QwtPlotDirectPainter(3) Qwt User's Guide QwtPlotDirectPainter(3)
NAME
QwtPlotDirectPainter -
Painter object trying to paint incrementally.
SYNOPSIS
#include <qwt_plot_directpainter.h>
Public Types
enum Attribute { AtomicPainter = 0x01, FullRepaint = 0x02, CopyBackingStore = 0x04 }
typedef QFlags< Attribute > Attributes
Public Member Functions
QwtPlotDirectPainter (QObject *parent=NULL)
virtual ~QwtPlotDirectPainter ()
void setAttribute (Attribute, bool on)
bool testAttribute (Attribute) const
void setClipping (bool)
bool hasClipping () const
void setClipRegion (const QRegion &)
QRegion clipRegion () 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.
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 Typedef Documentation
typedef QFlags<Attribute> QwtPlotDirectPainter::Attributes
Paint attributes.
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 explicitely 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 backingstore to the canvas. This
flag can also be useful for settings, where Qt fills the the clip region with the widget background.
Constructor & Destructor Documentation
QwtPlotDirectPainter::QwtPlotDirectPainter (QObject *parent = NULL)
Constructor.
QwtPlotDirectPainter::~QwtPlotDirectPainter () [virtual]
Destructor.
Member Function Documentation
QRegion QwtPlotDirectPainter::clipRegion () const Returns:
Currently set clip region.
See also:
setClipRegion(), setClipping(), hasClipping()
void QwtPlotDirectPainter::drawSeries (QwtPlotAbstractSeriesItem *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::eventFilter (QObject *, QEvent *event) [virtual]
Event filter.
bool QwtPlotDirectPainter::hasClipping () const Returns:
true, when clipping is enabled
See also:
setClipping(), clipRegion(), setClipRegion()
void QwtPlotDirectPainter::reset ()
Close the internal QPainter.
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 ®ion)
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 Check if a attribute is set.
Parameters:
attribute Attribute to be tested
See also:
Attribute, setAttribute()
Author
Generated automatically by Doxygen for Qwt User's Guide from the source code.
Version 6.0.0 Fri Apr 15 2011 QwtPlotDirectPainter(3)