A paint device for scalable graphics. More...

#include <qwt_graphic.h>

Inheritance diagram for QwtGraphic:

Public Types
enum	RenderHint { RenderPensUnscaled = 0x1 }

typedef QFlags< RenderHint >	RenderHints
	Render hints. More...

Public Types inherited from QwtNullPaintDevice
enum	Mode { NormalMode, PolygonPathMode, PathMode }
	Render mode. More...

Public Member Functions
	QwtGraphic ()
	Constructor. More...

	QwtGraphic (const QwtGraphic &)
	Copy constructor. More...

virtual	~QwtGraphic ()
	Destructor.

QwtGraphic &	operator= (const QwtGraphic &)
	Assignment operator. More...

void	reset ()
	Clear all stored commands. More...

bool	isNull () const

bool	isEmpty () const

void	render (QPainter *) const
	Replay all recorded painter commands. More...

void	render (QPainter *, const QSizeF &, Qt::AspectRatioMode=Qt::IgnoreAspectRatio) const
	Replay all recorded painter commands. More...

void	render (QPainter *, const QRectF &, Qt::AspectRatioMode=Qt::IgnoreAspectRatio) const
	Replay all recorded painter commands. More...

void	render (QPainter *, const QPointF &, Qt::Alignment=Qt::AlignTop\|Qt::AlignLeft) const
	Replay all recorded painter commands. More...

QPixmap	toPixmap () const
	Convert the graphic to a QPixmap. More...

QPixmap	toPixmap (const QSize &, Qt::AspectRatioMode=Qt::IgnoreAspectRatio) const
	Convert the graphic to a QPixmap. More...

QImage	toImage () const
	Convert the graphic to a QImage. More...

QImage	toImage (const QSize &, Qt::AspectRatioMode=Qt::IgnoreAspectRatio) const
	Convert the graphic to a QImage. More...

QRectF	scaledBoundingRect (double sx, double sy) const
	Calculate the target rectangle for scaling the graphic. More...

QRectF	boundingRect () const

QRectF	controlPointRect () const

const QVector< QwtPainterCommand > &	commands () const

void	setCommands (QVector< QwtPainterCommand > &)
	Append paint commands. More...

void	setDefaultSize (const QSizeF &)
	Set a default size. More...

QSizeF	defaultSize () const
	Default size. More...

void	setRenderHint (RenderHint, bool on=true)

bool	testRenderHint (RenderHint) const

Public Member Functions inherited from QwtNullPaintDevice
	QwtNullPaintDevice ()
	Constructor.

virtual	~QwtNullPaintDevice ()
	Destructor.

void	setMode (Mode)

Mode	mode () const

virtual QPaintEngine *	paintEngine () const
	See QPaintDevice::paintEngine()

virtual int	metric (PaintDeviceMetric) const

virtual void	drawRects (const QRect *, int)
	See QPaintEngine::drawRects()

virtual void	drawRects (const QRectF *, int)
	See QPaintEngine::drawRects()

virtual void	drawLines (const QLine *, int)
	See QPaintEngine::drawLines()

virtual void	drawLines (const QLineF *, int)
	See QPaintEngine::drawLines()

virtual void	drawEllipse (const QRectF &)
	See QPaintEngine::drawEllipse()

virtual void	drawEllipse (const QRect &)
	See QPaintEngine::drawEllipse()

virtual void	drawPoints (const QPointF *, int)
	See QPaintEngine::drawPoints()

virtual void	drawPoints (const QPoint *, int)
	See QPaintEngine::drawPoints()

virtual void	drawPolygon (const QPointF *, int, QPaintEngine::PolygonDrawMode)
	See QPaintEngine::drawPolygon()

virtual void	drawPolygon (const QPoint *, int, QPaintEngine::PolygonDrawMode)
	See QPaintEngine::drawPolygon()

virtual void	drawTextItem (const QPointF &, const QTextItem &)
	See QPaintEngine::drawTextItem()

virtual void	drawTiledPixmap (const QRectF &, const QPixmap &, const QPointF &)
	See QPaintEngine::drawTiledPixmap()

Protected Member Functions
virtual QSize	sizeMetrics () const

virtual void	drawPath (const QPainterPath &)

virtual void	drawPixmap (const QRectF &, const QPixmap &, const QRectF &)
	Store a pixmap command in the command list. More...

virtual void	drawImage (const QRectF &, const QImage &, const QRectF &, Qt::ImageConversionFlags)
	Store a image command in the command list. More...

virtual void	updateState (const QPaintEngineState &state)
	Store a state command in the command list. More...

