Qwt User's Guide  6.1.1
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QwtSymbol Class Reference

A class for drawing symbols. More...

#include <qwt_symbol.h>

Public Types

enum  Style {
  NoSymbol = -1, Ellipse, Rect, Diamond,
  Triangle, DTriangle, UTriangle, LTriangle,
  RTriangle, Cross, XCross, HLine,
  VLine, Star1, Star2, Hexagon,
  Path, Pixmap, Graphic, SvgDocument,
  UserStyle = 1000
}
 
enum  CachePolicy { NoCache, Cache, AutoCache }
 

Public Member Functions

 QwtSymbol (Style=NoSymbol)
 
 QwtSymbol (Style, const QBrush &, const QPen &, const QSize &)
 Constructor. More...
 
 QwtSymbol (const QPainterPath &, const QBrush &, const QPen &)
 Constructor. More...
 
virtual ~QwtSymbol ()
 Destructor.
 
void setCachePolicy (CachePolicy)
 
CachePolicy cachePolicy () const
 
void setSize (const QSize &)
 
void setSize (int width, int height=-1)
 Specify the symbol's size. More...
 
const QSize & size () const
 
void setPinPoint (const QPointF &pos, bool enable=true)
 Set and enable a pin point. More...
 
QPointF pinPoint () const
 
void setPinPointEnabled (bool)
 
bool isPinPointEnabled () const
 
virtual void setColor (const QColor &)
 Set the color of the symbol. More...
 
void setBrush (const QBrush &b)
 Assign a brush. More...
 
const QBrush & brush () const
 
void setPen (const QColor &, qreal width=0.0, Qt::PenStyle=Qt::SolidLine)
 
void setPen (const QPen &)
 
const QPen & pen () const
 
void setStyle (Style)
 
Style style () const
 
void setPath (const QPainterPath &)
 Set a painter path as symbol. More...
 
const QPainterPath & path () const
 
void setPixmap (const QPixmap &)
 
const QPixmap & pixmap () const
 
void setGraphic (const QwtGraphic &)
 
const QwtGraphicgraphic () const
 
void setSvgDocument (const QByteArray &)
 
void drawSymbol (QPainter *, const QRectF &) const
 Draw the symbol into a rectangle. More...
 
void drawSymbol (QPainter *, const QPointF &) const
 Draw the symbol at a specified position. More...
 
void drawSymbols (QPainter *, const QPolygonF &) const
 Draw symbols at the specified points. More...
 
void drawSymbols (QPainter *, const QPointF *, int numPoints) const
 
virtual QRect boundingRect () const
 
void invalidateCache ()
 

Protected Member Functions

virtual void renderSymbols (QPainter *, const QPointF *, int numPoints) const
 

Detailed Description

A class for drawing symbols.

Member Enumeration Documentation

Depending on the render engine and the complexity of the symbol shape it might be faster to render the symbol to a pixmap and to paint this pixmap.

F.e. the raster paint engine is a pure software renderer where in cache mode a draw operation usually ends in raster operation with the the backing store, that are usually faster, than the algorithms for rendering polygons. But the opposite can be expected for graphic pipelines that can make use of hardware acceleration.

The default setting is AutoCache

See Also
setCachePolicy(), cachePolicy()
Note
The policy has no effect, when the symbol is painted to a vector graphics format ( PDF, SVG ).
Warning
Since Qt 4.8 raster is the default backend on X11
Enumerator
NoCache 

Don't use a pixmap cache.

Cache 

Always use a pixmap cache.

AutoCache 

Use a cache when one of the following conditions is true:

  • The symbol is rendered with the software renderer ( QPaintEngine::Raster )

Symbol Style

See Also
setStyle(), style()
Enumerator
NoSymbol 

No Style. The symbol cannot be drawn.

Ellipse 

Ellipse or circle.

Rect 

Rectangle.

Diamond 

Diamond.

Triangle 

Triangle pointing upwards.

DTriangle 

Triangle pointing downwards.

UTriangle 

Triangle pointing upwards.

LTriangle 

Triangle pointing left.

RTriangle 

Triangle pointing right.

Cross 

Cross (+)

XCross 

Diagonal cross (X)

HLine 

Horizontal line.

VLine 

Vertical line.

Star1 

X combined with +.

Star2 

Six-pointed star.

Hexagon 

Hexagon.

Path 

The symbol is represented by a painter path, where the origin ( 0, 0 ) of the path coordinate system is mapped to the position of the symbol.

See Also
setPath(), path()
Pixmap 

The symbol is represented by a pixmap. The pixmap is centered or aligned to its pin point.

