assistant: Handle scrolls in AssistantCardElementView

When AssistantCardElementView is focused, the true focused item is a
node in the contained web contents. We override ScrollRectToVisible()
to defer the scroll to FocusedNodeChanged() called by the contents.

In addition, when
View::HandleAccessibleAction(ax::mojom::Action::kScrollToMakeVisible)
is called on AssistantCardElementView, it will scroll to currently
focused node.

Bug: b/143370952
Test: manual
Change-Id: I315db0131e5517bf98d3e76f41203d00555237b3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1902709
Commit-Queue: Tao Wu <wutao@chromium.org>
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Reviewed-by: Xiaohui Chen <xiaohuic@chromium.org>
Cr-Commit-Position: refs/heads/master@{#715093}

ash/assistant/ui/main_stage/assistant_card_element_view.cc

@@ -17,6 +17,7 @@
 #include "ui/events/event_utils.h"
 #include "ui/views/accessibility/view_accessibility.h"
 #include "ui/views/layout/fill_layout.h"
+#include "ui/views/view.h"
 
 namespace ash {
 
@@ -91,6 +92,8 @@ void AssistantCardElementView::ChildPreferredSizeChanged(views::View* child) {
 
 void AssistantCardElementView::AboutToRequestFocusFromTabTraversal(
     bool reverse) {
+  // Focus in the web contents will be reset in FocusThroughTabTraversal().
+  focused_node_rect_ = gfx::Rect();
   contents_->FocusThroughTabTraversal(reverse);
 }
 
@@ -141,6 +144,24 @@ void AssistantCardElementView::OnGestureEvent(ui::GestureEvent* event) {
   cursor_manager->UnlockCursor();
 }
 
+void AssistantCardElementView::ScrollRectToVisible(const gfx::Rect& rect) {
+  // We expect this method is called outside this class to show its local
+  // bounds. Inside this class, should call views::View::ScrollRectToVisible()
+  // to show the focused node in the web contents.
+  DCHECK(rect == GetLocalBounds());
+
+  // When this view is focused, View::Focus() calls ScrollViewToVisible(), which
+  // calls ScrollRectToVisible().  But we don't want that call to do anything,
+  // since the true focused item is not this view but a node in the contained
+  // web contents.  That will be scrolled into view by FocusedNodeChanged()
+  // below, so just no-op here.
+  if (focused_node_rect_.IsEmpty())
+    return;
+
+  // Make the focused node visible.
+  views::View::ScrollRectToVisible(focused_node_rect_);
+}
+
 void AssistantCardElementView::DidAutoResizeView(const gfx::Size& new_size) {
   contents_->GetView()->view()->SetPreferredSize(new_size);
 }
@@ -164,8 +185,8 @@ void AssistantCardElementView::FocusedNodeChanged(
 
   gfx::Point origin = node_bounds_in_screen.origin();
   ConvertPointFromScreen(this, &origin);
-  gfx::Rect focused_rect_in_local(origin, node_bounds_in_screen.size());
-  ScrollRectToVisible(focused_rect_in_local);
+  focused_node_rect_ = gfx::Rect(origin, node_bounds_in_screen.size());
+  views::View::ScrollRectToVisible(focused_node_rect_);
 }
 
 void AssistantCardElementView::InitLayout(

ash/assistant/ui/main_stage/assistant_card_element_view.h

@@ -33,6 +33,7 @@ class COMPONENT_EXPORT(ASSISTANT_UI) AssistantCardElementView
   void AboutToRequestFocusFromTabTraversal(bool reverse) override;
   void OnFocus() override;
   void OnGestureEvent(ui::GestureEvent* event) override;
+  void ScrollRectToVisible(const gfx::Rect& rect) override;
 
   // content::NavigableContentsObserver:
   void DidAutoResizeView(const gfx::Size& new_size) override;
@@ -56,6 +57,9 @@ class COMPONENT_EXPORT(ASSISTANT_UI) AssistantCardElementView
   // Owned by AssistantCardElement.
   content::NavigableContents* const contents_;
 
+  // Rect of the focused node in the |contents_|.
+  gfx::Rect focused_node_rect_;
+
   DISALLOW_COPY_AND_ASSIGN(AssistantCardElementView);
 };