Introduced very basic cache system to the web snapshots.

This cache returns a raw UIView which is not copied at all, so if there are multiple views which refers the cache it would be broken. We need to fix this by returning "copied view" or UIImage snapshot instead.
akisute · Dec 14, 2013 · d675178 · d675178
1 parent 4ab60e5
commit d675178
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Showing 2 changed files with 59 additions and 11 deletions.
diff --git a/TwitterClient/TwitterMediaCache.m b/TwitterClient/TwitterMediaCache.m
@@ -34,7 +34,8 @@ + (TwitterWebRenderRequestItem *)infoWithRenderRequest:(TwitterWebRenderRequest
 @interface TwitterMediaCache ()
 @property (nonatomic) NSURLSession *mediaSession;
 @property (nonatomic) TwitterWebRenderWorker *webRenderWorker;
-@property (nonatomic) NSMutableArray *webRenderRequestQueue;    // must be locked before read/write
+@property (nonatomic) NSMutableArray *webRenderRequestQueue;    // V=TwitterWebRenderRequestItem. Must be locked before read/write.
+@property (nonatomic) NSCache *webSnapshotCache;                // V=UIView, K=TwitterWebRenderRequest.
 @end
 
 @implementation TwitterMediaCache
@@ -66,10 +67,14 @@ - (id)init
         // Setup web render worker and queue
         self.webRenderWorker = [[TwitterWebRenderWorker alloc] init];
         self.webRenderRequestQueue = [NSMutableArray array];
+        self.webSnapshotCache = [[NSCache alloc] init];
+        self.webSnapshotCache.totalCostLimit = 20*1000*1000;
     }
     return self;
 }
 
+#pragma mark - Public
+
 - (BOOL)imageWithURL:(NSURL *)url completionHandler:(TwitterMediaCacheImageCompletionHandler)completionHandler
 {
     TwitterMediaCacheImageCompletionHandler callback = [completionHandler copy];
@@ -99,15 +104,21 @@ - (BOOL)snapshotViewWithRenderRequest:(TwitterWebRenderRequest *)renderRequest c
      3. Dequeue URL requests into render workers whenever they are available
      4. When URL requests are finished in render workers, call resizableSnapshotViewFromRect:afterScreenUpdates:withCapInsets: to grab the snapshot, then return it
      
-     For current implementation, only 1 render worker is available at a time. Having multiple render workers could result in very complecated code.
+     For current implementation, only 1 render worker is available at a time.
      
      For current implementation, only portrait mode is available. The UIWebView doesn't handle view rotation itself without any support of UIViewControllers, so we need some solutions to this
      */
 
-    // TODO: need a cache system
-
-    [self __enqueueSnapshotViewRenderRequest:renderRequest completionHandler:completionHandler];
-    [self __popSnapshotViewRenderRequest:NO];
+    UIView *cachedView = [self __cachedSnapshotViewForRenderRequest:renderRequest];
+    if (cachedView) {
+        TwitterMediaCacheSnapshotViewCompletionHandler callback = [completionHandler copy];
+        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
+            callback(cachedView);
+        });
+    } else {
+        [self __enqueueSnapshotViewRenderRequest:renderRequest completionHandler:completionHandler];
+        [self __popSnapshotViewRenderRequest:NO];
+    }
     return YES;
 }
 
@@ -132,6 +143,8 @@ - (void)cancelSnapshotViewRequestWithRequestID:(NSString *)requestID
     }
 }
 
+#pragma mark - Private
+
 - (void)__enqueueSnapshotViewRenderRequest:(TwitterWebRenderRequest *)renderRequest completionHandler:(TwitterMediaCacheSnapshotViewCompletionHandler)completionHandler
 {
     NSLog(@"enqueueing render request: %@", renderRequest.url);
@@ -161,13 +174,34 @@ - (void)__popSnapshotViewRenderRequest:(BOOL)force
     }
 
     NSLog(@"consuming render request: %@", item.renderRequest.url);
-    [self.webRenderWorker startRenderingWithRenderRequest:item.renderRequest completionHandler:^(UIView *view, NSURL *url) {
-        NSLog(@"render request completed: %@", url);
-        item.callback(view);
+    UIView *cachedView = [self __cachedSnapshotViewForRenderRequest:item.renderRequest];
+    if (cachedView) {
         dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
-            [self __popSnapshotViewRenderRequest:YES];
+            item.callback(cachedView);
+            dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
+                [self __popSnapshotViewRenderRequest:YES];
+            });
         });
-    }];
+    } else {
+        [self.webRenderWorker startRenderingWithRenderRequest:item.renderRequest completionHandler:^(UIView *view, NSURL *url) {
+            NSLog(@"render request completed: %@", url);
+            [self __storeSnapshotView:view forRenderRequest:item.renderRequest];
+            item.callback(view);
+            dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
+                [self __popSnapshotViewRenderRequest:YES];
+            });
+        }];
+    }
+}
+
+- (void)__storeSnapshotView:(UIView *)view forRenderRequest:(TwitterWebRenderRequest *)renderRequest
+{
+    [self.webSnapshotCache setObject:view forKey:renderRequest cost:(view.bounds.size.width * view.bounds.size.height * 8)];
+}
+
+- (UIView *)__cachedSnapshotViewForRenderRequest:(TwitterWebRenderRequest *)renderRequest
+{
+    return [self.webSnapshotCache objectForKey:renderRequest];
 }
 
 @end
diff --git a/TwitterClient/TwitterWebRenderRequest.m b/TwitterClient/TwitterWebRenderRequest.m
@@ -18,4 +18,18 @@ + (TwitterWebRenderRequest *)renderRequestWithURL:(NSURL *)url mode:(TwitterWebR
     return renderRequest;
 }
 
+- (NSUInteger)hash
+{
+    return [self.url hash] + self.mode;
+}
+
+- (BOOL)isEqual:(id)object
+{
+    if ([object isKindOfClass:[TwitterWebRenderRequest class]]) {
+        TwitterWebRenderRequest *request = object;
+        return [self.url isEqual:request.url] && self.mode == request.mode;
+    }
+    return NO;
+}
+
 @end