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