TEXT selection dilemma - getCharNumAtPosition

Baron, Randy {PRG~Basel} Fri, 18 Oct 2002 03:03:46 -0700

(not sure if this message got through the first time...)

Hi,

I hope this could be a trivial problem for someone on the list, because it’s not for me.

I am trying to use SVGTextElement methods getStartPositionOfChar and getCharNumAtPosition to find out which character in a string was clicked on (code below). The only thing I get though is a runtime error:

java.lang.RuntimeException: !!! SVGOMTextContentElement.getStartPositionOfChar()

at org.apache.batik.dom.svg.SVGOMTextContentElement.getStartPositionOfChar(Unknown Source)

at svgstuff.SVGTextSelectTest$OnMouseClick.handleEvent(SVGTextSelectTest.java:155)

at org.apache.batik.dom.events.EventSupport.fireEventListeners(Unknown Source)

etc...

I’m using JDK 1.4 and batik-1.5beta4b on Windows XP Professional.

Finding the position could probably also be done with various calculations of font size, mouse position, user coordinate system and so forth, but I thought that if batik provided a method for it, it would be easier (maybe not though).

Any pointers in the right direction would be appreciated

sincerely,

Randy Baron

*************** SVGMouseTracker.java source code:

package svgstuff;

* SVGMouseTracker.java

* Created on October 10, 2002, 1:57 PM

import java.io.*;

import java.awt.event.WindowAdapter;

import java.awt.event.WindowEvent;

import org.apache.batik.script.Window;

import javax.swing.JFrame;

import javax.swing.JFileChooser;

import org.apache.batik.swing.JSVGCanvas;

import org.w3c.dom.Document;

import org.w3c.dom.Element;

import org.apache.batik.swing.svg.SVGLoadEventDispatcherAdapter;

import org.apache.batik.swing.svg.SVGLoadEventDispatcherEvent;

import org.w3c.dom.events.Event;

import org.w3c.dom.events.EventListener;

import org.w3c.dom.events.EventTarget;

import org.w3c.dom.events.MouseEvent;

import org.w3c.dom.svg.SVGElement;

import org.w3c.dom.NodeList;

import org.apache.batik.dom.svg.SVGOMTextElement;

import org.apache.batik.gvt.event.SelectionListener;

import org.apache.batik.gvt.TextNode;

import org.w3c.dom.svg.SVGPoint;

/**

* @author baron

public class SVGTextSelectTest {

JFrame frame;

JSVGCanvas canvas;

Document document;

Window window;

/** Creates a new instance of SVGTextSelectTest */

public SVGTextSelectTest() {

// create java frame and batik svg canvas...

frame = new JFrame();

canvas = new JSVGCanvas();

// Force the canvas to always be dynamic even if the current

// document does not contain scripting or animation.

canvas.setDocumentState(JSVGCanvas.ALWAYS_DYNAMIC);

canvas.addSVGLoadEventDispatcherListener

(new SVGLoadEventDispatcherAdapter() {

public void svgLoadEventDispatchStarted

(SVGLoadEventDispatcherEvent e) {

// At this time the document is available...

document = canvas.getSVGDocument();

window = canvas.getUpdateManager().

getScriptingEnvironment().createWindow();

// Registers the listeners on the document

// just before the SVGLoad event is dispatched.

registerListeners();

// It is time to pack the frame.

frame.pack();

}

});

/** Pops up file chooser to choose the svg file to display */

frame.addWindowListener(new WindowAdapter() {

public void windowOpened(WindowEvent e) {

// The canvas is ready to load the base document

// now, from the AWT thread.

JFileChooser fc = new JFileChooser(".");

int choice = fc.showOpenDialog(canvas);

if (choice == JFileChooser.APPROVE_OPTION) {

File f = fc.getSelectedFile();

try {

canvas.setURI(f.toURL().toString());

} catch (IOException ex) {

ex.printStackTrace();

}

});

/** For closing the window and exiting when the user clicks the close box */

frame.addWindowListener(new WindowAdapter() {

public void windowClosing(WindowEvent e) {

System.exit(0);

}

});

frame.getContentPane().add(canvas);

frame.setSize(800, 600);

frame.show();

System.out.println("Constructor finished.");

}

public static void main (String[] args) {

System.out.println("Testing test selection methods...");

SVGTextSelectTest mtrack = new SVGTextSelectTest();

}

public void registerListeners() {

// register a listener on the root of the main svg doc

Element maindoc = (Element) document.getDocumentElement();

EventTarget doctarg = (EventTarget) maindoc;

doctarg.addEventListener("click", new OnMouseClick(), false);

}

public class OnMouseClick implements EventListener {

public void handleEvent(Event evt) {

int mx, my;

int sx, sy;

int i = 0;

AnSVGPoint spoint;

// Get mouse click coordinates

MouseEvent mevt = (MouseEvent) evt;

mx = mevt.getClientX();

my = mevt.getClientY();

sx = mevt.getScreenX();

sy = mevt.getScreenY();

SVGElement targ = (SVGElement) mevt.getTarget();

System.out.println("Mouse X:" + mx + " Y: " + my);

System.out.println(" in screen coordinates - x: " + sx + " y: " + sy);

System.out.println(" Type of event: " + mevt.getType());

System.out.println(" getTarget: " + mevt.getTarget());

System.out.println(" getCurrentTarget: " + mevt.getCurrentTarget());

System.out.println(" Element id = " + targ.getId());

if (targ instanceof org.apache.batik.dom.svg.SVGOMTextElement) {

SVGOMTextElement texttarg = (SVGOMTextElement) targ;

System.out.println("HIT SOME TEXT!");

// This block is not entirely relevant to the getCharNumAtPosition problem; just for info

// see if there are any subnodes:

NodeList nlist = targ.getChildNodes();

System.out.println(" text node length: " + nlist.getLength());

while (nlist.item(i) != null) {

System.out.println(" text node item " + i + ": " + nlist.item(i++));

}

//ERROR OCCURS HERE ---

System.out.println(" ...and here comes the error");

// Try to get position of first character in the text string with getStartPositionOfChar (returns an SVGPoint)

// SVGPoint interface is implemented below

// Using character zero for example (0 or 1, makes no difference).

spoint = (AnSVGPoint) texttarg.getStartPositionOfChar(0);

System.out.println(" try getStartPositionOfChar: " + spoint.getX());

// Try to get character under the position where the mouse was clicked.

spoint.setX((float) mx);

spoint.setY((float) my);

System.out.println(" try getCharNumAtPosition: " + texttarg.getCharNumAtPosition(spoint) );

}

class AnSVGPoint implements SVGPoint {

float x, y;

public float getX() {

return this.x;

}

public float getY() {

return this.y;

}

public org.w3c.dom.svg.SVGPoint matrixTransform(org.w3c.dom.svg.SVGMatrix sVGMatrix) {

// do nothing;

return this;

}

public void setX(float param) throws org.w3c.dom.DOMException {

this.x = param;

}

public void setY(float param) throws org.w3c.dom.DOMException {

this.y = param;

}

************** Sample SVG file which displays two lines of text:

<?xml version="1.0" standalone="no"?>

<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 20010904//EN" "http://www.w3.org/TR/2001/REC-SVG-20010904/DTD/svg10.dtd">

<text id="lineone" font-size="25" x="20" y="40" fill="purple"> ABCDEFGHIJKLMNOPQRSTUVWXYZ</text>

</g>

</svg>

TEXT selection dilemma - getCharNumAtPosition

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