image/LookupResult.h

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* This Source Code Form is subject to the terms of the Mozilla Public
   3  * License, v. 2.0. If a copy of the MPL was not distributed with this
   4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   5
   6 /**
   7  * LookupResult is the return type of SurfaceCache's Lookup*() functions. It
   8  * combines a surface with relevant metadata tracked by SurfaceCache.
   9  */
  10
  11 #ifndef mozilla_image_LookupResult_h
  12 #define mozilla_image_LookupResult_h
  13
  14 #include "mozilla/Attributes.h"
  15 #include "mozilla/gfx/Point.h"  // for IntSize
  16 #include "mozilla/Move.h"
  17 #include "ISurfaceProvider.h"
  18
  19 namespace mozilla {
  20 namespace image {
  21
  22 enum class MatchType : uint8_t {
  23   NOT_FOUND,  // No matching surface and no placeholder.
  24   PENDING,    // Found a matching placeholder, but no surface.
  25   EXACT,      // Found a surface that matches exactly.
  26   SUBSTITUTE_BECAUSE_NOT_FOUND,  // No exact match, but found a similar one.
  27   SUBSTITUTE_BECAUSE_PENDING,    // Found a similar surface and a placeholder
  28                                  // for an exact match.
  29
  30   /* No exact match, but this should be considered an exact match for purposes
  31    * of deciding whether or not to request a new decode. This is because the
  32    * cache has determined that callers require too many size variants of this
  33    * image. It determines the set of sizes which best represent the image, and
  34    * will only suggest decoding of unavailable sizes from that set. */
  35   SUBSTITUTE_BECAUSE_BEST
  36 };
  37
  38 /**
  39  * LookupResult is the return type of SurfaceCache's Lookup*() functions. It
  40  * combines a surface with relevant metadata tracked by SurfaceCache.
  41  */
  42 class MOZ_STACK_CLASS LookupResult {
  43  public:
  44   explicit LookupResult(MatchType aMatchType) : mMatchType(aMatchType) {
  45     MOZ_ASSERT(
  46         mMatchType == MatchType::NOT_FOUND || mMatchType == MatchType::PENDING,
  47         "Only NOT_FOUND or PENDING make sense with no surface");
  48   }
  49
  50   LookupResult(LookupResult&& aOther)
  51       : mSurface(std::move(aOther.mSurface)),
  52         mMatchType(aOther.mMatchType),
  53         mSuggestedSize(aOther.mSuggestedSize) {}
  54
  55   LookupResult(DrawableSurface&& aSurface, MatchType aMatchType)
  56       : mSurface(std::move(aSurface)), mMatchType(aMatchType) {
  57     MOZ_ASSERT(!mSurface || !(mMatchType == MatchType::NOT_FOUND ||
  58                               mMatchType == MatchType::PENDING),
  59                "Only NOT_FOUND or PENDING make sense with no surface");
  60     MOZ_ASSERT(mSurface || mMatchType == MatchType::NOT_FOUND ||
  61                    mMatchType == MatchType::PENDING,
  62                "NOT_FOUND or PENDING do not make sense with a surface");
  63   }
  64
  65   LookupResult(MatchType aMatchType, const gfx::IntSize& aSuggestedSize)
  66       : mMatchType(aMatchType), mSuggestedSize(aSuggestedSize) {
  67     MOZ_ASSERT(
  68         mMatchType == MatchType::NOT_FOUND || mMatchType == MatchType::PENDING,
  69         "Only NOT_FOUND or PENDING make sense with no surface");
  70   }
  71
  72   LookupResult(DrawableSurface&& aSurface, MatchType aMatchType,
  73                const gfx::IntSize& aSuggestedSize)
  74       : mSurface(std::move(aSurface)),
  75         mMatchType(aMatchType),
  76         mSuggestedSize(aSuggestedSize) {
  77     MOZ_ASSERT(!mSurface || !(mMatchType == MatchType::NOT_FOUND ||
  78                               mMatchType == MatchType::PENDING),
  79                "Only NOT_FOUND or PENDING make sense with no surface");
  80     MOZ_ASSERT(mSurface || mMatchType == MatchType::NOT_FOUND ||
  81                    mMatchType == MatchType::PENDING,
  82                "NOT_FOUND or PENDING do not make sense with a surface");
  83   }
  84
  85   LookupResult& operator=(LookupResult&& aOther) {
  86     MOZ_ASSERT(&aOther != this, "Self-move-assignment is not supported");
  87     mSurface = std::move(aOther.mSurface);
  88     mMatchType = aOther.mMatchType;
  89     mSuggestedSize = aOther.mSuggestedSize;
  90     return *this;
  91   }
  92
  93   DrawableSurface& Surface() { return mSurface; }
  94   const DrawableSurface& Surface() const { return mSurface; }
  95   const gfx::IntSize& SuggestedSize() const { return mSuggestedSize; }
  96
  97   /// @return true if this LookupResult contains a surface.
  98   explicit operator bool() const { return bool(mSurface); }
  99
 100   /// @return what kind of match this is (exact, substitute, etc.)
 101   MatchType Type() const { return mMatchType; }
 102
 103  private:
 104   LookupResult(const LookupResult&) = delete;
 105   LookupResult& operator=(const LookupResult& aOther) = delete;
 106
 107   DrawableSurface mSurface;
 108   MatchType mMatchType;
 109
 110   /// mSuggestedSize will be the size of the returned surface if the result is
 111   /// SUBSTITUTE_BECAUSE_BEST. It will be empty for EXACT, and can contain a
 112   /// non-empty size possibly different from the returned surface (if any) for
 113   /// all other results. If non-empty, it will always be the size the caller
 114   /// should request any decodes at.
 115   gfx::IntSize mSuggestedSize;
 116 };
 117
 118 }  // namespace image
 119 }  // namespace mozilla
 120
 121 #endif  // mozilla_image_LookupResult_h