenScale > 1.0)
+        zoom += 1.0;
+
+    return zoom;
+}
+
+- (void)setTileSourcesZoom:(float)tileSourcesZoom
+{
+    tileSourcesZoom = floorf(tileSourcesZoom);
+
+    if ( ! self.adjustTilesForRetinaDisplay && _screenScale > 1.0)
+        tileSourcesZoom -= 1.0;
+
+    [self setZoom:tileSourcesZoom];
+}
+
 - (void)setEnableClustering:(BOOL)doEnableClustering
 {
     _enableClustering = doEnableClustering;
@@ -2904,9 +2948,9 @@
             _userHeadingTrackingView.contentMode = UIViewContentModeTop;
 
             _userHeadingTrackingView.autoresizingMask = UIViewAutoresizingFlexibleLeftMargin  |
-                                                       UIViewAutoresizingFlexibleRightMargin |
-                                                       UIViewAutoresizingFlexibleTopMargin   |
-                                                       UIViewAutoresizingFlexibleBottomMargin;
+                                                        UIViewAutoresizingFlexibleRightMargin |
+                                                        UIViewAutoresizingFlexibleTopMargin   |
+                                                        UIViewAutoresizingFlexibleBottomMargin;
 
             _userHeadingTrackingView.alpha = 0.0;
 
@@ -2918,9 +2962,9 @@
                                                           round([self bounds].size.height / 2));
 
             _userLocationTrackingView.autoresizingMask = UIViewAutoresizingFlexibleLeftMargin  |
-                                                        UIViewAutoresizingFlexibleRightMargin |
-                                                        UIViewAutoresizingFlexibleTopMargin   |
-                                                        UIViewAutoresizingFlexibleBottomMargin;
+                                                         UIViewAutoresizingFlexibleRightMargin |
+                                                         UIViewAutoresizingFlexibleTopMargin   |
+                                                         UIViewAutoresizingFlexibleBottomMargin;
             
             [self insertSubview:_userLocationTrackingView aboveSubview:_userHeadingTrackingView];
 

@@ -177,4 +177,20 @@
     });
 }
 
+- (void)removeAllCachedImagesForCacheKey:(NSString *)cacheKey
+{
+    dispatch_barrier_async(_memoryCacheQueue, ^{
+
+        NSMutableArray *keysToRemove = [NSMutableArray array];
+
+        [_memoryCache enumerateKeysAndObjectsUsingBlock:^(id key, RMCacheObject *cachedObject, BOOL *stop) {
+            if ([[cachedObject cacheKey] isEqualToString:cacheKey])
+                [keysToRemove addObject:key];
+        }];
+
+        [_memoryCache removeObjectsForKeys:keysToRemove];
+
+    });
+}
+
 @end

@@ -37,6 +37,8 @@
     self.minZoom = 1;
     self.maxZoom = 18;
 
+    self.opaque = NO;
+
 	return self;
 }
 

@@ -80,7 +80,7 @@
 }
 
 // DEPRECATED. Use RMShape instead.
-- (id)initWithView:(RMMapView *)aMapView __attribute__ ((deprecated));;
+- (id)initWithView:(RMMapView *)aMapView __attribute__ ((deprecated));
 
 @property (nonatomic, assign) CGPathDrawingMode drawingMode;
 @property (nonatomic, assign) CGLineCap lineCap;

@@ -66,6 +66,7 @@ typedef enum : short {
 
 /** Removes all tile images from a cache. */
 - (void)removeAllCachedImages;
+- (void)removeAllCachedImagesForCacheKey:(NSString *)cacheKey;
 
 @end
 

@@ -217,6 +217,20 @@
     });
 }
 
+- (void)removeAllCachedImagesForCacheKey:(NSString *)cacheKey
+{
+    [_memoryCache removeAllCachedImagesForCacheKey:cacheKey];
+
+    dispatch_sync(_tileCacheQueue, ^{
+
+        for (id<RMTileCache> cache in _tileCaches)
+        {
+            [cache removeAllCachedImagesForCacheKey:cacheKey];
+        }
+
+    });
+}
+
 @end
 
 #pragma mark -

@@ -51,6 +51,12 @@
 /** The maximum zoom level supported by the tile source. */
 @property (nonatomic, assign) float maxZoom;
 
