1 files changed, 90 insertions, 0 deletions
diff --git a/image/LookupResult.h b/image/LookupResult.h
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--- /dev/null
+++ b/image/LookupResult.h
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+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * LookupResult is the return type of SurfaceCache's Lookup*() functions. It
+ * combines a surface with relevant metadata tracked by SurfaceCache.
+ */
+
+#ifndef mozilla_image_LookupResult_h
+#define mozilla_image_LookupResult_h
+
+#include "mozilla/Attributes.h"
+#include "mozilla/Move.h"
+#include "ISurfaceProvider.h"
+
+namespace mozilla {
+namespace image {
+
+enum class MatchType : uint8_t
+{
+  NOT_FOUND,  // No matching surface and no placeholder.
+  PENDING,    // Found a matching placeholder, but no surface.
+  EXACT,      // Found a surface that matches exactly.
+  SUBSTITUTE_BECAUSE_NOT_FOUND,  // No exact match, but found a similar one.
+  SUBSTITUTE_BECAUSE_PENDING     // Found a similar surface and a placeholder
+                                 // for an exact match.
+};
+
+/**
+ * LookupResult is the return type of SurfaceCache's Lookup*() functions. It
+ * combines a surface with relevant metadata tracked by SurfaceCache.
+ */
+class MOZ_STACK_CLASS LookupResult
+{
+public:
+  explicit LookupResult(MatchType aMatchType)
+    : mMatchType(aMatchType)
+  {
+    MOZ_ASSERT(mMatchType == MatchType::NOT_FOUND ||
+               mMatchType == MatchType::PENDING,
+               "Only NOT_FOUND or PENDING make sense with no surface");
+  }
+
+  LookupResult(LookupResult&& aOther)
+    : mSurface(Move(aOther.mSurface))
+    , mMatchType(aOther.mMatchType)
+  { }
+
+  LookupResult(DrawableSurface&& aSurface, MatchType aMatchType)
+    : mSurface(Move(aSurface))
+    , mMatchType(aMatchType)
+  {
+    MOZ_ASSERT(!mSurface || !(mMatchType == MatchType::NOT_FOUND ||
+                              mMatchType == MatchType::PENDING),
+               "Only NOT_FOUND or PENDING make sense with no surface");
+    MOZ_ASSERT(mSurface || mMatchType == MatchType::NOT_FOUND ||
+                           mMatchType == MatchType::PENDING,
+               "NOT_FOUND or PENDING do not make sense with a surface");
+  }
+
+  LookupResult& operator=(LookupResult&& aOther)
+  {
+    MOZ_ASSERT(&aOther != this, "Self-move-assignment is not supported");
+    mSurface = Move(aOther.mSurface);
+    mMatchType = aOther.mMatchType;
+    return *this;
+  }
+
+  DrawableSurface& Surface() { return mSurface; }
+  const DrawableSurface& Surface() const { return mSurface; }
+
+  /// @return true if this LookupResult contains a surface.
+  explicit operator bool() const { return bool(mSurface); }
+
+  /// @return what kind of match this is (exact, substitute, etc.)
+  MatchType Type() const { return mMatchType; }
+
+private:
+  LookupResult(const LookupResult&) = delete;
+
+  DrawableSurface mSurface;
+  MatchType mMatchType;
+};
+
+} // namespace image
+} // namespace mozilla
+
+#endif // mozilla_image_LookupResult_h