accessible/base/Pivot.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 #ifndef mozilla_a11y_Pivot_h_
   7 #define mozilla_a11y_Pivot_h_
   8
   9 #include <stdint.h>
  10 #include "mozilla/a11y/Role.h"
  11 #include "mozilla/dom/ChildIterator.h"
  12
  13 namespace mozilla {
  14 namespace a11y {
  15
  16 class DocAccessible;
  17 class Accessible;
  18
  19 class PivotRule {
  20  public:
  21   // A filtering function that returns a bitmask from
  22   // nsIAccessibleTraversalRule: FILTER_IGNORE (0x0): Don't match this
  23   // accessible. FILTER_MATCH (0x1): Match this accessible FILTER_IGNORE_SUBTREE
  24   // (0x2): Ignore accessible's subtree.
  25   virtual uint16_t Match(Accessible* aAcc) = 0;
  26 };
  27
  28 // The Pivot class is used for searching for accessible nodes in a given subtree
  29 // with a given criteria. Since it only holds a weak reference to the root,
  30 // this class is meant to be used primarily on the stack.
  31 class Pivot final {
  32  public:
  33   explicit Pivot(Accessible* aRoot);
  34   Pivot() = delete;
  35   Pivot(const Pivot&) = delete;
  36   Pivot& operator=(const Pivot&) = delete;
  37
  38   ~Pivot();
  39
  40   // Return the next accessible after aAnchor in pre-order that matches the
  41   // given rule. If aIncludeStart, return aAnchor if it matches the rule.
  42   Accessible* Next(Accessible* aAnchor, PivotRule& aRule,
  43                    bool aIncludeStart = false);
  44
  45   // Return the previous accessible before aAnchor in pre-order that matches the
  46   // given rule. If aIncludeStart, return aAnchor if it matches the rule.
  47   Accessible* Prev(Accessible* aAnchor, PivotRule& aRule,
  48                    bool aIncludeStart = false);
  49
  50   // Return the first accessible within the root that matches the pivot rule.
  51   Accessible* First(PivotRule& aRule);
  52
  53   // Return the last accessible within the root that matches the pivot rule.
  54   Accessible* Last(PivotRule& aRule);
  55
  56   // Return the accessible at the given screen coordinate if it matches the
  57   // pivot rule.
  58   Accessible* AtPoint(int32_t aX, int32_t aY, PivotRule& aRule);
  59
  60  private:
  61   Accessible* AdjustStartPosition(Accessible* aAnchor, PivotRule& aRule,
  62                                   uint16_t* aFilterResult);
  63
  64   // Search in preorder for the first accessible to match the rule.
  65   Accessible* SearchForward(Accessible* aAnchor, PivotRule& aRule,
  66                             bool aSearchCurrent);
  67
  68   // Reverse search in preorder for the first accessible to match the rule.
  69   Accessible* SearchBackward(Accessible* aAnchor, PivotRule& aRule,
  70                              bool aSearchCurrent);
  71
  72   Accessible* mRoot;
  73 };
  74
  75 /**
  76  * This rule matches accessibles on a given role, filtering out non-direct
  77  * descendants if necessary.
  78  */
  79 class PivotRoleRule : public PivotRule {
  80  public:
  81   explicit PivotRoleRule(role aRole);
  82   explicit PivotRoleRule(role aRole, Accessible* aDirectDescendantsFrom);
  83
  84   virtual uint16_t Match(Accessible* aAcc) override;
  85
  86  protected:
  87   role mRole;
  88   Accessible* mDirectDescendantsFrom;
  89 };
  90
  91 /**
  92  * This rule matches accessibles with a given state.
  93  */
  94 class PivotStateRule : public PivotRule {
  95  public:
  96   explicit PivotStateRule(uint64_t aState);
  97
  98   virtual uint16_t Match(Accessible* aAcc) override;
  99
 100  protected:
 101   uint64_t mState;
 102 };
 103
 104 /**
 105  * This rule matches any local LocalAccessible (i.e. not RemoteAccessible) in
 106  * the same document as the anchor. That is, it includes any descendant
 107  * OuterDocAccessible, but not its descendants.
 108  */
 109 class LocalAccInSameDocRule : public PivotRule {
 110  public:
 111   virtual uint16_t Match(Accessible* aAcc) override;
 112 };
 113
 114 /**
 115  * This rule matches remote radio button accessibles with the given name
 116  * attribute. It assumes the cache is enabled.
 117  */
 118 class PivotRadioNameRule : public PivotRule {
 119  public:
 120   explicit PivotRadioNameRule(const nsString& aName);
 121
 122   virtual uint16_t Match(Accessible* aAcc) override;
 123
 124  protected:
 125   const nsString& mName;
 126 };
 127
 128 /**
 129  * This rule doesn't search iframes. Subtrees that should be
 130  * pruned by way of nsAccUtils::MustPrune are also not searched.
 131  */
 132
 133 class MustPruneSameDocRule : public PivotRule {
 134  public:
 135   virtual uint16_t Match(Accessible* aAcc) override;
 136 };
 137
 138 }  // namespace a11y
 139 }  // namespace mozilla
 140
 141 #endif  // mozilla_a11y_Pivot_h_