- Qt 5.15
- Qt XML Patterns
- C++ Classes
- QXmlFormatter
- Qt 5.15.19 Reference Documentation

# QXmlFormatter Class

The QXmlFormatter class is an implementation of QXmlSerializer for transforming XQuery output into formatted XML. More...

Header: | #include <QXmlFormatter>
qmake: | QT += xmlpatterns
Since: | Qt 4.4
Inherits: | QXmlSerializer

This class was introduced in Qt 4.4.

- List of all members, including inherited members

Note: All functions in this class are reentrant.

## Public Functions

| QXmlFormatter(const QXmlQuery &query, QIODevice *outputDevice)
int | indentationDepth() const
void | setIndentationDepth(int depth)

## Reimplemented Public Functions

virtual void | atomicValue(const QVariant &value) override
virtual void | attribute(const QXmlName &name, const QStringRef &value) override
virtual void | characters(const QStringRef &value) override
virtual void | comment(const QString &value) override
virtual void | endDocument() override
virtual void | endElement() override
virtual void | endOfSequence() override
virtual void | processingInstruction(const QXmlName &name, const QString &value) override
virtual void | startDocument() override
virtual void | startElement(const QXmlName &name) override
virtual void | startOfSequence() override

## Detailed Description

QXmlFormatter is a subclass of QXmlSerializer that formats the XML output to make it easier for humans to read.

QXmlSerializer outputs XML without adding unnecessary whitespace. In particular, it does not add newlines and indentation. To make the XML output easier to read, QXmlFormatter adds newlines and indentation by adding, removing, and modifying sequence nodes that only consist of whitespace. It also modifies whitespace in other places where it is not significant; e.g., between attributes and in the document prologue.

For example, where the base class QXmlSerializer would output this:

     <a><b/><c/><p>Some Text</p></a>

QXmlFormatter outputs this:

     <a>
        <b/>
        <c/>
        <p>Some Text</p>
     </a>

If you just want to serialize your XML in a human-readable format, use QXmlFormatter as it is. The default indentation level is 4 spaces, but you can set your own indentation value setIndentationDepth().

The newlines and indentation added by QXmlFormatter are suitable for common formats, such as XHTML, SVG, or Docbook, where whitespace is not significant. However, if your XML will be used as input where whitespace is significant, then you must write your own subclass of QXmlSerializer or QAbstractXmlReceiver.

Note that using QXmlFormatter instead of QXmlSerializer will increase computational overhead and document storage size due to the insertion of whitespace.

Note also that the indentation style used by QXmlFormatter remains loosely defined and may change in future versions of Qt. If a specific indentation style is required then either use the base class QXmlSerializer directly, or write your own subclass of QXmlSerializer or QAbstractXmlReceiver. Alternatively, you can subclass QXmlFormatter and reimplement the callbacks there.

     QXmlQuery query;
     query.setQuery("doc('index.html')/html/body/p[1]");

     QXmlFormatter formatter(query, myOutputDevice);
     formatter.setIndentationDepth(2);
     query.evaluateTo(&formatter);

## Member Function Documentation

### QXmlFormatter::QXmlFormatter(const QXmlQuery &query, QIODevice *outputDevice)

Constructs a formatter that uses the name pool and message handler in query, and writes the result to outputDevice as formatted XML.

outputDevice is passed directly to QXmlSerializer's constructor.

See also QXmlSerializer.

### `[override virtual]` void QXmlFormatter::atomicValue(const QVariant &value)

Reimplements: QXmlSerializer::atomicValue(const QVariant &value).

### `[override virtual]` void QXmlFormatter::attribute(const QXmlName &name, const QStringRef &value)

Reimplements: QXmlSerializer::attribute(const QXmlName &name, const QStringRef &value).

### `[override virtual]` void QXmlFormatter::characters(const QStringRef &value)

Reimplements: QXmlSerializer::characters(const QStringRef &value).

### `[override virtual]` void QXmlFormatter::comment(const QString &value)

Reimplements: QXmlSerializer::comment(const QString &value).

### `[override virtual]` void QXmlFormatter::endDocument()

Reimplements: QXmlSerializer::endDocument().

### `[override virtual]` void QXmlFormatter::endElement()

Reimplements: QXmlSerializer::endElement().

### `[override virtual]` void QXmlFormatter::endOfSequence()

Reimplements: QXmlSerializer::endOfSequence().

### int QXmlFormatter::indentationDepth() const

Returns the number of spaces QXmlFormatter will output for each indentation level. The default is four.

See also setIndentationDepth().

### `[override virtual]` void QXmlFormatter::processingInstruction(const QXmlName &name, const QString &value)

Reimplements: QXmlSerializer::processingInstruction(const QXmlName &name, const QString &value).

### void QXmlFormatter::setIndentationDepth(int depth)

Sets depth to be the number of spaces QXmlFormatter will output for level of indentation. The default is four.

See also indentationDepth().

### `[override virtual]` void QXmlFormatter::startDocument()

Reimplements: QXmlSerializer::startDocument().

### `[override virtual]` void QXmlFormatter::startElement(const QXmlName &name)

Reimplements: QXmlSerializer::startElement(const QXmlName &name).

### `[override virtual]` void QXmlFormatter::startOfSequence()

Reimplements: QXmlSerializer::startOfSequence().