diff -r 000000000000 -r 6474c204b198 layout/style/nsIMediaList.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/layout/style/nsIMediaList.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,213 @@
+/* -*- 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/. */
+
+/*
+ * representation of media lists used when linking to style sheets or by
+ * @media rules
+ */
+
+#ifndef nsIMediaList_h_
+#define nsIMediaList_h_
+
+#include "nsIDOMMediaList.h"
+#include "nsTArray.h"
+#include "nsIAtom.h"
+#include "nsCSSValue.h"
+#include "nsWrapperCache.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/ErrorResult.h"
+
+class nsPresContext;
+class nsCSSStyleSheet;
+class nsAString;
+struct nsMediaFeature;
+
+struct nsMediaExpression {
+  enum Range { eMin, eMax, eEqual };
+
+  const nsMediaFeature *mFeature;
+  Range mRange;
+  nsCSSValue mValue;
+
+  // aActualValue must be obtained from mFeature->mGetter
+  bool Matches(nsPresContext* aPresContext,
+                 const nsCSSValue& aActualValue) const;
+};
+
+/**
+ * An nsMediaQueryResultCacheKey records what feature/value combinations
+ * a set of media query results are valid for.  This allows the caller
+ * to quickly learn whether a prior result of media query evaluation is
+ * still valid (e.g., due to a window size change) without rerunning all
+ * of the evaluation and rebuilding the list of rules.
+ *
+ * This object may not be used after any media rules in any of the
+ * sheets it was given to have been modified.  However, this is
+ * generally not a problem since ClearRuleCascades is called on the
+ * sheet whenever this happens, and these objects are stored inside the
+ * rule cascades.  (FIXME: We're not actually doing this all the time.)
+ *
+ * The implementation could be further optimized in the future to store
+ * ranges (combinations of less-than, less-than-or-equal, greater-than,
+ * greater-than-or-equal, equal, not-equal, present, not-present) for
+ * each feature rather than simply storing the list of expressions.
+ * However, this requires combining any such ranges.
+ */
+class nsMediaQueryResultCacheKey {
+public:
+  nsMediaQueryResultCacheKey(nsIAtom* aMedium)
+    : mMedium(aMedium)
+  {}
+
+  /**
+   * Record that aExpression was tested while building the cached set
+   * that this cache key is for, and that aExpressionMatches was whether
+   * it matched.
+   */
+  void AddExpression(const nsMediaExpression* aExpression,
+                     bool aExpressionMatches);
+  bool Matches(nsPresContext* aPresContext) const;
+private:
+  struct ExpressionEntry {
+    // FIXME: if we were better at maintaining invariants about clearing
+    // rule cascades when media lists change, this could be a |const
+    // nsMediaExpression*| instead.
+    nsMediaExpression mExpression;
+    bool mExpressionMatches;
+  };
+  struct FeatureEntry {
+    const nsMediaFeature *mFeature;
+    InfallibleTArray<ExpressionEntry> mExpressions;
+  };
+  nsCOMPtr<nsIAtom> mMedium;
+  nsTArray<FeatureEntry> mFeatureCache;
+};
+
+class nsMediaQuery {
+public:
+  nsMediaQuery()
+    : mNegated(false)
+    , mHasOnly(false)
+    , mTypeOmitted(false)
+    , mHadUnknownExpression(false)
+  {
+  }
+
+private:
+  // for Clone only
+  nsMediaQuery(const nsMediaQuery& aOther)
+    : mNegated(aOther.mNegated)
+    , mHasOnly(aOther.mHasOnly)
+    , mTypeOmitted(aOther.mTypeOmitted)
+    , mHadUnknownExpression(aOther.mHadUnknownExpression)
+    , mMediaType(aOther.mMediaType)
+    , mExpressions(aOther.mExpressions)
+  {
+    MOZ_ASSERT(mExpressions.Length() == aOther.mExpressions.Length());
+  }
+
+public:
+
+  void SetNegated()                     { mNegated = true; }
+  void SetHasOnly()                     { mHasOnly = true; }
+  void SetTypeOmitted()                 { mTypeOmitted = true; }
+  void SetHadUnknownExpression()        { mHadUnknownExpression = true; }
+  void SetType(nsIAtom* aMediaType)     { 
+                                          NS_ASSERTION(aMediaType,
+                                                       "expected non-null");
+                                          mMediaType = aMediaType;
+                                        }
+
+  // Return a new nsMediaExpression in the array for the caller to fill
+  // in.  The caller must either fill it in completely, or call
+  // SetHadUnknownExpression on this nsMediaQuery.
