Add low priority download mode. Low priorities run NSUrlConnection in NSEventTrackingRunLoopMode

SDWebImageDownloader.h

@@ -21,13 +21,16 @@ extern NSString *const SDWebImageDownloadStopNotification;
     NSURLConnection *connection;
     NSMutableData *imageData;
 	id userInfo;
+    BOOL lowPriority;
 }
 
 @property (nonatomic, retain) NSURL *url;
 @property (nonatomic, assign) id<SDWebImageDownloaderDelegate> delegate;
 @property (nonatomic, retain) NSMutableData *imageData;
 @property (nonatomic, retain) id userInfo;
+@property (nonatomic, readwrite) BOOL lowPriority;
 
++ (id)downloaderWithURL:(NSURL *)url delegate:(id<SDWebImageDownloaderDelegate>)delegate userInfo:(id)userInfo lowPriority:(BOOL)lowPriority;
 + (id)downloaderWithURL:(NSURL *)url delegate:(id<SDWebImageDownloaderDelegate>)delegate userInfo:(id)userInfo;
 + (id)downloaderWithURL:(NSURL *)url delegate:(id<SDWebImageDownloaderDelegate>)delegate;
 - (void)start;

SDWebImageDownloader.m

@@ -16,7 +16,7 @@ NSString *const SDWebImageDownloadStopNotification = @"SDWebImageDownloadStopNot
 @end
 
 @implementation SDWebImageDownloader
-@synthesize url, delegate, connection, imageData, userInfo;
+@synthesize url, delegate, connection, imageData, userInfo, lowPriority;
 
 #pragma mark Public Methods
 
@@ -28,6 +28,11 @@ NSString *const SDWebImageDownloadStopNotification = @"SDWebImageDownloadStopNot
 + (id)downloaderWithURL:(NSURL *)url delegate:(id<SDWebImageDownloaderDelegate>)delegate userInfo:(id)userInfo
 {
 
+    return [[self class] downloaderWithURL:url delegate:delegate userInfo:userInfo lowPriority:NO];
+}
+
++ (id)downloaderWithURL:(NSURL *)url delegate:(id<SDWebImageDownloaderDelegate>)delegate userInfo:(id)userInfo lowPriority:(BOOL)lowPriority
+{
     // Bind SDNetworkActivityIndicator if available (download it here: http://github.com/rs/SDNetworkActivityIndicator )
     // To use it, just add #import "SDNetworkActivityIndicator.h" in addition to the SDWebImage import
     if (NSClassFromString(@"SDNetworkActivityIndicator"))
@@ -45,6 +50,7 @@ NSString *const SDWebImageDownloadStopNotification = @"SDWebImageDownloadStopNot
     downloader.url = url;
     downloader.delegate = delegate;
     downloader.userInfo = userInfo;
+    downloader.lowPriority = lowPriority;
     [downloader performSelectorOnMainThread:@selector(start) withObject:nil waitUntilDone:YES];
     return downloader;
 }
@@ -59,8 +65,12 @@ NSString *const SDWebImageDownloadStopNotification = @"SDWebImageDownloadStopNot
     // In order to prevent from potential duplicate caching (NSURLCache + SDImageCache) we disable the cache for image requests
     NSURLRequest *request = [[NSURLRequest alloc] initWithURL:url cachePolicy:NSURLRequestReloadIgnoringLocalCacheData timeoutInterval:15];
     self.connection = [[[NSURLConnection alloc] initWithRequest:request delegate:self startImmediately:NO] autorelease];
-    // Ensure we aren't blocked by UI manipulations (default runloop mode for NSURLConnection is NSEventTrackingRunLoopMode)
-    [connection scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSRunLoopCommonModes];
+
+    // If not in low priority mode, ensure we aren't blocked by UI manipulations (default runloop mode for NSURLConnection is NSEventTrackingRunLoopMode)
+    if (!lowPriority)
+    {
+        [connection scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSRunLoopCommonModes];
+    }
     [connection start];
     [request release];
 

SDWebImageManager.h

@@ -23,6 +23,7 @@
 - (UIImage *)imageWithURL:(NSURL *)url;
 - (void)downloadWithURL:(NSURL *)url delegate:(id<SDWebImageManagerDelegate>)delegate;
 - (void)downloadWithURL:(NSURL *)url delegate:(id<SDWebImageManagerDelegate>)delegate retryFailed:(BOOL)retryFailed;
+- (void)downloadWithURL:(NSURL *)url delegate:(id<SDWebImageManagerDelegate>)delegate retryFailed:(BOOL)retryFailed lowPriority:(BOOL)lowPriority;
 - (void)cancelForDelegate:(id<SDWebImageManagerDelegate>)delegate;
 
 @end

SDWebImageManager.m

@@ -60,6 +60,11 @@ static SDWebImageManager *instance;
 }
 
 - (void)downloadWithURL:(NSURL *)url delegate:(id<SDWebImageManagerDelegate>)delegate retryFailed:(BOOL)retryFailed
+{
+    [self downloadWithURL:url delegate:delegate retryFailed:retryFailed lowPriority:NO];
+}
+
+- (void)downloadWithURL:(NSURL *)url delegate:(id<SDWebImageManagerDelegate>)delegate retryFailed:(BOOL)retryFailed lowPriority:(BOOL)lowPriority
 {
     if (!url || !delegate || (!retryFailed && [failedURLs containsObject:url]))
     {
@@ -67,7 +72,7 @@ static SDWebImageManager *instance;
     }
     
     // Check the on-disk cache async so we don't block the main thread
-    NSDictionary *info = [NSDictionary dictionaryWithObjectsAndKeys:delegate, @"delegate", url, @"url", nil];
+    NSDictionary *info = [NSDictionary dictionaryWithObjectsAndKeys:delegate, @"delegate", url, @"url", [NSNumber numberWithBool:lowPriority], @"low_priority", nil];
     [[SDImageCache sharedImageCache] queryDiskCacheForKey:[url absoluteString] delegate:self userInfo:info];    
 }
 
@@ -110,16 +115,21 @@ static SDWebImageManager *instance;
 {
     NSURL *url = [info objectForKey:@"url"];
     id<SDWebImageManagerDelegate> delegate = [info objectForKey:@"delegate"];
+    BOOL lowPriority = [[info objectForKey:@"low_priority"] boolValue];
 
     // Share the same downloader for identical URLs so we don't download the same URL several times
     SDWebImageDownloader *downloader = [downloaderForURL objectForKey:url];
 
     if (!downloader)
     {
-        downloader = [SDWebImageDownloader downloaderWithURL:url delegate:self];
+        downloader = [SDWebImageDownloader downloaderWithURL:url delegate:self userInfo:nil lowPriority:lowPriority];
         [downloaderForURL setObject:downloader forKey:url];
     }
     
+    // If we get a normal priority request, make sure to change type since downloader is shared
+    if (!lowPriority && downloader.lowPriority)
+        downloader.lowPriority = NO;
+    
     [delegates addObject:delegate];
     [downloaders addObject:downloader];
 }