A paint device for rendering using the HTML 5 <canvas> element. More...

#include <Wt/WCanvasPaintDevice.h>

Inheritance diagram for Wt::WCanvasPaintDevice:

Public Member Functions
	WCanvasPaintDevice (const WLength &width, const WLength &height, bool paintUpdate=false)
	Create a canvas paint device.

virtual WFlags< PaintDeviceFeatureFlag >	features () const override
	Returns device features.

virtual void	setChanged (WFlags< PainterChangeFlag > flags) override
	Indicates changes in painter state. More...

virtual void	drawArc (const WRectF &rect, double startAngle, double spanAngle) override
	Draws an arc. More...

virtual void	drawImage (const WRectF &rect, const std::string &imgUri, int imgWidth, int imgHeight, const WRectF &sourceRect) override
	Draws an image. More...

virtual void	drawLine (double x1, double y1, double x2, double y2) override
	Draws a line. More...

virtual void	drawPath (const WPainterPath &path) override
	Draws a path. More...

virtual void	drawRect (const WRectF &rectangle) override
	Draws a rectangle. More...

virtual void	drawText (const WRectF &rect, WFlags< AlignmentFlag > alignmentFlags, TextFlag textFlag, const WString &text, const WPointF *clipPoint) override
	Draws text. More...

virtual WTextItem	measureText (const WString &text, double maxWidth=-1, bool wordWrap=false) override
	Measures rendered text size. More...

virtual WFontMetrics	fontMetrics () override
	Returns font metrics. More...

virtual void	init () override
	Initializes the device for painting. More...

virtual void	done () override
	Finishes painting on the device. More...

virtual bool	paintActive () const override
	Returns whether painting is active. More...

virtual WLength	width () const override
	Returns the device width. More...

virtual WLength	height () const override
	Returns the device height. More...

Public Member Functions inherited from Wt::WObject
void	addChild (std::unique_ptr< WObject > child)
	Add a child WObject whose lifetime is determined by this WObject.

template<typename Child >
Child *	addChild (std::unique_ptr< Child > child)
	Add a child WObject, returning a raw pointer. More...

std::unique_ptr< WObject >	removeChild (WObject *child)
	Remove a child WObject, so its lifetime is no longer determined by this WObject.

template<typename Child >
std::unique_ptr< Child >	removeChild (Child *child)
	Remove a child WObject, so its lifetime is no longer determined by this WObject. More...

virtual const std::string	id () const
	Returns the (unique) identifier for this object. More...

virtual void	setObjectName (const std::string &name)
	Sets an object name. More...

virtual std::string	objectName () const
	Returns the object name. More...

void	resetLearnedSlots ()
	Resets learned stateless slot implementations. More...

template<class T >
void	resetLearnedSlot (void(T::*method)())
	Resets a learned stateless slot implementation. More...

template<class T >
WStatelessSlot *	implementStateless (void(T::*method)())
	Declares a slot to be stateless and learn client-side behaviour on first invocation. More...

template<class T >
WStatelessSlot *	implementStateless (void(T::method)(), void(T::undoMethod)())
	Declares a slot to be stateless and learn client-side behaviour in advance. More...

void	isNotStateless ()
	Marks the current function as not stateless. More...

template<class T >
WStatelessSlot *	implementJavaScript (void(T::*method)(), const std::string &jsCode)
	Provides a JavaScript implementation for a method. More...

Public Member Functions inherited from Wt::Core::observable
	observable () noexcept
	Default constructor.

virtual	~observable ()
	Destructor. More...

template<typename... Args, typename C >
auto	bindSafe (void(C::*method)(Args...)) noexcept
	Protects a method call against object destruction. More...

template<typename... Args, typename C >
auto	bindSafe (void(C::*method)(Args...) const) const noexcept
	Protects a const method call against object destruction. More...

template<typename Function >
auto	bindSafe (const Function &function) noexcept
	Protects a function against object destruction. More...

Public Member Functions inherited from Wt::WPaintDevice
virtual	~WPaintDevice ()
	Destructor. More...

Protected Member Functions
virtual WPainter *	painter () const override
	Returns the painter that is currently painting on the device. More...

virtual void	setPainter (WPainter *painter) override
	Sets the painter.

Protected Member Functions inherited from Wt::WObject
virtual WStatelessSlot *	getStateless (Method method)
	On-demand stateless slot implementation. More...

Additional Inherited Members
Public Types inherited from Wt::WObject
typedef void(WObject::*	Method) ()
	Typedef for a WObject method without arguments.

Public Types inherited from Wt::WPaintDevice
typedef PaintDeviceFeatureFlag	FeatureFlag
	Typedef for enum Wt::PaintDeviceFeatureFlag.

Detailed Description

A paint device for rendering using the HTML 5 <canvas> element.

The WCanvasPaintDevice is used by WPaintedWidget to render to the browser using the HTML 5 <canvas> element. You usually will not use the device directly, but rather rely on WPaintedWidget to use this device when appropriate.

Note: Older browsers do not have text support in <canvas>. Text is then rendered in an overlayed DIV and a consequence text is not subject to rotation and scaling components of the current transformation (but does take into account translation). On most browser you can use the WSvgImage or WVmlImage paint devices which do support text natively.

