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

#include <Wt/WCanvasPaintDevice>

Inheritance diagram for Wt::WCanvasPaintDevice:

Public Member Functions
	WCanvasPaintDevice (const WLength &width, const WLength &height, WObject *parent=0, bool paintUpdate=false)
	Create a canvas paint device.

virtual WFlags< FeatureFlag >	features () const
	Returns device features.

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

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

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

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

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

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

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

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

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

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

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

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

Public Member Functions inherited from Wt::WObject
	WObject (WObject *parent=0)
	Create a WObject with a given parent object. More...

virtual	~WObject ()
	Destructor. 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...

void	addChild (WObject *child)
	Adds a child object. More...

virtual void	removeChild (WObject *child)
	Removes a child object. More...

const std::vector< WObject * > &	children () const
	Returns the children.

WObject *	parent () const
	Returns the parent object.

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

virtual void	setChanged (WFlags< ChangeFlag > flags)=0
	Indicates changes in painter state. More...

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

virtual void	setPainter (WPainter *painter)
	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
Static Protected Member Functions inherited from Wt::WObject
static WObject *	sender ()
	Returns the sender of the current slot call. More...

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

void Wt::WCanvasPaintDevice::done ( )

virtual

Finishes painting on the device.

This method is called when a WPainter stopped painting.

See also: WPainter::end()

Implements Wt::WPaintDevice.

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

virtual

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.

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

virtual

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.

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

virtual

Draws a line.

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

Implements Wt::WPaintDevice.

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

virtual

Draws a path.

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

Implements Wt::WPaintDevice.

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

virtual

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.

WFontMetrics Wt::WCanvasPaintDevice::fontMetrics ( )

virtual

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.

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

virtual

Returns the device height.

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

Implements Wt::WPaintDevice.

void Wt::WCanvasPaintDevice::init ( )

virtual

Initializes the device for painting.

This method is called when a WPainter starts painting.

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

Implements Wt::WPaintDevice.

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

virtual

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.

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

virtual

Returns whether painting is active.