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 "Role.h"
  11 #include "mozilla/dom/ChildIterator.h"
  12
  13 namespace mozilla {
  14 namespace a11y {
  15
  16 class LocalAccessible;
  17 class HyperTextAccessible;
  18 class DocAccessible;
  19 class Accessible;
  20
  21 class PivotRule {
  22  public:
  23   // A filtering function that returns a bitmask from
  24   // nsIAccessibleTraversalRule: FILTER_IGNORE (0x0): Don't match this
  25   // accessible. FILTER_MATCH (0x1): Match this accessible FILTER_IGNORE_SUBTREE
  26   // (0x2): Ignore accessible's subtree.
  27   virtual uint16_t Match(Accessible* aAcc) = 0;
  28 };
  29
  30 // The Pivot class is used for searching for accessible nodes in a given subtree
  31 // with a given criteria. Since it only holds a weak reference to the root,
  32 // this class is meant to be used primarily on the stack.
  33 class Pivot final {
  34  public:
  35   explicit Pivot(Accessible* aRoot);
  36   Pivot() = delete;
  37   Pivot(const Pivot&) = delete;
  38   Pivot& operator=(const Pivot&) = delete;
  39
  40   ~Pivot();
  41
  42   // Return the next accessible after aAnchor in pre-order that matches the
  43   // given rule. If aIncludeStart, return aAnchor if it matches the rule.
  44   Accessible* Next(Accessible* aAnchor, PivotRule& aRule,
  45                    bool aIncludeStart = false);
  46
  47   // Return the previous accessible before aAnchor in pre-order that matches the
  48   // given rule. If aIncludeStart, return aAnchor if it matches the rule.
  49   Accessible* Prev(Accessible* aAnchor, PivotRule& aRule,
  50                    bool aIncludeStart = false);
  51
  52   // Return the first accessible within the root that matches the pivot rule.
  53   Accessible* First(PivotRule& aRule);
  54
  55   // Return the last accessible within the root that matches the pivot rule.
  56   Accessible* Last(PivotRule& aRule);
  57
  58   // Return the next range of text according to the boundary type.
  59   LocalAccessible* NextText(LocalAccessible* aAnchor, int32_t* aStartOffset,
  60                             int32_t* aEndOffset, int32_t aBoundaryType);
  61
  62   // Return the previous range of text according to the boundary type.
  63   LocalAccessible* PrevText(LocalAccessible* aAnchor, int32_t* aStartOffset,
  64                             int32_t* aEndOffset, int32_t aBoundaryType);
  65
  66   // Return the accessible at the given screen coordinate if it matches the
  67   // pivot rule.
  68   Accessible* AtPoint(int32_t aX, int32_t aY, PivotRule& aRule);
  69
  70  private:
  71   Accessible* AdjustStartPosition(Accessible* aAnchor, PivotRule& aRule,
  72                                   uint16_t* aFilterResult);
  73
  74   // Search in preorder for the first accessible to match the rule.
  75   Accessible* SearchForward(Accessible* aAnchor, PivotRule& aRule,
  76                             bool aSearchCurrent);
  77
  78   // Reverse search in preorder for the first accessible to match the rule.
  79   Accessible* SearchBackward(Accessible* aAnchor, PivotRule& aRule,
  80                              bool aSearchCurrent);
  81
  82   // Search in preorder for the first text accessible.
  83   HyperTextAccessible* SearchForText(LocalAccessible* aAnchor, bool aBackward);
  84
  85   Accessible* mRoot;
  86 };
  87
  88 /**
  89  * This rule matches accessibles on a given role, filtering out non-direct
  90  * descendants if necessary.
  91  */
  92 class PivotRoleRule : public PivotRule {
  93  public:
  94   explicit PivotRoleRule(role aRole);
  95   explicit PivotRoleRule(role aRole, Accessible* aDirectDescendantsFrom);
  96
  97   virtual uint16_t Match(Accessible* aAcc) override;
  98
  99  protected:
 100   role mRole;
 101   Accessible* mDirectDescendantsFrom;
 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 }  // namespace a11y
 115 }  // namespace mozilla
 116
 117 #endif  // mozilla_a11y_Pivot_h_