See Also
setPinPoint()
Graphic 

The symbol is represented by a graphic. The graphic is centered or aligned to its pin point.

See Also
setPinPoint()
SvgDocument 

The symbol is represented by a SVG graphic. The graphic is centered or aligned to its pin point.

See Also
setPinPoint()
UserStyle 

Styles >= QwtSymbol::UserSymbol are reserved for derived classes of QwtSymbol that overload drawSymbols() with additional application specific symbol types.

Constructor & Destructor Documentation

QwtSymbol::QwtSymbol ( Style  style = NoSymbol)

Default Constructor

Parameters
styleSymbol Style

The symbol is constructed with gray interior, black outline with zero width, no size and style 'NoSymbol'.

QwtSymbol::QwtSymbol ( QwtSymbol::Style  style,
const QBrush &  brush,
const QPen &  pen,
const QSize &  size 
)

Constructor.

Parameters
styleSymbol Style
brushbrush to fill the interior
penoutline pen
sizesize
See Also
setStyle(), setBrush(), setPen(), setSize()
QwtSymbol::QwtSymbol ( const QPainterPath &  path,
const QBrush &  brush,
const QPen &  pen 
)

Constructor.

The symbol gets initialized by a painter path. The style is set to QwtSymbol::Path, the size is set to empty ( the path is displayed unscaled ).

Parameters
pathpainter path
brushbrush to fill the interior
penoutline pen
See Also
setPath(), setBrush(), setPen(), setSize()

Member Function Documentation

QRect QwtSymbol::boundingRect ( ) const
virtual

Calculate the bounding rectangle for a symbol at position (0,0).

Returns
Bounding rectangle
const QBrush & QwtSymbol::brush ( ) const
Returns
Brush
See Also
setBrush()
QwtSymbol::CachePolicy QwtSymbol::cachePolicy ( ) const
Returns
Cache policy
See Also
CachePolicy, setCachePolicy()
void QwtSymbol::drawSymbol ( QPainter *  painter,
const QRectF &  rect 
) const

Draw the symbol into a rectangle.

The symbol is painted centered and scaled into the target rectangle. It is always painted uncached and the pin point is ignored.

This method is primarily intended for drawing a symbol to the legend.

Parameters
painterPainter
rectTarget rectangle for the symbol
void QwtSymbol::drawSymbol ( QPainter *  painter,
const QPointF &  pos 
) const
inline

Draw the symbol at a specified position.

Parameters
painterPainter
posPosition of the symbol in screen coordinates
void QwtSymbol::drawSymbols ( QPainter *  painter,
const QPolygonF &  points 
) const
inline

Draw symbols at the specified points.

Parameters
painterPainter
pointsPositions of the symbols in screen coordinates
void QwtSymbol::drawSymbols ( QPainter *  painter,
const QPointF *  points,
int  numPoints 
) const

Render an array of symbols

Painting several symbols is more effective than drawing symbols one by one, as a couple of layout calculations and setting of pen/brush can be done once for the complete array.

Parameters
painterPainter
pointsArray of points
numPointsNumber of points
const QwtGraphic & QwtSymbol::graphic ( ) const
Returns
Assigned graphic
See Also
setGraphic()
void QwtSymbol::invalidateCache ( )

Invalidate the cached symbol pixmap

The symbol invalidates its cache, whenever an attribute is changed that has an effect ob how to display a symbol. In case of derived classes with individual styles ( >= QwtSymbol::UserStyle ) it might be necessary to call invalidateCache() for attributes that are relevant for this style.

See Also
CachePolicy, setCachePolicy(), drawSymbols()
bool QwtSymbol::isPinPointEnabled ( ) const
Returns
True, when the pin point translation is enabled
See Also
setPinPoint(), setPinPointEnabled()
const QPainterPath & QwtSymbol::path ( ) const
Returns
Painter path for displaying the symbol
See Also
setPath()
const QPen & QwtSymbol::pen ( ) const
Returns
Pen
See Also
setPen(), brush()
QPointF QwtSymbol::pinPoint ( ) const
Returns
Pin point
See Also
setPinPoint(), setPinPointEnabled()
const QPixmap & QwtSymbol::pixmap ( ) const
Returns
Assigned pixmap
See Also
setPixmap()
void QwtSymbol::renderSymbols ( QPainter *  painter,
const QPointF *  points,
int  numPoints 
) const
protectedvirtual

Render the symbol to series of points

Parameters
painterQt painter
pointsPositions of the symbols
numPointsNumber of points
void QwtSymbol::setBrush ( const QBrush &  brush)

Assign a brush.

The brush is used to draw the interior of the symbol.

Parameters
brushBrush
See Also
brush()
void QwtSymbol::setCachePolicy ( QwtSymbol::CachePolicy  policy)

Change the cache policy

The default policy is AutoCache

Parameters
policyCache policy
See Also
CachePolicy, cachePolicy()
void QwtSymbol::setColor ( const QColor &  color)
virtual

Set the color of the symbol.

Change the color of the brush for symbol types with a filled area. For all other symbol types the color will be assigned to the pen.

Parameters
colorColor
See Also
setBrush(), setPen(), brush(), pen()
void QwtSymbol::setGraphic ( const QwtGraphic graphic)

Set a graphic as symbol

Parameters
graphicGraphic
See Also
graphic(), setPixmap()
Note
the style() is set to QwtSymbol::Graphic
brush() and pen() have no effect
void QwtSymbol::setPath ( const QPainterPath &  path)

Set a painter path as symbol.

The symbol is represented by a painter path, where the origin ( 0, 0 ) of the path coordinate system is mapped to the position of the symbol.

When the symbol has valid size the painter path gets scaled to fit into the size. Otherwise the symbol size depends on the bounding rectangle of the path.

The following code defines a symbol drawing an arrow:

#include <qwt_symbol.h>

QwtSymbol *symbol = new QwtSymbol();

QPen pen( Qt::black, 2 );
pen.setJoinStyle( Qt::MiterJoin );

symbol->setPen( pen );
symbol->setBrush( Qt::red );

QPainterPath path;
path.moveTo( 0, 8 );
path.lineTo( 0, 5 );
path.lineTo( -3, 5 );
path.lineTo( 0, 0 );
path.lineTo( 3, 5 );
path.lineTo( 0, 5 );

QTransform transform;
transform.rotate( -30.0 );
path = transform.map( path );

symbol->setPath( path );
symbol->setPinPoint( QPointF( 0.0, 0.0 ) );

setSize( 10, 14 );
Parameters
pathPainter path
Note
The style is implicitely set to QwtSymbol::Path.
See Also
path(), setSize()
void QwtSymbol::setPen ( const QColor &  color,
qreal  width = 0.0,
Qt::PenStyle  style = Qt::SolidLine 
)

Build and assign a pen

In Qt5 the default pen width is 1.0 ( 0.0 in Qt4 ) what makes it non cosmetic ( see QPen::isCosmetic() ). This method has been introduced to hide this incompatibility.

Parameters
colorPen color
widthPen width
stylePen style
See Also
pen(), brush()
void QwtSymbol::setPen ( const QPen &  pen)

Assign a pen

The pen is used to draw the symbol's outline.

Parameters
penPen
See Also
pen(), setBrush()
void QwtSymbol::setPinPoint ( const QPointF &  pos,
bool  enable = true 
)

Set and enable a pin point.

The position of a complex symbol is not always aligned to its center ( f.e an arrow, where the peak points to a position ). The pin point defines the position inside of a Pixmap, Graphic, SvgDocument or PainterPath symbol where the represented point has to be aligned to.

Parameters
posPosition
enableEn/Disable the pin point alignment
See Also
pinPoint(), setPinPointEnabled()
void QwtSymbol::setPinPointEnabled ( bool  on)

En/Disable the pin point alignment

Parameters
onEnabled, when on is true
See Also
setPinPoint(), isPinPointEnabled()
void QwtSymbol::setPixmap ( const QPixmap &  pixmap)

Set a pixmap as symbol

Parameters
pixmapPixmap
See Also
pixmap(), setGraphic()
Note
the style() is set to QwtSymbol::Pixmap
brush() and pen() have no effect
void QwtSymbol::setSize ( const QSize &  size)

Set the symbol's size

Parameters
sizeSize
See Also
size()
void QwtSymbol::setSize ( int  width,
int  height = -1 
)

Specify the symbol's size.

If the 'h' parameter is left out or less than 0, and the 'w' parameter is greater than or equal to 0, the symbol size will be set to (w,w).

Parameters
widthWidth
heightHeight (defaults to -1)
See Also
size()
void QwtSymbol::setStyle ( QwtSymbol::Style  style)

Specify the symbol style

Parameters
styleStyle
See Also
style()
void QwtSymbol::setSvgDocument ( const QByteArray &  svgDocument)

Set a SVG icon as symbol

Parameters
svgDocumentSVG icon
See Also
setGraphic(), setPixmap()
Note
the style() is set to QwtSymbol::SvgDocument
brush() and pen() have no effect
const QSize & QwtSymbol::size ( ) const
Returns
Size
See Also
setSize()
QwtSymbol::Style QwtSymbol::style ( ) const
Returns
Current symbol style
See Also
setStyle()