Detailed Description

A paint device for scalable graphics.

QwtGraphic is the representation of a graphic that is tailored for scalability. Like QPicture it will be initialized by QPainter operations and can be replayed later to any target paint device.

While the usual image representations QImage and QPixmap are not scalable Qt offers two paint devices, that might be candidates for representing a vector graphic:

QPicture
Unfortunately QPicture had been forgotten, when Qt4 introduced floating point based render engines. Its API is still on integers, what make it unusable for proper scaling.
QSvgRenderer/QSvgGenerator
Unfortunately QSvgRenderer hides to much information about its nodes in internal APIs, that are necessary for proper layout calculations. Also it is derived from QObject and can't be copied like QImage/QPixmap.

QwtGraphic maps all scalable drawing primitives to a QPainterPath and stores them together with the painter state changes ( pen, brush, transformation ... ) in a list of QwtPaintCommands. For being a complete QPaintDevice it also stores pixmaps or images, what is somehow against the idea of the class, because these objects can't be scaled without a loss in quality.

The main issue about scaling a QwtGraphic object are the pens used for drawing the outlines of the painter paths. While non cosmetic pens ( QPen::isCosmetic() ) are scaled with the same ratio as the path, cosmetic pens have a fixed width. A graphic might have paths with different pens - cosmetic and non-cosmetic.

QwtGraphic caches 2 different rectangles:

control point rectangle
The control point rectangle is the bounding rectangle of all control point rectangles of the painter paths, or the target rectangle of the pixmaps/images.
bounding rectangle
The bounding rectangle extends the control point rectangle by what is needed for rendering the outline with an unscaled pen.

Because the offset for drawing the outline depends on the shape of the painter path ( the peak of a triangle is different than the flat side ) scaling with a fixed aspect ratio always needs to be calculated from the control point rectangle.

See also: QwtPainterCommand

Member Typedef Documentation

◆ RenderHints

typedef QFlags<RenderHint> QwtGraphic::RenderHints

Render hints.

The default setting is to disable all hints

Member Enumeration Documentation

◆ RenderHint

enum QwtGraphic::RenderHint

Hint how to render a graphic

See also: setRenderHint(), testRenderHint()

Enumerator

RenderPensUnscaled

When rendering a QwtGraphic a specific scaling between the controlPointRect() and the coordinates of the target rectangle is set up internally in render().

When RenderPensUnscaled is set this specific scaling is applied for the control points only, but not for the pens. All other painter transformations ( set up by application code ) are supposed to work like usual.

See also: render();

Constructor & Destructor Documentation

◆ QwtGraphic() [1/2]

QwtGraphic::QwtGraphic ( )

Constructor.

Initializes a null graphic

See also: isNull()

◆ QwtGraphic() [2/2]

QwtGraphic::QwtGraphic ( const QwtGraphic & other )

Copy constructor.

Parameters

other Source

See also: operator=()

Member Function Documentation

◆ boundingRect()

QRectF QwtGraphic::boundingRect ( ) const

The bounding rectangle is the controlPointRect() extended by the areas needed for rendering the outlines with unscaled pens.

Returns: Bounding rectangle of the graphic

See also: controlPointRect(), scaledBoundingRect()

◆ commands()

const QVector< QwtPainterCommand > & QwtGraphic::commands ( ) const

Returns: List of recorded paint commands

See also: setCommands()

◆ controlPointRect()

QRectF QwtGraphic::controlPointRect ( ) const

The control point rectangle is the bounding rectangle of all control points of the paths and the target rectangles of the images/pixmaps.

Returns: Control point rectangle

See also: boundingRect(), scaledBoundingRect()

◆ defaultSize()

QSizeF QwtGraphic::defaultSize ( ) const

Default size.

When a non empty size has been assigned by setDefaultSize() this size will be returned. Otherwise the default size is the size of the bounding rectangle.

