---
name: "QwtAbstractScaleDraw"
section: "3"
platform: "linux"
package: "libqwt-doc"
version: "6.1.4-2"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/QwtAbstractScaleDraw"
---

# QwtAbstractScaleDraw(3)

A abstract base class for drawing scales.

## NAME

QwtAbstractScaleDraw - 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*

### 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()**

## Author

*Generated automatically by Doxygen for Qwt User's Guide from the source code.*