Improve support for multiselect list box accessibility on Windows.

content/browser/accessibility/browser_accessibility_win.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/accessibility/browser_accessibility_win.h"
 
 #include "base/string_number_conversions.h"
 #include "base/string_util.h"
 #include "base/utf_string_conversions.h"
+#include "base/win/enum_variant.h"
 #include "base/win/scoped_comptr.h"
 #include "content/browser/accessibility/browser_accessibility_manager_win.h"
 #include "content/common/view_messages.h"
 #include "net/base/escape.h"
 #include "ui/base/accessibility/accessible_text_utils.h"
 
 using webkit_glue::WebAccessibility;
 
 // The GUID for the ISimpleDOM service is not defined in the IDL files.
 // This is taken directly from the Mozilla sources
@@ skipping 141 matching lines @@
 
 BrowserAccessibilityWin* BrowserAccessibility::toBrowserAccessibilityWin() {
   return static_cast<BrowserAccessibilityWin*>(this);
 }
 
 BrowserAccessibilityWin::BrowserAccessibilityWin()
     : ia_role_(0),
       ia_state_(0),
       ia2_role_(0),
       ia2_state_(0),
-      first_time_(true) {
+      first_time_(true),
+      old_ia_state_(0) {
 }
 
 BrowserAccessibilityWin::~BrowserAccessibilityWin() {
   for (size_t i = 0; i < relations_.size(); ++i)
     relations_[i]->Release();
 }
 
 //
 // IAccessible methods.
 //
@@ skipping 340 matching lines @@
 
 STDMETHODIMP BrowserAccessibilityWin::get_accHelpTopic(
     BSTR* help_file, VARIANT var_id, LONG* topic_id) {
   return E_NOTIMPL;
 }
 
 STDMETHODIMP BrowserAccessibilityWin::get_accSelection(VARIANT* selected) {
   if (!instance_active_)
     return E_FAIL;
 
+  if (role_ == WebAccessibility::ROLE_LISTBOX && children_.size() > 0) {
+    unsigned long selected_count = 0;
+    for (size_t i = 0; i < children_.size(); i++) {
+      if (children_[i]->HasState(WebAccessibility::STATE_SELECTED))
+        selected_count++;
+    }
+
+    if (selected_count == 0) {
+      selected->vt = VT_EMPTY;
+      return S_OK;
+    }
+
+    if (selected_count == 1) {
+      for (size_t i = 0; i < children_.size(); i++) {
+        if (children_[i]->HasState(WebAccessibility::STATE_SELECTED)) {
+          selected->vt = VT_DISPATCH;
+          selected->pdispVal =
+              children_[i]->toBrowserAccessibilityWin()->NewReference();
+          return S_OK;
+        }
+      }
+    }
+
+    // Multiple items are selected.
+    base::win::EnumVariant* enum_variant =
+        new base::win::EnumVariant(selected_count);
+    unsigned long index = 0;
+    for (size_t i = 0; i < children_.size(); i++) {
+      if (children_[i]->HasState(WebAccessibility::STATE_SELECTED)) {
+        enum_variant->ItemAt(index)->vt = VT_DISPATCH;
+        enum_variant->ItemAt(index)->pdispVal =
+            children_[i]->toBrowserAccessibilityWin()->NewReference();
+        index++;
+      }
+    }
+    selected->vt = VT_UNKNOWN;
+    selected->punkVal = enum_variant;
+  }
+
   return E_NOTIMPL;

[M-A Ruel, 2011/11/22 14:42:30]

The error code isn't correct now. If clidren_size() == 0, S_FALSE would make
more sense, and setting the variant to empty? And I'd vote for an early exit
instead of whole indentation unless it would be sensible to add other role_
implementation.

[dmazzoni, 2011/11/23 06:18:10]

You're right, it doesn't make sense to return E_NOTIMPL for an empty list. I
changed it to do an early exit of E_NOTIMPL if it's any other role. (We may add
support for other roles as needed.)

While it's common to return S_FALSE for an empty result, the get_accSelection
docs specifically say to return S_OK. Also, this matches Firefox's impl (I
checked the source).

Returning E_NOTIMPL rather than empty for roles we don't support yet is very
important, because assistive technology may try another method to figure out
information if it gets E_NOTIMPL. If it get S_FALSE it might assume this method
is supported but this object has no selection, which may be incorrect and may be
a regression from the current behavior.

