QSvgRenderer Class

The QSvgRenderer class is used to draw the contents of SVG files onto paint devices. More...

Header: #include <QSvgRenderer>
CMake: find_package(Qt6 REQUIRED COMPONENTS Svg)
target_link_libraries(mytarget PRIVATE Qt6::Svg)
qmake: QT += svg
Inherits: QObject

Note: All functions in this class are reentrant.

Properties

Public Functions

QSvgRenderer(QObject *parent = nullptr)
QSvgRenderer(const QString &filename, QObject *parent = nullptr)
QSvgRenderer(const QByteArray &contents, QObject *parent = nullptr)
QSvgRenderer(QXmlStreamReader *contents, QObject *parent = nullptr)
virtual ~QSvgRenderer()
bool animated() const
Qt::AspectRatioMode aspectRatioMode() const
QRectF boundsOnElement(const QString &id) const
QSize defaultSize() const
bool elementExists(const QString &id) const
int framesPerSecond() const
bool isValid() const
void setAspectRatioMode(Qt::AspectRatioMode mode)
void setFramesPerSecond(int num)
void setViewBox(const QRect &viewbox)
void setViewBox(const QRectF &viewbox)
QTransform transformForElement(const QString &id) const
QRect viewBox() const
QRectF viewBoxF() const

Public Slots

bool load(const QString &filename)
bool load(const QByteArray &contents)
bool load(QXmlStreamReader *contents)
void render(QPainter *painter)
void render(QPainter *painter, const QRectF &bounds)
void render(QPainter *painter, const QString &elementId, const QRectF &bounds = QRectF())

Signals

void repaintNeeded()

Detailed Description

Using QSvgRenderer, Scalable Vector Graphics (SVG) can be rendered onto any QPaintDevice subclass, including QWidget, QImage, and QGLWidget.

QSvgRenderer provides an API that supports basic features of SVG rendering, such as loading and rendering of static drawings, and more interactive features like animation. Since the rendering is performed using QPainter, SVG drawings can be rendered on any subclass of QPaintDevice.

SVG drawings are either loaded when an QSvgRenderer is constructed, or loaded later using the load() functions. Data is either supplied directly as serialized XML, or indirectly using a file name. If a valid file has been loaded, either when the renderer is constructed or at some later time, isValid() returns true; otherwise it returns false. QSvgRenderer provides the render() slot to render the current document, or the current frame of an animated document, using a given painter.

The defaultSize() function provides information about the amount of space that is required to render the currently loaded SVG file. This is useful for paint devices, such as QWidget, that often need to supply a size hint to their parent layout. The default size of a drawing may differ from its visible area, found using the viewBox property.

Animated SVG drawings are supported, and can be controlled with a simple collection of functions and properties:

  • The animated() function indicates whether a drawing contains animation information.
  • The framesPerSecond property contains the rate at which the animation plays.

Finally, the QSvgRenderer class provides the repaintNeeded() signal which is emitted whenever the rendering of the document needs to be updated.

See also QSvgWidget, Qt SVG C++ Classes, SVG Viewer Example, and QPicture.

Property Documentation

aspectRatioMode : Qt::AspectRatioMode

how rendering adheres to the SVG view box aspect ratio

The accepted modes are:

  • Qt::IgnoreAspectRatio (the default): the aspect ratio is ignored and the rendering is stretched to the target bounds.
  • Qt::KeepAspectRatio: rendering is centered and scaled as large as possible within the target bounds while preserving aspect ratio.

Access functions:

Qt::AspectRatioMode aspectRatioMode() const
void setAspectRatioMode(Qt::AspectRatioMode mode)

framesPerSecond : int

This property holds the number of frames per second to be shown

The number of frames per second is 0 if the current document is not animated.

Access functions:

int framesPerSecond() const
void setFramesPerSecond(int num)

See also animated().

viewBox : QRectF

This property holds the rectangle specifying the visible area of the document in logical coordinates

Access functions:

QRectF viewBoxF() const
void setViewBox(const QRect &viewbox)
void setViewBox(const QRectF &viewbox)

Member Function Documentation

QSvgRenderer::QSvgRenderer(QObject *parent = nullptr)

Constructs a new renderer with the given parent.

QSvgRenderer::QSvgRenderer(const QString &filename, QObject *parent = nullptr)

Constructs a new renderer with the given parent and loads the contents of the SVG file with the specified filename.

QSvgRenderer::QSvgRenderer(const QByteArray &contents, QObject *parent = nullptr)

Constructs a new renderer with the given parent and loads the SVG data from the byte array specified by contents.

QSvgRenderer::QSvgRenderer(QXmlStreamReader *contents, QObject *parent = nullptr)

Constructs a new renderer with the given parent and loads the SVG data using the stream reader specified by contents.

[virtual] QSvgRenderer::~QSvgRenderer()

Destroys the renderer.

bool QSvgRenderer::animated() const

Returns true if the current document contains animated elements; otherwise returns false.

See also framesPerSecond().

QRectF QSvgRenderer::boundsOnElement(const QString &id) const

Returns bounding rectangle of the item with the given id. The transformation matrix of parent elements is not affecting the bounds of the element.

See also transformForElement().

QSize QSvgRenderer::defaultSize() const

Returns the default size of the document contents.

bool QSvgRenderer::elementExists(const QString &id) const

Returns true if the element with the given id exists in the currently parsed SVG file and is a renderable element.

Note: this method returns true only for elements that can be rendered. Which implies that elements that are considered part of the fill/stroke style properties, e.g. radialGradients even tough marked with "id" attributes will not be found by this method.

bool QSvgRenderer::isValid() const

Returns true if there is a valid current document; otherwise returns false.

[slot] bool QSvgRenderer::load(const QString &filename)

Loads the SVG file specified by filename, returning true if the content was successfully parsed; otherwise returns false.

[slot] bool QSvgRenderer::load(const QByteArray &contents)

Loads the specified SVG format contents, returning true if the content was successfully parsed; otherwise returns false.

[slot] bool QSvgRenderer::load(QXmlStreamReader *contents)

Loads the specified SVG in contents, returning true if the content was successfully parsed; otherwise returns false.

The reader will be used from where it currently is positioned. If contents is null, behavior is undefined.

[slot] void QSvgRenderer::render(QPainter *painter)

Renders the current document, or the current frame of an animated document, using the given painter.

[slot] void QSvgRenderer::render(QPainter *painter, const QRectF &bounds)

Renders the current document, or the current frame of an animated document, using the given painter on the specified bounds within the painter. If bounds is not empty, the output will be scaled to fill it, ignoring any aspect ratio implied by the SVG.

[slot] void QSvgRenderer::render(QPainter *painter, const QString &elementId, const QRectF &bounds = QRectF())

Renders the given element with elementId using the given painter on the specified bounds. If the bounding rectangle is not specified the SVG element is mapped to the whole paint device.

[signal] void QSvgRenderer::repaintNeeded()

This signal is emitted whenever the rendering of the document needs to be updated, usually for the purposes of animation.

QTransform QSvgRenderer::transformForElement(const QString &id) const

Returns the transformation matrix for the element with the given id. The matrix is a product of the transformation of the element's parents. The transformation of the element itself is not included.

To find the bounding rectangle of the element in logical coordinates, you can apply the matrix on the rectangle returned from boundsOnElement().

See also boundsOnElement().

QRect QSvgRenderer::viewBox() const

Returns viewBoxF().toRect().

See also setViewBox() and viewBoxF().

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