QwtPlotDirectPainter类 参考

Painter object trying to paint incrementally 更多...

#include <qwt_plot_directpainter.h>

类 QwtPlotDirectPainter 继承关系图:

类
class	PrivateData

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

Public 成员函数
	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

详细描述

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.

警告

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

成员枚举类型说明

Attribute

enum QwtPlotDirectPainter::Attribute

Paint attributes

参见

setAttribute(), testAttribute(), drawSeries()

枚举值
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.

构造及析构函数说明

QwtPlotDirectPainter()

QwtPlotDirectPainter::QwtPlotDirectPainter ( QObject *  parent = nullptr )

explicit

Constructor

参数

[in]

parent

Parent object

Destructor

成员函数说明

clipRegion()

QRegion QwtPlotDirectPainter::clipRegion

(

)

const

Get the currently set clip region

返回

Currently set clip region

参见

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.

参数

[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

参数

[in]	object	Object
[in]	event	Event

返回

True if the event was handled

hasClipping()

bool QwtPlotDirectPainter::hasClipping

(

)

const

Check if clipping is enabled

返回

true, when clipping is enabled

参见

setClipping(), clipRegion(), setClipRegion()

setAttribute()

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

Change an attribute

参数

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

参见

Attribute, testAttribute()

setClipping()

void QwtPlotDirectPainter::setClipping

(

bool

enable

)

Enable or disable clipping

参数

[in]

enable

Enables clipping if true, disables it otherwise

参见

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.

参数

[in]

region

Clip region

参见

clipRegion(), hasClipping(), setClipping()

testAttribute()

bool QwtPlotDirectPainter::testAttribute

(

Attribute

attribute

)

const

Test an attribute

参数

[in]

attribute

Attribute to be tested

返回

True, when attribute is enabled

参见

Attribute, setAttribute()

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该类的文档由以下文件生成:

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