 }
 
 STDMETHODIMP BrowserAccessibilityWin::accSelect(
     LONG flags_sel, VARIANT var_id) {
   if (!instance_active_)
     return E_FAIL;
 
   if (flags_sel & SELFLAG_TAKEFOCUS) {
     manager_->SetFocus(this, true);
     return S_OK;
@@ skipping 133 matching lines @@
     return S_FALSE;
 
   for (long i = 0; i < count; ++i) {
     relations_[i]->AddRef();
     relations[i] = relations_[i];
   }
 
   return S_OK;
 }
 
+STDMETHODIMP BrowserAccessibilityWin::get_groupPosition(
+    LONG* group_level,
+    LONG* similar_items_in_group,
+    LONG* position_in_group) {
+  if (role_ == WebAccessibility::ROLE_LISTBOX_OPTION &&
+      parent_ &&
+      parent_->role() == WebAccessibility::ROLE_LISTBOX) {
+    *group_level = 0;
+    *similar_items_in_group = parent_->child_count();
+    *position_in_group = index_in_parent_ + 1;
+    return S_OK;
+  }
+
+  return E_NOTIMPL;

[M-A Ruel, 2011/11/22 14:42:30]

same

[dmazzoni, 2011/11/23 06:18:10]

I think this one is right - see reasoning above.

+}
+
 //
 // IAccessibleImage methods.
 //
 
 STDMETHODIMP BrowserAccessibilityWin::get_description(BSTR* desc) {
   if (!instance_active_)
     return E_FAIL;
 
   if (!desc)
     return E_INVALIDARG;
@@ skipping 1632 matching lines @@
   }
 
   // Expose the "display" and "tag" attributes.
   StringAttributeToIA2(WebAccessibility::ATTR_DISPLAY, "display");
   StringAttributeToIA2(WebAccessibility::ATTR_HTML_TAG, "tag");
   StringAttributeToIA2(WebAccessibility::ATTR_ROLE, "xml-roles");
 
   // Expose "level" attribute for tree nodes.
   IntAttributeToIA2(WebAccessibility::ATTR_HIERARCHICAL_LEVEL, "level");
 
+  // Expose the set size and position in set for listbox options.
+  if (role_ == WebAccessibility::ROLE_LISTBOX_OPTION &&
+      parent_ &&
+      parent_->role() == WebAccessibility::ROLE_LISTBOX) {
+    ia2_attributes_.push_back(
+        L"setsize:" + base::IntToString16(parent_->child_count()));
+    ia2_attributes_.push_back(
+        L"setsize:" + base::IntToString16(index_in_parent_ + 1));
+  }
+
   // Expose live region attributes.
   StringAttributeToIA2(WebAccessibility::ATTR_LIVE_STATUS, "live");
   StringAttributeToIA2(WebAccessibility::ATTR_LIVE_RELEVANT, "relevant");
   BoolAttributeToIA2(WebAccessibility::ATTR_LIVE_ATOMIC, "atomic");
   BoolAttributeToIA2(WebAccessibility::ATTR_LIVE_BUSY, "busy");
 
   // Expose container live region attributes.
   StringAttributeToIA2(WebAccessibility::ATTR_CONTAINER_LIVE_STATUS,
                        "container-live");
   StringAttributeToIA2(WebAccessibility::ATTR_CONTAINER_LIVE_RELEVANT,
@@ skipping 32 matching lines @@
       }
       if (index >= 0) {
         ia2_attributes_.push_back(string16(L"table-cell-index:") +
                                   base::IntToString16(index));
       }
     } else {
       NOTREACHED();
     }
   }
 
-  // If this is static text, put the text in the name rather than the value.
-  if (role_ == WebAccessibility::ROLE_STATIC_TEXT && name_.empty())
+  if (name_.empty() &&
+      (role_ == WebAccessibility::ROLE_LISTBOX_OPTION ||
+       role_ == WebAccessibility::ROLE_STATIC_TEXT)) {
     name_.swap(value_);
+  }
 
   // If this object doesn't have a name but it does have a description,
   // use the description as its name - because some screen readers only
   // announce the name.
   if (name_.empty())
     GetStringAttribute(WebAccessibility::ATTR_DESCRIPTION, &name_);
 
   // If this doesn't have a value and is linked then set its value to the url
   // attribute. This allows screen readers to read an empty link's destination.
   string16 url;
@@ skipping 33 matching lines @@
       manager_->NotifyAccessibilityEvent(
           ViewHostMsg_AccEvent::OBJECT_SHOW, this);
     }
 
     // TODO(dmazzoni): Look into HIDE events, too.
 
