A paint device for scalable graphics. More...

#include <qwt_graphic.h>

Inheritance diagram for QwtGraphic:

Classes
class	PathInfo

class	PrivateData

Public Types
enum	RenderHint { RenderPensUnscaled = 0x1 }
	Hint how to render a graphic. More...

enum	CommandType { VectorData = 1 << 0 , RasterData = 1 << 1 , Transformation = 1 << 2 }
	Indicator if the graphic contains a specific type of painter command. More...

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

Public Member Functions
	QwtGraphic ()
	Constructor.

	QwtGraphic (const QwtGraphic &)

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

void	reset ()
	Clear all stored commands.

bool	isNull () const
	Check if the graphic is null.

bool	isEmpty () const
	Check if the graphic is empty.

CommandTypes	commandTypes () const
	Get the types of painter commands being used.

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

void	render (QPainter *, const QSizeF &, Qt::AspectRatioMode=Qt::IgnoreAspectRatio) const
	Replay all recorded painter commands scaled to fit into given size.

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

void	render (QPainter *, const QRectF &, Qt::AspectRatioMode=Qt::IgnoreAspectRatio) const
	Replay all recorded painter commands scaled to fit into given rectangle.

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

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

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

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

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

QRectF	boundingRect () const
	Get the bounding rectangle.

QRectF	controlPointRect () const
	Get the control point rectangle.

const QVector< QwtPainterCommand > &	commands () const
	Get the list of recorded paint commands.

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

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

QSizeF	defaultSize () const
	Get the default size.

qreal	heightForWidth (qreal width) const
	Find the height for a given width.

qreal	widthForHeight (qreal height) const
	Find the width for a given height.

void	setRenderHint (RenderHint, bool on=true)
	Toggle a render hint.

bool	testRenderHint (RenderHint) const
	Test a render hint.

RenderHints	renderHints () const
	Get the render hints.

Public Member Functions inherited from QwtNullPaintDevice
	QwtNullPaintDevice ()
	Constructor.

	~QwtNullPaintDevice () override
	Destructor.

void	setMode (Mode)
	Set the render mode.

Mode	mode () const
	Get the render mode.

virtual QPaintEngine *	paintEngine () const override
	Return the paint engine.

virtual int	metric (PaintDeviceMetric) const override
	Return metric information for the paint device.

virtual void	drawRects (const QRect *, int)
	Draw rectangles (integer version)

virtual void	drawRects (const QRectF *, int)
	Draw rectangles (floating point version)

virtual void	drawLines (const QLine *, int)
	Draw lines (integer version)

virtual void	drawLines (const QLineF *, int)
	Draw lines (floating point version)

virtual void	drawEllipse (const QRectF &)
	Draw ellipse (floating point version)

virtual void	drawEllipse (const QRect &)
	Draw ellipse (integer version)

virtual void	drawPoints (const QPointF *, int)
	Draw points (floating point version)

virtual void	drawPoints (const QPoint *, int)
	Draw points (integer version)

virtual void	drawPolygon (const QPointF *, int, QPaintEngine::PolygonDrawMode)
	Draw polygon (floating point version)

virtual void	drawPolygon (const QPoint *, int, QPaintEngine::PolygonDrawMode)
	Draw polygon (integer version)

virtual void	drawTextItem (const QPointF &, const QTextItem &)
	Draw a text item.

virtual void	drawTiledPixmap (const QRectF &, const QPixmap &, const QPointF &)
	Draw a tiled pixmap.

Protected Member Functions
virtual QSize	sizeMetrics () const override

virtual void	drawPath (const QPainterPath &) override
	Store a path command in the command list.

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 too 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.

Member Enumeration Documentation

◆ CommandType

enum QwtGraphic::CommandType

Indicator if the graphic contains a specific type of painter command.

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.

◆ RenderHint

enum QwtGraphic::RenderHint

Hint how to render a graphic.

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.

Constructor & Destructor Documentation

◆ QwtGraphic()

QwtGraphic::QwtGraphic ( )

Constructor.

Initializes a null graphic.

Copy constructor

Parameters

[in] other Source graphic to copy from

Destructor

Deletes private data.

