Painter object trying to paint incrementally. More...

#include <qwt_plot_directpainter.h>

Inheritance diagram for QwtPlotDirectPainter:

Classes
class	PrivateData

Public Types
enum	Attribute { AtomicPainter = 0x01 , FullRepaint = 0x02 , CopyBackingStore = 0x04 }
	Paint attributes. More...

Public Member Functions
	QwtPlotDirectPainter (QObject *parent=nullptr)
	Constructor.

void	setAttribute (Attribute, bool on)
	Change an attribute.

bool	testAttribute (Attribute) const
	Test an attribute.

void	setClipping (bool)
	Enable or disable clipping.

bool	hasClipping () const
	Check if clipping is enabled.

void	setClipRegion (const QRegion &)
	Assign a clip region and enable clipping.

QRegion	clipRegion () const
	Get the currently set clip region.

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.

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. When FullRepaint is set the plot canvas is explicitly repainted after the samples have been rendered.
FullRepaint	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.

Constructor & Destructor Documentation

◆ QwtPlotDirectPainter()

QwtPlotDirectPainter::QwtPlotDirectPainter ( QObject * parent = nullptr )

explicit

Constructor.

Parameters

[in] parent Parent object

Destructor

Member Function Documentation

◆ clipRegion()

QRegion QwtPlotDirectPainter::clipRegion ( ) const

Get the currently set clip region.

Returns: Currently set clip region

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

◆ drawSeries()

void QwtPlotDirectPainter::drawSeries	(	QwtPlotSeriesItem *	seriesItem,
		int	from,
		int	to
	)

Draw a set of points of a seriesItem.

When observing a 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

[in]	seriesItem	Item to be painted
[in]	from	Index of the first point to be painted
[in]	to	Index of the last point to be painted. If to < 0 the series will be painted to its last point.

◆ eventFilter()

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

overridevirtual

Event filter.

Parameters

[in]	object	Object
[in]	event	Event

Returns: True if the event was handled

◆ hasClipping()

bool QwtPlotDirectPainter::hasClipping ( ) const

Check if clipping is enabled.

Returns: true, when clipping is enabled

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

◆ setAttribute()

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

Change an attribute.

Parameters

[in]	attribute	Attribute to change
[in]	on	On/Off

See also: Attribute, testAttribute()

◆ setClipping()

void QwtPlotDirectPainter::setClipping ( bool enable )

Enable or disable clipping.

Parameters

[in] enable Enables clipping if true, disables it otherwise

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

◆ 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. E.g. on Qt embedded only the clipped part of the backing store will be copied to a (maybe unaccelerated) frame buffer device.

Parameters

[in] region Clip region

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

◆ testAttribute()

bool QwtPlotDirectPainter::testAttribute ( Attribute attribute ) const

Test an attribute.

Parameters

[in] attribute Attribute to be tested

Returns: True, when attribute is enabled

See also: Attribute, setAttribute()

The documentation for this class was generated from the following files:

/home/runner/work/QWT/QWT/src/plot/qwt_plot_directpainter.h
/home/runner/work/QWT/QWT/src/plot/qwt_plot_directpainter.cpp

Classes

Public Types

Public Member Functions

Detailed Description

Member Enumeration Documentation

◆ Attribute

Constructor & Destructor Documentation

◆ QwtPlotDirectPainter()

Member Function Documentation

◆ clipRegion()

◆ drawSeries()

◆ eventFilter()

◆ hasClipping()

◆ setAttribute()

◆ setClipping()

◆ setClipRegion()

◆ testAttribute()