     old_text_ = previous_text_;
     previous_text_ = text;
   }
 
+  // Fire events if the state has changed.
+  if (!first_time_ && ia_state_ != old_ia_state_) {
+    // Normally focus events are handled elsewhere, however
+    // focus for managed descendants is platform-specific.
+    // Fire a focus event if the focused descendant in a multi-select
+    // list box changes.
+    if (role_ == WebAccessibility::ROLE_LISTBOX_OPTION &&
+        (ia_state_ & STATE_SYSTEM_FOCUSABLE) &&
+        (ia_state_ & STATE_SYSTEM_SELECTABLE) &&
+        (ia_state_ & STATE_SYSTEM_FOCUSED) &&
+        !(old_ia_state_ & STATE_SYSTEM_FOCUSED)) {
+      ::NotifyWinEvent(EVENT_OBJECT_FOCUS,
+                       manager_->GetParentView(),
+                       OBJID_CLIENT,
+                       child_id());
+    }
+
+    if ((ia_state_ & STATE_SYSTEM_SELECTED) &&
+        !(old_ia_state_ & STATE_SYSTEM_SELECTED)) {
+      ::NotifyWinEvent(EVENT_OBJECT_SELECTIONADD,
+                       manager_->GetParentView(),
+                       OBJID_CLIENT,
+                       child_id());
+    } else if (!(ia_state_ & STATE_SYSTEM_SELECTED) &&
+               (old_ia_state_ & STATE_SYSTEM_SELECTED)) {
+      ::NotifyWinEvent(EVENT_OBJECT_SELECTIONREMOVE,
+                       manager_->GetParentView(),
+                       OBJID_CLIENT,
+                       child_id());
+    }
+
+    old_ia_state_ = ia_state_;
+  }
+
   first_time_ = false;
 }
 
 void BrowserAccessibilityWin::NativeAddReference() {
   AddRef();
 }
 
 void BrowserAccessibilityWin::NativeReleaseReference() {
   Release();
 }
@@ skipping 108 matching lines @@
 BrowserAccessibilityWin* BrowserAccessibilityWin::GetFromRendererID(
     int32 renderer_id) {
   return manager_->GetFromRendererID(renderer_id)->toBrowserAccessibilityWin();
 }
 
 void BrowserAccessibilityWin::InitRoleAndState() {
   ia_state_ = 0;
   ia2_state_ = IA2_STATE_OPAQUE;
   ia2_attributes_.clear();
 
