QwtAbstractScaleDraw.qt5 - Man Page


#include <qwt_abstract_scale_draw.h>

Inherited by QwtRoundScaleDraw, and QwtScaleDraw.

Public Types

enum ScaleComponent { Backbone =  1, Ticks =  2, Labels =  4 }

Public Member Functions

QwtAbstractScaleDraw ()
QwtAbstractScaleDraw (const QwtAbstractScaleDraw &)
virtual ~QwtAbstractScaleDraw ()
virtual void draw (QPainter *, const QPalette &) const
void enableComponent (ScaleComponent, bool enable=true)
virtual int extent (const QPen &, const QFont &) const =0
bool hasComponent (ScaleComponent) const
virtual QwtText label (double) const
int majTickLength () const
const QwtScaleMap & map () const
int minimumExtent () const
QwtAbstractScaleDraw & operator= (const QwtAbstractScaleDraw &)
const QwtScaleDiv & scaleDiv () const
QwtScaleMap & scaleMap ()
void setMinimumExtent (int)
void setScaleDiv (const QwtScaleDiv &s)
void setSpacing (int margin)
void setTickLength (QwtScaleDiv::TickType, int length)
void setTransformation (QwtScaleTransformation *)
int spacing () const
int tickLength (QwtScaleDiv::TickType) const

Protected Member Functions

virtual void drawBackbone (QPainter *painter) const =0
virtual void drawLabel (QPainter *painter, double value) const =0
virtual void drawTick (QPainter *painter, double value, int len) const =0
void invalidateCache ()
const QwtText & tickLabel (const QFont &, double value) const

Detailed Description

A abstract base class for drawing scales.

QwtAbstractScaleDraw can be used to draw linear or logarithmic scales.

After a scale division has been specified as a QwtScaleDiv object using QwtAbstractScaleDraw::setScaleDiv(const QwtScaleDiv &s), the scale can be drawn with the QwtAbstractScaleDraw::draw() member.

Member Enumeration Documentation

enum QwtAbstractScaleDraw::ScaleComponent

Components of a scale

  • Backbone
  • Ticks
  • Labels

See also:

enableComponent(), hasComponent

Constructor & Destructor Documentation

QwtAbstractScaleDraw::QwtAbstractScaleDraw ()

Constructor. The range of the scale is initialized to [0, 100], The spacing (distance between ticks and labels) is set to 4, the tick lengths are set to 4,6 and 8 pixels

Member Function Documentation

void QwtAbstractScaleDraw::draw (QPainter *painter, const QPalette &palette) const [virtual]

Draw the scale. Parameters:

painter The painter
palette Palette, text color is used for the labels, foreground color for ticks and backbone

virtual void QwtAbstractScaleDraw::drawBackbone (QPainter *painter) const [protected], [pure virtual]

Draws the baseline of the scale


painter Painter

See also:

drawTick(), drawLabel()

Implemented in QwtScaleDraw, and QwtRoundScaleDraw.

virtual void QwtAbstractScaleDraw::drawLabel (QPainter *painter, doublevalue) const [protected], [pure virtual]

Draws the label for a major scale tick


painter Painter
value Value

See also:

drawTick, drawBackbone

Implemented in QwtScaleDraw, and QwtRoundScaleDraw.

virtual void QwtAbstractScaleDraw::drawTick (QPainter *painter, doublevalue, intlen) const [protected], [pure virtual]

Draw a tick


painter Painter
value Value of the tick
len Lenght of the tick

See also:

drawBackbone(), drawLabel()

Implemented in QwtScaleDraw, and QwtRoundScaleDraw.

void QwtAbstractScaleDraw::enableComponent (ScaleComponentcomponent, boolenable = true)

En/Disable a component of the scale


component Scale component
enable On/Off

See also:


virtual int QwtAbstractScaleDraw::extent (const QPen &, const QFont &) const [pure virtual]

Calculate the extent

The extent is the distcance from the baseline to the outermost pixel of the scale draw in opposite to its orientation. It is at least minimumExtent() pixels.

See also:

setMinimumExtent(), minimumExtent()

Implemented in QwtRoundScaleDraw, and QwtScaleDraw.

bool QwtAbstractScaleDraw::hasComponent (ScaleComponentcomponent) const

Check if a component is enabled

See also:


void QwtAbstractScaleDraw::invalidateCache () [protected]

Invalidate the cache used by QwtAbstractScaleDraw::tickLabel

The cache is invalidated, when a new QwtScaleDiv is set. If the labels need to be changed. while the same QwtScaleDiv is set, QwtAbstractScaleDraw::invalidateCache needs to be called manually.

QwtText QwtAbstractScaleDraw::label (doublevalue) const [virtual]

Convert a value into its representing label. The value is converted to a plain text using QLocale::system().toString(value). This method is often overloaded by applications to have individual labels.


value Value


Label string.

Reimplemented in QwtDialScaleDraw.

int QwtAbstractScaleDraw::majTickLength () const

The same as QwtAbstractScaleDraw::tickLength(QwtScaleDiv::MajorTick).

const QwtScaleMap & QwtAbstractScaleDraw::map () const


Map how to translate between scale and pixel values

int QwtAbstractScaleDraw::minimumExtent () const

Get the minimum extent

See also:

extent(), setMinimumExtent()

const QwtScaleDiv & QwtAbstractScaleDraw::scaleDiv () const


scale division

QwtScaleMap & QwtAbstractScaleDraw::scaleMap ()


Map how to translate between scale and pixel values

void QwtAbstractScaleDraw::setMinimumExtent (intminExtent)

Set a minimum for the extent. The extent is calculated from the coomponents of the scale draw. In situations, where the labels are changing and the layout depends on the extent (f.e scrolling a scale), setting an upper limit as minimum extent will avoid jumps of the layout.


minExtent Minimum extent

See also:

extent(), minimumExtent()

void QwtAbstractScaleDraw::setScaleDiv (const QwtScaleDiv &sd)

Change the scale division


sd New scale division

void QwtAbstractScaleDraw::setSpacing (intspacing)

Set the spacing between tick and labels. The spacing is the distance between ticks and labels. The default spacing is 4 pixels.


spacing Spacing

See also:


void QwtAbstractScaleDraw::setTickLength (QwtScaleDiv::TickTypetickType, intlength)

Set the length of the ticks


tickType Tick type
length New length


the length is limited to [0..1000]

void QwtAbstractScaleDraw::setTransformation (QwtScaleTransformation *transformation)

Change the transformation of the scale


transformation New scale transformation

int QwtAbstractScaleDraw::spacing () const

Get the spacing. The spacing is the distance between ticks and labels. The default spacing is 4 pixels.

See also:


const QwtText & QwtAbstractScaleDraw::tickLabel (const QFont &font, doublevalue) const [protected]

Convert a value into its representing label and cache it. The conversion between value and label is called very often in the layout and painting code. Unfortunately the calculation of the label sizes might be slow (really slow for rich text in Qt4), so it's necessary to cache the labels.


font Font
value Value


Tick label

int QwtAbstractScaleDraw::tickLength (QwtScaleDiv::TickTypetickType) const

Return the length of the ticks

See also:

setTickLength(), majTickLength()


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Tue Nov 20 2012 Version 5.2.3 Qwt User's Guide