content/renderer/renderer_accessibility.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef CONTENT_RENDERER_RENDERER_ACCESSIBILITY_H_
   6 #define CONTENT_RENDERER_RENDERER_ACCESSIBILITY_H_
   7
   8 #include "content/common/accessibility_messages.h"
   9 #include "content/public/renderer/render_view_observer.h"
  10 #include "third_party/WebKit/Source/WebKit/chromium/public/WebAccessibilityNotification.h"
  11
  12 namespace WebKit {
  13 class WebAccessibilityObject;
  14 class WebDocument;
  15 };
  16
  17 namespace content {
  18 class RenderViewImpl;
  19
  20 // The browser process implement native accessibility APIs, allowing
  21 // assistive technology (e.g., screen readers, magnifiers) to access and
  22 // control the web contents with high-level APIs. These APIs are also used
  23 // by automation tools, and Windows 8 uses them to determine when the
  24 // on-screen keyboard should be shown.
  25 //
  26 // An instance of this class (or rather, a subclass) belongs to RenderViewImpl.
  27 // Accessibility is initialized based on the AccessibilityMode of
  28 // RenderViewImpl; it lazily starts as Off or EditableTextOnly depending on
  29 // the operating system, and switches to Complete if assistive technology is
  30 // detected or a flag is set.
  31 //
  32 // A tree of accessible objects is built here and sent to the browser process;
  33 // the browser process maintains this as a tree of platform-native
  34 // accessible objects that can be used to respond to accessibility requests
  35 // from other processes.
  36 //
  37 // This base class just contains common code and will not do anything by itself.
  38 // The two subclasses are:
  39 //
  40 //   RendererAccessibilityComplete - turns on WebKit accessibility and
  41 //       provides a full accessibility implementation for when
  42 //       assistive technology is running.
  43 //
  44 //   RendererAccessibilityFocusOnly - does not turn on WebKit
  45 //       accessibility. Only sends a minimal accessible tree to the
  46 //       browser whenever focus changes. This mode is currently used
  47 //       to support opening the on-screen keyboard in response to
  48 //       touch events on Windows 8 in Metro mode.
  49 //
  50 // What both subclasses have in common is that they are responsible for
  51 //
  52 class RendererAccessibility : public RenderViewObserver {
  53  public:
  54   explicit RendererAccessibility(RenderViewImpl* render_view);
  55   virtual ~RendererAccessibility();
  56
  57   // Called when an accessibility notification occurs in WebKit.
  58   virtual void HandleWebAccessibilityNotification(
  59       const WebKit::WebAccessibilityObject& obj,
  60       WebKit::WebAccessibilityNotification notification) = 0;
  61
  62  protected:
  63   // Returns the main top-level document for this page, or NULL if there's
  64   // no view or frame.
  65   WebKit::WebDocument GetMainDocument();
  66
  67 #ifndef NDEBUG
  68   const std::string AccessibilityNotificationToString(
  69       AccessibilityNotification notification);
  70 #endif
  71
  72   // The RenderViewImpl that owns us.
  73   RenderViewImpl* render_view_;
  74
  75   // True if verbose logging of accessibility events is on.
  76   bool logging_;
  77
  78   DISALLOW_COPY_AND_ASSIGN(RendererAccessibility);
  79 };
  80
  81 }  // namespace content
  82
  83 #endif  // CONTENT_RENDERER_RENDERER_ACCESSIBILITY_H_