Package eu.webtoolkit.jwt

Class WCanvasPaintDevice

  • All Implemented Interfaces:
    WPaintDevice
    public class WCanvasPaintDevice
extends WObject
implements WPaintDevice
    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.

    Note: To paint an image (WPainter#drawImage()), this requires its uri.

    See Also:
    WAbstractDataInfo

    • Constructor Detail

      • WCanvasPaintDevice

        public WCanvasPaintDevice​(WLength width,
                          WLength height,
                          boolean paintUpdate)
        Create a canvas paint device.

    • Method Detail

      • setChanged

        public void setChanged​(java.util.EnumSet<PainterChangeFlag> flags)
        Description copied from interface: WPaintDevice
        Indicates changes in painter state.

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

        Specified by:
        setChanged in interface WPaintDevice

      • drawArc

        public void drawArc​(WRectF rect,
                    double startAngle,
                    double spanAngle)
        Description copied from interface: WPaintDevice
        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.

        Specified by:
        drawArc in interface WPaintDevice

      • drawImage

        public void drawImage​(WRectF rect,
                      java.lang.String imageUri,
                      int imgWidth,
                      int imgHeight,
                      WRectF sourceRect)
        Description copied from interface: WPaintDevice
        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.

        Specified by:
        drawImage in interface WPaintDevice

      • drawImage

        public void drawImage​(WRectF rect,
                      WAbstractDataInfo info,
                      int imgWidth,
                      int imgHeight,
                      WRectF sourceRect)
        Description copied from interface: WPaintDevice
        Draws an image.

        Draws sourceRect from the image with the information contained in imageInfo and original dimensions imgWidth and imgHeight to the location, into the rectangle defined by rect.

        The image is transformed using the current painter settings.

        Specified by:
        drawImage in interface WPaintDevice

      • drawLine

        public void drawLine​(double x1,
                     double y1,
                     double x2,
                     double y2)
        Description copied from interface: WPaintDevice
        Draws a line.

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

        Specified by:
        drawLine in interface WPaintDevice

      • drawPath

        public void drawPath​(WPainterPath path)
        Description copied from interface: WPaintDevice
        Draws a path.

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

        Specified by:
        drawPath in interface WPaintDevice

      • drawStencilAlongPath

        public void drawStencilAlongPath​(WPainterPath stencil,
                                 WPainterPath path,
                                 boolean softClipping)

      • drawRect

        public void drawRect​(WRectF rectangle)
        Description copied from interface: WPaintDevice
        Draws a rectangle.

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

        Specified by:
        drawRect in interface WPaintDevice

      • drawText

        public void drawText​(WRectF rect,
                     java.util.EnumSet<AlignmentFlag> flags,
                     TextFlag textFlag,
                     java.lang.CharSequence text,
                     WPointF clipPoint)
        Description copied from interface: WPaintDevice
        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.

        Specified by:
        drawText in interface WPaintDevice

      • drawTextOnPath

        public void drawTextOnPath​(WRectF rect,
                           java.util.EnumSet<AlignmentFlag> alignmentFlags,
                           java.util.List<WString> text,
                           WTransform transform,
                           WPainterPath path,
                           double angle,
                           double lineHeight,
                           boolean softClipping)

      • measureText

        public WTextItem measureText​(java.lang.CharSequence text,
                             double maxWidth,
                             boolean wordWrap)
        Description copied from interface: WPaintDevice
        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.

        Specified by:
        measureText in interface WPaintDevice

      • getFontMetrics

        public WFontMetrics getFontMetrics()
        Description copied from interface: WPaintDevice
        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.

        Specified by:
        getFontMetrics in interface WPaintDevice

      • render

        public void render​(java.lang.String paintedWidgetJsRef,
                   java.lang.String canvasId,
                   DomElement text,
                   java.lang.String updateAreasJs)

      • renderPaintCommands

        public void renderPaintCommands​(java.io.StringWriter js_target,
                                java.lang.String canvasElement)

      • getWidth

        public WLength getWidth()
        Description copied from interface: WPaintDevice
        Returns the device width.

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

        Specified by:
        getWidth in interface WPaintDevice

      • getHeight

        public WLength getHeight()
        Description copied from interface: WPaintDevice
        Returns the device height.

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

        Specified by:
        getHeight in interface WPaintDevice