Member Function Documentation

◆ done()

void Wt::WCanvasPaintDevice::done ( )

overridevirtual

Finishes painting on the device.

This method is called when a WPainter stopped painting.

See also: WPainter::end()

Implements Wt::WPaintDevice.

◆ drawArc()

void Wt::WCanvasPaintDevice::drawArc	(	const WRectF &	rect,
		double	startAngle,
		double	spanAngle
	)

overridevirtual

Draws an arc.

The arc describes the segment of an ellipse enclosed by the rect. The segment starts at startAngle, and spans an angle given by spanAngle. These angles have as unit degree, and are measured counter-clockwise starting from the 3 o'clock position.

The arc must be stroked, filled, and transformed using the current painter settings.

Implements Wt::WPaintDevice.

◆ drawImage()

void Wt::WCanvasPaintDevice::drawImage	(	const WRectF &	rect,
		const std::string &	imageUri,
		int	imgWidth,
		int	imgHeight,
		const WRectF &	sourceRect
	)

overridevirtual

Draws an image.

Draws sourceRect from the image with URL imageUri and original dimensions imgWidth and imgHeight to the location, into the rectangle defined by rect.

The image is transformed using the current painter settings.

Implements Wt::WPaintDevice.

◆ drawLine()

void Wt::WCanvasPaintDevice::drawLine	(	double	x1,
		double	y1,
		double	x2,
		double	y2
	)

overridevirtual

Draws a line.

The line must be stroked and transformed using the current painter settings.

Implements Wt::WPaintDevice.

◆ drawPath()

void Wt::WCanvasPaintDevice::drawPath ( const WPainterPath & path )

overridevirtual

Draws a path.

The path must be stroked, filled, and transformed using the current painter settings.

Implements Wt::WPaintDevice.

◆ drawRect()

void Wt::WCanvasPaintDevice::drawRect ( const WRectF & rectangle )

overridevirtual

Draws a rectangle.

The rect must be stroked, filled, and transformed using the current painter settings.

Implements Wt::WPaintDevice.

◆ drawText()

void Wt::WCanvasPaintDevice::drawText	(	const WRectF &	rect,
		WFlags< AlignmentFlag >	alignmentFlags,
		TextFlag	textFlag,
		const WString &	text,
		const WPointF *	clipPoint
	)

overridevirtual

Draws text.

The text must be rendered, stroked and transformed using the current painter settings.

If clipPoint is not null, a check is performed whether the point is inside of the current clip area. If not, the text is not drawn.

Implements Wt::WPaintDevice.

◆ fontMetrics()

WFontMetrics Wt::WCanvasPaintDevice::fontMetrics ( )

overridevirtual

Returns font metrics.

This returns font metrics for the current font.

Throws a std::logic_error if the underlying device does not provide font metrics.

Implements Wt::WPaintDevice.

◆ height()

virtual WLength Wt::WCanvasPaintDevice::height ( ) const

overridevirtual

Returns the device height.

The device height, in pixels, establishes the height of the device coordinate system.

Implements Wt::WPaintDevice.

◆ init()

void Wt::WCanvasPaintDevice::init ( )

overridevirtual

Initializes the device for painting.

This method is called when a WPainter starts painting.

See also: WPainter::begin(WPaintDevice *), painter()

Implements Wt::WPaintDevice.

◆ measureText()

WTextItem Wt::WCanvasPaintDevice::measureText	(	const WString &	text,
		double	maxWidth = `-1`,
		bool	wordWrap = `false`
	)

overridevirtual

Measures rendered text size.

Returns the bounding rect of the given text when rendered using the current font.

If maxWidth != -1, then the text is truncated to fit in the width.

If wordWrap = true then text is truncated only at word boundaries. Note that in this case the whitespace at the truncated position is included in the text but not accounted for by the returned width (since usually you will not render the whitespace at the end of a line).

Throws a std::logic_error if the underlying device does not provide font metrics.

Implements Wt::WPaintDevice.

◆ paintActive()

virtual bool Wt::WCanvasPaintDevice::paintActive ( ) const

overridevirtual

Returns whether painting is active.

See also: init(), painter()

Implements Wt::WPaintDevice.

◆ painter()

virtual WPainter* Wt::WCanvasPaintDevice::painter ( ) const

overrideprotectedvirtual

Returns the painter that is currently painting on the device.

See also: init()

Implements Wt::WPaintDevice.

◆ setChanged()

void Wt::WCanvasPaintDevice::setChanged ( WFlags< PainterChangeFlag > flags )

overridevirtual

Indicates changes in painter state.

The flags argument is the logical OR of one or more change flags.

See also: ChangeFlag

Implements Wt::WPaintDevice.

◆ width()

virtual WLength Wt::WCanvasPaintDevice::width ( ) const

overridevirtual

Returns the device width.

The device width, in pixels, establishes the width of the device coordinate system.

Implements Wt::WPaintDevice.

Public Member Functions

Protected Member Functions

Additional Inherited Members

Detailed Description

Member Function Documentation

◆ done()

◆ drawArc()

◆ drawImage()

◆ drawLine()

◆ drawPath()

◆ drawRect()

◆ drawText()

◆ fontMetrics()

◆ height()

◆ init()

◆ measureText()

◆ paintActive()

◆ painter()

◆ setChanged()

◆ width()