delegatesFocus: Share code in Element::focus() and...

delegatesFocus: Share code in Element::focus() and MouseEventManager::SlideFocusOnShadowHostIfNecessary()

This CL has no behavior changes.

Bug: 1014094
Change-Id: I88dc1ca15210ff96c698f32416c3d284859ad583
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1880899Reviewed-by: Rakina Zata Amni <rakina@chromium.org>
Commit-Queue: Kent Tamura <tkent@chromium.org>
Cr-Commit-Position: refs/heads/master@{#709784}

third_party/blink/renderer/core/dom/element.cc

@@ -3977,6 +3977,32 @@ bool Element::hasAttributeNS(const AtomicString& namespace_uri,
   return GetElementData()->Attributes().Find(q_name);
 }
 
+// Step 1 of https://html.spec.whatwg.org/C/#focusing-steps in a case
+// where |new focus target| is an element.
+Element* Element::FindActualFocusTarget() const {
+  // TODO(crbug.com/1018619): Support AREA -> IMG delegation.
+  if (!AuthorShadowRoot() || !AuthorShadowRoot()->delegatesFocus())
+    return nullptr;
+  Document& doc = GetDocument();
+  UseCounter::Count(doc, WebFeature::kDelegateFocus);
+
+  // TODO(https://github.com/w3c/webcomponents/issues/840): We'd like to
+  // standardize this behavior.
+  Element* focused_element = doc.FocusedElement();
+  if (focused_element && IsShadowIncludingInclusiveAncestorOf(*focused_element))
+    return focused_element;
+
+  // Slide the focus to its inner node.
+  // TODO(crbug.com/1014094): We should pick the first focusable element in
+  // the flat tree.
+  Element* found =
+      doc.GetPage()->GetFocusController().FindFocusableElementInShadowHost(
+          *this);
+  if (found && IsShadowIncludingInclusiveAncestorOf(*found))
+    return found;
+  return nullptr;
+}
+
 void Element::focus(const FocusOptions* options) {
   focus(FocusParams(SelectionBehaviorOnFocus::kRestore, kWebFocusTypeNone,
                     nullptr, options));
@@ -4002,25 +4028,20 @@ void Element::focus(const FocusParams& params) {
 
   DisplayLockUtilities::ScopedChainForcedUpdate scoped_update_forced(this);
   GetDocument().UpdateStyleAndLayoutTree();
-  if (!IsFocusable()) {
-    if (AuthorShadowRoot() && AuthorShadowRoot()->delegatesFocus()) {
-      UseCounter::Count(GetDocument(), WebFeature::kDelegateFocus);
-      Element* focused_element = GetDocument().FocusedElement();
-      if (focused_element &&
-          IsShadowIncludingInclusiveAncestorOf(*focused_element))
-        return;
 
-      // Slide the focus to its inner node.
-      Element* found = GetDocument()
-                           .GetPage()
-                           ->GetFocusController()
-                           .FindFocusableElementInShadowHost(*this);
-      if (found && IsShadowIncludingInclusiveAncestorOf(*found)) {
-        found->focus(FocusParams(SelectionBehaviorOnFocus::kReset,
-                                 kWebFocusTypeForward, nullptr,
-                                 params.options));
-      }
+  // https://html.spec.whatwg.org/C/#focusing-steps
+  //
+  // 1. If new focus target is not a focusable area, ...
+  if (!IsFocusable()) {
+    if (Element* new_focus_target = FindActualFocusTarget()) {
+      // Unlike the specification, we re-run focus() for new_focus_target
+      // because we can't change |this| in a member function.
+      new_focus_target->focus(FocusParams(SelectionBehaviorOnFocus::kReset,
+                                          kWebFocusTypeForward, nullptr,
+                                          params.options));
     }
+    // 2. If new focus target is null, then:
+    //  2.1. If no fallback target was specified, then return.
     return;
   }
   // If script called focus(), then the type would be none. This means we are

third_party/blink/renderer/core/dom/element.h

@@ -645,6 +645,7 @@ class CORE_EXPORT Element : public ContainerNode, public Animatable {
   virtual const AtomicString ImageSourceURL() const;
   virtual Image* ImageContents() { return nullptr; }
 
+  Element* FindActualFocusTarget() const;
   virtual void focus(const FocusParams& = FocusParams());
   void focus(const FocusOptions*);
 

third_party/blink/renderer/core/input/mouse_event_manager.cc

@@ -649,30 +649,12 @@ WebInputEventResult MouseEventManager::HandleMouseFocus(
 
 bool MouseEventManager::SlideFocusOnShadowHostIfNecessary(
     const Element& element) {
-  if (element.AuthorShadowRoot() &&
-      element.AuthorShadowRoot()->delegatesFocus()) {
-    Document* doc = frame_->GetDocument();
-    UseCounter::Count(doc, WebFeature::kDelegateFocus);
-    Element* focused_element = doc->FocusedElement();
-    if (focused_element &&
-        element.IsShadowIncludingInclusiveAncestorOf(*focused_element)) {
-      // If the inner element is already focused, do nothing.
-      return true;
-    }
-
-    // If the host has a focusable inner element, focus it. Otherwise, the host
-    // takes focus.
-    Page* page = frame_->GetPage();
-    DCHECK(page);
-    Element* found =
-        page->GetFocusController().FindFocusableElementInShadowHost(element);
-    if (found && element.IsShadowIncludingInclusiveAncestorOf(*found)) {
-      // Use WebFocusTypeForward instead of WebFocusTypeMouse here to mean the
-      // focus has slided.
-      found->focus(FocusParams(SelectionBehaviorOnFocus::kReset,
-                               kWebFocusTypeForward, nullptr));
-      return true;
-    }
+  if (Element* delegated_target = element.FindActualFocusTarget()) {
+    // Use WebFocusTypeForward instead of WebFocusTypeMouse here to mean the
+    // focus has slided.
+    delegated_target->focus(FocusParams(SelectionBehaviorOnFocus::kReset,
+                                        kWebFocusTypeForward, nullptr));
+    return true;
   }
   return false;
 }