+/** A Boolean value indicating whether the tiles from this source should be cached. */
+@property (nonatomic, assign, getter=isCacheable) BOOL cacheable;
+
+/** A Boolean value indicating whether the tiles from this source are opaque. Setting this correctly is important when using RMCompositeSource so that alpha transparency can be preserved when compositing tile images. */
+@property (nonatomic, assign, getter=isOpaque) BOOL opaque;
+
 @property (nonatomic, readonly) RMFractalTileProjection *mercatorToTileProjection;
 @property (nonatomic, readonly) RMProjection *projection;
 
@@ -93,6 +99,11 @@
 *   @return An image to display. */
 - (UIImage *)imageForTile:(RMTile)tile inCache:(RMTileCache *)tileCache;
 
+/** Check if the tile source can provide the requested tile.
+ *  @param tile The map tile in question.
+ *  @return A Boolean value indicating whether the tile source can provide the requested tile. */
+- (BOOL)tileSourceHasTile:(RMTile)tile;
+
 - (void)cancelAllDownloads;
 
 - (void)didReceiveMemoryWarning;

@@ -33,8 +33,6 @@
 
 @interface RMTileSourcesContainer : NSObject
 
-@property (nonatomic, readonly) NSArray *tileSources;
-
 // These are the minimum and maximum zoom levels across all tile sources.
 @property (nonatomic, assign) float minZoom;
 @property (nonatomic, assign) float maxZoom;
@@ -49,6 +47,12 @@
 
 #pragma mark -
 
+@property (nonatomic, readonly) NSArray *tileSources;
+
+- (id <RMTileSource>)tileSourceForUniqueTilecacheKey:(NSString *)uniqueTilecacheKey;
+
+#pragma mark -
+
 - (BOOL)setTileSource:(id <RMTileSource>)tileSource;
 - (BOOL)setTileSources:(NSArray *)tileSources;
 

@@ -28,6 +28,8 @@
 
 #import "RMTileSourcesContainer.h"
 
+#import "RMCompositeSource.h"
+
 @implementation RMTileSourcesContainer
 {
     NSMutableArray *_tileSources;
@@ -87,6 +89,38 @@
     return [tileSources autorelease];
 }
 
+- (id <RMTileSource>)tileSourceForUniqueTilecacheKey:(NSString *)uniqueTilecacheKey
+{
+    if (!uniqueTilecacheKey)
+        return nil;
+
+    id result = nil;
+
+    [_tileSourcesLock lock];
+
+    NSMutableArray *tileSources = [NSMutableArray arrayWithArray:_tileSources];
+
+    while ([tileSources count])
+    {
+        id <RMTileSource> currentTileSource = [tileSources objectAtIndex:0];
+        [tileSources removeObjectAtIndex:0];
+
+        if ([currentTileSource isKindOfClass:[RMCompositeSource class]])
+        {
+            [tileSources addObjectsFromArray:[(RMCompositeSource *)currentTileSource tileSources]];
+        }
+        else if ([[currentTileSource uniqueTilecacheKey] isEqualToString:uniqueTilecacheKey])
+        {
+            result = [currentTileSource retain];
+            break;
+        }
+    }
+
+    [_tileSourcesLock unlock];
+
+    return [result autorelease];
+}
+
 - (BOOL)setTileSource:(id <RMTileSource>)tileSource
 {
     BOOL result;

