Wt  3.3.9
Public Member Functions | Protected Member Functions | List of all members
Wt::WCanvasPaintDevice Class Reference

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

#include <Wt/WCanvasPaintDevice>

Inheritance diagram for Wt::WCanvasPaintDevice:
Inheritance graph
[legend]

Public Member Functions

 WCanvasPaintDevice (const WLength &width, const WLength &height, WObject *parent=0, bool paintUpdate=false)
 Create a canvas paint device.
 
virtual WFlags< FeatureFlagfeatures () 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.
 
WObjectparent () 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 WPainterpainter () 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 WObjectsender ()
 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.

See also
init(), painter()

Implements Wt::WPaintDevice.

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

Returns the painter that is currently painting on the device.

See also
init()

Implements Wt::WPaintDevice.

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

Returns the device width.

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

Implements Wt::WPaintDevice.


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