QWebElement Class Reference

The QWebElement class provides convenient access to DOM elements in a QWebFrame. More...

 #include <QWebElement>

This class was introduced in Qt 4.6.

Public Types

enum StyleResolveStrategy { InlineStyle, CascadedStyle, ComputedStyle }

Public Functions

QWebElement ()
QWebElement ( const QWebElement & other )
~QWebElement ()
void addClass ( const QString & name )
void appendInside ( const QString & markup )
void appendInside ( const QWebElement & element )
void appendOutside ( const QString & markup )
void appendOutside ( const QWebElement & element )
QString attribute ( const QString & name, const QString & defaultValue = QString() ) const
QString attributeNS ( const QString & namespaceUri, const QString & name, const QString & defaultValue = QString() ) const
QStringList attributeNames ( const QString & namespaceUri = QString() ) const
QStringList classes () const
QWebElement clone () const
QWebElement document () const
void encloseContentsWith ( const QWebElement & element )
void encloseContentsWith ( const QString & markup )
void encloseWith ( const QString & markup )
void encloseWith ( const QWebElement & element )
QVariant evaluateJavaScript ( const QString & scriptSource )
QWebElementCollection findAll ( const QString & selectorQuery ) const
QWebElement findFirst ( const QString & selectorQuery ) const
QWebElement firstChild () const
QRect geometry () const
bool hasAttribute ( const QString & name ) const
bool hasAttributeNS ( const QString & namespaceUri, const QString & name ) const
bool hasAttributes () const
bool hasClass ( const QString & name ) const
bool hasFocus () const
bool isNull () const
QWebElement lastChild () const
QString localName () const
QString namespaceUri () const
QWebElement nextSibling () const
QWebElement parent () const
QString prefix () const
void prependInside ( const QString & markup )
void prependInside ( const QWebElement & element )
void prependOutside ( const QString & markup )
void prependOutside ( const QWebElement & element )
QWebElement previousSibling () const
void removeAllChildren ()
void removeAttribute ( const QString & name )
void removeAttributeNS ( const QString & namespaceUri, const QString & name )
void removeClass ( const QString & name )
void removeFromDocument ()
void render ( QPainter * painter )
void render ( QPainter * painter, const QRect & clip )
void replace ( const QString & markup )
void replace ( const QWebElement & element )
void setAttribute ( const QString & name, const QString & value )
void setAttributeNS ( const QString & namespaceUri, const QString & name, const QString & value )
void setFocus ()
void setInnerXml ( const QString & markup )
void setOuterXml ( const QString & markup )
void setPlainText ( const QString & text )
void setStyleProperty ( const QString & name, const QString & value )
QString styleProperty ( const QString & name, StyleResolveStrategy strategy ) const
QString tagName () const
QWebElement & takeFromDocument ()
QString toInnerXml () const
QString toOuterXml () const
QString toPlainText () const
void toggleClass ( const QString & name )
QWebFrame * webFrame () const
bool operator!= ( const QWebElement & o ) const
QWebElement & operator= ( const QWebElement & other )
bool operator== ( const QWebElement & o ) const

Detailed Description

The QWebElement class provides convenient access to DOM elements in a QWebFrame.

A QWebElement object allows easy access to the document model, represented by a tree-like structure of DOM elements. The root of the tree is called the document element and can be accessed using QWebFrame::documentElement().

Specific elements can be accessed using findAll() and findFirst(). These elements are identified using CSS selectors. The code snippet below demonstrates the use of findAll().

     QWebElement document = frame->documentElement();
     /* Assume the document has the following structure:

        <p class=intro>
          <span>Intro</span>
          <span>Snippets</span>
        </p>
        <p>
          <span>Content</span>
          <span>Here</span>
        </p>
     */

     QWebElementCollection allSpans = document.findAll("span");
     QWebElementCollection introSpans = document.findAll("p.intro span");

The first list contains all span elements in the document. The second list contains span elements that are children of p, classified with intro.

Using findFirst() is more efficient than calling findAll(), and extracting the first element only in the list returned.

