Wt  3.2.1
Public Member Functions | Protected Member Functions
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]

List of all members.

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 setChanged (WFlags< ChangeFlag > flags)
 Indicates changes in painter state.
virtual void drawArc (const WRectF &rect, double startAngle, double spanAngle)
 Draws an arc.
virtual void drawImage (const WRectF &rect, const std::string &imgUri, int imgWidth, int imgHeight, const WRectF &sourceRect)
 Draws an image.
virtual void drawLine (double x1, double y1, double x2, double y2)
 Draws a line.
virtual void drawPath (const WPainterPath &path)
 Draws a path.
virtual void drawText (const WRectF &rect, WFlags< AlignmentFlag > alignmentFlags, TextFlag textFlag, const WString &text)
 Draws text.
virtual WTextItem measureText (const WString &text, double maxWidth=-1, bool wordWrap=false)
 Measures rendered text size.
virtual WFontMetrics fontMetrics ()
 Returns font metrics.
virtual void init ()
 Initializes the device for painting.
virtual void done ()
 Finishes painting on the device.
virtual bool paintActive () const
 Returns whether painting is active.
virtual WLength width () const
 Returns the device width.
virtual WLength height () const
 Returns the device height.

Protected Member Functions

virtual WPainterpainter () const
 Returns the painter that is currently painting on the device.
virtual void setPainter (WPainter *painter)
 Sets the painter.

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 is defined as in WPainter::drawArc(const WRectF& rectangle, int startAngle, int spanAngle)

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 
) [virtual]

Draws text.

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

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 [protected, virtual]

Returns the painter that is currently painting on the device.

See also:
init()

Implements Wt::WPaintDevice.

void Wt::WCanvasPaintDevice::setChanged ( WFlags< ChangeFlag flags) [virtual]

Indicates changes in painter state.

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

See also:
ChangeFlag

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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