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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 */
#include "mozilla/Maybe.h"
#include "mozilla/SVGContextPaint.h"
#include "mozilla/SVGPreserveAspectRatio.h"
#include "Units.h"
class nsIFrame;
namespace mozilla {
class ComputedStyle;
// SVG image-specific rendering context. For imgIContainer::Draw.
// Used to pass information such as
// - viewport information from CSS, and
// - overridden attributes from an SVG <image> element
// to the image's internal SVG document when it's drawn.
class SVGImageContext {
SVGImageContext() = default;
* Currently it seems that the aViewportSize parameter ends up being used
* for different things by different pieces of code, and probably in some
* cases being used incorrectly (specifically in the case of pixel snapping
* under the nsLayoutUtils::Draw*Image() methods). An unfortunate result of
* the messy code is that aViewportSize is currently a Maybe<T> since it
* is difficult to create a utility function that consumers can use up
* front to get the "correct" viewport size (i.e. which for compatibility
* with the current code (bugs and all) would mean the size including all
* the snapping and resizing magic that happens in various places under the
* nsLayoutUtils::Draw*Image() methods on the way to DrawImageInternal
* creating |fallbackContext|). Using Maybe<T> allows code to pass Nothing()
* in order to get the size that's created for |fallbackContext|. At some
* point we need to clean this code up, make our abstractions clear, create
* that utility and stop using Maybe for this parameter.
explicit SVGImageContext(
const Maybe<CSSIntSize>& aViewportSize,
const Maybe<SVGPreserveAspectRatio>& aPreserveAspectRatio = Nothing())
: mViewportSize(aViewportSize),
mPreserveAspectRatio(aPreserveAspectRatio) {}
static void MaybeStoreContextPaint(Maybe<SVGImageContext>& aContext,
nsIFrame* aFromFrame,
imgIContainer* aImgContainer);
static void MaybeStoreContextPaint(Maybe<SVGImageContext>& aContext,
const ComputedStyle* aFromComputedStyle,
imgIContainer* aImgContainer);
const Maybe<CSSIntSize>& GetViewportSize() const { return mViewportSize; }
void SetViewportSize(const Maybe<CSSIntSize>& aSize) {
mViewportSize = aSize;
const Maybe<SVGPreserveAspectRatio>& GetPreserveAspectRatio() const {
return mPreserveAspectRatio;
void SetPreserveAspectRatio(const Maybe<SVGPreserveAspectRatio>& aPAR) {
mPreserveAspectRatio = aPAR;
const SVGEmbeddingContextPaint* GetContextPaint() const {
return mContextPaint.get();
void ClearContextPaint() { mContextPaint = nullptr; }
bool operator==(const SVGImageContext& aOther) const {
bool contextPaintIsEqual =
// neither have context paint, or they have the same object:
(mContextPaint == aOther.mContextPaint) ||
// or both have context paint that are different but equivalent objects:
(mContextPaint && aOther.mContextPaint &&
*mContextPaint == *aOther.mContextPaint);
return contextPaintIsEqual && mViewportSize == aOther.mViewportSize &&
mPreserveAspectRatio == aOther.mPreserveAspectRatio;
bool operator!=(const SVGImageContext& aOther) const {
return !(*this == aOther);
PLDHashNumber Hash() const {
PLDHashNumber hash = 0;
if (mContextPaint) {
hash = HashGeneric(hash, mContextPaint->Hash());
return HashGeneric(hash,,;
static PLDHashNumber HashSize(const CSSIntSize& aSize) {
return HashGeneric(aSize.width, aSize.height);
static PLDHashNumber HashPAR(const SVGPreserveAspectRatio& aPAR) {
return aPAR.Hash();
// NOTE: When adding new member-vars, remember to update Hash() & operator==.
RefPtr<SVGEmbeddingContextPaint> mContextPaint;
Maybe<CSSIntSize> mViewportSize;
Maybe<SVGPreserveAspectRatio> mPreserveAspectRatio;
} // namespace mozilla