Qwt User's Guide
QwtAbstractScaleDraw Class Reference

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

#include <qwt_abstract_scale_draw.h>

Inheritance diagram for QwtAbstractScaleDraw:

Public Types

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

Public Member Functions

 QwtAbstractScaleDraw ()
 Constructor.
virtual ~QwtAbstractScaleDraw ()
 Destructor.
void setScaleDiv (const QwtScaleDiv &s)
const QwtScaleDivscaleDiv () const
void setTransformation (QwtTransform *)
const QwtScaleMapscaleMap () const
QwtScaleMapscaleMap ()
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.
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 QwtTexttickLabel (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

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

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:
painterThe painter
palettePalette, 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:
painterPainter
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:
painterPainter
valueValue
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:
painterPainter
valueValue of the tick
lenLength 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:
componentScale component
enableOn/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:
fontFont used for drawing the tick labels
Returns:
Number of pixels
See also:
setMinimumExtent(), minimumExtent()

Implemented in QwtScaleDraw, and QwtRoundScaleDraw.

Check if a component is enabled

Parameters:
componentComponent type
Returns:
true, when component is enabled
See also:
enableComponent()

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:
valueValue
Returns:
Label string.

Reimplemented in QwtDateScaleDraw, and QwtCompassScaleDraw.

Returns:
Length of the longest tick

Useful for layout calculations

See also:
tickLength(), setTickLength()

Get the minimum extent

Returns:
Minimum extent
See also:
extent(), setMinimumExtent()
Returns:
Scale pen width
See also:
setPenWidth()
Returns:
scale division
Returns:
Map how to translate between scale and pixel values
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:
minExtentMinimum extent
See also:
extent(), minimumExtent()
void QwtAbstractScaleDraw::setPenWidth ( int  width)

Specify the width of the scale pen.

Parameters:
widthPen width
See also:
penWidth()
void QwtAbstractScaleDraw::setScaleDiv ( const QwtScaleDiv scaleDiv)

Change the scale division

Parameters:
scaleDivNew 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:
spacingSpacing
See also:
spacing()
void QwtAbstractScaleDraw::setTickLength ( QwtScaleDiv::TickType  tickType,
double  length 
)

Set the length of the ticks

Parameters:
tickTypeTick type
lengthNew length
Warning:
the length is limited to [0..1000]

Change the transformation of the scale

Parameters:
transformationNew scale transformation

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:
fontFont
valueValue
Returns:
Tick label
Returns:
Length of the ticks
See also:
setTickLength(), maxTickLength()

List of all members.

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