layout/style/CSSVariableResolver.h

   1 /* vim: set shiftwidth=2 tabstop=8 autoindent cindent expandtab: */
   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 /* object that resolves CSS variables using specified and inherited variable
   7  * values
   8  */
   9
  10 #ifndef mozilla_CSSVariableResolver_h
  11 #define mozilla_CSSVariableResolver_h
  12
  13 #include "mozilla/DebugOnly.h"
  14 #include "nsCSSParser.h"
  15 #include "nsCSSScanner.h"
  16 #include "nsDataHashtable.h"
  17 #include "nsTArray.h"
  18
  19 namespace mozilla {
  20
  21 class CSSVariableDeclarations;
  22 class CSSVariableValues;
  23 class EnumerateVariableReferencesData;
  24
  25 class CSSVariableResolver
  26 {
  27   friend class CSSVariableDeclarations;
  28   friend class CSSVariableValues;
  29   friend class EnumerateVariableReferencesData;
  30 public:
  31   /**
  32    * Creates a new CSSVariableResolver that will output a set of resolved,
  33    * computed variables into aOutput.
  34    */
  35   explicit CSSVariableResolver(CSSVariableValues* aOutput)
  36     : mOutput(aOutput)
  37 #ifdef DEBUG
  38     , mResolved(false)
  39 #endif
  40   {
  41     MOZ_ASSERT(aOutput);
  42   }
  43
  44   /**
  45    * Resolves the set of inherited variables from aInherited and the
  46    * set of specified variables from aSpecified.  The resoled variables
  47    * are written in to mOutput.
  48    */
  49   void Resolve(const CSSVariableValues* aInherited,
  50                const CSSVariableDeclarations* aSpecified);
  51
  52 private:
  53   struct Variable
  54   {
  55     Variable(const nsAString& aVariableName,
  56              nsString aValue,
  57              nsCSSTokenSerializationType aFirstToken,
  58              nsCSSTokenSerializationType aLastToken,
  59              bool aWasInherited)
  60       : mVariableName(aVariableName)
  61       , mValue(aValue)
  62       , mFirstToken(aFirstToken)
  63       , mLastToken(aLastToken)
  64       , mWasInherited(aWasInherited)
  65       , mResolved(false)
  66       , mReferencesNonExistentVariable(false)
  67       , mInStack(false)
  68       , mIndex(0)
  69       , mLowLink(0) { }
  70
  71     nsString mVariableName;
  72     nsString mValue;
  73     nsCSSTokenSerializationType mFirstToken;
  74     nsCSSTokenSerializationType mLastToken;
  75
  76     // Whether this variable came from the set of inherited variables.
  77     bool mWasInherited;
  78
  79     // Whether this variable has been resolved yet.
  80     bool mResolved;
  81
  82     // Whether this variables includes any references to non-existent variables.
  83     bool mReferencesNonExistentVariable;
  84
  85     // Bookkeeping for the cycle remover algorithm.
  86     bool mInStack;
  87     size_t mIndex;
  88     size_t mLowLink;
  89   };
  90
  91   /**
  92    * Adds or modifies an existing entry in the set of variables to be resolved.
  93    * This is intended to be called by the AddVariablesToResolver functions on
  94    * the CSSVariableDeclarations and CSSVariableValues objects passed in to
  95    * Resolve.
  96    *
  97    * @param aName The variable name (not including any "--" prefix that would
  98    *   be part of the custom property name) whose value is to be set.
  99    * @param aValue The variable value.
 100    * @param aFirstToken The type of token at the start of the variable value.
 101    * @param aLastToken The type of token at the en of the variable value.
 102    * @param aWasInherited Whether this variable came from the set of inherited
 103    *   variables.
 104    */
 105   void Put(const nsAString& aVariableName,
 106            nsString aValue,
 107            nsCSSTokenSerializationType aFirstToken,
 108            nsCSSTokenSerializationType aLastToken,
 109            bool aWasInherited);
 110
 111   // Helper functions for Resolve.
 112   void RemoveCycles(size_t aID);
 113   void ResolveVariable(size_t aID);
 114
 115   // A mapping of variable names to an ID that indexes into mVariables
 116   // and mReferences.
 117   nsDataHashtable<nsStringHashKey, size_t> mVariableIDs;
 118
 119   // The set of variables.
 120   nsTArray<Variable> mVariables;
 121
 122   // The list of variables that each variable references.
 123   nsTArray<nsTArray<size_t> > mReferences;
 124
 125   // The next index to assign to a variable found during the cycle removing
 126   // algorithm's traversal of the variable reference graph.
 127   size_t mNextIndex;
 128
 129   // Stack of variable IDs that we push to as we traverse the variable reference
 130   // graph while looking for cycles.  Variable::mInStack reflects whether a
 131   // given variable has its ID in mStack.
 132   nsTArray<size_t> mStack;
 133
 134   // CSS parser to use for parsing property values with variable references.
 135   nsCSSParser mParser;
 136
 137   // The object to output the resolved variables into.
 138   CSSVariableValues* mOutput;
 139
 140 #ifdef DEBUG
 141   // Whether Resolve has been called.
 142   bool mResolved;
 143 #endif
 144 };
 145
 146 }
 147
 148 #endif