Android a11y: do not mark as scrollable unless user scrollable

When objects are only programmatically scrollable, e.g. overflow:hidden,
as opposed to overflow:auto|scroll, do not mark them as scrollable.

Bug: 1055344
Change-Id: Ib5ade11a7a92720d6571acf6d65112696f2a2535
Cq-Do-Not-Cancel-Tryjobs: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2070232Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Commit-Queue: Aaron Leventhal <aleventhal@chromium.org>
Auto-Submit: Aaron Leventhal <aleventhal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#745498}

content/browser/accessibility/browser_accessibility_android.cc

@@ -327,7 +327,7 @@ bool BrowserAccessibilityAndroid::IsRangeType() const {
 }
 
 bool BrowserAccessibilityAndroid::IsScrollable() const {
-  return HasIntAttribute(ax::mojom::IntAttribute::kScrollXMax);
+  return GetBoolAttribute(ax::mojom::BoolAttribute::kScrollable);
 }
 
 bool BrowserAccessibilityAndroid::IsSelected() const {

content/renderer/accessibility/blink_ax_tree_source.cc

@@ -1161,7 +1161,11 @@ void BlinkAXTreeSource::SerializeNode(WebAXObject src,
   }
 
   if (src.IsScrollableContainer()) {
-    dst->AddBoolAttribute(ax::mojom::BoolAttribute::kScrollable, true);
+    // Only mark as scrollable if user has actual scrollbars to use.
+    dst->AddBoolAttribute(ax::mojom::BoolAttribute::kScrollable,
+                          src.IsUserScrollable());
+    // Provide x,y scroll info if scrollable in any way (programmatically or via
+    // user).
     const gfx::Point& scroll_offset = src.GetScrollOffset();
     dst->AddIntAttribute(ax::mojom::IntAttribute::kScrollX, scroll_offset.x());
     dst->AddIntAttribute(ax::mojom::IntAttribute::kScrollY, scroll_offset.y());

content/test/data/accessibility/html/iframe-coordinates-expected-android.txt

-android.webkit.WebView focusable focused scrollable
+android.webkit.WebView focusable focused
 ++android.view.View
 ++++android.widget.Button role_description='button' clickable focusable name='Button'
 ++android.view.View

content/test/data/accessibility/html/scrollable-overflow-expected-android.txt

+android.webkit.WebView focusable focused scrollable
+++android.view.View name='no overflow'
+++android.view.View
+++++android.view.View name='clipped'
+++android.widget.EditText clickable editable_text focusable has_non_empty_value multiline scrollable name='ab cd' text_change_added_count=5
+++android.view.View
+++++android.view.View name='tiny'
+++android.view.View scrollable
+++++android.view.View name='x=hidden'
+++android.view.View scrollable name='x=auto'
+++++android.view.View name='x=auto'
+++android.view.View scrollable name='x=scroll'
+++++android.view.View name='x=scroll'
+++android.view.View name='x=visible'
+++android.view.View scrollable
+++++android.view.View name='y=hidden'
+++android.view.View scrollable name='y=auto'
+++++android.view.View name='y=auto'
+++android.view.View scrollable name='y=scroll'
+++++android.view.View name='y=scroll'
+++android.view.View name='y=visible'
\ No newline at end of file

content/test/data/accessibility/html/scrollable-overflow-expected-auralinux.txt

+[document web]
+++[paragraph]
+++++[static] name='no overflow'
+++[section]
+++++[paragraph]
+++++++[static] name='clipped'
+++[entry] selectable-text
+++[section]
+++++[paragraph]
+++++++[static] name='tiny'
+++[section]
+++++[paragraph]
+++++++[static] name='x=hidden'
+++[section] name='x=auto'
+++++[paragraph]
+++++++[static] name='x=auto'
+++[section] name='x=scroll'
+++++[paragraph]
+++++++[static] name='x=scroll'
+++[paragraph]
+++++[static] name='x=visible'
+++[section]
+++++[paragraph]
+++++++[static] name='y=hidden'
+++[section] name='y=auto'
+++++[paragraph]
+++++++[static] name='y=auto'
+++[section] name='y=scroll'
+++++[paragraph]
+++++++[static] name='y=scroll'
+++[paragraph]
+++++[static] name='y=visible'
\ No newline at end of file