Alternatively you can traverse the document manually using firstChild() and nextSibling():

     frame->setHtml("<html><body><p>First Paragraph</p><p>Second Paragraph</p></body></html>");
     QWebElement doc = frame->documentElement();
     QWebElement body = doc.firstChild();
     QWebElement firstParagraph = body.firstChild();
     QWebElement secondParagraph = firstParagraph.nextSibling();

Individual elements can be inspected or changed using methods such as attribute() or setAttribute(). For examle, to capture the user's input in a text field for later use (auto-completion), a browser could do something like this:

     QWebElement firstTextInput = document.findFirst("input[type=text]");
     QString storedText = firstTextInput.attribute("value");

When the same page is later revisited, the browser can fill in the text field automatically by modifying the value attribute of the input element:

     QWebElement firstTextInput = document.findFirst("input[type=text]");
     textInput.setAttribute("value", storedText);

Another use case is to emulate a click event on an element. The following code snippet demonstrates how to call the JavaScript DOM method click() of a submit button:

     QWebElement document = frame->documentElement();
     /* Assume that the document has the following structure:

         <form name="myform" action="submit_form.asp" method="get">
             <input type="text" name="myfield">
             <input type="submit" value="Submit">
         </form>

      */

     QWebElement button = document.findFirst("input[type=submit]");
     button.evaluateJavaScript("this.click()");

The underlying content of QWebElement is explicitly shared. Creating a copy of a QWebElement does not create a copy of the content. Instead, both instances point to the same element.

The contents of child elements can be converted to plain text with toPlainText(); to XHTML using toInnerXml(). To include the element's tag in the output, use toOuterXml().

It is possible to replace the contents of child elements using setPlainText() and setInnerXml(). To replace the element itself and its contents, use setOuterXml().

Examples

The DOM Traversal Example shows one way to traverse documents in a running example.

The Simple Selector Example can be used to experiment with the searching features of this class and provides sample code you can start working with.

Member Type Documentation

enum QWebElement::StyleResolveStrategy

This enum describes how QWebElement's styleProperty resolves the given property name.

ConstantValueDescription
QWebElement::InlineStyle0Return the property value as it is defined in the element, without respecting style inheritance and other CSS rules.
QWebElement::CascadedStyle1The property's value is determined using the inheritance and importance rules defined in the document's stylesheet.
QWebElement::ComputedStyle2The property's value is the absolute value of the style property resolved from the environment.

Member Function Documentation

QWebElement::QWebElement ()

Constructs a null web element.

QWebElement::QWebElement ( const QWebElement & other )

Constructs a copy of other.

QWebElement::~QWebElement ()

Destroys the element. However, the underlying DOM element is not destroyed.

void QWebElement::addClass ( const QString & name )

Adds the specified class with the given name to the element.

void QWebElement::appendInside ( const QString & markup )

Appends the result of parsing markup as the element's last child.

Calling this function on a null element does nothing.

See also prependInside(), prependOutside(), and appendOutside().

void QWebElement::appendInside ( const QWebElement & element )

Appends the given element as the element's last child.

If element is the child of another element, it is re-parented to this element. If element is a child of this element, then its position in the list of children is changed.

Calling this function on a null element does nothing.

See also prependInside(), prependOutside(), and appendOutside().

void QWebElement::appendOutside ( const QString & markup )

Inserts the result of parsing markup after this element.

Calling this function on a null element does nothing.

See also appendInside(), prependInside(), and prependOutside().

void QWebElement::appendOutside ( const QWebElement & element )

Inserts the given element after this element.

If element is the child of another element, it is re-parented to the parent of this element.

Calling this function on a null element does nothing.

See also appendInside(), prependInside(), and prependOutside().

QString QWebElement::attribute ( const QString & name, const QString & defaultValue = QString() ) const

Returns the attribute with the given name. If the attribute does not exist, defaultValue is returned.

See also setAttribute(), setAttributeNS(), and attributeNS().

QString QWebElement::attributeNS ( const QString & namespaceUri, const QString & name, const QString & defaultValue = QString() ) const

Returns the attribute with the given name in namespaceUri. If the attribute does not exist, defaultValue is returned.

See also setAttributeNS(), setAttribute(), and attribute().

QStringList QWebElement::attributeNames ( const QString & namespaceUri = QString() ) const

Return the list of attributes for the namespace given as namespaceUri.

See also attribute() and setAttribute().

QStringList QWebElement::classes () const

Returns the list of classes of this element.

QWebElement QWebElement::clone () const

Returns a clone of this element.

The clone may be inserted at any point in the document.

See also appendInside(), prependInside(), prependOutside(), and appendOutside().

QWebElement QWebElement::document () const

Returns the document which this element belongs to.

void QWebElement::encloseContentsWith ( const QWebElement & element )

Encloses the contents of this element with element. This element becomes the child of the deepest descendant within element.

### illustration

See also encloseWith().

void QWebElement::encloseContentsWith ( const QString & markup )

Encloses the contents of this element with the result of parsing markup. This element becomes the child of the deepest descendant within markup.

See also encloseWith().

void QWebElement::encloseWith ( const QString & markup )

Encloses this element with the result of parsing markup. This element becomes the child of the deepest descendant within markup.

