CopperSpice API  1.7.2
QTextLayout Class Reference

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 *p, const QPointF &pos, const QVector< FormatRange > &selections=QVector< FormatRange >(), const QRectF &clip=QRectF ()) const
 
void drawCursor (QPainter *p, const QPointF &pos, int cursorPosition) const
 
void drawCursor (QPainter *p, const QPointF &pos, int cursorPosition, int width) const
 
void endLayout ()
 
QFont font () const
 
QVector< FormatRangeformats () const
 
QList< QGlyphRunglyphRuns (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 &f)
 
void setFormats (const QVector< FormatRange > &overrides)
 
void setPosition (const QPointF &p)
 
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 QTextOptiontextOption () 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

ConstantValue
QTextLayout::SkipCharacters0
QTextLayout::SkipWords1

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 p,
const QPointF pos,
const QVector< FormatRange > &  selections = QVector<FormatRange>(),
const QRectF clip = QRectF() 
) const

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

void QTextLayout::drawCursor ( QPainter painter,
const QPointF position,
int  cursorPosition 
) const

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

void QTextLayout::drawCursor ( QPainter painter,
const QPointF position,
int  cursorPosition,
int  width 
) const

Draws a text cursor with the current pen and the specified width at the given position 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 p)

Moves the text layout to point p.

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)

Property documentation pending.

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()