Blur immediately if an attribute change made an element unfocasable.

third_party/WebKit/Source/core/html/HTMLFieldSetElement.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2010 Apple Inc. All rights reserved.
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
@@ skipping 12 matching lines @@
  */
 
 #include "core/html/HTMLFieldSetElement.h"
 
 #include "core/HTMLNames.h"
 #include "core/dom/ElementTraversal.h"
 #include "core/dom/NodeListsNodeData.h"
 #include "core/html/HTMLCollection.h"
 #include "core/html/HTMLLegendElement.h"
 #include "core/layout/LayoutFieldset.h"
+#include "platform/EventDispatchForbiddenScope.h"
 #include "wtf/StdLibExtras.h"
 
 namespace blink {
 
 using namespace HTMLNames;
 
 inline HTMLFieldSetElement::HTMLFieldSetElement(Document& document)
     : HTMLFormControlElement(fieldsetTag, document) {}
 
 HTMLFieldSetElement* HTMLFieldSetElement::create(Document& document) {
@@ skipping 12 matching lines @@
         return false;
     }
   }
   return true;
 }
 
 bool HTMLFieldSetElement::isSubmittableElement() {
   return false;
 }
 
-void HTMLFieldSetElement::invalidateDisabledStateUnder(Element& base) {
-  for (HTMLFormControlElement& element :
-       Traversal<HTMLFormControlElement>::descendantsOf(base))
-    element.ancestorDisabledStateWasChanged();
+// Returns a focused element if it's in descendants of |base|.
+Element* HTMLFieldSetElement::invalidateDisabledStateUnder(Element& base) {

[kochi, 2016/12/21 05:58:09]

The name of the function and return value seem irrelevant.

[tkent, 2016/12/21 06:51:15]

invalidateDescendantDisabledStateAndFindFocusedOne ?

[kochi, 2016/12/21 08:05:19]

Yeah, long but readable.
As the function only called from 2 functions below, and they
can fit in one screen - so we should not worry too much about
the naming :)

+  Element* focusedElement = adjustedFocusedElementInTreeScope();
+  bool shouldBlur = false;
+  {
+    EventDispatchForbiddenScope eventForbidden;
+    for (HTMLFormControlElement& element :
+         Traversal<HTMLFormControlElement>::descendantsOf(base)) {
+      element.ancestorDisabledStateWasChanged();
+      if (focusedElement == &element && element.isDisabledFormControl())
+        shouldBlur = true;
+    }
+  }
+  return shouldBlur ? focusedElement : nullptr;
 }
 
 void HTMLFieldSetElement::disabledAttributeChanged() {
   // This element must be updated before the style of nodes in its subtree gets
   // recalculated.
   HTMLFormControlElement::disabledAttributeChanged();
-  invalidateDisabledStateUnder(*this);
+  if (Element* focusedElement = invalidateDisabledStateUnder(*this))
+    focusedElement->blur();
 }
 
 void HTMLFieldSetElement::childrenChanged(const ChildrenChange& change) {
   HTMLFormControlElement::childrenChanged(change);
-  for (HTMLLegendElement& legend :
-       Traversal<HTMLLegendElement>::childrenOf(*this))
-    invalidateDisabledStateUnder(legend);
+  Element* focusedElement = nullptr;
+  {
+    EventDispatchForbiddenScope eventForbidden;
+    for (HTMLLegendElement& legend :
+         Traversal<HTMLLegendElement>::childrenOf(*this)) {
+      if (Element* element = invalidateDisabledStateUnder(legend))
+        focusedElement = element;
+    }
+  }
+  if (focusedElement)
+    focusedElement->blur();
 }
 
 bool HTMLFieldSetElement::supportsFocus() const {
   return HTMLElement::supportsFocus() && !isDisabledFormControl();
 }
 
 const AtomicString& HTMLFieldSetElement::formControlType() const {
   DEFINE_STATIC_LOCAL(const AtomicString, fieldset, ("fieldset"));
   return fieldset;
 }
 
 LayoutObject* HTMLFieldSetElement::createLayoutObject(const ComputedStyle&) {
   return new LayoutFieldset(this);
 }
 
 HTMLLegendElement* HTMLFieldSetElement::legend() const {
   return Traversal<HTMLLegendElement>::firstChild(*this);
 }
 
 HTMLCollection* HTMLFieldSetElement::elements() {
   return ensureCachedCollection<HTMLCollection>(FormControls);
 }
 
 int HTMLFieldSetElement::tabIndex() const {
   return HTMLElement::tabIndex();
 }
 
 }  // namespace blink