Expose user-select:none to accessibility.

This CL makes user-select:none property visible to accessibility
features via a new boolean attribute, kNotUserSelectable. This is,
for example, useful for select-to-speak, which we expect to skip
non-user-selectable text.

The property is default-false in order to be memory-efficient and
backwards-compatible. Most nodes in the DOM will not have user:select
none, so this property will be omitted from the tree unless the user
explicitly marks user:select=none.

Bug: 830106
Change-Id: I7c8ea7b994514c102389a23bfc5d372ea4737da9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2353127
Commit-Queue: Ajit Narayanan <ajitnarayanan@google.com>
Reviewed-by: Nektarios Paisios <nektar@chromium.org>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Reviewed-by: David Tseng <dtseng@chromium.org>
Reviewed-by: Alex Gough <ajgo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#798398}

content/browser/accessibility/dump_accessibility_tree_browsertest.cc

@@ -2343,6 +2343,11 @@ IN_PROC_BROWSER_TEST_P(DumpAccessibilityTreeTest, AccessibilityUl) {
   RunHtmlTest(FILE_PATH_LITERAL("ul.html"));
 }
 
+IN_PROC_BROWSER_TEST_P(DumpAccessibilityTreeTest,
+                       AccessibilityNotUserSelectable) {
+  RunCSSTest(FILE_PATH_LITERAL("user-select.html"));
+}
+
 IN_PROC_BROWSER_TEST_P(DumpAccessibilityTreeTest, AccessibilityVar) {
   RunHtmlTest(FILE_PATH_LITERAL("var.html"));
 }

content/test/data/accessibility/css/user-select-expected-blink.txt

+rootWebArea
+++genericContainer ignored
+++++genericContainer ignored
+++++++genericContainer notUserSelectableStyle=true
+++++++++staticText name='1. unselectable' notUserSelectableStyle=true
+++++++++++inlineTextBox name='1. unselectable'
+++++++genericContainer
+++++++++staticText name='2. Selectable'
+++++++++++inlineTextBox name='2. Selectable'
+++++++genericContainer notUserSelectableStyle=true
+++++++++staticText name='3. unselectable' notUserSelectableStyle=true
+++++++++++inlineTextBox name='3. unselectable'
+++++++genericContainer
+++++++++staticText name='4. Selectable'
+++++++++++inlineTextBox name='4. Selectable'
+++++++list
+++++++++listItem
+++++++++++listMarker name='• '
+++++++++++++staticText name='• '
+++++++++++++++inlineTextBox name='• '
+++++++++++staticText name='One'
+++++++++++++inlineTextBox name='One'
+++++++genericContainer ignored notUserSelectableStyle=true
+++++++++genericContainer notUserSelectableStyle=true
+++++++++++staticText name='Inner' notUserSelectableStyle=true
+++++++++++++inlineTextBox name='Inner'

content/test/data/accessibility/css/user-select.html

+<!--
+@BLINK-ALLOW:notUserSelectableStyle*
+-->
+<div style="user-select:none">1. unselectable </div>
+<div style="user-select:text"> 2. Selectable </div>
+<div style="user-select:none"> 3. unselectable </div>
+<div style="user-select:text"> 4. Selectable </div>
+<!-- List bullets are not selectable, but that is not due to user-select, 
+    so they will not have the notUserSelectableStyle attribute -->
+<ul>
+    <li>One</li>
+</ul>
+<!-- Should inherit -->
+<div style="user-select:none">
+    <div style="user-select:inherit">Inner</div>
+</div>
\ No newline at end of file

third_party/blink/renderer/modules/accessibility/ax_layout_object.cc

@@ -523,6 +523,18 @@ bool AXLayoutObject::IsSelectedFromFocus() const {
                                         is_selected);
 }
 
