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