QwtAbstractScaleDraw - Man Page

A abstract base class for drawing scales.

Synopsis

#include <qwt_abstract_scale_draw.h>

Inherited by QwtRoundScaleDraw, and QwtScaleDraw.

Public Types

enum ScaleComponent { Backbone = 0x01, Ticks = 0x02, Labels = 0x04 }
typedef QFlags< ScaleComponent > ScaleComponents
Scale components.

Public Member Functions

QwtAbstractScaleDraw ()
Constructor.
virtual ~QwtAbstractScaleDraw ()
Destructor.
void setScaleDiv (const QwtScaleDiv &)
const QwtScaleDiv & scaleDiv () const
void setTransformation (QwtTransform *)
const QwtScaleMap & scaleMap () const
QwtScaleMap & scaleMap ()
void enableComponent (ScaleComponent, bool enable=true)
bool hasComponent (ScaleComponent) const
void setTickLength (QwtScaleDiv::TickType, double length)
double tickLength (QwtScaleDiv::TickType) const
double maxTickLength () const
void setSpacing (double)
Set the spacing between tick and labels.
double spacing () const
Get the spacing.
void setPenWidth (int width)
Specify the width of the scale pen.
int penWidth () const
virtual void draw (QPainter *, const QPalette &) const
Draw the scale.
virtual QwtText label (double) const
Convert a value into its representing label.
virtual double extent (const QFont &font) const =0
void setMinimumExtent (double)
Set a minimum for the extent.
double minimumExtent () const

Protected Member Functions

virtual void drawTick (QPainter *painter, double value, double len) const =0
virtual void drawBackbone (QPainter *painter) const =0
virtual void drawLabel (QPainter *painter, double value) const =0
void invalidateCache ()
const QwtText & tickLabel (const QFont &, double value) const
Convert a value into its representing label and cache it.

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 setScaleDiv(), the scale can be drawn with the draw() member.

Member Enumeration Documentation

enum QwtAbstractScaleDraw::ScaleComponent

Components of a scale

See also

enableComponent(), hasComponent

Enumerator

Backbone

Backbone = the line where the ticks are located.

Ticks

Ticks.

Labels

Labels.

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

Parameters

painter Painter

See also

drawTick(), drawLabel()

Implemented in QwtScaleDraw, and QwtRoundScaleDraw.

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

Draws the label for a major scale tick

Parameters

painter Painter
value Value

See also

drawTick(), drawBackbone()

Implemented in QwtScaleDraw, and QwtRoundScaleDraw.

virtual void QwtAbstractScaleDraw::drawTick (QPainter * painter, double value, double len) const [protected], [pure virtual]

Draw a tick

Parameters

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

See also

drawBackbone(), drawLabel()

Implemented in QwtScaleDraw, and QwtRoundScaleDraw.

void QwtAbstractScaleDraw::enableComponent (ScaleComponent component, bool enable = true)

En/Disable a component of the scale

Parameters

component Scale component
enable On/Off

See also

hasComponent()

virtual double QwtAbstractScaleDraw::extent (const QFont & font) const [pure virtual]

Calculate the extent

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

Parameters

font Font used for drawing the tick labels

Returns

Number of pixels

See also

setMinimumExtent(), minimumExtent()

Implemented in QwtScaleDraw, and QwtRoundScaleDraw.

bool QwtAbstractScaleDraw::hasComponent (ScaleComponent component) const

Check if a component is enabled

Parameters

component Component type

Returns

true, when component is enabled

See also

enableComponent()

void QwtAbstractScaleDraw::invalidateCache () [protected]

Invalidate the cache used by tickLabel()

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

QwtText QwtAbstractScaleDraw::label (double value) const [virtual]

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

Parameters

value Value

Returns

Label string.

Reimplemented in QwtDateScaleDraw, and QwtCompassScaleDraw.

double QwtAbstractScaleDraw::maxTickLength () const

Returns

Length of the longest tick

Useful for layout calculations

See also

tickLength(), setTickLength()

double QwtAbstractScaleDraw::minimumExtent () const

Get the minimum extent

Returns

Minimum extent

See also

extent(), setMinimumExtent()

int QwtAbstractScaleDraw::penWidth () const

Returns

Scale pen width

See also

setPenWidth()

const QwtScaleDiv & QwtAbstractScaleDraw::scaleDiv () const

Returns

scale division

QwtScaleMap & QwtAbstractScaleDraw::scaleMap ()

Returns

Map how to translate between scale and pixel values

const QwtScaleMap & QwtAbstractScaleDraw::scaleMap () const

Returns

Map how to translate between scale and pixel values

void QwtAbstractScaleDraw::setMinimumExtent (double minExtent)

Set a minimum for the extent. The extent is calculated from the components 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.

Parameters

minExtent Minimum extent

See also

extent(), minimumExtent()

void QwtAbstractScaleDraw::setPenWidth (int width)

Specify the width of the scale pen.

Parameters

width Pen width

See also

penWidth()

void QwtAbstractScaleDraw::setScaleDiv (const QwtScaleDiv & scaleDiv)

Change the scale division

Parameters

scaleDiv New scale division

void QwtAbstractScaleDraw::setSpacing (double spacing)

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

Parameters

spacing Spacing

See also

spacing()

void QwtAbstractScaleDraw::setTickLength (QwtScaleDiv::TickType tickType, double length)

Set the length of the ticks

Parameters

tickType Tick type
length New length

Warning

the length is limited to [0..1000]

void QwtAbstractScaleDraw::setTransformation (QwtTransform * transformation)

Change the transformation of the scale

Parameters

transformation New scale transformation

double QwtAbstractScaleDraw::spacing () const

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

Returns

Spacing

See also

setSpacing()

const QwtText & QwtAbstractScaleDraw::tickLabel (const QFont & font, double value) 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.

Parameters

font Font
value Value

Returns

Tick label

double QwtAbstractScaleDraw::tickLength (QwtScaleDiv::TickType tickType) const

Returns

Length of the ticks

See also

setTickLength(), maxTickLength()

Author

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Info

Mon Jun 1 2020 Version 6.1.5 Qwt User's Guide