Qwt User's Guide 6.1.1

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QwtScaleDraw Class Reference

A class for drawing scales. More...

`#include <qwt_scale_draw.h>`

Inheritance diagram for QwtScaleDraw:
[legend]

## Public Types
enum | Alignment { BottomScale, TopScale, LeftScale, RightScale }
Public Types inherited from QwtAbstractScaleDraw
enum | ScaleComponent { Backbone = 0x01, Ticks = 0x02, Labels = 0x04 }
typedef QFlags< ScaleComponent > | ScaleComponents
| Scale components.

## Public Member Functions
| QwtScaleDraw ()
| Constructor. More...
virtual | ~QwtScaleDraw ()
| Destructor.
void | getBorderDistHint (const QFont &, int &start, int &end) const
| Determine the minimum border distance. More...
int | minLabelDist (const QFont &) const
int | minLength (const QFont &) const
virtual double | extent (const QFont &) const
void | move (double x, double y)
void | move (const QPointF &)
| Move the position of the scale. More...
void | setLength (double length)
Alignment | alignment () const
void | setAlignment (Alignment)
Qt::Orientation | orientation () const
QPointF | pos () const
double | length () const
void | setLabelAlignment (Qt::Alignment)
| Change the label flags. More...
Qt::Alignment | labelAlignment () const
void | setLabelRotation (double rotation)
double | labelRotation () const
int | maxLabelHeight (const QFont &) const
int | maxLabelWidth (const QFont &) const
QPointF | labelPosition (double val) const
QRectF | labelRect (const QFont &, double val) const
QSizeF | labelSize (const QFont &, double val) const
QRect | boundingLabelRect (const QFont &, double val) const
| Find the bounding rectangle for the label. More...
Public Member Functions inherited from QwtAbstractScaleDraw
| 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...
void | setMinimumExtent (double)
| Set a minimum for the extent. More...
double | minimumExtent () const

## Protected Member Functions
QTransform | labelTransformation (const QPointF &, const QSizeF &) const
virtual void | drawTick (QPainter *, double val, double len) const
virtual void | drawBackbone (QPainter *) const
virtual void | drawLabel (QPainter *, double val) const
Protected Member Functions inherited from QwtAbstractScaleDraw
void | invalidateCache ()
const QwtText & | tickLabel (const QFont &, double value) const
| Convert a value into its representing label and cache it. More...

## Detailed Description

A class for drawing scales.

QwtScaleDraw can be used to draw linear or logarithmic scales. A scale has a position, an alignment and a length, which can be specified . The labels can be rotated and aligned to the ticks using setLabelRotation() and setLabelAlignment().

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 QwtScaleDraw::Alignment

Alignment of the scale draw

See Also
  setAlignment(), alignment()

Enumerator
BottomScale | The scale is below.
TopScale | The scale is above.
LeftScale | The scale is left.
RightScale | The scale is right.

## Constructor & Destructor Documentation

QwtScaleDraw::QwtScaleDraw | ( |  | ) |

Constructor.

The range of the scale is initialized to [0, 100], The position is at (0, 0) with a length of 100. The orientation is QwtAbstractScaleDraw::Bottom.

## Member Function Documentation

QwtScaleDraw::Alignment QwtScaleDraw::alignment | ( |  | ) | const

Return alignment of the scale

See Also
  setAlignment()

Returns
  Alignment of the scale

QRect QwtScaleDraw::boundingLabelRect | ( | const QFont & | font,
|  | double | value
| ) |  | const

Find the bounding rectangle for the label.

The coordinates of the rectangle are absolute ( calculated from pos() ). in direction of the tick.

Parameters

  font | Font used for painting
  value | Value

Returns
  Bounding rectangle

See Also
  labelRect()

void QwtScaleDraw::drawBackbone | ( | QPainter * | painter | ) | const
| protected virtual

Draws the baseline of the scale

Parameters

  painter | Painter

See Also
  drawTick(), drawLabel()

Implements QwtAbstractScaleDraw.

void QwtScaleDraw::drawLabel | ( | QPainter * | painter,
|  | double | value
| ) |  | const
| protected virtual

Draws the label for a major scale tick

Parameters

  painter | Painter
  value | Value

See Also
  drawTick(), drawBackbone(), boundingLabelRect()

Implements QwtAbstractScaleDraw.

void QwtScaleDraw::drawTick | ( | QPainter * | painter,
|  | double | value,
|  | double | len
| ) |  | const
| protected virtual

Draw a tick

Parameters

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

See Also
  drawBackbone(), drawLabel()

Implements QwtAbstractScaleDraw.

double QwtScaleDraw::extent | ( | const QFont & | font | ) | const
| virtual

Calculate the width/height that is needed for a vertical/horizontal scale.

The extent is calculated from the pen width of the backbone, the major tick length, the spacing and the maximum width/height of the labels.

Parameters

  font | Font used for painting the labels

Returns
  Extent

See Also
  minLength()

Implements QwtAbstractScaleDraw.

void QwtScaleDraw::getBorderDistHint | ( | const QFont & | font,
|  | int & | start,
|  | int & | end
| ) |  | const

Determine the minimum border distance.

This member function returns the minimum space needed to draw the mark labels at the scale's endpoints.

Parameters

  font | Font
  start | Start border distance
  end | End border distance

Qt::Alignment QwtScaleDraw::labelAlignment | ( |  | ) | const

Returns
  the label flags

See Also
  setLabelAlignment(), labelRotation()

QPointF QwtScaleDraw::labelPosition | ( | double | value | ) | const

Find the position, where to paint a label

The position has a distance that depends on the length of the ticks in direction of the alignment().