+// Returns true if the object is marked user-select:none
+bool AXLayoutObject::IsNotUserSelectable() const {
+  if (!GetLayoutObject())
+    return false;
+
+  const ComputedStyle* style = GetLayoutObject()->Style();
+  if (!style)
+    return false;
+
+  return (style->UserSelect() == EUserSelect::kNone);
+}
+
 // Returns true if the node's aria-selected attribute should be set to true
 // when the node is focused. This is true for only a subset of roles.
 bool AXLayoutObject::SelectionShouldFollowFocus() const {

third_party/blink/renderer/modules/accessibility/ax_layout_object.h

@@ -96,6 +96,7 @@ class MODULES_EXPORT AXLayoutObject : public AXNodeObject {
   AccessibilityGrabbedState IsGrabbed() const override;
   AccessibilitySelectedState IsSelected() const override;
   bool IsSelectedFromFocus() const override;
+  bool IsNotUserSelectable() const override;
 
   // Whether objects are ignored, i.e. not included in the tree.
   AXObjectInclusion DefaultObjectInclusion(

third_party/blink/renderer/modules/accessibility/ax_object.cc

@@ -790,6 +790,11 @@ void AXObject::Serialize(ui::AXNodeData* node_data) {
         IsSelectedFromFocus());
   }
 
+  if (IsNotUserSelectable()) {
+    node_data->AddBoolAttribute(
+        ax::mojom::blink::BoolAttribute::kNotUserSelectableStyle, true);
+  }
+
   if (IsRichlyEditable())
     node_data->AddState(ax::mojom::blink::State::kRichlyEditable);
 

third_party/blink/renderer/modules/accessibility/ax_object.h

@@ -501,6 +501,7 @@ class MODULES_EXPORT AXObject : public GarbageCollected<AXObject> {
   // Is the object selected because selection is following focus?
   virtual bool IsSelectedFromFocus() const { return false; }
   virtual bool IsSelectedOptionActive() const { return false; }
+  virtual bool IsNotUserSelectable() const { return false; }
   virtual bool IsVisible() const;
   virtual bool IsVisited() const { return false; }
 

ui/accessibility/ax_enum_util.cc

@@ -1882,6 +1882,8 @@ const char* ToString(ax::mojom::BoolAttribute bool_attribute) {
       return "clickable";
     case ax::mojom::BoolAttribute::kClipsChildren:
       return "clipsChildren";
+    case ax::mojom::BoolAttribute::kNotUserSelectableStyle:
+      return "notUserSelectableStyle";
     case ax::mojom::BoolAttribute::kSelected:
       return "selected";
     case ax::mojom::BoolAttribute::kSelectedFromFocus:
@@ -1926,6 +1928,8 @@ ax::mojom::BoolAttribute ParseBoolAttribute(const char* bool_attribute) {
     return ax::mojom::BoolAttribute::kClickable;
   if (0 == strcmp(bool_attribute, "clipsChildren"))
     return ax::mojom::BoolAttribute::kClipsChildren;
+  if (0 == strcmp(bool_attribute, "notUserSelectableStyle"))
+    return ax::mojom::BoolAttribute::kNotUserSelectableStyle;
   if (0 == strcmp(bool_attribute, "selected"))
     return ax::mojom::BoolAttribute::kSelected;
   if (0 == strcmp(bool_attribute, "selectedFromFocus"))

ui/accessibility/ax_enums.mojom

@@ -733,6 +733,12 @@ enum BoolAttribute {
   // overflow: hidden or clip children by default.
   kClipsChildren,
 
+  // Indicates that this node is not selectable because the style has
+  // user-select: none. Note that there may be other reasons why a node is
+  // not selectable - for example, bullets in a list. However, this attribute
+  // is only set on user-select: none.
+  kNotUserSelectableStyle,
+
   // Indicates whether this node is selected or unselected.
   kSelected,
 

ui/accessibility/ax_node_data.cc

@@ -1575,6 +1575,9 @@ std::string AXNodeData::ToString() const {
       case ax::mojom::BoolAttribute::kClipsChildren:
         result += " clips_children=" + value;
         break;
+      case ax::mojom::BoolAttribute::kNotUserSelectableStyle:
+        result += " not_user_selectable=" + value;
+        break;
       case ax::mojom::BoolAttribute::kSelected:
         result += " selected=" + value;
         break;