See also replace().

void QWebElement::encloseWith ( const QWebElement & element )

Encloses this element with element. This element becomes the child of the deepest descendant within element.

See also replace().

QVariant QWebElement::evaluateJavaScript ( const QString & scriptSource )

Executes scriptSource with this element as this object.

QWebElementCollection QWebElement::findAll ( const QString & selectorQuery ) const

Returns a new list of child elements matching the given CSS selector selectorQuery. If there are no matching elements, an empty list is returned.

Standard CSS2 selector syntax is used for the query.

Note: This search is performed recursively.

See also findFirst().

QWebElement QWebElement::findFirst ( const QString & selectorQuery ) const

Returns the first child element that matches the given CSS selector selectorQuery.

Standard CSS2 selector syntax is used for the query.

Note: This search is performed recursively.

See also findAll().

QWebElement QWebElement::firstChild () const

Returns the element's first child.

See also lastChild(), previousSibling(), and nextSibling().

QRect QWebElement::geometry () const

Returns the geometry of this element, relative to its containing frame.

See also tagName().

bool QWebElement::hasAttribute ( const QString & name ) const

Returns true if this element has an attribute with the given name; otherwise returns false.

See also attribute() and setAttribute().

bool QWebElement::hasAttributeNS ( const QString & namespaceUri, const QString & name ) const

Returns true if this element has an attribute with the given name, in namespaceUri; otherwise returns false.

See also attributeNS() and setAttributeNS().

bool QWebElement::hasAttributes () const

Returns true if the element has any attributes defined; otherwise returns false;

See also attribute() and setAttribute().

bool QWebElement::hasClass ( const QString & name ) const

Returns true if this element has a class with the given name; otherwise returns false.

bool QWebElement::hasFocus () const

Returns true if the element has keyboard input focus; otherwise, returns false

See also setFocus().

bool QWebElement::isNull () const

Returns true if the element is a null element; otherwise returns false.

QWebElement QWebElement::lastChild () const

Returns the element's last child.

See also firstChild(), previousSibling(), and nextSibling().

QString QWebElement::localName () const

Returns the local name of the element. If the element does not use namespaces, an empty string is returned.

QString QWebElement::namespaceUri () const

Returns the namespace URI of this element. If the element has no namespace URI, an empty string is returned.

QWebElement QWebElement::nextSibling () const

Returns the element's next sibling.

See also firstChild(), previousSibling(), and lastChild().

QWebElement QWebElement::parent () const

Returns the parent element of this elemen. If this element is the root document element, a null element is returned.

QString QWebElement::prefix () const

Returns the namespace prefix of the element. If the element has no namespace prefix, empty string is returned.

void QWebElement::prependInside ( const QString & markup )

Prepends the result of parsing markup as the element's first child.

Calling this function on a null element does nothing.

See also appendInside(), prependOutside(), and appendOutside().

void QWebElement::prependInside ( const QWebElement & element )

Prepends element as the element's first child.

If element is the child of another element, it is re-parented to this element. If element is a child of this element, then its position in the list of children is changed.

Calling this function on a null element does nothing.

See also appendInside(), prependOutside(), and appendOutside().

void QWebElement::prependOutside ( const QString & markup )

Inserts the result of parsing markup before this element.

Calling this function on a null element does nothing.

See also appendInside(), prependInside(), and appendOutside().

void QWebElement::prependOutside ( const QWebElement & element )

Inserts the given element before this element.

If element is the child of another element, it is re-parented to the parent of this element.

Calling this function on a null element does nothing.

See also appendInside(), prependInside(), and appendOutside().

QWebElement QWebElement::previousSibling () const

Returns the element's previous sibling.

See also firstChild(), nextSibling(), and lastChild().

void QWebElement::removeAllChildren ()

Removes all children from this element.

See also removeFromDocument() and takeFromDocument().

void QWebElement::removeAttribute ( const QString & name )

Removes the attribute with the given name from this element.

See also attribute(), setAttribute(), and hasAttribute().

void QWebElement::removeAttributeNS ( const QString & namespaceUri, const QString & name )

Removes the attribute with the given name, in namespaceUri, from this element.

See also attributeNS(), setAttributeNS(), and hasAttributeNS().

void QWebElement::removeClass ( const QString & name )

Removes the specified class with the given name from the element.

void QWebElement::removeFromDocument ()

Removes this element from the document and makes it a null element.

See also removeAllChildren() and takeFromDocument().

void QWebElement::render ( QPainter * painter )

Render the element into painter .

void QWebElement::render ( QPainter * painter, const QRect & clip )

Render the element into painter clipping to clip.

void QWebElement::replace ( const QString & markup )

Replaces this element with the result of parsing markup.

