[ios, macos] Improve snap shotter documentation.

5 files changed, 91 insertions, 55 deletions

diff --git a/platform/darwin/src/MGLMapSnapshotter.h b/platform/darwin/src/MGLMapSnapshotter.h
index a2a4f1b331..d39b252b51 100644
--- a/platform/darwin/src/MGLMapSnapshotter.h
+++ b/platform/darwin/src/MGLMapSnapshotter.h
@@ -12,40 +12,46 @@ MGL_EXPORT
 @interface MGLMapSnapshotOptions : NSObject
 
 /**
- Creates a set of options with the minimum required information
- @param styleURL the style url to use
- @param camera the camera settings
- @param size the image size
+ Creates a set of options with the minimum required information.
+ 
+ @param styleURL URL of the map style to snapshot. The URL may be a full HTTP or HTTPS URL,
+ a Mapbox URL indicating the style’s map ID (mapbox://styles/{user}/{style}), or a path
+ to a local file relative to the application’s resource path. Specify nil for the default style.
+ @param size The image size.
  */
-- (instancetype)initWithStyleURL:(NSURL*)styleURL camera:(MGLMapCamera*)camera size:(CGSize)size;
+- (instancetype)initWithStyleURL:(nullable NSURL*)styleURL camera:(MGLMapCamera*)camera size:(CGSize)size;
 
-#pragma mark - Configuring the map
+#pragma mark - Configuring the Map
 
 /**
-  The style URL for these options.
+ URL of the map style to snapshot. The URL may be a full HTTP or HTTPS URL,
+ a Mapbox URL indicating the style’s map ID (mapbox://styles/{user}/{style}), or a path
+ to a local file relative to the application’s resource path. Specify nil for the default style.
  */
-@property (nonatomic, readonly) NSURL* styleURL;
+@property (nonatomic, readonly) NSURL *styleURL;
 
 /**
- The zoom. Default is 0.
+ The default zoom level is 0. Overrides the altitude in the mapCamera options if set.
  */
-@property (nonatomic) double zoom;
+@property (nonatomic) double zoomLevel;
 
 /**
- The `MGLMapcamera` options to use.
+ A camera representing the viewport visible in the snapshot.
  */
-@property (nonatomic) MGLMapCamera* camera;
+@property (nonatomic) MGLMapCamera *camera;
 
 /**
- A region to capture. Overrides the center coordinate
- in the mapCamera options if set
+ The cooordinate rectangle that encompasses the bounds to capture. Overrides the center coordinate
+ in the mapCamera options if set.
  */
-@property (nonatomic) MGLCoordinateBounds region;
+@property (nonatomic) MGLCoordinateBounds coordinateBounds;
 
-#pragma mark - Configuring the image
+#pragma mark - Configuring the Image
 
 /**
- The size of the output image. Minimum is 64x64
+ The size of the output image.
+ 
+ The image may be no less than 64 pixels wide and no less than 64 pixels tall.
  */
 @property (nonatomic, readonly) CGSize size;
 
@@ -57,18 +63,26 @@ MGL_EXPORT
 
 @end
 
+#if TARGET_OS_IPHONE
 /**
  A block to processes the result or error of a snapshot request.
  
- The result will be either an `MGLImage` or a `NSError`
+ @param snapshot The `UIImage` that was generated or `nil` if an error occurred.
+ @param error The error that occured or `nil` when succesful.
+ */
+typedef void (^MGLMapSnapshotCompletionHandler)(UIImage* _Nullable snapshot, NSError* _Nullable error);
+#else
+/**
+ A block to processes the result or error of a snapshot request.
  
- @param snapshot The image that was generated or `nil` if an error occurred.
+ @param snapshot The `NSImage` that was generated or `nil` if an error occurred.
  @param error The eror that occured or `nil` when succesful.
  */
-typedef void (^MGLMapSnapshotCompletionHandler)(MGLImage* _Nullable snapshot, NSError* _Nullable error);
+typedef void (^MGLMapSnapshotCompletionHandler)(NSImage* _Nullable snapshot, NSError* _Nullable error);
+#endif
 
 /**
- A utility object for capturing map-based images.
+ An immutable utility object for capturing map-based images.
  */
 MGL_EXPORT
 @interface MGLMapSnapshotter : NSObject
@@ -92,6 +106,9 @@ MGL_EXPORT
 
