a11y: Add a11y information to views::Tab and manually ignore its a11y children.

ui/accessibility/platform/ax_platform_node_mac.mm

 // Copyright 2014 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.
 
 #import "ui/accessibility/platform/ax_platform_node_mac.h"
 
 #import <Cocoa/Cocoa.h>
 #include <stddef.h>
 
 #include "base/macros.h"
 #include "base/strings/sys_string_conversions.h"
+#include "chrome/grit/generated_resources.h"
 #include "ui/accessibility/ax_action_data.h"
 #include "ui/accessibility/ax_node_data.h"
 #include "ui/accessibility/platform/ax_platform_node_delegate.h"
+#include "ui/base/l10n/l10n_util.h"
 #import "ui/gfx/mac/coordinate_conversion.h"
 
 namespace {
 
 struct RoleMapEntry {
   ui::AXRole value;
   NSString* nativeValue;
 };
 
 struct EventMapEntry {
@@ skipping 152 matching lines @@
       {ui::AX_ROLE_MAIN, @"AXLandmarkMain"},
       {ui::AX_ROLE_MARQUEE, @"AXApplicationMarquee"},
       {ui::AX_ROLE_MATH, @"AXDocumentMath"},
       {ui::AX_ROLE_NAVIGATION, @"AXLandmarkNavigation"},
       {ui::AX_ROLE_NOTE, @"AXDocumentNote"},
       {ui::AX_ROLE_REGION, @"AXDocumentRegion"},
       {ui::AX_ROLE_SEARCH, @"AXLandmarkSearch"},
       {ui::AX_ROLE_SEARCH_BOX, @"AXSearchField"},
       {ui::AX_ROLE_STATUS, @"AXApplicationStatus"},
       {ui::AX_ROLE_SWITCH, @"AXSwitch"},
+      {ui::AX_ROLE_TAB, @"AXTab"},
       {ui::AX_ROLE_TAB_PANEL, @"AXTabPanel"},
       {ui::AX_ROLE_TIMER, @"AXApplicationTimer"},
       {ui::AX_ROLE_TOGGLE_BUTTON, @"AXToggleButton"},
       {ui::AX_ROLE_TOOLTIP, @"AXUserInterfaceTooltip"},
       {ui::AX_ROLE_TREE_ITEM, NSAccessibilityOutlineRowSubrole},
   };
 
   RoleMap subrole_map;
   for (size_t i = 0; i < arraysize(subroles); ++i)
     subrole_map[subroles[i].value] = subroles[i].nativeValue;
@@ skipping 165 matching lines @@
     default:
       break;
   }
   return axAttributes.autorelease();
 }
 
 - (BOOL)accessibilityIsAttributeSettable:(NSString*)attributeName {
   // Allow certain attributes to be written via an accessibility client. A
   // writable attribute will only appear as such if the accessibility element
   // has a value set for that attribute.
-  if ([attributeName isEqualToString:NSAccessibilitySelectedAttribute] ||
-      [attributeName
+  if ([attributeName
           isEqualToString:NSAccessibilitySelectedChildrenAttribute] ||
       [attributeName
           isEqualToString:NSAccessibilitySelectedTextRangeAttribute] ||
       [attributeName
           isEqualToString:NSAccessibilityVisibleCharacterRangeAttribute]) {
     return NO;
   }
 
+  // Tabs are a special case. For whatever reason,

[tapted, 2017/01/03 00:29:27]

The reason might be that in Cocoa, using role=AXRadioButton for NSTabView and
NSSegmentedControl is a bit of a "hack". E.g. "value" maps logically to a radio
button, but not so much to a tab. If I understand correctly, I think we can
mention that. I.e. "Since tabs use the Radio Button role on Mac, the standard
way to set them is via the value attributed rather than the selected attribute".

[Patti Lor, 2017/01/06 02:02:29]

Done.

+  // NSAccessibilitySelectedAttribute isn't used for them, so allow editing of
+  // the value attribute to select unselected tabs instead.
+  if ([attributeName isEqualToString:NSAccessibilityValueAttribute] &&
+      node_->GetData().role == ui::AX_ROLE_TAB) {
+    return !node_->GetData().HasStateFlag(ui::AX_STATE_SELECTED);
+  }
+
   if ([attributeName isEqualToString:NSAccessibilityValueAttribute] ||
       [attributeName isEqualToString:NSAccessibilitySelectedTextAttribute])
     return !ui::AXNodeData::IsFlagSet(node_->GetData().state,
                                       ui::AX_STATE_READ_ONLY);
 
   if ([attributeName isEqualToString:NSAccessibilityFocusedAttribute]) {
     return ui::AXNodeData::IsFlagSet(node_->GetData().state,
                                      ui::AX_STATE_FOCUSABLE);
   }
 
   // TODO(patricialor): Add callbacks for updating the above attributes except
   // NSAccessibilityValueAttribute and return YES.
   return NO;
 }
 
