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 {
  24   NOT_FOUND,  // No matching surface and no placeholder.
  25   PENDING,    // Found a matching placeholder, but no surface.
  26   EXACT,      // Found a surface that matches exactly.
  27   SUBSTITUTE_BECAUSE_NOT_FOUND,  // No exact match, but found a similar one.
  28   SUBSTITUTE_BECAUSE_PENDING,    // Found a similar surface and a placeholder
  29                                  // for an exact match.
  30
  31   /* No exact match, but this should be considered an exact match for purposes
  32    * of deciding whether or not to request a new decode. This is because the
  33    * cache has determined that callers require too many size variants of this
  34    * image. It determines the set of sizes which best represent the image, and
  35    * will only suggest decoding of unavailable sizes from that set. */
  36   SUBSTITUTE_BECAUSE_BEST
  37 };
  38
  39 /**
  40  * LookupResult is the return type of SurfaceCache's Lookup*() functions. It
  41  * combines a surface with relevant metadata tracked by SurfaceCache.
  42  */
  43 class MOZ_STACK_CLASS LookupResult
  44 {
  45 public:
  46   explicit LookupResult(MatchType aMatchType)
  47     : mMatchType(aMatchType)
  48   {
  49     MOZ_ASSERT(mMatchType == MatchType::NOT_FOUND ||
  50                mMatchType == MatchType::PENDING,
  51                "Only NOT_FOUND or PENDING make sense with no surface");
  52   }
  53
  54   LookupResult(LookupResult&& aOther)
  55     : mSurface(Move(aOther.mSurface))
  56     , mMatchType(aOther.mMatchType)
  57     , mSuggestedSize(aOther.mSuggestedSize)
  58   { }
  59
  60   LookupResult(DrawableSurface&& aSurface, MatchType aMatchType)
  61     : mSurface(Move(aSurface))
  62     , mMatchType(aMatchType)
  63   {
  64     MOZ_ASSERT(!mSurface || !(mMatchType == MatchType::NOT_FOUND ||
  65                               mMatchType == MatchType::PENDING),
  66                "Only NOT_FOUND or PENDING make sense with no surface");
  67     MOZ_ASSERT(mSurface || mMatchType == MatchType::NOT_FOUND ||
  68                            mMatchType == MatchType::PENDING,
  69                "NOT_FOUND or PENDING do not make sense with a surface");
  70   }
  71
  72   LookupResult(DrawableSurface&& aSurface, MatchType aMatchType,
  73                const gfx::IntSize& aSuggestedSize)
  74     : mSurface(Move(aSurface))
  75     , mMatchType(aMatchType)
  76     , mSuggestedSize(aSuggestedSize)
  77   {
  78     MOZ_ASSERT(!mSurface || !(mMatchType == MatchType::NOT_FOUND ||
  79                               mMatchType == MatchType::PENDING),
  80                "Only NOT_FOUND or PENDING make sense with no surface");
  81     MOZ_ASSERT(mSurface || mMatchType == MatchType::NOT_FOUND ||
  82                            mMatchType == MatchType::PENDING,
  83                "NOT_FOUND or PENDING do not make sense with a surface");
  84   }
  85
  86   LookupResult& operator=(LookupResult&& aOther)
  87   {
  88     MOZ_ASSERT(&aOther != this, "Self-move-assignment is not supported");
  89     mSurface = Move(aOther.mSurface);
  90     mMatchType = aOther.mMatchType;
  91     mSuggestedSize = aOther.mSuggestedSize;
  92     return *this;
  93   }
  94
  95   DrawableSurface& Surface() { return mSurface; }
  96   const DrawableSurface& Surface() const { return mSurface; }
  97   const gfx::IntSize& SuggestedSize() const { return mSuggestedSize; }
  98
  99   /// @return true if this LookupResult contains a surface.
 100   explicit operator bool() const { return bool(mSurface); }
 101
 102   /// @return what kind of match this is (exact, substitute, etc.)
 103   MatchType Type() const { return mMatchType; }
 104
 105 private:
 106   LookupResult(const LookupResult&) = delete;
 107   LookupResult& operator=(const LookupResult& aOther) = delete;
 108
 109   DrawableSurface mSurface;
 110   MatchType mMatchType;
 111
 112   /// If given, the size the caller should request a decode at. This may or may
 113   /// not match the size the caller requested from the cache.
 114   gfx::IntSize mSuggestedSize;
 115 };
 116
 117 } // namespace image
 118 } // namespace mozilla
 119
 120 #endif // mozilla_image_LookupResult_h