content/test/data/accessibility/html/scrollable-overflow-expected-blink.txt

-rootWebArea scrollXMin=0
+rootWebArea scrollXMin=0 scrollable=true
 ++genericContainer ignored
 ++++genericContainer ignored
 ++++++paragraph
 ++++++++staticText name='no overflow'
 ++++++++++inlineTextBox name='no overflow'
+++++genericContainer scrollXMin=0
+++++++paragraph
+++++++++staticText name='clipped'
+++++++++++inlineTextBox name='clipped'
+++++textField multiline value='ab cd' scrollXMin=0 scrollable=true
+++++++genericContainer
+++++++++staticText name='ab cd'
+++++++++++inlineTextBox name='ab'
+++++++++++inlineTextBox name=' '
+++++++++++inlineTextBox name='cd'
 ++++genericContainer ignored
 ++++++genericContainer
 ++++++++paragraph
 ++++++++++staticText name='tiny'
 ++++++++++++inlineTextBox name='tiny'
 ++++genericContainer ignored
-++++++genericContainer scrollXMin=0
+++++++genericContainer scrollXMin=0 scrollable=true
 ++++++++paragraph
 ++++++++++staticText name='x=hidden'
 ++++++++++++inlineTextBox name='x=hidden'
-++++++genericContainer name='x=auto' scrollXMin=0
+++++++genericContainer name='x=auto' scrollXMin=0 scrollable=true
 ++++++++paragraph
 ++++++++++staticText name='x=auto'
 ++++++++++++inlineTextBox name='x=auto'
-++++++genericContainer name='x=scroll' scrollXMin=0
+++++++genericContainer name='x=scroll' scrollXMin=0 scrollable=true
 ++++++++paragraph
 ++++++++++staticText name='x=scroll'
 ++++++++++++inlineTextBox name='x=scroll'
@@ -27,15 +37,15 @@ rootWebArea scrollXMin=0
 ++++++++++staticText name='x=visible'
 ++++++++++++inlineTextBox name='x=visible'
 ++++genericContainer ignored
-++++++genericContainer scrollXMin=0
+++++++genericContainer scrollXMin=0 scrollable=true
 ++++++++paragraph
 ++++++++++staticText name='y=hidden'
 ++++++++++++inlineTextBox name='y=hidden'
-++++++genericContainer name='y=auto' scrollXMin=0
+++++++genericContainer name='y=auto' scrollXMin=0 scrollable=true
 ++++++++paragraph
 ++++++++++staticText name='y=auto'
 ++++++++++++inlineTextBox name='y=auto'
-++++++genericContainer name='y=scroll' scrollXMin=0
+++++++genericContainer name='y=scroll' scrollXMin=0 scrollable=true
 ++++++++paragraph
 ++++++++++staticText name='y=scroll'
 ++++++++++++inlineTextBox name='y=scroll'