Member Function Documentation

◆ boundingRect()

QRectF QwtGraphic::boundingRect ( ) const

Get the bounding rectangle.

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

Returns: Bounding rectangle of the graphic

◆ commands()

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

Get the list of recorded paint commands.

Returns: List of recorded paint commands

◆ commandTypes()

QwtGraphic::CommandTypes QwtGraphic::commandTypes ( ) const

Get the types of painter commands being used.

Returns: Types of painter commands

◆ controlPointRect()

QRectF QwtGraphic::controlPointRect ( ) const

Get the control point rectangle.

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

◆ defaultSize()

QSizeF QwtGraphic::defaultSize ( ) const

Get the 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

◆ 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.

◆ 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.

◆ 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.

◆ 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

[in] width Width to calculate height for

Returns: Calculated height

◆ isEmpty()

bool QwtGraphic::isEmpty ( ) const

Check if the graphic is empty.

Returns: True when the bounding rectangle is empty

◆ isNull()

bool QwtGraphic::isNull ( ) const

Check if the graphic is null.

Returns: True when no painter commands have been stored

◆ operator=()

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

Assignment operator.

Parameters

[in] other Source graphic to assign from

Returns: Reference to this object

◆ render() [1/4]

void QwtGraphic::render ( QPainter * painter ) const

Replay all recorded painter commands.

Parameters

[in] 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 aligned to a position.

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

Parameters

[in]	painter	Qt painter
[in]	pos	Reference point, where to render
[in]	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 scaled to fit into given rectangle.

Parameters

[in]	painter	Qt painter
[in]	rect	Rectangle for the scaled graphic
[in]	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 scaled to fit into given size.

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

Parameters

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

◆ renderHints()

QwtGraphic::RenderHints QwtGraphic::renderHints ( ) const

Get the render hints.

Returns: Render hints

◆ reset()

void QwtGraphic::reset ( )

Clear all stored commands.

Resets the graphic to its initial null state.

◆ scaledBoundingRect()

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

Calculate the target rectangle for scaling the graphic.

Parameters

[in]	sx	Horizontal scaling factor
[in]	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

◆ setCommands()

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

Append paint commands.

Parameters

[in] commands Paint commands to append

◆ 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

[in] size Default size

◆ setRenderHint()

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

Toggle a render hint.

Parameters

[in]	hint	Render hint to toggle
[in]	on	true to enable, false to disable

◆ sizeMetrics()

QSize QwtGraphic::sizeMetrics ( ) const

overrideprotectedvirtual

Returns: Ceiled defaultSize()

Implements QwtNullPaintDevice.

◆ testRenderHint()

bool QwtGraphic::testRenderHint ( RenderHint hint ) const

Test a render hint.

Parameters

[in] hint Render hint to test

Returns: true if the hint is enabled, false otherwise

◆ 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 with specified size.

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

[in]	size	Size of the image ( will be multiplied by the devicePixelRatio )
[in]	aspectRatioMode	Aspect ratio how to scale the graphic
[in]	devicePixelRatio	Device pixel ratio for the image. If devicePixelRatio <= 0.0 the pixmap is initialized with the system default.

Returns: The graphic as image

◆ toImage() [2/2]

QImage QwtGraphic::toImage ( qreal devicePixelRatio = 0.0 ) const

Convert the graphic to a QImage in default size.

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

[in] 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

◆ 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 with specified size.

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

Parameters

[in]	size	Size of the image
[in]	aspectRatioMode	Aspect ratio how to scale the graphic
[in]	devicePixelRatio	Device pixel ratio for the pixmap. If devicePixelRatio <= 0.0 the pixmap is initialized with the system default.

Returns: The graphic as pixmap

◆ toPixmap() [2/2]

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

Convert the graphic to a QPixmap in default size.

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

[in] 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

◆ 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.

◆ 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

[in] height Height to calculate width for

Returns: Calculated width

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

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

Classes

Public Types

Public Member Functions

Protected Member Functions

Detailed Description

Member Enumeration Documentation

◆ CommandType

◆ RenderHint

Constructor & Destructor Documentation

◆ 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()