The QTextLayout class is used to lay out and render text. More...

Classes
class	FormatRange
	This structure is used to apply extra formatting information More...

Public Types
enum	CursorMode

Public Methods
	QTextLayout ()

	QTextLayout (const QString &text)

	QTextLayout (const QString &text, const QFont &font, QPaintDevice *paintdevice=nullptr)

	~QTextLayout ()

void	beginLayout ()

QRectF	boundingRect () const

bool	cacheEnabled () const

void	clearFormats ()

void	clearLayout ()

QTextLine	createLine ()

Qt::CursorMoveStyle	cursorMoveStyle () const

void	draw (QPainter *painter, const QPointF &point, const QVector< FormatRange > &selections=QVector< FormatRange >(), const QRectF &clip=QRectF ()) const

void	drawCursor (QPainter *painter, const QPointF &point, int cursorPosition, int width=1) const

void	endLayout ()

QFont	font () const

QVector< FormatRange >	formats () const

QList< QGlyphRun >	glyphRuns (int from=-1, int length=-1) const

bool	isValidCursorPosition (int pos) const

int	leftCursorPosition (int oldPos) const

QTextLine	lineAt (int i) const

int	lineCount () const

QTextLine	lineForTextPosition (int pos) const

qreal	maximumWidth () const

qreal	minimumWidth () const

int	nextCursorPosition (int oldPos, CursorMode mode=SkipCharacters) const

QPointF	position () const

int	preeditAreaPosition () const

QString	preeditAreaText () const

int	previousCursorPosition (int oldPos, CursorMode mode=SkipCharacters) const

int	rightCursorPosition (int oldPos) const

void	setCacheEnabled (bool enable)

void	setCursorMoveStyle (Qt::CursorMoveStyle style)

void	setFont (const QFont &font)

void	setFormats (const QVector< FormatRange > &formats)

void	setPosition (const QPointF &point)

void	setPreeditArea (int position, const QString &text)

void	setRawFont (const QRawFont &rawFont)

void	setText (const QString &string)

void	setTextOption (const QTextOption &option)

QString	text () const

const QTextOption &	textOption () const

Friends
class	QGraphicsSimpleTextItem

class	QPainter

Detailed Description

The QTextLayout class is used to lay out and render text. It offers many features expected from a modern text layout engine, including Unicode compliant rendering, line breaking and handling of cursor positioning. It can also produce and render device independent layout, something that is important for WYSIWYG applications.

The class has a low level API and unless you intend to implement your own text rendering for some specialized widget, you probably will not need to use it directly.

QTextLayout can be used with both plain and rich text. It can also be used to create a sequence of QTextLine instances with given widths and can position them independently on the screen. Once the layout is done, these lines can be drawn on a paint device. The text to be laid out can be provided in the constructor or set with setText().

The layout can be seen as a sequence of QTextLine objects, use createLine() to create a QTextLine instance, and lineAt() or lineForTextPosition() to retrieve created lines.

For a given position in the text you can find a valid cursor position with isValidCursorPosition(), nextCursorPosition(), and previousCursorPosition(). The QTextLayout itself can be positioned with setPosition(); it has a boundingRect(), and a minimumWidth() and a maximumWidth().

Example

The following code demonstrates the layout and draw process.

void MyClass::layoutText() {
   int leading  = fontMetrics.leading();
   qreal height = 0;
 
   textLayout.beginLayout();
 
   while (1) {
     QTextLine line = textLayout.createLine();
 
     if (! line.isValid()) {
         break;
     }
 
     line.setLineWidth(lineWidth);
     height += leading;
 
     line.setPosition(QPointF(0, height));
     height += line.height();
   }
 
   textLayout.endLayout();
}
 
void MyClass::drawText() {
   // used to draw the text
 
   QPainter painter(this);
   textLayout.draw(&painter, QPoint(0, 0));
}

See also: QStaticText

Member Enumeration Documentation

enum QTextLayout::CursorMode

Constant	Value
`QTextLayout::SkipCharacters`	`0`
`QTextLayout::SkipWords`	`1`

Constructor & Destructor Documentation

QTextLayout::QTextLayout ( )

Constructs an empty text layout.