@@ -24,6 +24,8 @@
 		161E563B1594664E00B00BB6 /* RMOpenSeaMapLayer.m in Sources */ = {isa = PBXBuildFile; fileRef = 161E56391594664E00B00BB6 /* RMOpenSeaMapLayer.m */; };
 		1656665515A1DF7900EF3DC7 /* RMCoordinateGridSource.h in Headers */ = {isa = PBXBuildFile; fileRef = 1656665315A1DF7900EF3DC7 /* RMCoordinateGridSource.h */; };
 		1656665615A1DF7900EF3DC7 /* RMCoordinateGridSource.m in Sources */ = {isa = PBXBuildFile; fileRef = 1656665415A1DF7900EF3DC7 /* RMCoordinateGridSource.m */; };
+		16E5A63A15E531F200C92A5A /* RMCompositeSource.h in Headers */ = {isa = PBXBuildFile; fileRef = 16E5A63815E531F200C92A5A /* RMCompositeSource.h */; };
+		16E5A63B15E531F200C92A5A /* RMCompositeSource.m in Sources */ = {isa = PBXBuildFile; fileRef = 16E5A63915E531F200C92A5A /* RMCompositeSource.m */; };
 		16EC85D2133CA6C300219947 /* RMAbstractMercatorTileSource.h in Headers */ = {isa = PBXBuildFile; fileRef = 16EC85CC133CA6C300219947 /* RMAbstractMercatorTileSource.h */; };
 		16EC85D3133CA6C300219947 /* RMAbstractMercatorTileSource.m in Sources */ = {isa = PBXBuildFile; fileRef = 16EC85CD133CA6C300219947 /* RMAbstractMercatorTileSource.m */; };
 		16EC85D4133CA6C300219947 /* RMAbstractWebMapSource.h in Headers */ = {isa = PBXBuildFile; fileRef = 16EC85CE133CA6C300219947 /* RMAbstractWebMapSource.h */; };
@@ -156,6 +158,8 @@
 		161E56391594664E00B00BB6 /* RMOpenSeaMapLayer.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = RMOpenSeaMapLayer.m; sourceTree = "<group>"; };
 		1656665315A1DF7900EF3DC7 /* RMCoordinateGridSource.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = RMCoordinateGridSource.h; sourceTree = "<group>"; };
 		1656665415A1DF7900EF3DC7 /* RMCoordinateGridSource.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = RMCoordinateGridSource.m; sourceTree = "<group>"; };
+		16E5A63815E531F200C92A5A /* RMCompositeSource.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = RMCompositeSource.h; sourceTree = "<group>"; };
+		16E5A63915E531F200C92A5A /* RMCompositeSource.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = RMCompositeSource.m; sourceTree = "<group>"; };
 		16EC85CC133CA6C300219947 /* RMAbstractMercatorTileSource.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = RMAbstractMercatorTileSource.h; sourceTree = "<group>"; };
 		16EC85CD133CA6C300219947 /* RMAbstractMercatorTileSource.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = RMAbstractMercatorTileSource.m; sourceTree = "<group>"; };
 		16EC85CE133CA6C300219947 /* RMAbstractWebMapSource.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = RMAbstractWebMapSource.h; sourceTree = "<group>"; };
@@ -295,6 +299,8 @@
 		16EC85CB133CA69A00219947 /* Map sources */ = {
 			isa = PBXGroup;
 			children = (
+				16E5A63815E531F200C92A5A /* RMCompositeSource.h */,
+				16E5A63915E531F200C92A5A /* RMCompositeSource.m */,
 				1656665315A1DF7900EF3DC7 /* RMCoordinateGridSource.h */,
 				1656665415A1DF7900EF3DC7 /* RMCoordinateGridSource.m */,
 				D1437B33122869E400888DAE /* RMDBMapSource.h */,
@@ -619,8 +625,9 @@
 				161E563A1594664E00B00BB6 /* RMOpenSeaMapLayer.h in Headers */,
 				1656665515A1DF7900EF3DC7 /* RMCoordinateGridSource.h in Headers */,
 				DD5A200B15CAD09400FE4157 /* GRMustache.h in Headers */,
-				DD5FA1EB15E2B020004EB6C5 /* RMLoadingTileView.h in Headers */,
 				DD4BE198161CE296003EF677 /* MapBox.h in Headers */,
+				16E5A63A15E531F200C92A5A /* RMCompositeSource.h in Headers */,
+				DD5FA1EB15E2B020004EB6C5 /* RMLoadingTileView.h in Headers */,
 				DD4195C9162356900049E6BA /* RMBingSource.h in Headers */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
@@ -739,6 +746,7 @@
 				16FBF07715936BF1004ECAD1 /* RMTileSourcesContainer.m in Sources */,
 				161E563B1594664E00B00BB6 /* RMOpenSeaMapLayer.m in Sources */,
 				1656665615A1DF7900EF3DC7 /* RMCoordinateGridSource.m in Sources */,
+				16E5A63B15E531F200C92A5A /* RMCompositeSource.m in Sources */,
 				DD5FA1EC15E2B020004EB6C5 /* RMLoadingTileView.m in Sources */,
 				DD4195CA162356900049E6BA /* RMBingSource.m in Sources */,
 			);

@@ -41,8 +41,8 @@ Please note that you are responsible for getting permission to use the map data,
    [7]: https://github.com/mapbox/tilestream
    [8]: http://mbtiles.org
 
-Installing
-----------
+Installation
+------------
 
 There are three ways that you can install the SDK, depending upon your needs: