QwtPlotDirectPainter Class Reference

Painter object trying to paint incrementally. More...

#include <qwt_plot_directpainter.h>

List of all members.

Public Types

enum  Attribute {
  AtomicPainter = 1,
  FullRepaint = 2
}

Public Member Functions

 QwtPlotDirectPainter (QObject *parent=NULL)
virtual ~QwtPlotDirectPainter ()
void setAttribute (Attribute, bool on)
bool testAttribute (Attribute) const
void drawSeries (QwtPlotAbstractSeriesItem *, int from, int to)
void reset ()
virtual bool eventFilter (QObject *, QEvent *)

Detailed Description

Painter object trying to paint incrementally.

Often applications want to display samples while they are collected. When there are too many samples complete replots will be expensive to be processed in a collection cycle.

QwtPlotDirectPainter offers an API to paint subsets ( f.e all additions points ) without erasing/repainting the plot canvas.

Warning:
Incremental painting will only help when no replot is triggered by another operation ( like changing scales ) and nothing needs to be erased.

Member Enumeration Documentation

  • AtomicPainter
    Initializing a QPainter is an expensive operation. When AtomicPainter is set each call of drawSeries() opens/closes a temporary QPainter. Otherwise QwtPlotDirectPainter tries to use the same QPainter as long as possible.
  • FullRepaint
    When FullRepaint is set the plot canvas is explicitely repainted after the samples have been rendered.
See also:
setAttribute(), testAttribute(), drawSeries()

Constructor & Destructor Documentation

QwtPlotDirectPainter::QwtPlotDirectPainter ( QObject *  parent = NULL  ) 

Constructor.

QwtPlotDirectPainter::~QwtPlotDirectPainter (  )  [virtual]

Destructor.


Member Function Documentation

void QwtPlotDirectPainter::drawSeries ( QwtPlotAbstractSeriesItem seriesItem,
int  from,
int  to 
)

Draw a set of points of a seriesItem.

When observing an measurement while it is running, new points have to be added to an existing seriesItem. drawSeries can be used to display them avoiding a complete redraw of the canvas.

Setting plot()->canvas()->setAttribute(Qt::WA_PaintOutsidePaintEvent, true); will result in faster painting, if the paint engine of the canvas widget supports this feature.

Parameters:
seriesItem Item to be painted
from Index of the first point to be painted
to Index of the last point to be painted. If to < 0 the series will be painted to its last point.
bool QwtPlotDirectPainter::eventFilter ( QObject *  ,
QEvent *  event 
) [virtual]

Event filter.

void QwtPlotDirectPainter::reset (  ) 

Close the internal QPainter.

void QwtPlotDirectPainter::setAttribute ( Attribute  attribute,
bool  on 
)

Change an attribute

Parameters:
attribute Attribute to change
on On/Off
See also:
Attribute, testAttribute()
bool QwtPlotDirectPainter::testAttribute ( Attribute  attribute  )  const

Check if a attribute is set.

Parameters:
attribute Attribute to be tested
See also:
Attribute, setAttribute()
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