Customizing the conversion of a graphic object

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Subclassing a graphic object

Assume your graphic object is a subclass of a rectangle that draws a blue Bezier curve into a rectangle from the left bottom point to the right top point. The code is as follows:

package mypackage;

import java.awt.*;
import ilog.views.*;
import ilog.views.graphic.*;

public class MyGraphic extends IlvRectangle
{
  private IlvPoint[] pts = new IlvPoint[4];
  private float[] dash = {4, 2};

  public MyGraphic(IlvRect rect)
  {
     super(rect);
     for (int i = 0; i < 4; i++)
        pts[i] = new IlvPoint();
     computeBezier();
  }

  private computeBezier()
  {
    pts[0].x = drawrect.x;
    pts[0].y = drawrect.y + drawrect.height;
    pts[1].x = drawrect.x + drawrect.width / 4;
    pts[1].y = drawrect.y + drawrect.height / 4;
    pts[2].x = drawrect.x + 3*drawrect.width / 4;
    pts[2].y = drawrect.y + 3*drawrect.height / 4;
    pts[3].x = drawrect.x + drawrect.width;
    pts[3].y = drawrect.y;
  }

  public void draw(Graphics g, IlvTransformer t)
  {
     super.draw(g, t); // will draw the rectangle
     // Will draw a Bezier in blue
     g.setColor(Color.blue);
     IlvGraphicUtil.DrawBezier(g, pts, 4, 1,
                               IlvStroke.JOIN_MITER, IlvStroke.CAP_ROUND,
                               dash, t);     
  }

  public void applyTransform(IlvTransform t)
  {
     super.applyTransform(t);
     computeBezier();
  }

  // ...
}

Creating a translator and setting the builder configurator

If you do not want your object to use the generic translation mechanism, you should implement the SVGDocumentBuilderConfigurator.GraphicTranslator interface to be able to translate MyGraphic instances to SVG Element instances.

The translate method of your class should build a new Element instance, and, after filling it with the information contained in the graphic object and applying a style, should return that instance. To fill the Element , you can use regular DOM methods ( Element.setAttribute() ) or the methods provided by the SVG DOM. Note, however, that only limited support of SVG DOM is implemented in Rogue Wave JViews, and not all the methods are accessible.

The following code shows how to create the translator.

import org.w3c.dom.*;
import org.w3c.svg.dom.*;

public class MyGraphicTranslator 
       implements SVGDocumentBuilderConfigurator.GraphicTranslator
{
  // Method that translates the graphic to SVG
  public Element translate(IlvGraphic graphic, IlvTransformer t,
                           SVGDocumentBuilder builder)
  {
    SVGDocument doc = builder.getDocument();

    // The SVG ’group’ element will contain
    // all drawings necessary to display MyGraphic.
    SVGGElement group = (SVGGElement)doc.createElementNS
                                        ("http://www.w3.org/2000/svg", "g");

    // First add to the group the element corresponding
    // to the parent class of MyRect (IlvRectangle). 
    group.appendChild(builder.getConfigurator().
       getTranslator(“ilog.views.graphic.IlvRectangle”).
       translate(graphic, t));

    // Create the SVG element corresponding to 
    // the drawing added at MyGraphic level.
    SVGPathElement path = (SVGPathElement)doc.createElementNS
                                        ("http://www.w3.org/2000/svg", "path");
    IlvRect rect = graphic.boundingBox(graphic, t);
    SVGList list = path.getPathSegList();
    // Go to the beginning point of the Bezier.
    list.appendItem(path.createPathSegMovetoAbs(rect.x,
                                                rect.y + rect.height));
    // Add the Bezier.
    list.appendItem(path.
      createPathSegCurvetoCubicAbs(rect.x + rect.width,
                                   rect.y,
                                   rect.x + rect.width / 4,
                                   rect.y + rect.height / 4,
                                   rect.x + 3*rect.width / 4,
                                   rect.y + 3*rect.height / 4));


    // Start to style the path.
    builder.startStyleElement(path, null);
    // Really apply the style (blue color...).
    builder.appendStyle("stroke", "blue");
    builder.appendStyle("stroke-width", "1");
    builder.appendStyle("stroke-join", "miter");
    builder.appendStyle("stroke-cap", "round");
    builder.appendStyle("stroke-dasharray", "4 2");
    // Finish to style the path.
    builder.endStylingElement();    
    group.appendChild(path);

    return group;
  }
}

Customizing the SVG stream factory

You should create a well-configured builder configurator that refers to the new translator. If you are using an SVGOutputStream you can write the following code:

SVGStreamFactory factory = new SVGStreamFactory();
factory.getBuilderConfigurator().putTranslator("mypackage.MyGraphic", new
 MyGraphicTranslator());

Do not forget to set this new stream factory on your manager instead of the regular one.

If you are in SVG thin-client context, you just have to call putTranslator method on the SVGBuilderConfigurator instance you used for your Servlet.

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SVG advanced personalization