Add isTabStop attribute to Element

Source/core/dom/Element.cpp

Index: Source/core/dom/Element.cpp
diff --git a/Source/core/dom/Element.cpp b/Source/core/dom/Element.cpp
index 7ed385f12649b8ee4e6a28001d6003723a18e56c..449de0bc73c23771442ea3050f65d4366c9fa205 100644
--- a/Source/core/dom/Element.cpp
+++ b/Source/core/dom/Element.cpp
@@ -149,6 +149,7 @@ PassRefPtrWillBeRawPtr<Element> Element::create(const QualifiedName& tagName, Do
 Element::Element(const QualifiedName& tagName, Document* document, ConstructionType type)
     : ContainerNode(document, type)
     , m_tagName(tagName)
+    , m_isTabStop(true)
 {
 }
 
@@ -217,6 +218,8 @@ void Element::clearTabIndexExplicitlyIfNeeded()
 void Element::setTabIndexExplicitly(short tabIndex)
 {
     ensureElementRareData().setTabIndexExplicitly(tabIndex);
+    // isTabStop is overridden by setting tabindex.

[hayato, 2015/02/20 08:46:31]

Not sure how setting taxIndex attribute from JavaScript affects isTabStop
attribute and vice-verse.
What's the intentional behavior?

For example,

A)

element.setAttribute("isTabStop", false);
element.setAttribute("tabIndex", 1);
// What is the expectation of element.isTabStop here?

B)

element.setAttribute("tabIndex", 1);
element.setAttribute("isTabStop", false);
// What is the expectation of element.isTabStop here?

The result of element.isTabStop will differ for A and  B, won't it?
I'm afraid that that might be weird and will be likely to be misused.

[kochi, 2015/02/20 09:43:05]

A) isTabStop = true
B) isTabStop = false

This is because setting tabindex is stronger than isTabStop, for compatibility
reason.
In case A, when you explicitly set isTabStop to false first, but setting
"tabindex=1"
will reset the effect.

I'll add a layout test for these cases.

[hayato, 2015/02/20 10:28:45]

I understand the intention, however, I'm not sure whether it is good or not that
the result of isTabStop depends on the order in which attributes are specified.
Still looks strange to me...

For example (assuming that we cat set both attributes in declarative way):

<div tabindex="1" isTabStop="false">
<div isTabStop="false" tabindex="1">

In these cases, we expect that isTabStop == false in both cases. I expect that
the same thing will happen also in an imperative way.

Is there any way to make it order-independent?

+    m_isTabStop = (tabIndex >= 0);
 }
 
 void Element::setTabIndex(int value)
@@ -2250,6 +2253,17 @@ bool Element::isMouseFocusable() const
     return isFocusable();
 }
 
+bool Element::isTabStop() const
+{
+    // Any element which never supports focus will always return false.
+    return supportsFocus() && m_isTabStop;
+}
+
+void Element::setIsTabStop(bool flag)
+{
+    m_isTabStop = flag;
+}
+
 void Element::dispatchFocusEvent(Element* oldFocusedElement, WebFocusType type)
 {
     RefPtrWillBeRawPtr<FocusEvent> event = FocusEvent::create(EventTypeNames::focus, false, false, document().domWindow(), 0, oldFocusedElement);