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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this file,
* You can obtain one at */
// A class that handles style system image loads (other image loads are handled
// by the nodes in the content tree).
#ifndef mozilla_css_ImageLoader_h___
#define mozilla_css_ImageLoader_h___
#include "mozilla/CORSMode.h"
#include "nsClassHashtable.h"
#include "nsHashKeys.h"
#include "nsRect.h"
#include "nsTArray.h"
#include "mozilla/Attributes.h"
class nsIFrame;
class imgIContainer;
class imgIRequest;
class imgRequestProxy;
class nsPresContext;
class nsIURI;
class nsIPrincipal;
class nsIRequest;
namespace mozilla {
struct MediaFeatureChange;
struct StyleComputedUrl;
namespace dom {
class Document;
namespace css {
* NOTE: All methods must be called from the main thread unless otherwise
* specified.
class ImageLoader final {
static void Init();
static void Shutdown();
// We also associate flags alongside frames in the request-to-frames hashmap.
// These are used for special handling of events for requests.
enum class Flags : uint32_t {
// Used for bullets.
RequiresReflowOnSizeAvailable = 1u << 0,
// Used for shapes.
RequiresReflowOnFirstFrameCompleteAndLoadEventBlocking = 1u << 1,
// Internal flag, shouldn't be used by callers.
IsBlockingLoadEvent = 1u << 2,
explicit ImageLoader(dom::Document* aDocument) : mDocument(aDocument) {
void DropDocumentReference();
void AssociateRequestToFrame(imgIRequest*, nsIFrame*, Flags = Flags(0));
void DisassociateRequestFromFrame(imgIRequest*, nsIFrame*);
void DropRequestsForFrame(nsIFrame*);
void SetAnimationMode(uint16_t aMode);
// The prescontext for this ImageLoader's document. We need it to be passed
// in because this can be called during presentation destruction after the
// presshell pointer on the document has been cleared.
void ClearFrames(nsPresContext* aPresContext);
// Triggers an image load.
static already_AddRefed<imgRequestProxy> LoadImage(const StyleComputedUrl&,
// Usually, only one style value owns a given proxy. However, we have a hack
// to share image proxies in chrome documents under some circumstances. We
// need to keep track of this so that we don't stop tracking images too early.
// In practice it shouldn't matter as these chrome images are mostly static,
// but it is always good to keep sanity.
static void NoteSharedLoad(imgRequestProxy*);
// Undoes what `LoadImage` does.
static void UnloadImage(imgRequestProxy*);
// This is called whenever an image we care about notifies the
// GlobalImageObserver.
void Notify(imgIRequest*, int32_t aType, const nsIntRect* aData);
// Called when we stop caring about a given request.
void DeregisterImageRequest(imgIRequest*, nsPresContext*);
struct ImageReflowCallback;
~ImageLoader() = default;
// We need to be able to look up the frames associated with a request (for
// delivering notifications) and the requests associated with a frame (when
// the frame goes away). Thus we maintain hashtables going both ways. These
// should always be in sync.
struct FrameWithFlags {
explicit FrameWithFlags(nsIFrame* aFrame) : mFrame(aFrame) {
nsIFrame* const mFrame;
Flags mFlags{0};
// A helper class to compare FrameWithFlags by comparing mFrame and
// ignoring mFlags.
class FrameOnlyComparator {
bool Equals(const FrameWithFlags& aElem1,
const FrameWithFlags& aElem2) const {
return aElem1.mFrame == aElem2.mFrame;
bool LessThan(const FrameWithFlags& aElem1,
const FrameWithFlags& aElem2) const {
return aElem1.mFrame < aElem2.mFrame;
typedef nsTArray<FrameWithFlags> FrameSet;
typedef nsTArray<nsCOMPtr<imgIRequest>> RequestSet;
typedef nsClassHashtable<nsISupportsHashKey, FrameSet> RequestToFrameMap;
typedef nsClassHashtable<nsPtrHashKey<nsIFrame>, RequestSet>
nsPresContext* GetPresContext();
void ImageFrameChanged(imgIRequest*, bool aFirstFrame);
void UnblockOnloadIfNeeded(nsIFrame*, imgIRequest*);
void UnblockOnloadIfNeeded(FrameWithFlags&);
void OnSizeAvailable(imgIRequest* aRequest, imgIContainer* aImage);
void OnFrameComplete(imgIRequest* aRequest);
void OnImageIsAnimated(imgIRequest* aRequest);
void OnFrameUpdate(imgIRequest* aRequest);
void OnLoadComplete(imgIRequest* aRequest);
// Helpers for DropRequestsForFrame / DisassociateRequestFromFrame above.
void RemoveRequestToFrameMapping(imgIRequest* aRequest, nsIFrame* aFrame);
void RemoveFrameToRequestMapping(imgIRequest* aRequest, nsIFrame* aFrame);
// A map of imgIRequests to the nsIFrames that are using them.
RequestToFrameMap mRequestToFrameMap;
// A map of nsIFrames to the imgIRequests they use.
FrameToRequestMap mFrameToRequestMap;
// A weak pointer to our document. Nulled out by DropDocumentReference.
dom::Document* mDocument;
} // namespace css
} // namespace mozilla
#endif /* mozilla_css_ImageLoader_h___ */