See also: setText()

QTextLayout::QTextLayout ( const QString & text )

Constructs a text layout to lay out the given text.

QTextLayout::QTextLayout	(	const QString &	text,
		const QFont &	font,
		QPaintDevice *	paintdevice = `nullptr`
	)

Constructs a text layout to lay out the given text with the specified font. All the metric and layout calculations will be done in terms of the paintdevice. If paintdevice is a nullptr the calculations will be done in screen metrics.

QTextLayout::~QTextLayout ( )

Destructs the layout.

Method Documentation

void QTextLayout::beginLayout ( )

Begins the layout process.

See also: endLayout()

QRectF QTextLayout::boundingRect ( ) const

The smallest rectangle that contains all the lines in the layout.

bool QTextLayout::cacheEnabled ( ) const

Returns true if the complete layout information is cached, otherwise returns false.

See also: setCacheEnabled()

void QTextLayout::clearFormats ( )

Clears the list of additional formats supported by the text layout.

See also: formats(), setFormats()

void QTextLayout::clearLayout ( )

Clears the line information in the layout. After having called this method lineCount() will return 0.

QTextLine QTextLayout::createLine ( )

Returns a new text line to be laid out if there is text to be inserted into the layout, otherwise returns an invalid text line.

The text layout creates a new line object that starts after the last line in the layout, or at the beginning if the layout is empty. The layout maintains an internal cursor, and each line is filled with text from the cursor position onwards when the QTextLine::setLineWidth() function is called.

Once QTextLine::setLineWidth() is called, a new line can be created and filled with text. Repeating this process will lay out the whole block of text contained in the QTextLayout. If there is no text left to be inserted into the layout, the QTextLine returned will not be valid (isValid() will return false).

Qt::CursorMoveStyle QTextLayout::cursorMoveStyle ( ) const

The cursor movement style of this QTextLayout. The default is Qt::LogicalMoveStyle.

See also: setCursorMoveStyle()

void QTextLayout::draw	(	QPainter *	painter,
		const QPointF &	point,
		const QVector< FormatRange > &	selections = `QVector<FormatRange>()`,
		const QRectF &	clip = `QRectF()`
	)		const

Draws the whole layout on the painter at the position specified by point. The rendered layout includes the given selections and is clipped within the rectangle specified by clip.

void QTextLayout::drawCursor	(	QPainter *	painter,
		const QPointF &	point,
		int	cursorPosition,
		int	width = `1`
	)		const

Draws a text cursor with the current pen and the specified width at the given point using the painter specified. The corresponding position within the text is specified by cursorPosition.

void QTextLayout::endLayout ( )

Ends the layout process.

See also: beginLayout()

QFont QTextLayout::font ( ) const

Returns the current font that is used for the layout, or a default font if none is set.

See also: setFont()

QVector< FormatRange > QTextLayout::formats ( ) const

Returns the list of additional formats supported by the text layout.

See also: setFormats(), clearFormats()

QList< QGlyphRun > QTextLayout::glyphRuns	(	int	from = `-1`,
		int	length = `-1`
	)		const

Returns the glyphs corresponding to length code points of this text fragment starting at position from. The positions of the glyphs are relative to the position of the QTextBlock layout. If from is less than 0 the glyphs will start at the beginning. If length is less than 0 the glyphs will stop at the end of the fragment.

See also: draw(), QPainter::drawGlyphRun()

bool QTextLayout::isValidCursorPosition ( int pos ) const

Returns true if position pos is a valid cursor position. Some positions in the text are not valid cursor positions because the position is within a grapheme cluster.

int QTextLayout::leftCursorPosition ( int oldPos ) const

Returns the cursor position to the left of oldPos, next to it. The position is dependent on the visual position of characters, after bi-directional reordering.

See also: rightCursorPosition(), previousCursorPosition()

QTextLine QTextLayout::lineAt ( int i ) const

Returns the line of text at position i in this text layout.

See also: lineCount(), lineForTextPosition()

int QTextLayout::lineCount ( ) const

Returns the number of lines in this text layout.

