ios/chrome/browser/snapshots/snapshot_cache.h

   1 // Copyright 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef IOS_CHROME_BROWSER_SNAPSHOTS_SNAPSHOT_CACHE_H_
   6 #define IOS_CHROME_BROWSER_SNAPSHOTS_SNAPSHOT_CACHE_H_
   7
   8 #import <UIKit/UIKit.h>
   9
  10 #include "base/mac/objc_property_releaser.h"
  11 #include "base/mac/scoped_nsobject.h"
  12 #include "base/time/time.h"
  13
  14 typedef void (^GreyBlock)(UIImage*);
  15
  16 // A singleton providing an in-memory and on-disk cache of tab snapshots.
  17 // A snapshot is a full-screen image of the contents of the page at the current
  18 // scroll offset and zoom level, used to stand in for the UIWebView if it has
  19 // been purged from memory or when quickly switching tabs.
  20 // Persists to disk on a background thread each time a snapshot changes.
  21 @interface SnapshotCache : NSObject {
  22  @private
  23   // Dictionary to hold color snapshots in memory. n.b. Color snapshots are not
  24   // kept in memory on tablets.
  25   base::scoped_nsobject<NSMutableDictionary> imageDictionary_;
  26   // Temporary dictionary to hold grey snapshots for tablet side swipe. This
  27   // will be nil before -createGreyCache is called and after -removeGreyCache
  28   // is called.
  29   base::scoped_nsobject<NSMutableDictionary> greyImageDictionary_;
  30   NSSet* pinnedIDs_;
  31
  32   // Session ID of most recent pending grey snapshot request.
  33   base::scoped_nsobject<NSString> mostRecentGreySessionId_;
  34   // Block used by pending request for a grey snapshot.
  35   base::scoped_nsprotocol<GreyBlock> mostRecentGreyBlock_;
  36
  37   // Session ID and correspoinding UIImage for the snapshot that will likely
  38   // be requested to be saved to disk when the application is backgrounded.
  39   base::scoped_nsobject<NSString> backgroundingImageSessionId_;
  40   base::scoped_nsobject<UIImage> backgroundingColorImage_;
  41
  42   base::mac::ObjCPropertyReleaser propertyReleaser_SnapshotCache_;
  43 }
  44
  45 // Track session IDs to not release on low memory and to reload on
  46 // |UIApplicationDidBecomeActiveNotification|.
  47 @property(nonatomic, retain) NSSet* pinnedIDs;
  48
  49 + (SnapshotCache*)sharedInstance;
  50
  51 // The scale that should be used for snapshots.
  52 + (CGFloat)snapshotScaleForDevice;
  53
  54 // Retrieve a cached snapshot for the |sessionID| and return it via the callback
  55 // if it exists. The callback is guaranteed to be called synchronously if the
  56 // image is in memory. It will be called asynchronously if the image is on disk
  57 // or with nil if the image is not present at all.
  58 - (void)retrieveImageForSessionID:(NSString*)sessionID
  59                          callback:(void (^)(UIImage*))callback;
  60
  61 // Request the session's grey snapshot. If the image is already loaded in
  62 // memory, this will immediately call back on |callback|.
  63 - (void)retrieveGreyImageForSessionID:(NSString*)sessionID
  64                              callback:(void (^)(UIImage*))callback;
  65
  66 - (void)setImage:(UIImage*)img withSessionID:(NSString*)sessionID;
  67 - (void)removeImageWithSessionID:(NSString*)sessionID;
  68 // Purge the cache of snapshots that are older than |date|. The snapshots for
  69 // the sessions given in |liveSessionIds| will be kept. This will be done
  70 // asynchronously on a background thread.
  71 - (void)purgeCacheOlderThan:(const base::Time&)date
  72                     keeping:(NSSet*)liveSessionIds;
  73 // Hint that the snapshot for |sessionID| will likely be saved to disk when the
  74 // application is backgrounded.  The snapshot is then saved in memory, so it
  75 // does not need to be read off disk.
  76 - (void)willBeSavedGreyWhenBackgrounding:(NSString*)sessionID;
  77
  78 // Create temporary cache of grey images for tablet side swipe.
  79 - (void)createGreyCache:(NSArray*)sessionIDs;
  80 // Release all images in grey cache.
  81 - (void)removeGreyCache;
  82 // Request the session's grey snapshot. If the image is already loaded this will
  83 // immediately call back on |callback|. Otherwise, only use |callback| for the
  84 // most recent caller. The callback is not guaranteed to be called.
  85 - (void)greyImageForSessionID:(NSString*)sessionID
  86                      callback:(void (^)(UIImage*))callback;
  87
  88 // Write a grey copy of the snapshot for |sessionID| to disk, but if and only if
  89 // a color version of the snapshot already exists in memory or on disk.
  90 - (void)saveGreyInBackgroundForSessionID:(NSString*)sessionID;
  91 @end
  92
  93 #endif  // IOS_CHROME_BROWSER_SNAPSHOTS_SNAPSHOT_CACHE_H_