layout/svg/SVGImageContext.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
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef LAYOUT_SVG_SVGIMAGECONTEXT_H_
   8 #define LAYOUT_SVG_SVGIMAGECONTEXT_H_
   9
  10 #include "mozilla/Maybe.h"
  11 #include "mozilla/SVGContextPaint.h"
  12 #include "mozilla/SVGPreserveAspectRatio.h"
  13 #include "Units.h"
  14
  15 class nsIFrame;
  16 class nsISVGPaintContext;
  17
  18 namespace mozilla {
  19
  20 enum class ColorScheme : uint8_t;
  21 class ComputedStyle;
  22
  23 // SVG image-specific rendering context. For imgIContainer::Draw.
  24 // Used to pass information such as
  25 //  - viewport and color-scheme information from CSS, and
  26 //  - overridden attributes from an SVG <image> element
  27 // to the image's internal SVG document when it's drawn.
  28 class SVGImageContext {
  29  public:
  30   SVGImageContext() = default;
  31
  32   /**
  33    * Currently it seems that the aViewportSize parameter ends up being used
  34    * for different things by different pieces of code, and probably in some
  35    * cases being used incorrectly (specifically in the case of pixel snapping
  36    * under the nsLayoutUtils::Draw*Image() methods).  An unfortunate result of
  37    * the messy code is that aViewportSize is currently a Maybe<T> since it
  38    * is difficult to create a utility function that consumers can use up
  39    * front to get the "correct" viewport size (i.e. which for compatibility
  40    * with the current code (bugs and all) would mean the size including all
  41    * the snapping and resizing magic that happens in various places under the
  42    * nsLayoutUtils::Draw*Image() methods on the way to DrawImageInternal
  43    * creating |fallbackContext|).  Using Maybe<T> allows code to pass Nothing()
  44    * in order to get the size that's created for |fallbackContext|.  At some
  45    * point we need to clean this code up, make our abstractions clear, create
  46    * that utility and stop using Maybe for this parameter.
  47    */
  48   explicit SVGImageContext(
  49       const Maybe<CSSIntSize>& aViewportSize,
  50       const Maybe<SVGPreserveAspectRatio>& aPreserveAspectRatio = Nothing(),
  51       const Maybe<ColorScheme>& aColorScheme = Nothing())
  52       : mViewportSize(aViewportSize),
  53         mPreserveAspectRatio(aPreserveAspectRatio),
  54         mColorScheme(aColorScheme) {}
  55
  56   static void MaybeStoreContextPaint(SVGImageContext& aContext,
  57                                      nsIFrame* aFromFrame,
  58                                      imgIContainer* aImgContainer);
  59
  60   static void MaybeStoreContextPaint(SVGImageContext& aContext,
  61                                      const nsPresContext&, const ComputedStyle&,
  62                                      imgIContainer*);
  63
  64   static void MaybeStoreContextPaint(SVGImageContext& aContext,
  65                                      nsISVGPaintContext* aPaintContext,
  66                                      imgIContainer* aImgContainer);
  67
  68   const Maybe<CSSIntSize>& GetViewportSize() const { return mViewportSize; }
  69
  70   void SetViewportSize(const Maybe<CSSIntSize>& aSize) {
  71     mViewportSize = aSize;
  72   }
  73
  74   const Maybe<ColorScheme>& GetColorScheme() const { return mColorScheme; }
  75
  76   void SetColorScheme(const Maybe<ColorScheme>& aScheme) {
  77     mColorScheme = aScheme;
  78   }
  79
  80   const Maybe<SVGPreserveAspectRatio>& GetPreserveAspectRatio() const {
  81     return mPreserveAspectRatio;
  82   }
  83
  84   void SetPreserveAspectRatio(const Maybe<SVGPreserveAspectRatio>& aPAR) {
  85     mPreserveAspectRatio = aPAR;
  86   }
  87
  88   const SVGEmbeddingContextPaint* GetContextPaint() const {
  89     return mContextPaint.get();
  90   }
  91
  92   SVGEmbeddingContextPaint* GetOrCreateContextPaint() {
  93     if (!mContextPaint) {
  94       mContextPaint = MakeRefPtr<SVGEmbeddingContextPaint>();
  95     }
  96
  97     return mContextPaint.get();
  98   }
  99
 100   void ClearContextPaint() { mContextPaint = nullptr; }
 101
 102   bool operator==(const SVGImageContext& aOther) const {
 103     bool contextPaintIsEqual =
 104         // neither have context paint, or they have the same object:
 105         (mContextPaint == aOther.mContextPaint) ||
 106         // or both have context paint that are different but equivalent objects:
 107         (mContextPaint && aOther.mContextPaint &&
 108          *mContextPaint == *aOther.mContextPaint);
 109
 110     return contextPaintIsEqual && mViewportSize == aOther.mViewportSize &&
 111            mPreserveAspectRatio == aOther.mPreserveAspectRatio &&
 112            mColorScheme == aOther.mColorScheme;
 113   }
 114
 115   bool operator!=(const SVGImageContext& aOther) const {
 116     return !(*this == aOther);
 117   }
 118
 119   PLDHashNumber Hash() const {
 120     PLDHashNumber hash = 0;
 121     if (mContextPaint) {
 122       hash = HashGeneric(hash, mContextPaint->Hash());
 123     }
 124     return HashGeneric(hash, mViewportSize.map(HashSize).valueOr(0),
 125                        mPreserveAspectRatio.map(HashPAR).valueOr(0),
 126                        mColorScheme.map(HashColorScheme).valueOr(0));
 127   }
 128
 129  private:
 130   static PLDHashNumber HashSize(const CSSIntSize& aSize) {
 131     return HashGeneric(aSize.width, aSize.height);
 132   }
 133   static PLDHashNumber HashPAR(const SVGPreserveAspectRatio& aPAR) {
 134     return aPAR.Hash();
 135   }
 136   static PLDHashNumber HashColorScheme(ColorScheme aScheme) {
 137     return HashGeneric(uint8_t(aScheme));
 138   }
 139
 140   // NOTE: When adding new member-vars, remember to update Hash() & operator==.
 141   RefPtr<SVGEmbeddingContextPaint> mContextPaint;
 142   Maybe<CSSIntSize> mViewportSize;
 143   Maybe<SVGPreserveAspectRatio> mPreserveAspectRatio;
 144   Maybe<ColorScheme> mColorScheme;
 145 };
 146
 147 }  // namespace mozilla
 148
 149 #endif  // LAYOUT_SVG_SVGIMAGECONTEXT_H_