A paint device for scalable graphics. More...

#include <qwt_graphic.h>

Inheritance diagram for QwtGraphic:

Public Types
enum	RenderHint { RenderPensUnscaled = 0x1 }

enum	CommandType { VectorData = 1 << 0 , RasterData = 1 << 1 , Transformation = 1 << 2 }

typedef QFlags< RenderHint >	RenderHints

typedef QFlags< CommandType >	CommandTypes

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

Public Member Functions
	QwtGraphic ()
	Constructor.

	QwtGraphic (const QwtGraphic &)
	Copy constructor.

virtual	~QwtGraphic ()
	Destructor.

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

void	reset ()
	Clear all stored commands.

bool	isNull () const

bool	isEmpty () const

CommandTypes	commandTypes () const

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

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

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

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

QPixmap	toPixmap (qreal devicePixelRatio=0.0) const
	Convert the graphic to a QPixmap.

QPixmap	toPixmap (const QSize &, Qt::AspectRatioMode=Qt::IgnoreAspectRatio, qreal devicePixelRatio=0.0) const
	Convert the graphic to a QPixmap.

QImage	toImage (qreal devicePixelRatio=0.0) const
	Convert the graphic to a QImage.

QImage	toImage (const QSize &, Qt::AspectRatioMode=Qt::IgnoreAspectRatio, qreal devicePixelRatio=0.0) const
	Convert the graphic to a QImage.

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

QRectF	boundingRect () const

QRectF	controlPointRect () const

const QVector< QwtPainterCommand > &	commands () const

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

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

QSizeF	defaultSize () const
	Default size.

qreal	heightForWidth (qreal width) const

qreal	widthForHeight (qreal height) const

void	setRenderHint (RenderHint, bool on=true)

bool	testRenderHint (RenderHint) const

RenderHints	renderHints () const

Public Member Functions inherited from QwtNullPaintDevice
	QwtNullPaintDevice ()
	Constructor.

virtual	~QwtNullPaintDevice ()
	Destructor.

void	setMode (Mode)

Mode	mode () const

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

virtual int	metric (PaintDeviceMetric) const override

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 override

virtual void	drawPath (const QPainterPath &) override

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

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

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

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

Definition at line 75 of file qwt_graphic.h.

Member Typedef Documentation

◆ CommandTypes

typedef QFlags<CommandType > QwtGraphic::CommandTypes

An ORed combination of CommandType values.

Definition at line 117 of file qwt_graphic.h.

◆ RenderHints

typedef QFlags<RenderHint > QwtGraphic::RenderHints

An ORed combination of RenderHint values.

Definition at line 99 of file qwt_graphic.h.

Member Enumeration Documentation

◆ CommandType

enum QwtGraphic::CommandType

Indicator if the graphic contains a specific type of painter command

See also: CommandTypes, commandTypes();

Enumerator
VectorData	The graphic contains scalable vector data.
RasterData	The graphic contains raster data ( QPixmap or QImage )
Transformation	The graphic contains transformations beyond simple translations.

Definition at line 105 of file qwt_graphic.h.

◆ 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();

Definition at line 82 of file qwt_graphic.h.

Constructor & Destructor Documentation

◆ QwtGraphic() [1/2]

QwtGraphic::QwtGraphic ( )

Constructor.

Initializes a null graphic

See also: isNull()

Definition at line 355 of file qwt_graphic.cpp.

◆ QwtGraphic() [2/2]

QwtGraphic::QwtGraphic ( const QwtGraphic & other )

Copy constructor.

Parameters

other Source

See also: operator=()

Definition at line 367 of file qwt_graphic.cpp.

◆ ~QwtGraphic()

QwtGraphic::~QwtGraphic ( )

virtual

Destructor.

Definition at line 374 of file qwt_graphic.cpp.

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()

Definition at line 477 of file qwt_graphic.cpp.

◆ commands()

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

Returns: List of recorded paint commands

See also: setCommands()

Definition at line 1131 of file qwt_graphic.cpp.

◆ commandTypes()

QwtGraphic::CommandTypes QwtGraphic::commandTypes ( ) const

Returns: Types of painter commands being used

Definition at line 430 of file qwt_graphic.cpp.

◆ 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()

Definition at line 493 of file qwt_graphic.cpp.

◆ 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()

Definition at line 574 of file qwt_graphic.cpp.

◆ drawImage()

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

overrideprotectedvirtual

Store a image command in the command list.

Parameters

rect	target 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.

Definition at line 1059 of file qwt_graphic.cpp.

◆ drawPath()

void QwtGraphic::drawPath ( const QPainterPath & path )

overrideprotectedvirtual

Store a path command in the command list

Parameters

path	Painter path

See also: QPaintEngine::drawPath()

Reimplemented from QwtNullPaintDevice.

Definition at line 995 of file qwt_graphic.cpp.

◆ drawPixmap()

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

overrideprotectedvirtual

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.

Definition at line 1034 of file qwt_graphic.cpp.

◆ heightForWidth()

qreal QwtGraphic::heightForWidth ( qreal width ) const

Find the height for a given width

The height is calculated using the aspect ratio of defaultSize().

Parameters

width Width

Returns: Calculated height

See also: defaultSize()

Definition at line 592 of file qwt_graphic.cpp.

◆ isEmpty()

bool QwtGraphic::isEmpty ( ) const

Returns: True, when the bounding rectangle is empty

See also: boundingRect(), isNull()

Definition at line 422 of file qwt_graphic.cpp.

◆ isNull()

bool QwtGraphic::isNull ( ) const

Returns: True, when no painter commands have been stored

See also: isEmpty(), commands()

Definition at line 413 of file qwt_graphic.cpp.

◆ operator=()

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

Assignment operator.

