NAME

       QwtPlotDirectPainter -

       Painter object trying to paint incrementally.

SYNOPSIS

       #include <qwt_plot_directpainter.h>

       Inherits QObject.

   Public Types
       enum Attribute { AtomicPainter = 0x01, FullRepaint = 0x02, CopyBackingStore = 0x04 }
           Paint attributes.
       typedef QFlags< Attribute > Attributes
           Paint attributes.

   Public Member Functions
       QwtPlotDirectPainter (QObject *parent=NULL)
           Constructor.
       virtual ~QwtPlotDirectPainter ()
           Destructor.
       void setAttribute (Attribute, bool on)
       bool testAttribute (Attribute) const
       void setClipping (bool)
       bool hasClipping () const
       void setClipRegion (const QRegion &)
           Assign a clip region and enable clipping.
       QRegion clipRegion () const
       void drawSeries (QwtPlotSeriesItem *, int from, int to)
           Draw a set of points of a seriesItem.
       void reset ()
           Close the internal QPainter.
       virtual bool eventFilter (QObject *, QEvent *)
           Event filter.

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.

       On certain environments it might be important to calculate a proper clip region before
       painting. F.e. for Qt Embedded only the clipped part of the backing store will be copied
       to a ( maybe unaccelerated ) frame buffer.

       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

   enum QwtPlotDirectPainter::Attribute
       Paint attributes.

       See Also:
           setAttribute(), testAttribute(), drawSeries()

       Enumerator

       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 explicitly repainted after the samples
              have been rendered.

       CopyBackingStore
              When QwtPlotCanvas::BackingStore is enabled the painter has to paint to the backing
              store and the widget. In certain situations/environments it might be faster to
              paint to the backing store only and then copy the backing store to the canvas. This
              flag can also be useful for settings, where Qt fills the the clip region with the
              widget background.

Member Function Documentation

   QRegion QwtPlotDirectPainter::clipRegion () const
       Returns:
           Currently set clip region.

       See Also:
           setClipRegion(), setClipping(), hasClipping()

   void QwtPlotDirectPainter::drawSeries (QwtPlotSeriesItem *seriesItem, intfrom, intto)
       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::hasClipping () const
       Returns:
           true, when clipping is enabled

       See Also:
           setClipping(), clipRegion(), setClipRegion()

   void QwtPlotDirectPainter::setAttribute (Attributeattribute, boolon)
       Change an attribute

       Parameters:
           attribute Attribute to change
           on On/Off

       See Also:
           Attribute, testAttribute()

   void QwtPlotDirectPainter::setClipping (boolenable)
       En/Disables clipping

       Parameters:
           enable Enables clipping is true, disable it otherwise

       See Also:
           hasClipping(), clipRegion(), setClipRegion()

   void QwtPlotDirectPainter::setClipRegion (const QRegion &region)
       Assign a clip region and enable clipping. Depending on the environment setting a proper
       clip region might improve the performance heavily. F.e. on Qt embedded only the clipped
       part of the backing store will be copied to a ( maybe unaccelerated ) frame buffer device.

       Parameters:
           region Clip region

       See Also:
           clipRegion(), hasClipping(), setClipping()

   bool QwtPlotDirectPainter::testAttribute (Attributeattribute) const
       Returns:
           True, when attribute is enabled

       Parameters:
           attribute Attribute to be tested

       See Also:
           Attribute, setAttribute()

Author

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