 /**
  Cancels the snapshot creation request, if any.
+ 
+ Once you call this method, you cannot resume the snapshot. In order to obtain the
+ snapshot, create a new `MGLMapSnapshotter` object.
  */
 - (void)cancel;
 
diff --git a/platform/darwin/src/MGLMapSnapshotter.mm b/platform/darwin/src/MGLMapSnapshotter.mm
index c81fd39c4a..b1254b5d3b 100644
--- a/platform/darwin/src/MGLMapSnapshotter.mm
+++ b/platform/darwin/src/MGLMapSnapshotter.mm
@@ -13,6 +13,7 @@
 #import "MGLOfflineStorage_Private.h"
 #import "MGLGeometry_Private.h"
 #import "NSBundle+MGLAdditions.h"
+#import "MGLStyle.h"
 
 #if TARGET_OS_IPHONE
 #import "UIImage+MGLAdditions.h"
@@ -20,12 +21,18 @@
 #import "NSImage+MGLAdditions.h"
 #endif
 
+const CGPoint MGLLogoImagePosition = CGPointMake(8, 8);
+
 @implementation MGLMapSnapshotOptions
 
-- (instancetype _Nonnull)initWithStyleURL:(NSURL* _Nonnull)styleURL camera:(MGLMapCamera*)camera size:(CGSize) size;
+- (instancetype _Nonnull)initWithStyleURL:(nullable NSURL*)styleURL camera:(MGLMapCamera*)camera size:(CGSize) size;
 {
     self = [super init];
     if (self) {
+        if ( !styleURL)
+        {
+            styleURL = [MGLStyle streetsStyleURLWithVersion:MGLStyleDefaultVersion];
+        }
         _styleURL = styleURL;
         _size = size;
         _camera = camera;
@@ -73,17 +80,17 @@
             cameraOptions.center = MGLLatLngFromLocationCoordinate2D(options.camera.centerCoordinate);
         }
         cameraOptions.angle = MAX(0, options.camera.heading) * mbgl::util::DEG2RAD;
-        cameraOptions.zoom = MAX(0, options.zoom);
+        cameraOptions.zoom = MAX(0, options.zoomLevel);
         cameraOptions.pitch = MAX(0, options.camera.pitch);
         
         // Region
-        mbgl::optional<mbgl::LatLngBounds> region;
-        if (!MGLCoordinateBoundsIsEmpty(options.region)) {
-            region = MGLLatLngBoundsFromCoordinateBounds(options.region);
+        mbgl::optional<mbgl::LatLngBounds> coordinateBounds;
+        if (!MGLCoordinateBoundsIsEmpty(options.coordinateBounds)) {
+            coordinateBounds = MGLLatLngBoundsFromCoordinateBounds(options.coordinateBounds);
         }
         
         // Create the snapshotter
-        mbglMapSnapshotter = std::make_unique<mbgl::MapSnapshotter>(*mbglFileSource, *mbglThreadPool, styleURL, size, pixelRatio, cameraOptions, region);
+        mbglMapSnapshotter = std::make_unique<mbgl::MapSnapshotter>(*mbglFileSource, *mbglThreadPool, styleURL, size, pixelRatio, cameraOptions, coordinateBounds);
     }
     return self;
 }
@@ -96,7 +103,8 @@
 - (void)startWithQueue:(dispatch_queue_t)queue completionHandler:(MGLMapSnapshotCompletionHandler)completion;
 {
     if ([self isLoading]) {
-        NSDictionary *userInfo = @{NSLocalizedDescriptionKey: @"Already started this snapshotter"};
+        NSString *errorMessage = NSLocalizedStringWithDefaultValue(@"ALREADY_STARTED_SNAPSHOTTER", nil, nil, @"Already started this snapshotter", "User-friendly error description");
+        NSDictionary *userInfo = @{NSLocalizedDescriptionKey: errorMessage};
         NSError *error = [NSError errorWithDomain:MGLErrorDomain code:1 userInfo:userInfo];
         dispatch_async(queue, ^{
            completion(nil, error); 
@@ -112,7 +120,7 @@
             if (mbglError) {
                 NSString *description = @(mbgl::util::toString(mbglError).c_str());
                 NSDictionary *userInfo = @{NSLocalizedDescriptionKey: description};
-                NSError *error = [NSError errorWithDomain:MGLErrorDomain code:1 userInfo:userInfo];
+                NSError *error = [NSError errorWithDomain:MGLErrorDomain code:MGLErrorCodeSnapshotFailed userInfo:userInfo];
                 
                 // Dispatch result to origin queue
                 dispatch_async(queue, ^{
@@ -130,7 +138,7 @@
                     UIGraphicsBeginImageContext(mglImage.size);
                     
                     [mglImage drawInRect:CGRectMake(0, 0, mglImage.size.width, mglImage.size.height)];
-                    [logoImage drawInRect:CGRectMake(8, mglImage.size.height - (8 + logoImage.size.height), logoImage.size.width,logoImage.size.height)];
+                    [logoImage drawInRect:CGRectMake(MGLLogoImagePosition.x, mglImage.size.height - (MGLLogoImagePosition.y + logoImage.size.height), logoImage.size.width,logoImage.size.height)];
                     UIImage *compositedImage = UIGraphicsGetImageFromCurrentImageContext();
                     
