CSS4: Implement :placeholder-shown pseudo class

Source/core/html/HTMLTextFormControlElement.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, 2007 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 45 matching lines @@
 namespace blink {
 
 using namespace HTMLNames;
 
 HTMLTextFormControlElement::HTMLTextFormControlElement(const QualifiedName& tagName, Document& doc, HTMLFormElement* form)
     : HTMLFormControlElementWithState(tagName, doc, form)
     , m_lastChangeWasUserEdit(false)
     , m_cachedSelectionStart(0)
     , m_cachedSelectionEnd(0)
     , m_cachedSelectionDirection(SelectionHasNoDirection)
+    , m_isPlaceholderVisible(false)

[esprehn, 2015/08/21 10:18:10]

remove

[ramya.v, 2015/08/25 10:24:45]

Done.

 {
 }
 
 HTMLTextFormControlElement::~HTMLTextFormControlElement()
 {
 }
 
 Node::InsertionNotificationRequest HTMLTextFormControlElement::insertedInto(ContainerNode* insertionPoint)
 {
     HTMLFormControlElementWithState::insertedInto(insertionPoint);
     if (!insertionPoint->inDocument())
         return InsertionDone;
     String initialValue = value();
     setTextAsOfLastFormControlChangeEvent(initialValue.isNull() ? emptyString() : initialValue);
     return InsertionDone;
 }
 
 void HTMLTextFormControlElement::dispatchFocusEvent(Element* oldFocusedElement, WebFocusType type, InputDevice* sourceDevice)
 {
     if (supportsPlaceholder())
-        updatePlaceholderVisibility(false);
+        updatePlaceholderVisibility();
     handleFocusEvent(oldFocusedElement, type);
     HTMLFormControlElementWithState::dispatchFocusEvent(oldFocusedElement, type, sourceDevice);
 }
 
 void HTMLTextFormControlElement::dispatchBlurEvent(Element* newFocusedElement, WebFocusType type, InputDevice* sourceDevice)
 {
     if (supportsPlaceholder())
-        updatePlaceholderVisibility(false);
+        updatePlaceholderVisibility();
     handleBlurEvent();
     HTMLFormControlElementWithState::dispatchBlurEvent(newFocusedElement, type, sourceDevice);
 }
 
 void HTMLTextFormControlElement::defaultEventHandler(Event* event)
 {
     if (event->type() == EventTypeNames::webkitEditableContentChanged && layoutObject() && layoutObject()->isTextControl()) {
         m_lastChangeWasUserEdit = true;
         subtreeHasChanged();
         return;
@@ skipping 35 matching lines @@
 {
     const AtomicString& attributeValue = fastGetAttribute(placeholderAttr);
     return attributeValue.string().find(isNotLineBreak) == kNotFound;
 }
 
 bool HTMLTextFormControlElement::placeholderShouldBeVisible() const
 {
     return supportsPlaceholder()
         && isEmptyValue()
         && isEmptySuggestedValue()
-        && !isPlaceholderEmpty()
-        && (!layoutObject() || layoutObject()->style()->visibility() == VISIBLE);
+        && !isPlaceholderEmpty();

[esprehn, 2015/08/21 10:18:10]

This is a behavior change, can you explain why you did this?

[ramya.v, 2015/08/25 10:24:45]

In Webkit patch, below point is mentioned.
Remove the dependencies between the Element's style and the placeholder's style.
This is done by simply using display:none; on the placeholder so that its
parent's visibility is irrelevant.
Test is also added for (visible and invisible renderers not to affect
placeholder visibility state)(placeholder-shown-style-update.html)
Taken the same.

 }
 
 HTMLElement* HTMLTextFormControlElement::placeholderElement() const
 {
     return toHTMLElement(userAgentShadowRoot()->getElementById(ShadowElementNames::placeholder()));
 }
 
-void HTMLTextFormControlElement::updatePlaceholderVisibility(bool placeholderValueChanged)
+void HTMLTextFormControlElement::updatePlaceholderVisibility()
 {
-    if (!supportsPlaceholder())
+    HTMLElement* placeholder = placeholderElement();
+    if (!placeholder) {
+        updatePlaceholderText();
         return;
-    if (!placeholderElement() || placeholderValueChanged)
-        updatePlaceholderText();
-    HTMLElement* placeholder = placeholderElement();
-    if (!placeholder)
+    }
+
+    bool placeHolderWasVisible = m_isPlaceholderVisible;
+    m_isPlaceholderVisible = placeholderShouldBeVisible();
+    if (placeHolderWasVisible == m_isPlaceholderVisible)
         return;
 
-    placeholder->setInlineStyleProperty(CSSPropertyDisplay, placeholderShouldBeVisible() ? CSSValueBlock : CSSValueNone);
+    setNeedsStyleRecalc(SubtreeStyleChange, StyleChangeReasonForTracing::create(StyleChangeReason::PseudoClass));

[esprehn, 2015/08/21 10:18:10]

This should use the StyleInvalidator, you need to update
RuleFeatureSet::invalidationSetForSelector and then use
pseudoStateChanged(CSSSelector::PseudoPlaceholderShown)

[ramya.v, 2015/08/25 10:24:45]

Done.

+    placeholder->setInlineStyleProperty(CSSPropertyDisplay, m_isPlaceholderVisible ? CSSValueBlock : CSSValueNone, true);
 }
 
 void HTMLTextFormControlElement::setSelectionStart(int start)
 {
     setSelectionRange(start, std::max(start, selectionEnd()), selectionDirection());
 }
 
 void HTMLTextFormControlElement::setSelectionEnd(int end)
 {
     setSelectionRange(std::min(end, selectionStart()), end, selectionDirection());
@@ skipping 420 matching lines @@
     event->setTarget(this);
     document().enqueueUniqueAnimationFrameEvent(event.release());
 }
 
 void HTMLTextFormControlElement::parseAttribute(const QualifiedName& name, const AtomicString& value)
 {
     if (name == autocapitalizeAttr)
         UseCounter::count(document(), UseCounter::AutocapitalizeAttribute);
 
     if (name == placeholderAttr) {
-        updatePlaceholderVisibility(true);
+        updatePlaceholderText();
+        updatePlaceholderVisibility();
         UseCounter::count(document(), UseCounter::PlaceholderAttribute);
     } else {
         HTMLFormControlElementWithState::parseAttribute(name, value);
     }
 }
 
 bool HTMLTextFormControlElement::lastChangeWasUserEdit() const
 {
     if (!isTextFormControl())
         return false;
@@ skipping 382 matching lines @@
 }
 
 void HTMLTextFormControlElement::copyNonAttributePropertiesFromElement(const Element& source)
 {
     const HTMLTextFormControlElement& sourceElement = static_cast<const HTMLTextFormControlElement&>(source);
     m_lastChangeWasUserEdit = sourceElement.m_lastChangeWasUserEdit;
     HTMLFormControlElement::copyNonAttributePropertiesFromElement(source);
 }
 
 } // namespace blink