Qwt User's Guide 6.1.1

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QwtAbstractScaleDraw Class Referenceabstract

A abstract base class for drawing scales. More...

`#include <qwt_abstract_scale_draw.h>`

Inheritance diagram for QwtAbstractScaleDraw:
[legend]

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

## Public Member Functions
| QwtAbstractScaleDraw ()
| Constructor. More...
virtual | ~QwtAbstractScaleDraw ()
| Destructor.
void | setScaleDiv (const QwtScaleDiv &s)
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 margin)
| Set the spacing between tick and labels. More...
double | spacing () const
| Get the spacing. More...
void | setPenWidth (int width)
| Specify the width of the scale pen. More...
int | penWidth () const
virtual void | draw (QPainter *, const QPalette &) const
| Draw the scale. More...
virtual QwtText | label (double) const
| Convert a value into its representing label. More...
virtual double | extent (const QFont &font) const =0
void | setMinimumExtent (double)
| Set a minimum for the extent. More...
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. More...

## 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

const QwtScaleMap & QwtAbstractScaleDraw::scaleMap | ( |  | ) | const

Returns
  Map how to translate between scale and pixel values

QwtScaleMap & QwtAbstractScaleDraw::scaleMap | ( |  | ) |

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()