The default size is used in all methods rendering the graphic, where no size is explicitly specified.

Returns: Default size

See also: setDefaultSize(), boundingRect()

◆ drawImage()

void QwtGraphic::drawImage	(	const QRectF &	rect,
		const QImage &	image,
		const QRectF &	subRect,
		Qt::ImageConversionFlags	flags
	)

protectedvirtual

Store a image command in the command list.

Parameters

rect	traget rectangle
image	Image to be painted
subRect	Reactangle of the pixmap to be painted
flags	Image conversion flags

See also: QPaintEngine::drawImage()

Reimplemented from QwtNullPaintDevice.

◆ drawPath()

void QwtGraphic::drawPath ( const QPainterPath & path )

protectedvirtual

Store a path command in the command list

Parameters

path	Painter path

See also: QPaintEngine::drawPath()

Reimplemented from QwtNullPaintDevice.

◆ drawPixmap()

void QwtGraphic::drawPixmap	(	const QRectF &	rect,
		const QPixmap &	pixmap,
		const QRectF &	subRect
	)

protectedvirtual

Store a pixmap command in the command list.

Parameters

rect	target rectangle
pixmap	Pixmap to be painted
subRect	Reactangle of the pixmap to be painted

See also: QPaintEngine::drawPixmap()

Reimplemented from QwtNullPaintDevice.

◆ isEmpty()

bool QwtGraphic::isEmpty ( ) const

Returns: True, when the bounding rectangle is empty

See also: boundingRect(), isNull()

◆ isNull()

bool QwtGraphic::isNull ( ) const

Returns: True, when no painter commands have been stored

See also: isEmpty(), commands()

◆ operator=()

QwtGraphic & QwtGraphic::operator= ( const QwtGraphic & other )

Assignment operator.

Parameters

other Source

Returns: A reference of this object

◆ render() [1/4]

void QwtGraphic::render ( QPainter * painter ) const

Replay all recorded painter commands.

Parameters

painter Qt painter

◆ render() [2/4]

void QwtGraphic::render	(	QPainter *	painter,
		const QPointF &	pos,
		Qt::Alignment	alignment = `Qt::AlignTop \| Qt::AlignLeft`
	)		const

Replay all recorded painter commands.

The graphic is scaled to the defaultSize() and aligned to a position.

Parameters

painter	Qt painter
pos	Reference point, where to render
alignment	Flags how to align the target rectangle to pos.

◆ render() [3/4]

void QwtGraphic::render	(	QPainter *	painter,
		const QRectF &	rect,
		Qt::AspectRatioMode	aspectRatioMode = `Qt::IgnoreAspectRatio`
	)		const

Replay all recorded painter commands.

The graphic is scaled to fit into the given rectangle

Parameters

painter	Qt painter
rect	Rectangle for the scaled graphic
aspectRatioMode	Mode how to scale - See Qt::AspectRatioMode

◆ render() [4/4]

void QwtGraphic::render	(	QPainter *	painter,
		const QSizeF &	size,
		Qt::AspectRatioMode	aspectRatioMode = `Qt::IgnoreAspectRatio`
	)		const

Replay all recorded painter commands.

The graphic is scaled to fit into the rectangle of the given size starting at ( 0, 0 ).

Parameters

painter	Qt painter
size	Size for the scaled graphic
aspectRatioMode	Mode how to scale - See Qt::AspectRatioMode

◆ reset()

void QwtGraphic::reset ( )

Clear all stored commands.

See also: isNull()

◆ scaledBoundingRect()

QRectF QwtGraphic::scaledBoundingRect	(	double	sx,
		double	sy
	)		const

Calculate the target rectangle for scaling the graphic.

Parameters

sx	Horizontal scaling factor
sy	Vertical scaling factor

Note: In case of paths that are painted with a cosmetic pen ( see QPen::isCosmetic() ) the target rectangle is different to multiplying the bounding rectangle.

Returns: Scaled bounding rectangle

See also: boundingRect(), controlPointRect()

◆ setCommands()

void QwtGraphic::setCommands ( QVector< QwtPainterCommand > & commands )

Append paint commands.

