SVG text - total length changes depending on zoom

In SVG (for web-browsers), if i add a <text>-element and add some text to it the total rendered width of the text string will change depending on the scale of the text.

Lets say i add "mmmmmmmmmmmmmmmmmmmmmmmmmmA" as text, then i want to draw a vertical line(or other exactly positioned element) intersecting the very last character. Works fine but if i zoom out the text will become shorter or longer and the line will not intersect the text in the right place anymore. The error can be as much as +/- 5 characters width which is unacceptable. The error is also unpredictable, 150% and 160% zoom can add 3 characters length while 155% is 2 charlengths shorter.

My zoom is implemented as a scale-transform on the root element of my canvas which is a <g>. I have tried to multiply the font-size with 1000x and scale down equally on the zoom-transform and vice versa in case it was a floating point error but the result is the same.

I found the textLength-attribute[1] which is supposed to adjust the total length so the text always end where i choose but it only works in Webkit. Firefox and Opera seems to not care at all about this value (haven't tried in IE9 yet).

Is there a开发者_运维知识库ny way to render text exactly positioned without resorting to homemade filling of font-outlines?

[1] http://www.w3.org/TR/SVG11/text.html#TextElementTextLengthAttribute

Update

Snippet of the structure i'm using

<svg>
<g transform="scale(1)">      <!--This is the root, i'm changing the scale of this element to zoom -->
    <g transform="scale(0.014)"> <!--This is a wrapper for multi-line text, scaling, other grouping etc -->
        <text font-size="1000" textLength="40000">ABDCDEFGHIJKLMNOPQRSTUVXYZÅÄÖabcdefghijklmnopqrstxyzåäö1234567890</text>
    </g>
</g>

Interesting, since the webkit builds I have seem to fail on textLength (w3c testcase). Could you post your example?

Speaking for Opera we do support the 'textLength' attribute, as documented here.

The other option you have is to use the getBBox method to find a good position for drawing your line, that should work in all the browsers.