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 #include "AccessibleOrProxy.h"
  13
  14 namespace mozilla {
  15 namespace a11y {
  16
  17 class LocalAccessible;
  18 class HyperTextAccessible;
  19 class DocAccessible;
  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(const AccessibleOrProxy& aAccOrProxy) = 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(const AccessibleOrProxy& 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   AccessibleOrProxy Next(AccessibleOrProxy& 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   AccessibleOrProxy Prev(AccessibleOrProxy& aAnchor, PivotRule& aRule,
  50                          bool aIncludeStart = false);
  51
  52   // Return the first accessible within the root that matches the pivot rule.
  53   AccessibleOrProxy First(PivotRule& aRule);
  54
  55   // Return the last accessible within the root that matches the pivot rule.
  56   AccessibleOrProxy 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   AccessibleOrProxy AtPoint(int32_t aX, int32_t aY, PivotRule& aRule);
  69
  70  private:
  71   AccessibleOrProxy AdjustStartPosition(AccessibleOrProxy& aAnchor,
  72                                         PivotRule& aRule,
  73                                         uint16_t* aFilterResult);
  74
  75   // Search in preorder for the first accessible to match the rule.
  76   AccessibleOrProxy SearchForward(AccessibleOrProxy& aAnchor, PivotRule& aRule,
  77                                   bool aSearchCurrent);
  78
  79   // Reverse search in preorder for the first accessible to match the rule.
  80   AccessibleOrProxy SearchBackward(AccessibleOrProxy& aAnchor, PivotRule& aRule,
  81                                    bool aSearchCurrent);
  82
  83   // Search in preorder for the first text accessible.
  84   HyperTextAccessible* SearchForText(LocalAccessible* aAnchor, bool aBackward);
  85
  86   AccessibleOrProxy mRoot;
  87 };
  88
  89 /**
  90  * This rule matches accessibles on a given role, filtering out non-direct
  91  * descendants if necessary.
  92  */
  93 class PivotRoleRule : public PivotRule {
  94  public:
  95   explicit PivotRoleRule(role aRole);
  96   explicit PivotRoleRule(role aRole, AccessibleOrProxy& aDirectDescendantsFrom);
  97
  98   virtual uint16_t Match(const AccessibleOrProxy& aAccOrProxy) override;
  99
 100  protected:
 101   role mRole;
 102   AccessibleOrProxy mDirectDescendantsFrom;
 103 };
 104
 105 /**
 106  * This rule matches any local LocalAccessible (i.e. not RemoteAccessible) in
 107  * the same document as the anchor. That is, it includes any descendant
 108  * OuterDocAccessible, but not its descendants.
 109  */
 110 class LocalAccInSameDocRule : public PivotRule {
 111  public:
 112   virtual uint16_t Match(const AccessibleOrProxy& aAccOrProxy) override;
 113 };
 114
 115 }  // namespace a11y
 116 }  // namespace mozilla
 117
 118 #endif  // mozilla_a11y_Pivot_h_