 - (void)accessibilitySetValue:(id)value forAttribute:(NSString*)attribute {
   ui::AXActionData data;
   if ([value isKindOfClass:[NSString class]]) {
     data.value = base::SysNSStringToUTF16(value);
     if ([attribute isEqualToString:NSAccessibilityValueAttribute]) {
-      data.action = ui::AX_ACTION_SET_VALUE;
+      // Tabs have no other way to set their selected state via a11y, so use the
+      // value attribute here.
+      data.action = node_->GetData().role == ui::AX_ROLE_TAB
+                        ? ui::AX_ACTION_SET_SELECTION
+                        : ui::AX_ACTION_SET_VALUE;
     } else if ([attribute
                    isEqualToString:NSAccessibilitySelectedTextAttribute]) {
       data.action = ui::AX_ACTION_REPLACE_SELECTED_TEXT;
     }
   } else if ([value isKindOfClass:[NSNumber class]]) {
     if ([attribute isEqualToString:NSAccessibilityFocusedAttribute]) {
       data.action =
           [value boolValue] ? ui::AX_ACTION_FOCUS : ui::AX_ACTION_BLUR;
     }
   }
@@ skipping 48 matching lines @@
                                     ui::AX_STATE_PROTECTED))
         return NSAccessibilitySecureTextFieldSubrole;
       break;
     default:
       break;
   }
   return [AXPlatformNodeCocoa nativeSubroleFromAXRole:role];
 }
 
 - (NSString*)AXRoleDescription {
+  ui::AXRole role = node_->GetData().role;
+  switch (role) {

[tapted, 2017/01/03 00:29:27]

nit: switch (node_->GetData().role) {

[Patti Lor, 2017/01/06 02:02:29]

Done.

+    case ui::AX_ROLE_TAB:
+      return l10n_util::GetNSStringWithFixup(IDS_ACCNAME_TAB);

[Patti Lor, 2016/12/30 00:35:02]

There's no "NSAccessibilityTabRole" or similar, so using the same approach as
chrome/browser/ui/cocoa/tabs/tab_view.mm and setting role description manually.

[tapted, 2017/01/03 00:29:27]

Can we move IDS_ACCNAME_TAB to ui_resources.grd? I think that will fix the
layering stuff. Also can we add a note to the case e.g.

    // There is no NSAccessibilityTabRole or similar (AXRadioButton is used
instead). Do the same as NSTabView and put "tab" in the description.

(that's assuming what I said there is correct :)

[Patti Lor, 2017/01/06 02:02:29]

A recent patch (https://codereview.chromium.org/2518183002) conveniently added
ui/strings/ui_strings.h to ui/accessibility/DEPS, so I moved it there instead,
hopefully that's OK :)

+    default:
+      break;
+  }
   return NSAccessibilityRoleDescription([self AXRole], [self AXSubrole]);
 }
 
 - (NSValue*)AXSize {
   return [NSValue valueWithSize:self.boundsInScreen.size];
 }
 
 - (NSString*)AXTitle {
   return [self getStringAttribute:ui::AX_ATTR_NAME];
 }
 
 - (NSString*)AXValue {
+  if (node_->GetData().role == ui::AX_ROLE_TAB)
+    return [[self AXSelected] stringValue];
   return [self getStringAttribute:ui::AX_ATTR_VALUE];
 }
 
 - (NSValue*)AXEnabled {
   return [NSNumber
       numberWithBool:!ui::AXNodeData::IsFlagSet(node_->GetData().state,
                                                 ui::AX_STATE_DISABLED)];
 }
 
 - (NSValue*)AXFocused {
@@ skipping 50 matching lines @@
   int beginSelectionIndex = (end > start && !isReversed) ? start : end;
   return [NSValue
       valueWithRange:NSMakeRange(beginSelectionIndex, abs(end - start))];
 }
 
 - (NSValue*)AXVisibleCharacterRange {
   return [NSValue
       valueWithRange:NSMakeRange(0, [[self AXNumberOfCharacters] intValue])];
 }
 
+// Misc NSAccessibility attributes.
+
+- (NSNumber*)AXSelected {

[Patti Lor, 2016/12/30 00:35:02]

Not sure if we should leave this in; I can't tell if it does anything. It is
definitely called, though. WDYT?

[tapted, 2017/01/03 00:29:27]

This looks good.  I think it's fine to add anything from AXAttributeConstants.h

[Patti Lor, 2017/01/06 02:02:29]

Acknowledged.

+  return [NSNumber
+      numberWithBool:node_->GetData().HasStateFlag(ui::AX_STATE_SELECTED)];
+}
+
 @end
 
 namespace ui {
 
 // static
 AXPlatformNode* AXPlatformNode::Create(AXPlatformNodeDelegate* delegate) {
   AXPlatformNodeBase* node = new AXPlatformNodeMac();
   node->Init(delegate);
   return node;
 }
@@ skipping 33 matching lines @@
   }
   NotifyMacEvent(native_node_, event_type);
 }
 
 int AXPlatformNodeMac::GetIndexInParent() {
   // TODO(dmazzoni): implement this.  http://crbug.com/396137
   return -1;
 }
 
 }  // namespace ui