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QwtPlotTextLabel(3) Qwt User's Guide QwtPlotTextLabel(3)


QwtPlotTextLabel - A plot item, which displays a text label.


#include <qwt_plot_textlabel.h>

Inherits QwtPlotItem.

Public Member Functions

QwtPlotTextLabel ()
Constructor. virtual ~QwtPlotTextLabel ()
Destructor. virtual int rtti () const override
void setText (const QwtText &)
QwtText text () const
void setMargin (int margin)
int margin () const
virtual QRectF textRect (const QRectF &, const QSizeF &) const
Align the text label.

Protected Member Functions

virtual void draw (QPainter *, const QwtScaleMap &, const QwtScaleMap &, const QRectF &) const override
void invalidateCache ()
Invalidate all internal cache.

Additional Inherited Members

Detailed Description

A plot item, which displays a text label.

QwtPlotTextLabel displays a text label aligned to the plot canvas.

In opposite to QwtPlotMarker the position of the label is unrelated to plot coordinates.

As drawing a text is an expensive operation the label is cached in a pixmap to speed up replots.


The following code shows how to add a title.

QwtText title( "Plot Title" );
title.setRenderFlags( Qt::AlignHCenter | Qt::AlignTop );
QFont font;
font.setBold( true );
title.setFont( font );
QwtPlotTextLabel *titleItem = new QwtPlotTextLabel();
titleItem->setText( title );
titleItem->attach( plot );

See also


Definition at line 47 of file qwt_plot_textlabel.h.

Constructor & Destructor Documentation

QwtPlotTextLabel::QwtPlotTextLabel ()

Constructor. Initializes an text label with an empty text

Sets the following item attributes:

  • QwtPlotItem::AutoScale: true
  • QwtPlotItem::Legend: false

The z value is initialized by 150

See also

QwtPlotItem::setItemAttribute(), QwtPlotItem::setZ()

Definition at line 82 of file qwt_plot_textlabel.cpp.

Member Function Documentation

void QwtPlotTextLabel::draw (QPainter * painter, const QwtScaleMap & xMap, const QwtScaleMap & yMap, const QRectF & canvasRect) const [override], [protected], [virtual]

Draw the text label


painter Painter
xMap x Scale Map
yMap y Scale Map
canvasRect Contents rectangle of the canvas in painter coordinates

See also


Implements QwtPlotItem.

Definition at line 176 of file qwt_plot_textlabel.cpp.

int QwtPlotTextLabel::margin () const


Margin added to the contentsMargins() of the canvas

See also


Definition at line 160 of file qwt_plot_textlabel.cpp.

int QwtPlotTextLabel::rtti () const [override], [virtual]



Reimplemented from QwtPlotItem.

Definition at line 100 of file qwt_plot_textlabel.cpp.

void QwtPlotTextLabel::setMargin (int margin)

Set the margin

The margin is the distance between the contentsRect() of the plot canvas and the rectangle where the label can be displayed.


margin Margin

See also

margin(), textRect()

Definition at line 146 of file qwt_plot_textlabel.cpp.

void QwtPlotTextLabel::setText (const QwtText & text)

Set the text

The label will be aligned to the plot canvas according to the alignment flags of text.


text Text to be displayed

See also

text(), QwtText::renderFlags()

Definition at line 115 of file qwt_plot_textlabel.cpp.

QwtText QwtPlotTextLabel::text () const


Text to be displayed

See also


Definition at line 130 of file qwt_plot_textlabel.cpp.

QRectF QwtPlotTextLabel::textRect (const QRectF & rect, const QSizeF & textSize) const [virtual]

Align the text label.


rect Canvas rectangle with margins subtracted
textSize Size required to draw the text


A rectangle aligned according the the alignment flags of the text.

See also

setMargin(), QwtText::renderFlags(), QwtText::textSize()

Definition at line 263 of file qwt_plot_textlabel.cpp.


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Sun Jul 18 2021 Version 6.2.0