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From DeWeese Thomas <thomas.dewe...@gmail.com>
Subject Re: fonts & kerning
Date Sat, 10 Nov 2012 15:21:19 GMT
Hi Ruben,

   I'm fairly certain that getExtentOfChar works properly.  We have a fairly complete test
of it in "samples/tests/spec/scripting/text_content.svg" I added some hkern examples to the
SVG font that test includes and getExtentOfChar worked correctly in that context.  In looking
at that test one thing that occurred to me is the possibility that the coordinate system you
are adding the rectangles is slightly different from the texts coordinate system (note that
getExtentOfChar returns box in the text element not in the coordinate system of the parent
of the text which is likely where you are appending the rect).  You might want to adopt the
code that test uses to display it's rectangles for your rectangle display.

   BTW it's expected that the boxes don't overlap that doesn't indicate that the kerning is
being ignored.
The extent boxes for horizontal text are adjusted to just touch each other so they can be
used for hit detection.  If text selection works correctly for that text then getExtentOfChar
should work.

   As for the issue with getting the extent of a single space char I suspect the issue is
that we are required to remove
leading and trailing spaces from text elements in the normal case. I think you need to set
the "xml:space" attribute
to "preserve".

   I would strong recommend that you try and get the 'getExtentOfChar' approach to work for
you as that is a much better solution than dropping support for all the nice text features
in SVG.  It also seems to me like if you can't getExtentOfChar to work properly then it likely
means you don't really understand your coordinate systems which will likely lead to similar
issues down the road with your own solution eventually.


On Nov 7, 2012, at 9:34 AM, rm <ruben.malchow@googlemail.com> wrote:

> hi,
> i am having font kerning issues. 
> what i do is this: i dynamically convert a TTF font to an SVG font. in the SVG font,
there's all kinds of kerning hints. then i link to that svg font from my svg as follows:
> 			Element fontface = getSvg().createElementNS(svgNS, SVGConstants.SVG_FONT_FACE_TAG);
> 			fontface.setAttributeNS(null, "font-family", fontname);
> 			Element fontfacesrc = getSvg().createElementNS(svgNS, SVGConstants.SVG_FONT_FACE_SRC_TAG);
> 			Element fontfaceuri = getSvg().createElementNS(svgNS, SVGConstants.SVG_FONT_FACE_URI_TAG);
> 			fontfaceuri.setAttributeNS(svgNS, "xlink:href", uri+"#"+fontname);
> 			Element fontfaceformat = getSvg().createElementNS(svgNS, SVGConstants.SVG_FONT_FACE_FORMAT_TAG);
> 			fontfaceformat.setAttributeNS(svgNS, "string", "svg");
> 			fontfaceuri.appendChild(fontfaceformat);
> 			fontfacesrc.appendChild(fontfaceuri);
> 			fontface.appendChild(fontfacesrc);
> 			defs.appendChild(fontface);
> and then i create my textnode like this:
> 			Element text = svg.createElementNS(
> 			svgNS, 
> 			SVG12Constants.SVG_TEXT_TAG);
> 	  svg.getDocumentElement().appendChild(text);
> set the font face etc in the style att:
> 			text.setAttributeNS(
> 					null, 
> 					"font-size:"+fontSize+fontUnit+";"+
> 					"font-family:"+fontName+";"+
> 					"font-style:normal;"+
> 					"font-variant:normal;"+
> 					"font-weight:normal;"+
> 					"fill:#000000;"+
> 					"stroke:none"
> 			);
> and append the text content:
> 			Node fpText = text.getOwnerDocument().createTextNode(textContent);
> 			text.appendChild(fpText);
> now, if i get draw a bounding box for each character:
> 			SVGOMTextElement te = (SVGOMTextElement)text;
> 			for(int i=0;i<textContent.length();i++) {
> 				SVGRect rect = te.getExtentOfChar(i);
> 				Element e = svg.createElement("rect");
> 				e.setAttributeNS(null, "x", rect.getX()+"");
> 				e.setAttributeNS(null, "y", rect.getY()+"");
> 				e.setAttributeNS(null, "width", (rect.getWidth()-6)+"");
> 				e.setAttributeNS(null, "height", rect.getHeight()+"");
> 				e.setAttributeNS(null, "style", "fill:none;fill-opacity:1;stroke:#0000ff;stroke-width:6;stroke-opacity:1;stroke-dasharray:9,9;stroke-dashoffset:0");
> 				svg.appendChild(e);
> 			}
> i get a bunch of boxes that have the correct sizes, but don't honour the kerning hints
> basically, with each box exactly touching the previous one. the glyphs themselves are,
> laid out including the kerning. in the attachment, this is especially obvious in the
> combination. text bounding box and getComputedLength() are also too wide.
> it would be ok for me to switch kerning off completely, but setting kerning="0" does
not work 
> (or i misunderstand it's purpose), and WITH kerning, i cannot correctly calculate the
> and rotation. 
> any help, anyone?
> thanks!
> .rm
> <Untitled-1.jpg>

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