Parameters

  value | Value

Returns
  Position, where to paint a label

QRectF QwtScaleDraw::labelRect | ( | const QFont & | font,
|  | double | value
| ) |  | const

Find the bounding rectangle for the label. The coordinates of the rectangle are relative to spacing + tick length from the backbone in direction of the tick.

Parameters

  font | Font used for painting
  value | Value

Returns
  Bounding rectangle that is needed to draw a label

double QwtScaleDraw::labelRotation | ( |  | ) | const

Returns
  the label rotation

See Also
  setLabelRotation(), labelAlignment()

QSizeF QwtScaleDraw::labelSize | ( | const QFont & | font,
|  | double | value
| ) |  | const

Calculate the size that is needed to draw a label

Parameters

  font | Label font
  value | Value

Returns
  Size that is needed to draw a label

QTransform QwtScaleDraw::labelTransformation | ( | const QPointF & | pos,
|  | const QSizeF & | size
| ) |  | const
| protected

Calculate the transformation that is needed to paint a label depending on its alignment and rotation.

Parameters

  pos | Position where to paint the label
  size | Size of the label

Returns
  Transformation matrix

See Also
  setLabelAlignment(), setLabelRotation()

double QwtScaleDraw::length | ( |  | ) | const

Returns
  the length of the backbone

See Also
  setLength(), pos()

int QwtScaleDraw::maxLabelHeight | ( | const QFont & | font | ) | const

Parameters

  font | Font

Returns
  the maximum height of a label

int QwtScaleDraw::maxLabelWidth | ( | const QFont & | font | ) | const

Parameters

  font | Font

Returns
  the maximum width of a label

int QwtScaleDraw::minLabelDist | ( | const QFont & | font | ) | const

Determine the minimum distance between two labels, that is necessary that the texts don't overlap.

Parameters

  font | Font

Returns
  The maximum width of a label

See Also
  getBorderDistHint()

int QwtScaleDraw::minLength | ( | const QFont & | font | ) | const

Calculate the minimum length that is needed to draw the scale

Parameters

  font | Font used for painting the labels

Returns
  Minimum length that is needed to draw the scale

See Also
  extent()

void QwtScaleDraw::move | ( | double | x,
|  | double | y
| ) |  |
| inline

Move the position of the scale

Parameters

  x | X coordinate
  y | Y coordinate

See Also
  move(const QPointF &)

void QwtScaleDraw::move | ( | const QPointF & | pos | ) |

Move the position of the scale.

The meaning of the parameter pos depends on the alignment:

QwtScaleDraw::LeftScale
  The origin is the topmost point of the backbone. The backbone is a vertical line. Scale marks and labels are drawn at the left of the backbone.
QwtScaleDraw::RightScale
  The origin is the topmost point of the backbone. The backbone is a vertical line. Scale marks and labels are drawn at the right of the backbone.
QwtScaleDraw::TopScale
  The origin is the leftmost point of the backbone. The backbone is a horizontal line. Scale marks and labels are drawn above the backbone.
QwtScaleDraw::BottomScale
  The origin is the leftmost point of the backbone. The backbone is a horizontal line Scale marks and labels are drawn below the backbone.

Parameters

  pos | Origin of the scale

See Also
  pos(), setLength()

Qt::Orientation QwtScaleDraw::orientation | ( |  | ) | const

Return the orientation

TopScale, BottomScale are horizontal (Qt::Horizontal) scales, LeftScale, RightScale are vertical (Qt::Vertical) scales.

Returns
  Orientation of the scale

See Also
  alignment()

QPointF QwtScaleDraw::pos | ( |  | ) | const

Returns
  Origin of the scale

See Also
  move(), length()

void QwtScaleDraw::setAlignment | ( | Alignment | align | ) |

Set the alignment of the scale

Parameters

  align | Alignment of the scale

The default alignment is QwtScaleDraw::BottomScale

See Also
  alignment()

void QwtScaleDraw::setLabelAlignment | ( | Qt::Alignment | alignment | ) |

Change the label flags.

Labels are aligned to the point tick length + spacing away from the backbone.

The alignment is relative to the orientation of the label text. In case of an flags of 0 the label will be aligned depending on the orientation of the scale:

    QwtScaleDraw::TopScale: Qt::AlignHCenter | Qt::AlignTop\n
    QwtScaleDraw::BottomScale: Qt::AlignHCenter | Qt::AlignBottom\n
    QwtScaleDraw::LeftScale: Qt::AlignLeft | Qt::AlignVCenter\n
    QwtScaleDraw::RightScale: Qt::AlignRight | Qt::AlignVCenter\n

Changing the alignment is often necessary for rotated labels.

Parameters

  alignment | Or'd Qt::AlignmentFlags see <qnamespace.h>

See Also
  setLabelRotation(), labelRotation(), labelAlignment()

Warning
  The various alignments might be confusing. The alignment of the label is not the alignment of the scale and is not the alignment of the flags ( QwtText::flags() ) returned from QwtAbstractScaleDraw::label().

void QwtScaleDraw::setLabelRotation | ( | double | rotation | ) |

Rotate all labels.

When changing the rotation, it might be necessary to adjust the label flags too. Finding a useful combination is often the result of try and error.

Parameters

  rotation | Angle in degrees. When changing the label rotation, the label flags often needs to be adjusted too.

See Also
  setLabelAlignment(), labelRotation(), labelAlignment().

void QwtScaleDraw::setLength | ( | double | length | ) |

Set the length of the backbone.

The length doesn't include the space needed for overlapping labels.

Parameters

  length | Length of the backbone

See Also
  move(), minLabelDist()