layout/style/ImageLoader.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
   5  * You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 // A class that handles style system image loads (other image loads are handled
   8 // by the nodes in the content tree).
   9
  10 #ifndef mozilla_css_ImageLoader_h___
  11 #define mozilla_css_ImageLoader_h___
  12
  13 #include "mozilla/CORSMode.h"
  14 #include "nsClassHashtable.h"
  15 #include "nsHashKeys.h"
  16 #include "nsRect.h"
  17 #include "nsTArray.h"
  18 #include "mozilla/Attributes.h"
  19
  20 class nsIFrame;
  21 class imgIContainer;
  22 class imgIRequest;
  23 class imgRequestProxy;
  24 class nsPresContext;
  25 class nsIURI;
  26 class nsIPrincipal;
  27 class nsIRequest;
  28
  29 namespace mozilla {
  30 struct MediaFeatureChange;
  31 struct StyleComputedUrl;
  32 namespace dom {
  33 class Document;
  34 }
  35
  36 namespace css {
  37
  38 /**
  39  * NOTE: All methods must be called from the main thread unless otherwise
  40  * specified.
  41  */
  42 class ImageLoader final {
  43  public:
  44   static void Init();
  45   static void Shutdown();
  46
  47   // We also associate flags alongside frames in the request-to-frames hashmap.
  48   // These are used for special handling of events for requests.
  49   enum class Flags : uint32_t {
  50     // Used for bullets.
  51     RequiresReflowOnSizeAvailable = 1u << 0,
  52
  53     // Used for shapes.
  54     RequiresReflowOnFirstFrameCompleteAndLoadEventBlocking = 1u << 1,
  55
  56     // Internal flag, shouldn't be used by callers.
  57     IsBlockingLoadEvent = 1u << 2,
  58   };
  59
  60   explicit ImageLoader(dom::Document* aDocument) : mDocument(aDocument) {
  61     MOZ_ASSERT(mDocument);
  62   }
  63
  64   NS_INLINE_DECL_REFCOUNTING(ImageLoader)
  65
  66   void DropDocumentReference();
  67
  68   void AssociateRequestToFrame(imgIRequest*, nsIFrame*, Flags = Flags(0));
  69   void DisassociateRequestFromFrame(imgIRequest*, nsIFrame*);
  70   void DropRequestsForFrame(nsIFrame*);
  71
  72   void SetAnimationMode(uint16_t aMode);
  73
  74   // The prescontext for this ImageLoader's document. We need it to be passed
  75   // in because this can be called during presentation destruction after the
  76   // presshell pointer on the document has been cleared.
  77   void ClearFrames(nsPresContext* aPresContext);
  78
  79   // Triggers an image load.
  80   static already_AddRefed<imgRequestProxy> LoadImage(const StyleComputedUrl&,
  81                                                      dom::Document&);
  82
  83   // Usually, only one style value owns a given proxy. However, we have a hack
  84   // to share image proxies in chrome documents under some circumstances. We
  85   // need to keep track of this so that we don't stop tracking images too early.
  86   //
  87   // In practice it shouldn't matter as these chrome images are mostly static,
  88   // but it is always good to keep sanity.
  89   static void NoteSharedLoad(imgRequestProxy*);
  90
  91   // Undoes what `LoadImage` does.
  92   static void UnloadImage(imgRequestProxy*);
  93
  94   // This is called whenever an image we care about notifies the
  95   // GlobalImageObserver.
  96   void Notify(imgIRequest*, int32_t aType, const nsIntRect* aData);
  97
  98  private:
  99   // Called when we stop caring about a given request.
 100   void DeregisterImageRequest(imgIRequest*, nsPresContext*);
 101   struct ImageReflowCallback;
 102
 103   ~ImageLoader() = default;
 104
 105   // We need to be able to look up the frames associated with a request (for
 106   // delivering notifications) and the requests associated with a frame (when
 107   // the frame goes away). Thus we maintain hashtables going both ways.  These
 108   // should always be in sync.
 109
 110   struct FrameWithFlags {
 111     explicit FrameWithFlags(nsIFrame* aFrame) : mFrame(aFrame) {
 112       MOZ_ASSERT(mFrame);
 113     }
 114     nsIFrame* const mFrame;
 115     Flags mFlags{0};
 116   };
 117
 118   // A helper class to compare FrameWithFlags by comparing mFrame and
 119   // ignoring mFlags.
 120   class FrameOnlyComparator {
 121    public:
 122     bool Equals(const FrameWithFlags& aElem1,
 123                 const FrameWithFlags& aElem2) const {
 124       return aElem1.mFrame == aElem2.mFrame;
 125     }
 126
 127     bool LessThan(const FrameWithFlags& aElem1,
 128                   const FrameWithFlags& aElem2) const {
 129       return aElem1.mFrame < aElem2.mFrame;
 130     }
 131   };
 132
 133   typedef nsTArray<FrameWithFlags> FrameSet;
 134   typedef nsTArray<nsCOMPtr<imgIRequest>> RequestSet;
 135   typedef nsClassHashtable<nsISupportsHashKey, FrameSet> RequestToFrameMap;
 136   typedef nsClassHashtable<nsPtrHashKey<nsIFrame>, RequestSet>
 137       FrameToRequestMap;
 138
 139   nsPresContext* GetPresContext();
 140
 141   void ImageFrameChanged(imgIRequest*, bool aFirstFrame);
 142   void UnblockOnloadIfNeeded(nsIFrame*, imgIRequest*);
 143   void UnblockOnloadIfNeeded(FrameWithFlags&);
 144
 145   void OnSizeAvailable(imgIRequest* aRequest, imgIContainer* aImage);
 146   void OnFrameComplete(imgIRequest* aRequest);
 147   void OnImageIsAnimated(imgIRequest* aRequest);
 148   void OnFrameUpdate(imgIRequest* aRequest);
 149   void OnLoadComplete(imgIRequest* aRequest);
 150
 151   // Helpers for DropRequestsForFrame / DisassociateRequestFromFrame above.
 152   void RemoveRequestToFrameMapping(imgIRequest* aRequest, nsIFrame* aFrame);
 153   void RemoveFrameToRequestMapping(imgIRequest* aRequest, nsIFrame* aFrame);
 154
 155   // A map of imgIRequests to the nsIFrames that are using them.
 156   RequestToFrameMap mRequestToFrameMap;
 157
 158   // A map of nsIFrames to the imgIRequests they use.
 159   FrameToRequestMap mFrameToRequestMap;
 160
 161   // A weak pointer to our document. Nulled out by DropDocumentReference.
 162   dom::Document* mDocument;
 163 };
 164
 165 MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(ImageLoader::Flags)
 166
 167 }  // namespace css
 168 }  // namespace mozilla
 169
 170 #endif /* mozilla_css_ImageLoader_h___ */