-  if ((state_ >> WebAccessibility::STATE_BUSY) & 1)
+  if (HasState(WebAccessibility::STATE_BUSY))
     ia_state_|= STATE_SYSTEM_BUSY;
-  if ((state_ >> WebAccessibility::STATE_CHECKED) & 1)
+  if (HasState(WebAccessibility::STATE_CHECKED))
     ia_state_ |= STATE_SYSTEM_CHECKED;
-  if ((state_ >> WebAccessibility::STATE_COLLAPSED) & 1)
+  if (HasState(WebAccessibility::STATE_COLLAPSED))
     ia_state_|= STATE_SYSTEM_COLLAPSED;
-  if ((state_ >> WebAccessibility::STATE_EXPANDED) & 1)
+  if (HasState(WebAccessibility::STATE_EXPANDED))
     ia_state_|= STATE_SYSTEM_EXPANDED;
-  if ((state_ >> WebAccessibility::STATE_FOCUSABLE) & 1)
+  if (HasState(WebAccessibility::STATE_FOCUSABLE))
     ia_state_|= STATE_SYSTEM_FOCUSABLE;
-  if ((state_ >> WebAccessibility::STATE_HASPOPUP) & 1)
+  if (HasState(WebAccessibility::STATE_HASPOPUP))
     ia_state_|= STATE_SYSTEM_HASPOPUP;
-  if ((state_ >> WebAccessibility::STATE_HOTTRACKED) & 1)
+  if (HasState(WebAccessibility::STATE_HOTTRACKED))
     ia_state_|= STATE_SYSTEM_HOTTRACKED;
-  if ((state_ >> WebAccessibility::STATE_INDETERMINATE) & 1)
+  if (HasState(WebAccessibility::STATE_INDETERMINATE))
     ia_state_|= STATE_SYSTEM_INDETERMINATE;
-  if ((state_ >> WebAccessibility::STATE_INVISIBLE) & 1)
+  if (HasState(WebAccessibility::STATE_INVISIBLE))
     ia_state_|= STATE_SYSTEM_INVISIBLE;
-  if ((state_ >> WebAccessibility::STATE_LINKED) & 1)
+  if (HasState(WebAccessibility::STATE_LINKED))
     ia_state_|= STATE_SYSTEM_LINKED;
-  if ((state_ >> WebAccessibility::STATE_MULTISELECTABLE) & 1)
+  if (HasState(WebAccessibility::STATE_MULTISELECTABLE)) {
+    ia_state_|= STATE_SYSTEM_EXTSELECTABLE;
     ia_state_|= STATE_SYSTEM_MULTISELECTABLE;
+  }
   // TODO(ctguil): Support STATE_SYSTEM_EXTSELECTABLE/accSelect.
-  if ((state_ >> WebAccessibility::STATE_OFFSCREEN) & 1)
+  if (HasState(WebAccessibility::STATE_OFFSCREEN))
     ia_state_|= STATE_SYSTEM_OFFSCREEN;
-  if ((state_ >> WebAccessibility::STATE_PRESSED) & 1)
+  if (HasState(WebAccessibility::STATE_PRESSED))
     ia_state_|= STATE_SYSTEM_PRESSED;
-  if ((state_ >> WebAccessibility::STATE_PROTECTED) & 1)
+  if (HasState(WebAccessibility::STATE_PROTECTED))
     ia_state_|= STATE_SYSTEM_PROTECTED;
-  if ((state_ >> WebAccessibility::STATE_REQUIRED) & 1)
+  if (HasState(WebAccessibility::STATE_REQUIRED))
     ia2_state_|= IA2_STATE_REQUIRED;
-  if ((state_ >> WebAccessibility::STATE_SELECTABLE) & 1)
+  if (HasState(WebAccessibility::STATE_SELECTABLE))
     ia_state_|= STATE_SYSTEM_SELECTABLE;
-  if ((state_ >> WebAccessibility::STATE_SELECTED) & 1)
+  if (HasState(WebAccessibility::STATE_SELECTED))
     ia_state_|= STATE_SYSTEM_SELECTED;
-  if ((state_ >> WebAccessibility::STATE_TRAVERSED) & 1)
+  if (HasState(WebAccessibility::STATE_TRAVERSED))
     ia_state_|= STATE_SYSTEM_TRAVERSED;
-  if ((state_ >> WebAccessibility::STATE_UNAVAILABLE) & 1)
+  if (HasState(WebAccessibility::STATE_UNAVAILABLE))
     ia_state_|= STATE_SYSTEM_UNAVAILABLE;
-  if ((state_ >> WebAccessibility::STATE_VERTICAL) & 1) {
+  if (HasState(WebAccessibility::STATE_VERTICAL)) {
     ia2_state_|= IA2_STATE_VERTICAL;
   } else {
     ia2_state_|= IA2_STATE_HORIZONTAL;
   }
-  if ((state_ >> WebAccessibility::STATE_VISITED) & 1)
+  if (HasState(WebAccessibility::STATE_VISITED))
     ia_state_|= STATE_SYSTEM_TRAVERSED;
 
   // The meaning of the readonly state on Windows is very different from
   // the meaning of the readonly state in WebKit, so we ignore
   // WebAccessibility::STATE_READONLY, and instead just check the
   // aria readonly value, then there's additional logic below to set
   // the readonly state based on other criteria.
   bool aria_readonly = false;
   GetBoolAttribute(WebAccessibility::ATTR_ARIA_READONLY, &aria_readonly);
   if (aria_readonly)
@@ skipping 152 matching lines @@
       break;
     case WebAccessibility::ROLE_LIST:
       ia_role_ = ROLE_SYSTEM_LIST;
       ia_state_|= STATE_SYSTEM_READONLY;
       break;
     case WebAccessibility::ROLE_LISTBOX:
       ia_role_ = ROLE_SYSTEM_LIST;
       break;
     case WebAccessibility::ROLE_LISTBOX_OPTION:
       ia_role_ = ROLE_SYSTEM_LISTITEM;
+      if (ia_state_ & STATE_SYSTEM_SELECTABLE) {
+        ia_state_ |= STATE_SYSTEM_FOCUSABLE;
+        if (HasState(WebAccessibility::STATE_FOCUSED))
+          ia_state_|= STATE_SYSTEM_FOCUSED;
+      }
       break;
     case WebAccessibility::ROLE_LIST_ITEM:
       ia_role_ = ROLE_SYSTEM_LISTITEM;
       ia_state_|= STATE_SYSTEM_READONLY;
       break;
     case WebAccessibility::ROLE_LIST_MARKER:
       ia_role_ = ROLE_SYSTEM_TEXT;
       ia_state_|= STATE_SYSTEM_READONLY;
       break;
     case WebAccessibility::ROLE_MATH:
@@ skipping 165 matching lines @@
   }
 
   // The role should always be set.
   DCHECK(!role_name_.empty() || ia_role_);
 
   // If we didn't explicitly set the IAccessible2 role, make it the same
   // as the MSAA role.
   if (!ia2_role_)
     ia2_role_ = ia_role_;
 }