+  // Returns null on out-of-memory.
+  nsMediaExpression* NewExpression()    { return mExpressions.AppendElement(); }
+
+  void AppendToString(nsAString& aString) const;
+
+  nsMediaQuery* Clone() const;
+
+  // Does this query apply to the presentation?
+  // If |aKey| is non-null, add cache information to it.
+  bool Matches(nsPresContext* aPresContext,
+                 nsMediaQueryResultCacheKey* aKey) const;
+
+private:
+  bool mNegated;
+  bool mHasOnly; // only needed for serialization
+  bool mTypeOmitted; // only needed for serialization
+  bool mHadUnknownExpression;
+  nsCOMPtr<nsIAtom> mMediaType;
+  nsTArray<nsMediaExpression> mExpressions;
+};
+
+class nsMediaList MOZ_FINAL : public nsIDOMMediaList
+                            , public nsWrapperCache
+{
+public:
+  typedef mozilla::ErrorResult ErrorResult;
+
+  nsMediaList();
+
+  virtual JSObject*
+  WrapObject(JSContext* aCx) MOZ_OVERRIDE;
+  nsISupports* GetParentObject() const
+  {
+    return nullptr;
+  }
+
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+  NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS(nsMediaList)
+
+  NS_DECL_NSIDOMMEDIALIST
+
+  void GetText(nsAString& aMediaText);
+  void SetText(const nsAString& aMediaText);
+
+  // Does this query apply to the presentation?
+  // If |aKey| is non-null, add cache information to it.
+  bool Matches(nsPresContext* aPresContext,
+                 nsMediaQueryResultCacheKey* aKey);
+
+  nsresult SetStyleSheet(nsCSSStyleSheet* aSheet);
+  void AppendQuery(nsAutoPtr<nsMediaQuery>& aQuery) {
+    // Takes ownership of aQuery
+    mArray.AppendElement(aQuery.forget());
+  }
+
+  already_AddRefed<nsMediaList> Clone();
+
+  nsMediaQuery* MediumAt(int32_t aIndex) { return mArray[aIndex]; }
+  void Clear() { mArray.Clear(); }
+
+  // WebIDL
+  // XPCOM GetMediaText and SetMediaText are fine.
+  uint32_t Length() { return mArray.Length(); }
+  void IndexedGetter(uint32_t aIndex, bool& aFound, nsAString& aReturn);
+  // XPCOM Item is fine.
+  void DeleteMedium(const nsAString& aMedium, ErrorResult& aRv)
+  {
+    aRv = DeleteMedium(aMedium);
+  }
+  void AppendMedium(const nsAString& aMedium, ErrorResult& aRv)
+  {
+    aRv = AppendMedium(aMedium);
+  }
+
+protected:
+  ~nsMediaList();
+
+  nsresult Delete(const nsAString & aOldMedium);
+  nsresult Append(const nsAString & aOldMedium);
+
+  InfallibleTArray<nsAutoPtr<nsMediaQuery> > mArray;
+  // not refcounted; sheet will let us know when it goes away
+  // mStyleSheet is the sheet that needs to be dirtied when this medialist
+  // changes
+  nsCSSStyleSheet*         mStyleSheet;
+};
+#endif /* !defined(nsIMediaList_h_) */