content/test/data/accessibility/html/scrollable-overflow-expected-uia-win.txt

+Document IsScrollPatternAvailable=true IsScrollItemPatternAvailable=true Scroll.HorizontallyScrollable=true Scroll.VerticallyScrollable=false
+++Group IsControlElement=false IsScrollPatternAvailable=false IsScrollItemPatternAvailable=true
+++++Text Name='no overflow' IsScrollPatternAvailable=false IsScrollItemPatternAvailable=true
+++Group IsControlElement=false IsScrollPatternAvailable=true IsScrollItemPatternAvailable=true Scroll.HorizontallyScrollable=true Scroll.VerticallyScrollable=true
+++++Group IsControlElement=false IsScrollPatternAvailable=false IsScrollItemPatternAvailable=true
+++++++Text Name='clipped' IsScrollPatternAvailable=false IsScrollItemPatternAvailable=true
+++Edit IsScrollPatternAvailable=true IsScrollItemPatternAvailable=true Scroll.HorizontallyScrollable=false Scroll.VerticallyScrollable=true Value.Value='ab cd'
+++Group IsControlElement=false IsScrollPatternAvailable=false IsScrollItemPatternAvailable=true
+++++Group IsControlElement=false IsScrollPatternAvailable=false IsScrollItemPatternAvailable=true
+++++++Text Name='tiny' IsScrollPatternAvailable=false IsScrollItemPatternAvailable=true
+++Group IsControlElement=false IsScrollPatternAvailable=true IsScrollItemPatternAvailable=true Scroll.HorizontallyScrollable=true Scroll.VerticallyScrollable=false
+++++Group IsControlElement=false IsScrollPatternAvailable=false IsScrollItemPatternAvailable=true
+++++++Text Name='x=hidden' IsScrollPatternAvailable=false IsScrollItemPatternAvailable=true
+++Group Name='x=auto' IsScrollPatternAvailable=true IsScrollItemPatternAvailable=true Scroll.HorizontallyScrollable=true Scroll.VerticallyScrollable=false
+++++Group IsControlElement=false IsScrollPatternAvailable=false IsScrollItemPatternAvailable=true
+++++++Text Name='x=auto' IsScrollPatternAvailable=false IsScrollItemPatternAvailable=true
+++Group Name='x=scroll' IsScrollPatternAvailable=true IsScrollItemPatternAvailable=true Scroll.HorizontallyScrollable=true Scroll.VerticallyScrollable=false
+++++Group IsControlElement=false IsScrollPatternAvailable=false IsScrollItemPatternAvailable=true
+++++++Text Name='x=scroll' IsScrollPatternAvailable=false IsScrollItemPatternAvailable=true
+++Group IsControlElement=false IsScrollPatternAvailable=false IsScrollItemPatternAvailable=true
+++++Text Name='x=visible' IsScrollPatternAvailable=false IsScrollItemPatternAvailable=true
+++Group IsControlElement=false IsScrollPatternAvailable=true IsScrollItemPatternAvailable=true Scroll.HorizontallyScrollable=false Scroll.VerticallyScrollable=true
+++++Group IsControlElement=false IsScrollPatternAvailable=false IsScrollItemPatternAvailable=true
+++++++Text Name='y=hidden' IsScrollPatternAvailable=false IsScrollItemPatternAvailable=true
+++Group Name='y=auto' IsScrollPatternAvailable=true IsScrollItemPatternAvailable=true Scroll.HorizontallyScrollable=false Scroll.VerticallyScrollable=true
+++++Group IsControlElement=false IsScrollPatternAvailable=false IsScrollItemPatternAvailable=true
+++++++Text Name='y=auto' IsScrollPatternAvailable=false IsScrollItemPatternAvailable=true
+++Group Name='y=scroll' IsScrollPatternAvailable=true IsScrollItemPatternAvailable=true Scroll.HorizontallyScrollable=false Scroll.VerticallyScrollable=true
+++++Group IsControlElement=false IsScrollPatternAvailable=false IsScrollItemPatternAvailable=true
+++++++Text Name='y=scroll' IsScrollPatternAvailable=false IsScrollItemPatternAvailable=true
+++Group IsControlElement=false IsScrollPatternAvailable=false IsScrollItemPatternAvailable=true
+++++Text Name='y=visible' IsScrollPatternAvailable=false IsScrollItemPatternAvailable=true

content/test/data/accessibility/html/scrollable-overflow.html

 <!--
 * Test scrollXMin -- the presence of this indicates something is scrollable.
 @BLINK-ALLOW:scrollXMin=*
+@BLINK-ALLOW:scrollable=true
+@UIA-WIN-ALLOW:*ScrollItemPatternAvailable*
+@UIA-WIN-ALLOW:*ScrollPatternAvailable*
+@UIA-WIN-ALLOW:*Scrollable*
 -->
 <html>
   <style>
   body { font-style: monospace; width: 999px;}
+  .clipped { width: 25px; height: 25px; overflow: hidden; }
   .x-overflow > div { width: 25px; height: 50px;}
   .x-overflow > div > p { margin: 0; }
   .y-overflow > div { height: 25px; }
@@ -12,9 +17,15 @@
   </style>
   <body>
     <div class="no-overflow">  <!-- Not scrollable -->
-      <p>no overflow
+      <p>no overflow <!-- Default is overflow: visible -->
     </div>
 
+    <div class="clipped">  <!-- Not scrollable -->
+      <p>clipped <!-- Default is overflow: visible -->
+    </div>
+
+    <textarea rows="1" cols="2">ab cd</textarea>  <!-- User scrollable -->
+
     <div class="not-enough-content-to-scroll">  <!-- Not scrollable -->
       <div style="overflow: scroll; width: 100px; height: 100px">
         <p>tiny
@@ -22,13 +33,13 @@
     </div>
 
