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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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 */
* An interface for objects which can either store a surface or dynamically
* generate one, and various implementations.
#ifndef mozilla_image_ISurfaceProvider_h
#define mozilla_image_ISurfaceProvider_h
#include "mozilla/Attributes.h"
#include "mozilla/Maybe.h"
#include "mozilla/MemoryReporting.h"
#include "mozilla/NotNull.h"
#include "mozilla/TimeStamp.h"
#include "mozilla/gfx/2D.h"
#include "mozilla/image/WebRenderImageProvider.h"
#include "imgFrame.h"
#include "SurfaceCache.h"
namespace mozilla {
namespace image {
class CachedSurface;
class DrawableSurface;
* An interface for objects which can either store a surface or dynamically
* generate one.
class ISurfaceProvider : public WebRenderImageProvider {
// Subclasses may or may not be XPCOM classes, so we just require that they
// implement AddRef and Release.
/// @return key data used for identifying which image this ISurfaceProvider is
/// associated with in the surface cache.
ImageKey GetImageKey() const { return mImageKey; }
/// @return key data used to uniquely identify this ISurfaceProvider's cache
/// entry in the surface cache.
const SurfaceKey& GetSurfaceKey() const { return mSurfaceKey; }
/// @return a drawable reference to a surface.
DrawableSurface Surface();
/// @return true if DrawableRef() will return a completely decoded surface.
virtual bool IsFinished() const = 0;
/// @return true if the underlying decoder is currently fully decoded. For
/// animated images, this means that at least every frame has been decoded
/// at least once. It does not guarantee that all of the frames are present,
/// as the surface provider has the option to discard as it deems necessary.
virtual bool IsFullyDecoded() const { return IsFinished(); }
/// @return the number of bytes of memory this ISurfaceProvider is expected to
/// require. Optimizations may result in lower real memory usage. Trivial
/// overhead is ignored. Because this value is used in bookkeeping, it's
/// important that it be constant over the lifetime of this object.
virtual size_t LogicalSizeInBytes() const = 0;
typedef imgFrame::AddSizeOfCbData AddSizeOfCbData;
typedef imgFrame::AddSizeOfCb AddSizeOfCb;
/// @return the actual number of bytes of memory this ISurfaceProvider is
/// using. May vary over the lifetime of the ISurfaceProvider. The default
/// implementation is appropriate for static ISurfaceProviders.
virtual void AddSizeOfExcludingThis(MallocSizeOf aMallocSizeOf,
const AddSizeOfCb& aCallback) {
DrawableFrameRef ref = DrawableRef(/* aFrame = */ 0);
if (!ref) {
ref->AddSizeOfExcludingThis(aMallocSizeOf, aCallback);
virtual void Reset() {}
virtual void Advance(size_t aFrame) {}
virtual bool MayAdvance() const { return false; }
virtual void MarkMayAdvance() {}
/// @return the availability state of this ISurfaceProvider, which indicates
/// whether DrawableRef() could successfully return a surface. Should only be
/// called from SurfaceCache code as it relies on SurfaceCache for
/// synchronization.
AvailabilityState& Availability() { return mAvailability; }
const AvailabilityState& Availability() const { return mAvailability; }
ISurfaceProvider(const ImageKey aImageKey, const SurfaceKey& aSurfaceKey,
AvailabilityState aAvailability)
: WebRenderImageProvider(aImageKey),
mAvailability(aAvailability) {
MOZ_ASSERT(aImageKey, "Must have a valid image key");
virtual ~ISurfaceProvider() {}
/// @return an eagerly computed drawable reference to a surface. For
/// dynamically generated animation surfaces, @aFrame specifies the 0-based
/// index of the desired frame.
virtual DrawableFrameRef DrawableRef(size_t aFrame) = 0;
/// @return an imgFrame at the 0-based index of the desired frame, as
/// specified by @aFrame. Only applies for animated images.
virtual already_AddRefed<imgFrame> GetFrame(size_t aFrame) {
MOZ_ASSERT_UNREACHABLE("Surface provider does not support direct access!");
return nullptr;
/// @return true if this ISurfaceProvider is locked. (@see SetLocked())
/// Should only be called from SurfaceCache code as it relies on SurfaceCache
/// for synchronization.
virtual bool IsLocked() const = 0;
/// If @aLocked is true, hint that this ISurfaceProvider is in use and it
/// should avoid releasing its resources. Should only be called from
/// SurfaceCache code as it relies on SurfaceCache for synchronization.
virtual void SetLocked(bool aLocked) = 0;
friend class CachedSurface;
friend class DrawableSurface;
const ImageKey mImageKey;
const SurfaceKey mSurfaceKey;
AvailabilityState mAvailability;
* A reference to a surface (stored in an imgFrame) that holds the surface in
* memory, guaranteeing that it can be drawn. If you have a DrawableSurface
* |surf| and |if (surf)| returns true, then calls to |surf->Draw()| and
* |surf->GetSourceSurface()| are guaranteed to succeed.
