Wrong values of bounding box for text element using Batik

Question

I'm trying to draw a rectangle around a text element using getBBox(), the code is pretty straightforward, create document, add text element, boot document and add rectangle. The problem is that getBBox is returning some weird values, am I missing something?

DOMImplementation impl;
String svgNS;
SVGDocument doc;
Element svgRoot;

UserAgent userAgent;
DocumentLoader loader;
BridgeContext ctx;
GVTBuilder builder;
GraphicsNode rootGN;

...

// get a DOM and create a document
impl = SVGDOMImplementation.getDOMImplementation();
svgNS = SVGDOMImplementation.SVG_NAMESPACE_URI;
doc = (SVGDocument)impl.createDocument(svgNS, "svg", null);

// Get (the 'svg' element).
svgRoot = doc.getDocumentElement();

// Set the width and height attributes on the root 'svg' element.
svgRoot.setAttributeNS(svgNS, "width", "400");
svgRoot.setAttributeNS(svgNS, "height", "450");

// Add a text element
Element txtElem = doc.createElementNS(svgNS, "text");
txtElem.setAttributeNS(svgNS, "x", "30");
txtElem.setAttributeNS(svgNS, "y", "50");
txtElem.setAttributeNS(svgNS, "style", "font-family:Arial;font-size:20;stroke:#000000;#fill:#00ff00;");
txtElem.setTextContent("sometext");

svgRoot.appendChild(txtElem);

// boot the document
userAgent = new UserAgentAdapter();
loader = new DocumentLoader(userAgent);
ctx = new BridgeContext(userAgent, loader);
ctx.setDynamicState(BridgeContext.DYNAMIC);
builder = new GVTBuilder();
rootGN = builder.build(ctx, doc);

// add a bounding box to text elements
NodeList nodelist = doc.getElementsByTagName("text");
for (int i=0; i < nodelist.getLength(); i++) {
    SVGOMTextElement textElem = (SVGOMTextElement)nodelist.item(i);
    SVGRect bbox = textElem.getBBox();

    Element rectangle = doc.createElementNS(svgNS, "rect");
    rectangle.setAttributeNS(svgNS, "x", new Float(bbox.getX()).toString());
    rectangle.setAttributeNS(svgNS, "y", new Float(bbox.getY()).toString());
    rectangle.setAttributeNS(svgNS, "width", new Float(bbox.getWidth()).toString());
    rectangle.setAttributeNS(svgNS, "height", new Float(bbox.getHeight()).toString());
    rectangle.setAttributeNS(svgNS, "fill", "rgba(0,0,0,0)");
    rectangle.setAttributeNS(svgNS, "stroke", "#ff0000");
    rectangle.setAttributeNS(svgNS, "stroke-width", "1");

    svgRoot.appendChild(rectangle);
}

this is the SVG document that i'm getting, as you can see the rectangle has different X and Y values (width and height are also wrong).

<?xml version="1.0" encoding="UTF-8"?>
<svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" contentScriptType="text/ecmascript" zoomAndPan="magnify" width="400" contentStyleType="text/css" preserveAspectRatio="xMidYMid meet" height="450" version="1.0">
    <text x="30" style="font-family:Georgia;font-size:20;stroke:#000000;#fill:#00ff00;" y="50">sometext</text>
    <rect x="0.65234375" fill="rgba(0,0,0,0)" width="55.621094" stroke-width="1" stroke="#ff0000" height="8.597656" y="8.425781"/>
</svg>

Answer 1

The problem comes from the fact that you must use setAttribute instead of setAttributeNS. The specified x and y coordinates are ignored since they aren't the x and y attributes that Batik expects in the default namespace, they seem to be recognized as other unknown attributes. Just use this:

txtElem.setAttribute("x", "30");
txtElem.setAttribute("y", "50");
txtElem.setAttribute("style", "font-family:Arial;font-size:20;stroke:#000000;fill:#00ff00;");

Answer 2

Try this:

rectangle.setAttributeNS(null,

and leave svgNS only in createElementNS.