QwtGraphic(3) Qwt User's Guide QwtGraphic(3) NAME QwtGraphic - A paint device for scalable graphics. SYNOPSIS #include Inherits QwtNullPaintDevice. 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 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 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: o 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. o 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: o 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. o 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 typedef QFlags QwtGraphic::CommandTypes An ORed combination of CommandType values. Definition at line 117 of file qwt_graphic.h. typedef QFlags QwtGraphic::RenderHints An ORed combination of RenderHint values. Definition at line 99 of file qwt_graphic.h. Member Enumeration Documentation 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. 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::QwtGraphic () Constructor. Initializes a null graphic See also isNull() Definition at line 355 of file qwt_graphic.cpp. QwtGraphic::QwtGraphic (const QwtGraphic & other) Copy constructor. Parameters other Source See also operator=() Definition at line 367 of file qwt_graphic.cpp. Member Function Documentation 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. const QVector< QwtPainterCommand > & QwtGraphic::commands () const Returns List of recorded paint commands See also setCommands() Definition at line 1120 of file qwt_graphic.cpp. QwtGraphic::CommandTypes QwtGraphic::commandTypes () const Returns Types of painter commands being used Definition at line 430 of file qwt_graphic.cpp. 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. 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. void QwtGraphic::drawImage (const QRectF & rect, const QImage & image, const QRectF & subRect, Qt::ImageConversionFlags flags) [override], [protected], [virtual] 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 1048 of file qwt_graphic.cpp. void QwtGraphic::drawPath (const QPainterPath & path) [override], [protected], [virtual] Store a path command in the command list Parameters path Painter path See also QPaintEngine::drawPath() Reimplemented from QwtNullPaintDevice. Definition at line 984 of file qwt_graphic.cpp. void QwtGraphic::drawPixmap (const QRectF & rect, const QPixmap & pixmap, const QRectF & subRect) [override], [protected], [virtual] 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 1023 of file qwt_graphic.cpp. 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. 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. 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. 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. void QwtGraphic::render (QPainter * painter) const Replay all recorded painter commands. Parameters painter Qt painter Definition at line 624 of file qwt_graphic.cpp. 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. 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. 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. QwtGraphic::RenderHints QwtGraphic::renderHints () const Returns Render hints Definition at line 464 of file qwt_graphic.cpp. void QwtGraphic::reset () Clear all stored commands. See also isNull() Definition at line 397 of file qwt_graphic.cpp. 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. void QwtGraphic::setCommands (const QVector< QwtPainterCommand > & commands) Append paint commands. Parameters commands Paint commands See also commands() Definition at line 1131 of file qwt_graphic.cpp. 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. 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. QSize QwtGraphic::sizeMetrics () const [override], [protected], [virtual] Returns Ceiled defaultSize() Implements QwtNullPaintDevice. Definition at line 533 of file qwt_graphic.cpp. 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. 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 900 of file qwt_graphic.cpp. 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 943 of file qwt_graphic.cpp. 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 859 of file qwt_graphic.cpp. 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. void QwtGraphic::updateState (const QPaintEngineState & state) [override], [protected], [virtual] Store a state command in the command list. Parameters state State to be stored See also QPaintEngine::updateState() Reimplemented from QwtNullPaintDevice. Definition at line 1070 of file qwt_graphic.cpp. 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. Author Generated automatically by Doxygen for Qwt User's Guide from the source code. Version 6.2.0 Sun Jul 18 2021 QwtGraphic(3)