Qwt User's Guide 5.2.3

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QwtAbstractScaleDraw Class Reference

`#include <qwt_abstract_scale_draw.h>`

Inheritance diagram for QwtAbstractScaleDraw:
[legend]

List of all members.

## 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

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,
|  | int | len
| ) |  | const
| protected pure virtual

Draw a tick

Parameters:

  painter | Painter
  value | Value of the tick
  len | Lenght 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 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 | ( | ScaleComponent | component | ) | const

Check if a component is enabled

See also:
  enableComponent()

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 | ( | double | value | ) | 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.

Parameters:

  value | Value

Returns:
  Label string.

Reimplemented in QwtDialScaleDraw.

int QwtAbstractScaleDraw::majTickLength | ( |  | ) | const

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

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

Returns:
  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

Returns:
  scale division

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

Returns:
  Map how to translate between scale and pixel values

void QwtAbstractScaleDraw::setMinimumExtent | ( | int | minExtent | ) |

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.

Parameters:

  minExtent | Minimum extent

See also:
  extent(), minimumExtent()

void QwtAbstractScaleDraw::setScaleDiv | ( | const QwtScaleDiv & | sd | ) |

Change the scale division

Parameters:

  sd | New scale division

void QwtAbstractScaleDraw::setSpacing | ( | int | 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,
|  | int | 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 | ( | QwtScaleTransformation * | transformation | ) |

Change the transformation of the scale

Parameters:

  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:
  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

int QwtAbstractScaleDraw::tickLength | ( | QwtScaleDiv::TickType | tickType | ) | const

Return the length of the ticks

See also:
  setTickLength(), majTickLength()