QwtPlotCanvas Class Reference

Canvas of a QwtPlot. More...

#include <qwt_plot_canvas.h>

Inheritance diagram for QwtPlotCanvas:

Classes
class	PrivateData

Public Types
enum	PaintAttribute { BackingStore = 1 , Opaque = 2 , HackStyledBackground = 4 , ImmediatePaint = 8 }
	Paint attributes. More...
Public Types inherited from QwtPlotAbstractCanvas
enum	FocusIndicator { NoFocusIndicator , CanvasFocusIndicator , ItemFocusIndicator }
	Focus indicator. More...

Public Slots
void	replot ()
	Invalidate the paint cache and repaint the canvas.

Public Member Functions
	QwtPlotCanvas (QwtPlot *=nullptr)
	Constructor.
void	setPaintAttribute (PaintAttribute, bool on=true)
	Change the paint attributes.
bool	testPaintAttribute (PaintAttribute) const
	Test whether a paint attribute is enabled.
const QPixmap *	backingStore () const
	Get the backing store.
Q_INVOKABLE void	invalidateBackingStore ()
	Invalidate the internal backing store.
virtual bool	event (QEvent *) override
	Qt event handler for QEvent::PolishRequest and QEvent::StyleChange.
Q_INVOKABLE QPainterPath	borderPath (const QRect &) const
	Calculate the painter path for a styled or rounded border.
Public Member Functions inherited from QwtPlotAbstractCanvas
	QwtPlotAbstractCanvas (QWidget *canvasWidget)
	Constructor.
QwtPlot *	plot ()
	Return parent plot widget.
const QwtPlot *	plot () const
	Return parent plot widget.
void	setFocusIndicator (FocusIndicator)
	Set the focus indicator.
FocusIndicator	focusIndicator () const
	Get the focus indicator.
void	setBorderRadius (double)
	Set the radius for the corners of the border frame.
double	borderRadius () const
	Get the radius for the corners of the border frame.

Protected Member Functions
virtual void	paintEvent (QPaintEvent *) override
	Paint event handler.
virtual void	resizeEvent (QResizeEvent *) override
	Resize event handler.
virtual void	drawBorder (QPainter *) override
	Draw border.
Protected Member Functions inherited from QwtPlotAbstractCanvas
QWidget *	canvasWidget ()
const QWidget *	canvasWidget () const
virtual void	drawFocusIndicator (QPainter *)
	Draw the focus indication.
virtual void	drawBackground (QPainter *)
	Helper function for the derived plot canvas.
void	fillBackground (QPainter *)
	Helper function for the derived plot canvas.
void	drawCanvas (QPainter *)
	Draw the plot to the canvas.
void	drawStyled (QPainter *, bool)
	Helper function for the derived plot canvas.
void	drawUnstyled (QPainter *)
	Helper function for the derived plot canvas.
QPainterPath	canvasBorderPath (const QRect &rect) const
void	updateStyleSheetInfo ()
	Update the cached information about the current style sheet.

Properties
double	borderRadius

Detailed Description

Canvas of a QwtPlot.

Canvas is the widget where all plot items are displayed

See also

QwtPlot::setCanvas(), QwtPlotGLCanvas, QwtPlotOpenGLCanvas

Member Enumeration Documentation

PaintAttribute

enum QwtPlotCanvas::PaintAttribute

Paint attributes.

The default setting enables BackingStore and Opaque.

See also

setPaintAttribute(), testPaintAttribute()

Enumerator
BackingStore	BackingStore. Paint double buffered reusing the content of the pixmap buffer when possible. Using a backing store might improve the performance significantly, when working with widget overlays (like rubber bands). Disabling the cache might improve the performance for incremental paints (using QwtPlotDirectPainter). See also backingStore(), invalidateBackingStore()
Opaque	Opaque. Try to fill the complete contents rectangle of the plot canvas. When using styled backgrounds Qt assumes that the canvas doesn't fill its area completely (e.g. because of rounded borders) and fills the area below the canvas. When this is done with gradients it might result in a serious performance bottleneck — depending on the size. When the Opaque attribute is enabled the canvas tries to identify the gaps with some heuristics and to fill those only. Warning Will not work for semitransparent backgrounds.
HackStyledBackground	HackStyledBackground. Try to improve painting of styled backgrounds. QwtPlotCanvas supports the box model attributes for customizing the layout with style sheets. Unfortunately the design of Qt style sheets has no concept how to handle backgrounds with rounded corners — beside of padding. When HackStyledBackground is enabled the plot canvas tries to separate the background from the background border by reverse engineering to paint the background before and the border after the plot items. In this order the border gets perfectly antialiased and you can avoid some pixel artifacts in the corners.
ImmediatePaint	ImmediatePaint. When ImmediatePaint is set replot() calls repaint() instead of update(). See also replot(), QWidget::repaint(), QWidget::update()

Constructor & Destructor Documentation

QwtPlotCanvas()

QwtPlotCanvas::QwtPlotCanvas ( QwtPlot *  plot = nullptr )

explicit

Constructor.

Parameters

[in]

plot

Parent plot widget

See also

QwtPlot::setCanvas()

Destructor

Member Function Documentation

backingStore()

const QPixmap * QwtPlotCanvas::backingStore

(

)

const

Get the backing store.

Returns

Backing store pixmap, might be null

borderPath()

QPainterPath QwtPlotCanvas::borderPath

(

const QRect &

rect

)

const

Calculate the painter path for a styled or rounded border.

Parameters

[in]

rect

Bounding rectangle of the canvas

Returns

Painter path that can be used for clipping

When the canvas has no styled background or rounded borders, the painter path is empty.

drawBorder()

void QwtPlotCanvas::drawBorder ( QPainter *  painter )

overrideprotectedvirtual

Draw border.

Draw the border of the plot canvas.

Parameters

painter

Painter

See also

setBorderRadius()

Reimplemented from QwtPlotAbstractCanvas.

event()

bool QwtPlotCanvas::event ( QEvent *  event )

overridevirtual

Qt event handler for QEvent::PolishRequest and QEvent::StyleChange.

Parameters

[in]

event

Qt Event

Returns

See QFrame::event()

paintEvent()

void QwtPlotCanvas::paintEvent ( QPaintEvent *  event )

overrideprotectedvirtual

Paint event handler.

Paint event.

Parameters

event

Paint event

replot

void QwtPlotCanvas::replot ( )

slot

Invalidate the paint cache and repaint the canvas.

See also

invalidatePaintCache()

resizeEvent()

void QwtPlotCanvas::resizeEvent ( QResizeEvent *  event )

overrideprotectedvirtual

Resize event handler.

Resize event.

Parameters

event

Resize event

setPaintAttribute()

void QwtPlotCanvas::setPaintAttribute	(	PaintAttribute	attribute,
		bool	on = true
	)

Change the paint attributes.

Parameters

[in]	attribute	Paint attribute
[in]	on	On/Off

See also

testPaintAttribute(), backingStore()

testPaintAttribute()

bool QwtPlotCanvas::testPaintAttribute

(

PaintAttribute

attribute

)

const

Test whether a paint attribute is enabled.

Parameters

[in]

attribute

Paint attribute

Returns

true when attribute is enabled

See also

setPaintAttribute()

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

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