Parameters

other Source

Returns: A reference of this object

Definition at line 385 of file qwt_graphic.cpp.

◆ render() [1/4]

void QwtGraphic::render ( QPainter * painter ) const

Replay all recorded painter commands.

Parameters

painter Qt painter

Definition at line 624 of file qwt_graphic.cpp.

◆ 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.

Definition at line 762 of file qwt_graphic.cpp.

◆ 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

Definition at line 676 of file qwt_graphic.cpp.

◆ 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

Definition at line 660 of file qwt_graphic.cpp.

◆ renderHints()

QwtGraphic::RenderHints QwtGraphic::renderHints ( ) const

Returns: Render hints

Definition at line 464 of file qwt_graphic.cpp.

◆ reset()

void QwtGraphic::reset ( )

Clear all stored commands.

See also: isNull()

Definition at line 397 of file qwt_graphic.cpp.

◆ scaledBoundingRect()

QRectF QwtGraphic::scaledBoundingRect	(	qreal	sx,
		qreal	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()

Definition at line 514 of file qwt_graphic.cpp.

◆ setCommands()

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

Append paint commands.

Parameters

commands Paint commands

See also: commands()

Definition at line 1142 of file qwt_graphic.cpp.

◆ 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()

Definition at line 553 of file qwt_graphic.cpp.

◆ setRenderHint()

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

Toggle an render hint

Parameters

hint	Render hint
on	true/false

See also: testRenderHint(), RenderHint

Definition at line 443 of file qwt_graphic.cpp.

◆ sizeMetrics()

QSize QwtGraphic::sizeMetrics ( ) const

overrideprotectedvirtual

Returns: Ceiled defaultSize()

Implements QwtNullPaintDevice.

Definition at line 533 of file qwt_graphic.cpp.

◆ testRenderHint()

bool QwtGraphic::testRenderHint ( RenderHint hint ) const

Test a render hint

Parameters

hint	Render hint

Returns: true/false

See also: setRenderHint(), RenderHint

Definition at line 458 of file qwt_graphic.cpp.

◆ toImage() [1/2]

QImage QwtGraphic::toImage	(	const QSize &	size,
		Qt::AspectRatioMode	aspectRatioMode = Qt::IgnoreAspectRatio,
		qreal	devicePixelRatio = 0.0 ) 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 ( will be multiplied by the devicePixelRatio )
aspectRatioMode	Aspect ratio how to scale the graphic
devicePixelRatio	Device pixel ratio for the image. If devicePixelRatio <= 0.0 the pixmap is initialized with the system default.

Returns: The graphic as image

See also: toPixmap(), render()

Definition at line 907 of file qwt_graphic.cpp.

◆ toImage() [2/2]

QImage QwtGraphic::toImage ( qreal devicePixelRatio = 0.0 ) 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 multiplied by the devicePixelRatio.

Parameters

devicePixelRatio Device pixel ratio for the image. If devicePixelRatio <= 0.0 the pixmap is initialized with the system default.

Returns: The graphic as image in default size

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

Definition at line 953 of file qwt_graphic.cpp.

◆ toPixmap() [1/2]

QPixmap QwtGraphic::toPixmap	(	const QSize &	size,
		Qt::AspectRatioMode	aspectRatioMode = Qt::IgnoreAspectRatio,
		qreal	devicePixelRatio = 0.0 ) 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
devicePixelRatio	Device pixel ratio for the pixmap. If devicePixelRatio <= 0.0 the pixmap is initialized with the system default.

Returns: The graphic as pixmap

See also: toImage(), render()

Definition at line 863 of file qwt_graphic.cpp.

◆ toPixmap() [2/2]

QPixmap QwtGraphic::toPixmap ( qreal devicePixelRatio = 0.0 ) 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.

Parameters

devicePixelRatio Device pixel ratio for the pixmap. If devicePixelRatio <= 0.0 the pixmap is initialized with the system default.

Returns: The graphic as pixmap in default size

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

Definition at line 812 of file qwt_graphic.cpp.

◆ updateState()

void QwtGraphic::updateState ( const QPaintEngineState & state )

overrideprotectedvirtual

Store a state command in the command list.

Parameters

state State to be stored

See also: QPaintEngine::updateState()

Reimplemented from QwtNullPaintDevice.

Definition at line 1081 of file qwt_graphic.cpp.

◆ widthForHeight()

qreal QwtGraphic::widthForHeight ( qreal height ) const

Find the width for a given height

The width is calculated using the aspect ratio of defaultSize().

Parameters

height Height

Returns: Calculated width

See also: defaultSize()

Definition at line 611 of file qwt_graphic.cpp.

Public Types

Public Member Functions

Protected Member Functions

Detailed Description

Member Typedef Documentation

◆ CommandTypes

◆ RenderHints

Member Enumeration Documentation

◆ CommandType

◆ RenderHint

Constructor & Destructor Documentation

◆ QwtGraphic() [1/2]

◆ QwtGraphic() [2/2]

◆ ~QwtGraphic()

Member Function Documentation

◆ boundingRect()

◆ commands()

◆ commandTypes()

◆ controlPointRect()

◆ defaultSize()

◆ drawImage()

◆ drawPath()

◆ drawPixmap()

◆ heightForWidth()

◆ isEmpty()

◆ isNull()

◆ operator=()

◆ render() [1/4]

◆ render() [2/4]

◆ render() [3/4]

◆ render() [4/4]

◆ renderHints()

◆ reset()

◆ scaledBoundingRect()

◆ setCommands()

◆ setDefaultSize()

◆ setRenderHint()

◆ sizeMetrics()

◆ testRenderHint()

◆ toImage() [1/2]

◆ toImage() [2/2]

◆ toPixmap() [1/2]

◆ toPixmap() [2/2]

◆ updateState()

◆ widthForHeight()