accessible/base/TextUpdater.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_TextUpdater_h__
   7 #define mozilla_a11y_TextUpdater_h__
   8
   9 #include "AccEvent.h"
  10 #include "HyperTextAccessible.h"
  11
  12 namespace mozilla {
  13 namespace a11y {
  14
  15 /**
  16  * Used to find a difference between old and new text and fire text change
  17  * events.
  18  */
  19 class TextUpdater
  20 {
  21 public:
  22   /**
  23    * Start text of the text leaf update.
  24    */
  25   static void Run(DocAccessible* aDocument, TextLeafAccessible* aTextLeaf,
  26                   const nsAString& aNewText);
  27
  28 private:
  29   TextUpdater(DocAccessible* aDocument, TextLeafAccessible* aTextLeaf) :
  30     mDocument(aDocument), mTextLeaf(aTextLeaf), mHyperText(nullptr),
  31     mTextOffset(-1) { }
  32
  33   ~TextUpdater()
  34     { mDocument = nullptr; mTextLeaf = nullptr; mHyperText = nullptr; }
  35
  36   /**
  37    * Update text of the text leaf accessible, fire text change and value change
  38    * (if applicable) events for its container hypertext accessible.
  39    */
  40   void DoUpdate(const nsAString& aNewText, const nsAString& aOldText,
  41                 uint32_t aSkipStart);
  42
  43 private:
  44   TextUpdater();
  45   TextUpdater(const TextUpdater&);
  46   TextUpdater& operator=(const TextUpdater&);
  47
  48   /**
  49    * Fire text change events based on difference between strings.
  50    */
  51   void ComputeTextChangeEvents(const nsAString& aStr1,
  52                                const nsAString& aStr2,
  53                                uint32_t* aEntries,
  54                                nsTArray<nsRefPtr<AccEvent> >& aEvents);
  55
  56   /**
  57    * Helper to create text change events for inserted text.
  58    */
  59   inline void FireInsertEvent(const nsAString& aText, uint32_t aAddlOffset,
  60                               nsTArray<nsRefPtr<AccEvent> >& aEvents)
  61   {
  62     nsRefPtr<AccEvent> event =
  63       new AccTextChangeEvent(mHyperText, mTextOffset + aAddlOffset,
  64                              aText, true);
  65     aEvents.AppendElement(event);
  66   }
  67
  68   /**
  69    * Helper to create text change events for removed text.
  70    */
  71   inline void FireDeleteEvent(const nsAString& aText, uint32_t aAddlOffset,
  72                               nsTArray<nsRefPtr<AccEvent> >& aEvents)
  73   {
  74     nsRefPtr<AccEvent> event =
  75       new AccTextChangeEvent(mHyperText, mTextOffset + aAddlOffset,
  76                              aText, false);
  77     aEvents.AppendElement(event);
  78   }
  79
  80   /**
  81    * The constant used to skip string difference calculation in case of long
  82    * strings.
  83    */
  84   const static uint32_t kMaxStrLen = 1 << 6;
  85
  86 private:
  87   DocAccessible* mDocument;
  88   TextLeafAccessible* mTextLeaf;
  89   HyperTextAccessible* mHyperText;
  90   int32_t mTextOffset;
  91 };
  92
  93 } // namespace a11y
  94 } // namespace mozilla
  95
  96 #endif