                     UIGraphicsEndImageContext();
@@ -139,7 +147,7 @@
                     NSImage *compositedImage = mglImage;
                     
                     [compositedImage lockFocus];
-                    [logoImage drawInRect:CGRectMake(8, 8, logoImage.size.width,logoImage.size.height)];
+                    [logoImage drawInRect:CGRectMake(MGLLogoImagePosition.x, MGLLogoImagePosition.y, logoImage.size.width,logoImage.size.height)];
                     [compositedImage unlockFocus];
 #endif
                     
diff --git a/platform/darwin/src/MGLTypes.h b/platform/darwin/src/MGLTypes.h
index b3227e1cdf..5c32791c2f 100644
--- a/platform/darwin/src/MGLTypes.h
+++ b/platform/darwin/src/MGLTypes.h
@@ -47,6 +47,8 @@ typedef NS_ENUM(NSInteger, MGLErrorCode) {
     MGLErrorCodeParseStyleFailed = 4,
     /** An attempt to load the style failed. */
     MGLErrorCodeLoadStyleFailed = 5,
+    /** An error occurred while snapshotting the map. */
+    MGLErrorCodeSnapshotFailed = 6,
 };
 
 /** Options for enabling debugging features in an `MGLMapView` instance. */
diff --git a/platform/ios/app/MBXSnapshotsViewController.m b/platform/ios/app/MBXSnapshotsViewController.m
index d26479f085..ab5ad97c90 100644
--- a/platform/ios/app/MBXSnapshotsViewController.m
+++ b/platform/ios/app/MBXSnapshotsViewController.m
@@ -18,27 +18,27 @@
 
 @implementation MBXSnapshotsViewController {
     // Top row
-    MGLMapSnapshotter* snapshotterTL;
-    MGLMapSnapshotter* snapshotterTM;
-    MGLMapSnapshotter* snapshotterTR;
+    MGLMapSnapshotter* topLeftSnapshotter;
+    MGLMapSnapshotter* topCenterSnapshotter;
+    MGLMapSnapshotter* topRightSnapshotter;
     
     // Bottom row
-    MGLMapSnapshotter* snapshotterBL;
-    MGLMapSnapshotter* snapshotterBM;
-    MGLMapSnapshotter* snapshotterBR;
+    MGLMapSnapshotter* bottomLeftSnapshotter;
+    MGLMapSnapshotter* bottomCenterSnapshotter;
+    MGLMapSnapshotter* bottomRightSnapshotter;
 }
 
 - (void)viewDidLoad {
     [super viewDidLoad];
 
     // Start snapshotters
-    snapshotterTL = [self startSnapshotterForImageView:_snapshotImageViewTL coordinates:CLLocationCoordinate2DMake(37.7184, -122.4365)];
-    snapshotterTM = [self startSnapshotterForImageView:_snapshotImageViewTM coordinates:CLLocationCoordinate2DMake(38.8936, -77.0146)];
-    snapshotterTR = [self startSnapshotterForImageView:_snapshotImageViewTR coordinates:CLLocationCoordinate2DMake(-13.1356, -74.2442)];
+    topLeftSnapshotter = [self startSnapshotterForImageView:_snapshotImageViewTL coordinates:CLLocationCoordinate2DMake(37.7184, -122.4365)];
+    topCenterSnapshotter = [self startSnapshotterForImageView:_snapshotImageViewTM coordinates:CLLocationCoordinate2DMake(38.8936, -77.0146)];
+    topRightSnapshotter = [self startSnapshotterForImageView:_snapshotImageViewTR coordinates:CLLocationCoordinate2DMake(-13.1356, -74.2442)];
 
-    snapshotterBL = [self startSnapshotterForImageView:_snapshotImageViewBL coordinates:CLLocationCoordinate2DMake(52.5072, 13.4247)];
-    snapshotterBM = [self startSnapshotterForImageView:_snapshotImageViewBM coordinates:CLLocationCoordinate2DMake(60.2118, 24.6754)];
-    snapshotterBR = [self startSnapshotterForImageView:_snapshotImageViewBR coordinates:CLLocationCoordinate2DMake(31.2780, 121.4286)];
+    bottomLeftSnapshotter = [self startSnapshotterForImageView:_snapshotImageViewBL coordinates:CLLocationCoordinate2DMake(52.5072, 13.4247)];
+    bottomCenterSnapshotter = [self startSnapshotterForImageView:_snapshotImageViewBM coordinates:CLLocationCoordinate2DMake(60.2118, 24.6754)];
+    bottomRightSnapshotter = [self startSnapshotterForImageView:_snapshotImageViewBR coordinates:CLLocationCoordinate2DMake(31.2780, 121.4286)];
 }
 
