content/renderer/accessibility/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_ACCESSIBILITY_RENDERER_ACCESSIBILITY_H_
   6 #define CONTENT_RENDERER_ACCESSIBILITY_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/public/web/WebAXObject.h"
  11
  12 namespace blink {
  13 class WebDocument;
  14 };
  15
  16 namespace content {
  17 class RenderViewImpl;
  18
  19 enum RendererAccessibilityType {
  20   // Turns on Blink accessibility and provides a full accessibility
  21   // implementation for when assistive technology is running.
  22   RendererAccessibilityTypeComplete,
  23
  24   // Does not turn on Blink accessibility. Only sends a minimal accessible tree
  25   // to the browser whenever focus changes. This mode is currently used to
  26   // support opening the on-screen keyboard in response to touch events on
  27   // Windows 8 in Metro mode.
  28   RendererAccessibilityTypeFocusOnly
  29 };
  30
  31 // The browser process implement native accessibility APIs, allowing
  32 // assistive technology (e.g., screen readers, magnifiers) to access and
  33 // control the web contents with high-level APIs. These APIs are also used
  34 // by automation tools, and Windows 8 uses them to determine when the
  35 // on-screen keyboard should be shown.
  36 //
  37 // An instance of this class (or rather, a subclass) belongs to RenderViewImpl.
  38 // Accessibility is initialized based on the AccessibilityMode of
  39 // RenderViewImpl; it lazily starts as Off or EditableTextOnly depending on
  40 // the operating system, and switches to Complete if assistive technology is
  41 // detected or a flag is set.
  42 //
  43 // A tree of accessible objects is built here and sent to the browser process;
  44 // the browser process maintains this as a tree of platform-native
  45 // accessible objects that can be used to respond to accessibility requests
  46 // from other processes.
  47 //
  48 // This base class just contains common code and will not do anything by itself.
  49 // The two subclasses are:
  50 //
  51 //   RendererAccessibilityComplete - turns on Blink accessibility and
  52 //       provides a full accessibility implementation for when
  53 //       assistive technology is running.
  54 //
  55 //   RendererAccessibilityFocusOnly - does not turn on Blink
  56 //       accessibility. Only sends a minimal accessible tree to the
  57 //       browser whenever focus changes. This mode is currently used
  58 //       to support opening the on-screen keyboard in response to
  59 //       touch events on Windows 8 in Metro mode.
  60 //
  61 class CONTENT_EXPORT RendererAccessibility : public RenderViewObserver {
  62  public:
  63   explicit RendererAccessibility(RenderViewImpl* render_view);
  64   virtual ~RendererAccessibility();
  65
  66   // Called when an accessibility notification occurs in Blink.
  67   virtual void HandleWebAccessibilityEvent(
  68       const blink::WebAXObject& obj, blink::WebAXEvent event) = 0;
  69
  70   // Gets the type of this RendererAccessibility object. Primarily intended for
  71   // testing.
  72   virtual RendererAccessibilityType GetType() = 0;
  73
  74  protected:
  75   // Returns the main top-level document for this page, or NULL if there's
  76   // no view or frame.
  77   blink::WebDocument GetMainDocument();
  78
  79   // The RenderViewImpl that owns us.
  80   RenderViewImpl* render_view_;
  81
  82   DISALLOW_COPY_AND_ASSIGN(RendererAccessibility);
  83 };
  84
  85 }  // namespace content
  86
  87 #endif  // CONTENT_RENDERER_ACCESSIBILITY_RENDERER_ACCESSIBILITY_H_