     <div class="x-overflow">
-      <div style="overflow-x: hidden;">  <!-- Scrollable -->
+      <div style="overflow-x: hidden;">  <!-- Actually user scrollable, because overflow-x=hidden changes overflow-y to auto   -->
           <p>x=hidden
       </div>
-      <div style="overflow-x: auto;">  <!-- Scrollable -->
+      <div style="overflow-x: auto;">  <!-- User scrollable if overflow -->
           <p>x=auto
       </div>
-      <div style="overflow-x: scroll;">  <!-- Scrollable -->
+      <div style="overflow-x: scroll;">  <!-- User scrollable if overflow -->
           <p>x=scroll
       </div>
       <div style="overflow-x: visible;">  <!-- Not scrollable -->
@@ -37,13 +48,13 @@
     </div>
 
     <div class="y-overflow">
-      <div style="overflow-y: hidden;">  <!-- Scrollable -->
+      <div style="overflow-y: hidden;">  <!-- Actually user scrollable, because overflow-y=hidden changes overflow-x to auto   -->
           <p>y=hidden
       </div>
-      <div style="overflow-y: auto;">  <!-- Scrollable -->
+      <div style="overflow-y: auto;">  <!-- Use scrollable if overflow -->
           <p>y=auto
       </div>
-      <div style="overflow-y: scroll;">  <!-- Scrollable -->
+      <div style="overflow-y: scroll;">  <!-- Use scrollable if overflow  -->
           <p>y=scroll
       </div>
       <div style="overflow-y: visible;">  <!-- Not scrollable -->

third_party/blink/public/web/web_ax_object.h

@@ -355,7 +355,10 @@ class WebAXObject {
                                       WebVector<int>& ends) const;
 
   // Scrollable containers.
+  // Programmatically scrollable.
   BLINK_EXPORT bool IsScrollableContainer() const;
+  // Also scrollable by user.
+  BLINK_EXPORT bool IsUserScrollable() const;
   BLINK_EXPORT gfx::Point GetScrollOffset() const;
   BLINK_EXPORT gfx::Point MinimumScrollOffset() const;
   BLINK_EXPORT gfx::Point MaximumScrollOffset() const;

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

@@ -2749,6 +2749,17 @@ bool AXObject::IsScrollableContainer() const {
   return !!GetScrollableAreaIfScrollable();
 }
 
+bool AXObject::IsUserScrollable() const {
+  if (!GetScrollableAreaIfScrollable() || !GetLayoutObject())
+    return false;
+
+  const ComputedStyle* style = GetLayoutObject()->Style();
+  if (!style)
+    return false;
+
+  return style->ScrollsOverflowY() || style->ScrollsOverflowX();
+}
+
 IntPoint AXObject::GetScrollOffset() const {
   ScrollableArea* area = GetScrollableAreaIfScrollable();
   if (!area)

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

@@ -913,6 +913,7 @@ class MODULES_EXPORT AXObject : public GarbageCollected<AXObject> {
 
   // Scrollable containers.
   bool IsScrollableContainer() const;
+  bool IsUserScrollable() const;  // Only true if actual scrollbars are present.
   IntPoint GetScrollOffset() const;
   IntPoint MinimumScrollOffset() const;
   IntPoint MaximumScrollOffset() const;

third_party/blink/renderer/modules/exported/web_ax_object.cc

@@ -1528,6 +1528,12 @@ bool WebAXObject::IsScrollableContainer() const {
   return private_->IsScrollableContainer();
 }
 
+bool WebAXObject::IsUserScrollable() const {
+  if (IsDetached())
+    return false;
+
+  return private_->IsUserScrollable();
+}
 gfx::Point WebAXObject::GetScrollOffset() const {
   if (IsDetached())
     return gfx::Point();

ui/accessibility/ax_enums.mojom

@@ -719,7 +719,9 @@ enum BoolAttribute {
   // Set on a canvas element if it has fallback content.
   kCanvasHasFallback,
 
-  // Indicates this node is scrollable (Android only).
+  // Indicates this node is user-scrollable, e.g. overflow:scroll|auto, as
+  // opposed to only programmatically scrollable, like overflow:hidden, or
+  // not scrollable at all, e.g. overflow:visible.
   kScrollable,
 
   // A hint to clients that the node is clickable.