Parameters

commands Paint commands

See also: commands()

◆ setDefaultSize()

void QwtGraphic::setDefaultSize ( const QSizeF & size )

Set a default size.

The default size is used in all methods rendering the graphic, where no size is explicitly specified. Assigning an empty size means, that the default size will be calculated from the bounding rectangle.

The default setting is an empty size.

Parameters

size	Default size

See also: defaultSize(), boundingRect()

◆ setRenderHint()

void QwtGraphic::setRenderHint	(	RenderHint	hint,
		bool	on = `true`
	)

Toggle an render hint

Parameters

hint	Render hint
on	true/false

See also: testRenderHint(), RenderHint

◆ sizeMetrics()

QSize QwtGraphic::sizeMetrics ( ) const

protectedvirtual

Returns: Ceiled defaultSize()

Implements QwtNullPaintDevice.

◆ testRenderHint()

bool QwtGraphic::testRenderHint ( RenderHint hint ) const

Test a render hint

Parameters

hint	Render hint

Returns: true/false

See also: setRenderHint(), RenderHint

◆ toImage() [1/2]

QImage QwtGraphic::toImage ( ) const

Convert the graphic to a QImage.

All pixels of the image get initialized by 0 ( transparent ) before the graphic is scaled and rendered on it.

The format of the image is QImage::Format_ARGB32_Premultiplied.

The size of the image is the default size ( ceiled to integers ) of the graphic.

Returns: The graphic as image in default size

See also: defaultSize(), toPixmap(), render()

◆ toImage() [2/2]

QImage QwtGraphic::toImage	(	const QSize &	size,
		Qt::AspectRatioMode	aspectRatioMode = `Qt::IgnoreAspectRatio`
	)		const

Convert the graphic to a QImage.

All pixels of the image get initialized by 0 ( transparent ) before the graphic is scaled and rendered on it.

The format of the image is QImage::Format_ARGB32_Premultiplied.

Parameters

size	Size of the image
aspectRatioMode	Aspect ratio how to scale the graphic

Returns: The graphic as image

See also: toPixmap(), render()

◆ toPixmap() [1/2]

QPixmap QwtGraphic::toPixmap ( ) const

Convert the graphic to a QPixmap.

All pixels of the pixmap get initialized by Qt::transparent before the graphic is scaled and rendered on it.

The size of the pixmap is the default size ( ceiled to integers ) of the graphic.

Returns: The graphic as pixmap in default size

See also: defaultSize(), toImage(), render()

◆ toPixmap() [2/2]

QPixmap QwtGraphic::toPixmap	(	const QSize &	size,
		Qt::AspectRatioMode	aspectRatioMode = `Qt::IgnoreAspectRatio`
	)		const

Convert the graphic to a QPixmap.

All pixels of the pixmap get initialized by Qt::transparent before the graphic is scaled and rendered on it.

Parameters

size	Size of the image
aspectRatioMode	Aspect ratio how to scale the graphic

Returns: The graphic as pixmap

See also: toImage(), render()

◆ updateState()

void QwtGraphic::updateState ( const QPaintEngineState & state )

protectedvirtual

Store a state command in the command list.

Parameters

state State to be stored

See also: QPaintEngine::updateState()

Reimplemented from QwtNullPaintDevice.

Public Types

Public Member Functions

Protected Member Functions

Detailed Description

Member Typedef Documentation

◆ RenderHints

Member Enumeration Documentation

◆ RenderHint

Constructor & Destructor Documentation

◆ QwtGraphic() [1/2]

◆ QwtGraphic() [2/2]

Member Function Documentation

◆ boundingRect()

◆ commands()

◆ controlPointRect()

◆ defaultSize()

◆ drawImage()

◆ drawPath()

◆ drawPixmap()

◆ isEmpty()

◆ isNull()

◆ operator=()

◆ render() [1/4]

◆ render() [2/4]

◆ render() [3/4]

◆ render() [4/4]

◆ reset()

◆ scaledBoundingRect()

◆ setCommands()

◆ setDefaultSize()

◆ setRenderHint()

◆ sizeMetrics()

◆ testRenderHint()

◆ toImage() [1/2]

◆ toImage() [2/2]

◆ toPixmap() [1/2]

◆ toPixmap() [2/2]

◆ updateState()