QwtRoundScaleDraw - Man Page


QwtRoundScaleDraw —

A class for drawing round scales.  


#include <qwt_round_scale_draw.h>

Inherits QwtAbstractScaleDraw.

Inherited by QwtDialScaleDraw.

Public Types

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

Public Member Functions

QPoint center () const
virtual void draw (QPainter *, const QPalette &) const
void enableComponent (ScaleComponent, bool enable=true)
virtual int extent (const QPen &, const QFont &) const
bool hasComponent (ScaleComponent) const
virtual QwtText label (double) const
int majTickLength () const
const QwtScaleMap & map () const
int minimumExtent () const
void moveCenter (const QPoint &)
void moveCenter (int x, int y)
QwtRoundScaleDraw & operator= (const QwtRoundScaleDraw &other)
QwtRoundScaleDraw (const QwtRoundScaleDraw &)
QwtRoundScaleDraw ()
int radius () const
const QwtScaleDiv & scaleDiv () const
QwtScaleMap & scaleMap ()
void setAngleRange (double angle1, double angle2)
void setMinimumExtent (int)
void setRadius (int radius)
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
virtual ~QwtRoundScaleDraw ()

Protected Member Functions

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

Detailed Description

A class for drawing round scales.

QwtRoundScaleDraw can be used to draw round scales. The circle segment can be adjusted by QwtRoundScaleDraw::setAngleRange(). The geometry of the scale can be specified with QwtRoundScaleDraw::moveCenter() and QwtRoundScaleDraw::setRadius().

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 [inherited] Components of a scale

  • Backbone
  • Ticks
  • Labels

See also:

enableComponent(), hasComponent

Constructor & Destructor Documentation

QwtRoundScaleDraw::QwtRoundScaleDraw ()

Constructor. The range of the scale is initialized to [0, 100], The center is set to (50, 50) with a radius of 50. The angle range is set to [-135, 135].

QwtRoundScaleDraw::QwtRoundScaleDraw (const QwtRoundScaleDraw &other)

Copy constructor.

QwtRoundScaleDraw::~QwtRoundScaleDraw () [virtual]


Member Function Documentation

QPoint QwtRoundScaleDraw::center () const

Get the center of the scale.

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

Draw the scale. Parameters:

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

void QwtRoundScaleDraw::drawBackbone (QPainter *painter) const [protected, virtual] Draws the baseline of the scale


painter Painter

See also:

drawTick(), drawLabel()

Implements QwtAbstractScaleDraw.

void QwtRoundScaleDraw::drawLabel (QPainter *painter, doublevalue) const [protected, virtual] Draws the label for a major scale tick


painter Painter
value Value

See also:

drawTick(), drawBackbone()

Implements QwtAbstractScaleDraw.

void QwtRoundScaleDraw::drawTick (QPainter *painter, doublevalue, intlen) const [protected, virtual] Draw a tick


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

See also:

drawBackbone(), drawLabel()

Implements QwtAbstractScaleDraw.

void QwtAbstractScaleDraw::enableComponent (ScaleComponentcomponent, boolenable = true) [inherited] En/Disable a component of the scale


component Scale component
enable On/Off

See also:


int QwtRoundScaleDraw::extent (const QPen &pen, const QFont &font) const [virtual] Calculate the extent of the scale

The extent is the distcance between the baseline to the outermost pixel of the scale draw. radius() + extent() is an upper limit for the radius of the bounding circle.


pen Pen that is used for painting backbone and ticks
font Font used for painting the labels

See also:

setMinimumExtent(), minimumExtent()


The implemented algo is not too smart and calculates only an upper limit, that might be a few pixels too large

Implements QwtAbstractScaleDraw.

bool QwtAbstractScaleDraw::hasComponent (ScaleComponentcomponent) const [inherited] Check if a component is enabled

See also:


void QwtAbstractScaleDraw::invalidateCache () [protected, inherited] 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, inherited]

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 [inherited] The same as QwtAbstractScaleDraw::tickLength(QwtScaleDiv::MajorTick).

const QwtScaleMap & QwtAbstractScaleDraw::map () const [inherited] Returns

Map how to translate between scale and pixel values

int QwtAbstractScaleDraw::minimumExtent () const [inherited] Get the minimum extent

See also:

extent(), setMinimumExtent()

void QwtRoundScaleDraw::moveCenter (const QPoint &center) Move the center of the scale draw, leaving the radius unchanged


center New center

See also:


void QwtRoundScaleDraw::moveCenter (intx, inty) [inline]

Move the center of the scale draw, leaving the radius unchanged.

QwtRoundScaleDraw & QwtRoundScaleDraw::operator= (const QwtRoundScaleDraw &other)

Assignment operator.

int QwtRoundScaleDraw::radius () const Get the radius

Radius is the radius of the backbone without ticks and labels.

See also:

setRadius(), extent()

const QwtScaleDiv & QwtAbstractScaleDraw::scaleDiv () const [inherited] Returns

scale division

QwtScaleMap & QwtAbstractScaleDraw::scaleMap () [inherited] Returns

Map how to translate between scale and pixel values

void QwtRoundScaleDraw::setAngleRange (doubleangle1, doubleangle2)

Adjust the baseline circle segment for round scales. The baseline will be drawn from min(angle1,angle2) to max(angle1, angle2). The default setting is [ -135, 135 ]. An angle of 0 degrees corresponds to the 12 o'clock position, and positive angles count in a clockwise direction.


angle2 boundaries of the angle interval in degrees.

  • The angle range is limited to [-360, 360] degrees. Angles exceeding this range will be clipped.
  • For angles more than 359 degrees above or below min(angle1, angle2), scale marks will not be drawn.
  • If you need a counterclockwise scale, use QwtScaleDiv::setRange

void QwtAbstractScaleDraw::setMinimumExtent (intminExtent) [inherited]

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 QwtRoundScaleDraw::setRadius (intradius) Change of radius the scale

Radius is the radius of the backbone without ticks and labels.


radius New Radius

See also:


void QwtAbstractScaleDraw::setScaleDiv (const QwtScaleDiv &sd) [inherited] Change the scale division


sd New scale division

void QwtAbstractScaleDraw::setSpacing (intspacing) [inherited]

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) [inherited] Set the length of the ticks


tickType Tick type
length New length


the length is limited to [0..1000]

void QwtAbstractScaleDraw::setTransformation (QwtScaleTransformation *transformation) [inherited] Change the transformation of the scale


transformation New scale transformation

int QwtAbstractScaleDraw::spacing () const [inherited]

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, inherited]

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 [inherited] Return the length of the ticks

See also:

setTickLength(), majTickLength()


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Mon Aug 1 2011 Version 5.2.2 Qwt User's Guide