Improve support for multiselect list box accessibility on Windows.

content/browser/accessibility/browser_accessibility_win.cc

Index: content/browser/accessibility/browser_accessibility_win.cc
===================================================================
--- content/browser/accessibility/browser_accessibility_win.cc	(revision 110985)
+++ content/browser/accessibility/browser_accessibility_win.cc	(working copy)
@@ -7,6 +7,7 @@
 #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"
@@ -168,7 +169,8 @@
       ia_state_(0),
       ia2_role_(0),
       ia2_state_(0),
-      first_time_(true) {
+      first_time_(true),
+      old_ia_state_(0) {
 }
 
 BrowserAccessibilityWin::~BrowserAccessibilityWin() {
@@ -529,6 +531,45 @@
   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.

 }
 
@@ -683,6 +724,22 @@
   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.
 //
@@ -2335,6 +2392,16 @@
   // 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");
@@ -2387,9 +2454,11 @@
     }
   }
 
-  // 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
@@ -2443,6 +2512,40 @@
     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;
 }
 
@@ -2571,51 +2674,53 @@
   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
@@ -2788,6 +2893,11 @@
       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;