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 <utility>
  15
  16 #include "ISurfaceProvider.h"
  17 #include "mozilla/Attributes.h"
  18 #include "mozilla/gfx/Point.h"  // for IntSize
  19
  20 namespace mozilla {
  21 namespace image {
  22
  23 enum class MatchType : uint8_t {
  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  public:
  45   explicit LookupResult(MatchType aMatchType)
  46       : mMatchType(aMatchType), mFailedToRequestDecode(false) {
  47     MOZ_ASSERT(
  48         mMatchType == MatchType::NOT_FOUND || mMatchType == MatchType::PENDING,
  49         "Only NOT_FOUND or PENDING make sense with no surface");
  50   }
  51
  52   LookupResult(LookupResult&& aOther)
  53       : mSurface(std::move(aOther.mSurface)),
  54         mMatchType(aOther.mMatchType),
  55         mSuggestedSize(aOther.mSuggestedSize),
  56         mFailedToRequestDecode(aOther.mFailedToRequestDecode) {}
  57
  58   LookupResult(DrawableSurface&& aSurface, MatchType aMatchType)
  59       : mSurface(std::move(aSurface)),
  60         mMatchType(aMatchType),
  61         mFailedToRequestDecode(false) {
  62     MOZ_ASSERT(!mSurface || !(mMatchType == MatchType::NOT_FOUND ||
  63                               mMatchType == MatchType::PENDING),
  64                "Only NOT_FOUND or PENDING make sense with no surface");
  65     MOZ_ASSERT(mSurface || mMatchType == MatchType::NOT_FOUND ||
  66                    mMatchType == MatchType::PENDING,
  67                "NOT_FOUND or PENDING do not make sense with a surface");
  68   }
  69
  70   LookupResult(MatchType aMatchType, const gfx::IntSize& aSuggestedSize)
  71       : mMatchType(aMatchType),
  72         mSuggestedSize(aSuggestedSize),
  73         mFailedToRequestDecode(false) {
  74     MOZ_ASSERT(
  75         mMatchType == MatchType::NOT_FOUND || mMatchType == MatchType::PENDING,
  76         "Only NOT_FOUND or PENDING make sense with no surface");
  77   }
  78
  79   LookupResult(DrawableSurface&& aSurface, MatchType aMatchType,
  80                const gfx::IntSize& aSuggestedSize)
  81       : mSurface(std::move(aSurface)),
  82         mMatchType(aMatchType),
  83         mSuggestedSize(aSuggestedSize),
  84         mFailedToRequestDecode(false) {
  85     MOZ_ASSERT(!mSurface || !(mMatchType == MatchType::NOT_FOUND ||
  86                               mMatchType == MatchType::PENDING),
  87                "Only NOT_FOUND or PENDING make sense with no surface");
  88     MOZ_ASSERT(mSurface || mMatchType == MatchType::NOT_FOUND ||
  89                    mMatchType == MatchType::PENDING,
  90                "NOT_FOUND or PENDING do not make sense with a surface");
  91   }
  92
  93   LookupResult& operator=(LookupResult&& aOther) {
  94     MOZ_ASSERT(&aOther != this, "Self-move-assignment is not supported");
  95     mSurface = std::move(aOther.mSurface);
  96     mMatchType = aOther.mMatchType;
  97     mSuggestedSize = aOther.mSuggestedSize;
  98     mFailedToRequestDecode = aOther.mFailedToRequestDecode;
  99     return *this;
 100   }
 101
 102   DrawableSurface& Surface() { return mSurface; }
 103   const DrawableSurface& Surface() const { return mSurface; }
 104   const gfx::IntSize& SuggestedSize() const { return mSuggestedSize; }
 105
 106   /// @return true if this LookupResult contains a surface.
 107   explicit operator bool() const { return bool(mSurface); }
 108
 109   /// @return what kind of match this is (exact, substitute, etc.)
 110   MatchType Type() const { return mMatchType; }
 111
 112   void SetFailedToRequestDecode() { mFailedToRequestDecode = true; }
 113   bool GetFailedToRequestDecode() { return mFailedToRequestDecode; }
 114
 115  private:
 116   LookupResult(const LookupResult&) = delete;
 117   LookupResult& operator=(const LookupResult& aOther) = delete;
 118
 119   DrawableSurface mSurface;
 120   MatchType mMatchType;
 121
 122   /// mSuggestedSize will be the size of the returned surface if the result is
 123   /// SUBSTITUTE_BECAUSE_BEST. It will be empty for EXACT, and can contain a
 124   /// non-empty size possibly different from the returned surface (if any) for
 125   /// all other results. If non-empty, it will always be the size the caller
 126   /// should request any decodes at.
 127   gfx::IntSize mSuggestedSize;
 128
 129   // True if we tried to start a decode but failed, likely because the image was
 130   // too big to fit into the surface cache.
 131   bool mFailedToRequestDecode;
 132 };
 133
 134 }  // namespace image
 135 }  // namespace mozilla
 136
 137 #endif  // mozilla_image_LookupResult_h