See also: lineAt()

QTextLine QTextLayout::lineForTextPosition ( int pos ) const

Returns the line that contains the cursor position specified by pos.

See also: isValidCursorPosition(), lineAt()

qreal QTextLayout::maximumWidth ( ) const

The maximum width the layout could expand to; this is essentially the width of the entire text.

Warning: This method only returns a valid value after the layout has been done.

See also: minimumWidth()

qreal QTextLayout::minimumWidth ( ) const

The minimum width the layout needs. This is the width of the layout's smallest non-breakable substring.

Warning: This method only returns a valid value after the layout has been done.

See also: maximumWidth()

int QTextLayout::nextCursorPosition	(	int	oldPos,
		CursorMode	mode = `SkipCharacters`
	)		const

Returns the next valid cursor position after oldPos that respects the given cursor mode. Returns value of oldPos, if oldPos is not a valid cursor position.

See also: isValidCursorPosition(), previousCursorPosition()

QPointF QTextLayout::position ( ) const

The global position of the layout. This is independent of the bounding rectangle and of the layout process.

See also: setPosition()

int QTextLayout::preeditAreaPosition ( ) const

Returns the position of the area in the text layout that will be processed before editing occurs.

See also: preeditAreaText()

QString QTextLayout::preeditAreaText ( ) const

Returns the text that is inserted in the layout before editing occurs.

See also: preeditAreaPosition()

int QTextLayout::previousCursorPosition	(	int	oldPos,
		CursorMode	mode = `SkipCharacters`
	)		const

Returns the first valid cursor position before oldPos that respects the given cursor mode. Returns value of oldPos, if oldPos is not a valid cursor position.

See also: isValidCursorPosition(), nextCursorPosition()

int QTextLayout::rightCursorPosition ( int oldPos ) const

Returns the cursor position to the right of oldPos, next to it. The position is dependent on the visual position of characters, after bi-directional reordering.

See also: leftCursorPosition(), nextCursorPosition()

void QTextLayout::setCacheEnabled ( bool enable )

Enables caching of the complete layout information if enable is true, otherwise disables layout caching. Usually QTextLayout throws most of the layout information away after a call to endLayout() to reduce memory consumption. If you however want to draw the laid out text directly afterwards enabling caching might speed up drawing significantly.

See also: cacheEnabled()

void QTextLayout::setCursorMoveStyle ( Qt::CursorMoveStyle style )

Set the cursor movement style. If the QTextLayout is backed by a document, you can ignore this and use the option in QTextDocument, this option is for widgets like QLineEdit or custom widgets without a QTextDocument. Default value is Qt::LogicalMoveStyle.

See also: cursorMoveStyle()

void QTextLayout::setFont ( const QFont & font )

Sets the layout's font to the given font. The layout is invalidated and must be laid out again.

See also: font()

void QTextLayout::setFormats ( const QVector< FormatRange > & formats )

Sets the additional formats supported by the text layout to formats. The formats are applied with preedit area text in place.

See also: formats(), clearFormats()

void QTextLayout::setPosition ( const QPointF & point )

Moves the text layout to the given point.

See also: position()

void QTextLayout::setPreeditArea	(	int	position,
		const QString &	text
	)

Sets the position and text of the area in the layout that is processed before editing occurs.

See also: preeditAreaPosition(), preeditAreaText()

void QTextLayout::setRawFont ( const QRawFont & rawFont )

Sets the layout's font to the given rawFont. The layout is invalidated and must be laid out again.

void QTextLayout::setText ( const QString & string )

Sets the layout's text to the given string. The layout is invalidated and must be laid out again. When using this QTextLayout as part of a QTextDocument this method will have no effect.

See also: text()

void QTextLayout::setTextOption ( const QTextOption & option )

Sets the text option structure that controls the layout process to the given option.

See also: textOption()

QString QTextLayout::text ( ) const

Returns the layout's text.

See also: setText()

const QTextOption & QTextLayout::textOption ( ) const

Returns the current text option used to control the layout process.

See also: setTextOption()

Classes

Public Types

Public Methods

Friends

Detailed Description

Example

Member Enumeration Documentation

Constructor & Destructor Documentation

Method Documentation