* Note that the surface may be computed lazily, so a DrawableSurface should not
* be dereferenced (i.e., operator->() should not be called) until you're
* sure that you want to draw it.
class MOZ_STACK_CLASS DrawableSurface final {
DrawableSurface() : mHaveSurface(false) {}
explicit DrawableSurface(NotNull<ISurfaceProvider*> aProvider)
: mProvider(aProvider), mHaveSurface(true) {}
DrawableSurface(DrawableSurface&& aOther)
: mDrawableRef(std::move(aOther.mDrawableRef)),
mHaveSurface(aOther.mHaveSurface) {
aOther.mHaveSurface = false;
DrawableSurface& operator=(DrawableSurface&& aOther) {
MOZ_ASSERT(this != &aOther, "Self-moves are prohibited");
mDrawableRef = std::move(aOther.mDrawableRef);
mProvider = std::move(aOther.mProvider);
mHaveSurface = aOther.mHaveSurface;
aOther.mHaveSurface = false;
return *this;
* If this DrawableSurface is dynamically generated from an animation, attempt
* to seek to frame @aFrame, where @aFrame is a 0-based index into the frames
* of the animation. Otherwise, nothing will blow up at runtime, but we assert
* in debug builds, since calling this in an unexpected situation probably
* indicates a bug.
* @return a successful result if we could obtain frame @aFrame. Note that
* |mHaveSurface| being true means that we're guaranteed to have *some* frame,
* so the caller can dereference this DrawableSurface even if Seek() fails,
* but while nothing will blow up, the frame won't be the one they expect.
nsresult Seek(size_t aFrame) {
MOZ_ASSERT(mHaveSurface, "Trying to seek an empty DrawableSurface?");
if (!mProvider) {
MOZ_ASSERT_UNREACHABLE("Trying to seek a static DrawableSurface?");
mDrawableRef = mProvider->DrawableRef(aFrame);
return mDrawableRef ? NS_OK : NS_ERROR_FAILURE;
already_AddRefed<imgFrame> GetFrame(size_t aFrame) {
MOZ_ASSERT(mHaveSurface, "Trying to get on an empty DrawableSurface?");
if (!mProvider) {
MOZ_ASSERT_UNREACHABLE("Trying to get on a static DrawableSurface?");
return nullptr;
return mProvider->GetFrame(aFrame);
void Reset() {
if (!mProvider) {
MOZ_ASSERT_UNREACHABLE("Trying to reset a static DrawableSurface?");
void Advance(size_t aFrame) {
if (!mProvider) {
MOZ_ASSERT_UNREACHABLE("Trying to advance a static DrawableSurface?");
bool MayAdvance() const {
if (!mProvider) {
MOZ_ASSERT_UNREACHABLE("Trying to advance a static DrawableSurface?");
return false;
return mProvider->MayAdvance();
void MarkMayAdvance() {
if (!mProvider) {
MOZ_ASSERT_UNREACHABLE("Trying to advance a static DrawableSurface?");
bool IsFullyDecoded() const {
if (!mProvider) {
"Trying to check decoding state of a static DrawableSurface?");
return false;
return mProvider->IsFullyDecoded();
void TakeProvider(WebRenderImageProvider** aOutProvider) {
explicit operator bool() const { return mHaveSurface; }
imgFrame* operator->() { return DrawableRef().get(); }
DrawableSurface(const DrawableSurface& aOther) = delete;
DrawableSurface& operator=(const DrawableSurface& aOther) = delete;
DrawableFrameRef& DrawableRef() {
// If we weren't created with a DrawableFrameRef directly, we should've been
// created with an ISurfaceProvider which can give us one. Note that if
// Seek() has been called, we'll already have a DrawableFrameRef, so we
// won't need to get one here.
if (!mDrawableRef) {
mDrawableRef = mProvider->DrawableRef(/* aFrame = */ 0);
return mDrawableRef;
DrawableFrameRef mDrawableRef;
RefPtr<ISurfaceProvider> mProvider;
bool mHaveSurface;
// Surface() is implemented here so that DrawableSurface's definition is
// visible.
inline DrawableSurface ISurfaceProvider::Surface() {
return DrawableSurface(WrapNotNull(this));
* An ISurfaceProvider that stores a single surface.
class SimpleSurfaceProvider final : public ISurfaceProvider {
SimpleSurfaceProvider(const ImageKey aImageKey, const SurfaceKey& aSurfaceKey,
NotNull<imgFrame*> aSurface)
: ISurfaceProvider(aImageKey, aSurfaceKey,
mSurface(aSurface) {
MOZ_ASSERT(aSurfaceKey.Size() == mSurface->GetSize());
bool IsFinished() const override { return mSurface->IsFinished(); }
size_t LogicalSizeInBytes() const override {
gfx::IntSize size = mSurface->GetSize();
return size.width * size.height * mSurface->GetBytesPerPixel();
nsresult UpdateKey(layers::RenderRootStateManager* aManager,
wr::IpcResourceUpdateQueue& aResources,
wr::ImageKey& aKey) override;
DrawableFrameRef DrawableRef(size_t aFrame) override {
MOZ_ASSERT(aFrame == 0,
"Requesting an animation frame from a SimpleSurfaceProvider?");
return mSurface->DrawableRef();
bool IsLocked() const override { return bool(mLockRef); }
void SetLocked(bool aLocked) override {
if (aLocked == IsLocked()) {
return; // Nothing changed.
// If we're locked, hold a DrawableFrameRef to |mSurface|, which will keep
// any volatile buffer it owns in memory.
mLockRef = aLocked ? mSurface->DrawableRef() : DrawableFrameRef();
virtual ~SimpleSurfaceProvider() {}
NotNull<RefPtr<imgFrame>> mSurface;
DrawableFrameRef mLockRef;
} // namespace image
} // namespace mozilla
#endif // mozilla_image_ISurfaceProvider_h