This method will not replace the <html>, <head> or <body> elements.

See also encloseWith().

void QWebElement::replace ( const QWebElement & element )

Replaces this element with element.

This method will not replace the <html>, <head> or <body> elements.

See also encloseWith().

void QWebElement::setAttribute ( const QString & name, const QString & value )

Adds an attribute with the given name and value. If an attribute with the same name exists, its value is replaced by value.

See also attribute(), attributeNS(), and setAttributeNS().

void QWebElement::setAttributeNS ( const QString & namespaceUri, const QString & name, const QString & value )

Adds an attribute with the given name in namespaceUri with value. If an attribute with the same name exists, its value is replaced by value.

See also attributeNS(), attribute(), and setAttribute().

void QWebElement::setFocus ()

Gives keyboard input focus to this element

See also hasFocus().

void QWebElement::setInnerXml ( const QString & markup )

Replaces the contents of this element with markup. The string may contain HTML or XML tags, which is parsed and formatted before insertion into the document.

Note: This is currently implemented for (X)HTML elements only.

See also toInnerXml(), toOuterXml(), and setOuterXml().

void QWebElement::setOuterXml ( const QString & markup )

Replaces the contents of this element as well as its own tag with markup. The string may contain HTML or XML tags, which is parsed and formatted before insertion into the document.

Note: This is currently only implemented for (X)HTML elements.

See also toOuterXml(), toInnerXml(), and setInnerXml().

void QWebElement::setPlainText ( const QString & text )

Replaces the existing content of this element with text.

This is equivalent to setting the HTML innerText property.

See also toPlainText().

void QWebElement::setStyleProperty ( const QString & name, const QString & value )

Sets the value of the inline style with the given name to value.

Setting a value, does not necessarily mean that it will become the applied value, due to the fact that the style property's value might have been set earlier with a higher priority in external or embedded style declarations.

In order to ensure that the value will be applied, you may have to append "!important" to the value.

See also styleProperty().

QString QWebElement::styleProperty ( const QString & name, StyleResolveStrategy strategy ) const

Returns the value of the style with the given name using the specified strategy. If a style with name does not exist, an empty string is returned.

In CSS, the cascading part depends on which CSS rule has priority and is thus applied. Generally, the last defined rule has priority. Thus, an inline style rule has priority over an embedded block style rule, which in return has priority over an external style rule.

If the "!important" declaration is set on one of those, the declaration receives highest priority, unless other declarations also use the "!important" declaration. Then, the last "!important" declaration takes predecence.

See also setStyleProperty().

QString QWebElement::tagName () const

Returns the tag name of this element.

See also geometry().

QWebElement & QWebElement::takeFromDocument ()

Removes this element from the document and returns a reference to it.

The element is still valid after removal, and can be inserted into other parts of the document.

See also removeAllChildren() and removeFromDocument().

QString QWebElement::toInnerXml () const

Returns the XML content between the element's start and end tags.

Note: This is currently implemented for (X)HTML elements only.

Note: The format of the markup returned will obey the namespace of the document containing the element. This means the return value will obey XML formatting rules, such as self-closing tags, only if the document is 'text/xhtml+xml'.

See also setInnerXml(), setOuterXml(), and toOuterXml().

QString QWebElement::toOuterXml () const

Returns this element converted to XML, including the start and the end tags as well as its attributes.

Note: This is currently implemented for (X)HTML elements only.

Note: The format of the markup returned will obey the namespace of the document containing the element. This means the return value will obey XML formatting rules, such as self-closing tags, only if the document is 'text/xhtml+xml'.

See also setOuterXml(), setInnerXml(), and toInnerXml().

QString QWebElement::toPlainText () const

Returns the text between the start and the end tag of this element.

This is equivalent to reading the HTML innerText property.

See also setPlainText().

void QWebElement::toggleClass ( const QString & name )

Adds the specified class with the given name if it is not present. If the class is already present, it will be removed.

QWebFrame * QWebElement::webFrame () const

Returns the web frame which this element is a part of. If the element is a null element, null is returned.

bool QWebElement::operator!= ( const QWebElement & o ) const

Returns true if this element points to a different underlying DOM object than o; otherwise returns false.

QWebElement & QWebElement::operator= ( const QWebElement & other )

Assigns other to this element and returns a reference to this element.

bool QWebElement::operator== ( const QWebElement & o ) const

Returns true if this element points to the same underlying DOM object as o; otherwise returns false.

Notes provided by the Qt Community

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