QwtPlotDirectPainter Class Reference

Painter object trying to paint incrementally. More...

#include <qwt_plot_directpainter.h>

Inheritance diagram for QwtPlotDirectPainter:

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

Definition at line 39 of file qwt_plot_directpainter.h.

Member Typedef Documentation

Attributes

typedef QFlags<Attribute > QwtPlotDirectPainter::Attributes

An ORed combination of Attribute values.

Definition at line 73 of file qwt_plot_directpainter.h.

Member Enumeration Documentation

Attribute

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.

Definition at line 46 of file qwt_plot_directpainter.h.

Constructor & Destructor Documentation

QwtPlotDirectPainter()

QwtPlotDirectPainter::QwtPlotDirectPainter ( QObject * parent = NULL )

explicit

Constructor.

Definition at line 66 of file qwt_plot_directpainter.cpp.

~QwtPlotDirectPainter()

QwtPlotDirectPainter::~QwtPlotDirectPainter ( )

virtual

Destructor.

Definition at line 73 of file qwt_plot_directpainter.cpp.

Member Function Documentation

clipRegion()

QRegion QwtPlotDirectPainter::clipRegion

(

)

const

Returns

Currently set clip region.

See also

setClipRegion(), setClipping(), hasClipping()

Definition at line 151 of file qwt_plot_directpainter.cpp.

drawSeries()

void QwtPlotDirectPainter::drawSeries	(	QwtPlotSeriesItem *	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.

Definition at line 172 of file qwt_plot_directpainter.cpp.

eventFilter()

bool QwtPlotDirectPainter::eventFilter ( QObject * , QEvent * event )

overridevirtual

Event filter.

Definition at line 277 of file qwt_plot_directpainter.cpp.

hasClipping()

bool QwtPlotDirectPainter::hasClipping

(

)

const

Returns

true, when clipping is enabled

See also

setClipping(), clipRegion(), setClipRegion()

Definition at line 125 of file qwt_plot_directpainter.cpp.

reset()

void QwtPlotDirectPainter::reset

(

)

Close the internal QPainter.

Definition at line 264 of file qwt_plot_directpainter.cpp.

setAttribute()

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

Change an attribute

Parameters

attribute	Attribute to change
on	On/Off

See also

Attribute, testAttribute()

Definition at line 86 of file qwt_plot_directpainter.cpp.

setClipping()

void QwtPlotDirectPainter::setClipping

(

bool

enable

)

En/Disables clipping

Parameters

enable

Enables clipping is true, disable it otherwise

See also

hasClipping(), clipRegion(), setClipRegion()

Definition at line 116 of file qwt_plot_directpainter.cpp.

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()

Definition at line 141 of file qwt_plot_directpainter.cpp.

testAttribute()

bool QwtPlotDirectPainter::testAttribute

(

Attribute

attribute

)

const

Returns

True, when attribute is enabled

Parameters

attribute

Attribute to be tested

See also

Attribute, setAttribute()

Definition at line 105 of file qwt_plot_directpainter.cpp.