 - (MGLMapSnapshotter*) startSnapshotterForImageView:(UIImageView*) imageView coordinates:(CLLocationCoordinate2D) coordinates  {
@@ -46,8 +46,8 @@
     MGLMapCamera* mapCamera = [[MGLMapCamera alloc] init];
     mapCamera.pitch = 20;
     mapCamera.centerCoordinate = coordinates;
-    MGLMapSnapshotOptions* options = [[MGLMapSnapshotOptions alloc] initWithStyleURL:[NSURL URLWithString:@"mapbox://styles/mapbox/traffic-day-v2"] camera:mapCamera size:CGSizeMake(imageView.frame.size.width, imageView.frame.size.height)];
-    options.zoom = 10;
+    MGLMapSnapshotOptions* options = [[MGLMapSnapshotOptions alloc] initWithStyleURL:[MGLStyle satelliteStreetsStyleURL] camera:mapCamera size:CGSizeMake(imageView.frame.size.width, imageView.frame.size.height)];
+    options.zoomLevel = 10;
     
     // Create and start the snapshotter
     MGLMapSnapshotter* snapshotter = [[MGLMapSnapshotter alloc] initWithOptions:options];
diff --git a/platform/macos/app/MapDocument.m b/platform/macos/app/MapDocument.m
index 36ca4ad228..d466d2ef4b 100644
--- a/platform/macos/app/MapDocument.m
+++ b/platform/macos/app/MapDocument.m
@@ -163,7 +163,7 @@ NS_ARRAY_OF(id <MGLAnnotation>) *MBXFlattenedShapes(NS_ARRAY_OF(id <MGLAnnotatio
     MGLMapCamera *camera = self.mapView.camera;
     
     MGLMapSnapshotOptions* options = [[MGLMapSnapshotOptions alloc] initWithStyleURL:self.mapView.styleURL camera:camera size:self.mapView.bounds.size];
-    options.zoom = self.mapView.zoomLevel;
+    options.zoomLevel = self.mapView.zoomLevel;
     
     // Create and start the snapshotter
     snapshotter = [[MGLMapSnapshotter alloc] initWithOptions:options];
@@ -177,6 +177,7 @@ NS_ARRAY_OF(id <MGLAnnotation>) *MBXFlattenedShapes(NS_ARRAY_OF(id <MGLAnnotatio
             
             // Set the default name for the file and show the panel.
             NSSavePanel* panel = [NSSavePanel savePanel];
+            
             [panel setNameFieldStringValue:newName];
             [panel beginSheetModalForWindow:window completionHandler:^(NSInteger result){
                 if (result == NSFileHandlingPanelOKButton) {
@@ -196,16 +197,24 @@ NS_ARRAY_OF(id <MGLAnnotation>) *MBXFlattenedShapes(NS_ARRAY_OF(id <MGLAnnotatio
                         
                     }
                     
-                    NSString *extension = [[fileURL pathExtension] lowercaseString];
-                    NSBitmapImageFileType fileType;
-                    if ([extension isEqualToString:@"png"]) {
+                    NSString *uti;
+                    [fileURL getResourceValue:&uti forKey:NSURLTypeIdentifierKey error:nil];
+                    NSBitmapImageFileType fileType = NSTIFFFileType;
+                    
+                    if (UTTypeConformsTo((__bridge CFStringRef)uti, kUTTypePNG)) {
                         fileType = NSPNGFileType;
-                    } else if ([extension isEqualToString:@"gif"]) {
-                        fileType =  NSGIFFileType;
-                    } else if ([extension isEqualToString:@"jpg"] || [extension isEqualToString:@"jpeg"]) {
-                        fileType =  NSJPEGFileType;
-                    } else {
-                        fileType =  NSTIFFFileType;
+                    }
+                    if (UTTypeConformsTo((__bridge CFStringRef)uti, kUTTypeGIF)) {
+                        fileType = NSGIFFileType;
+                    }
+                    if (UTTypeConformsTo((__bridge CFStringRef)uti, kUTTypeJPEG)) {
+                        fileType = NSJPEGFileType;
+                    }
+                    if (UTTypeConformsTo((__bridge CFStringRef)uti, kUTTypeJPEG2000)) {
+                        fileType = NSJPEGFileType;
+                    }
+                    if (UTTypeConformsTo((__bridge CFStringRef)uti, kUTTypeBMP)) {
+                        fileType = NSBitmapImageFileTypeBMP;
                     }
                     
                     NSData *imageData = [bitmapRep representationUsingType:fileType properties:@{}];