How to determine width of text in OpenSCAD?

Question

In OpenSCAD, I want to be able to create a module which accepts a string then create a 3-D object with that string embedded in the surface as a text. I want the object to be slightly larger than the text, so I need to know how wide the text is in order to create a properly-sized object.

I'm not sure how to query the width of the text (the height is set by an input variable), or if that's even possible.

If it's not possible, is there a function that will accept a string and a font and predict the width of the rendered text?

Answer 1

There is currently no way to query the actual size of the generated text geometry. However, depending on the model that shall be created, it might be enough to calculate a rough estimation and use scale() to fit the text into the known size.

// Fit text into a randomly generated area

r = rands(10, 20, 2);
length = 3 * r[0];
w = r[1];

difference() {
    cube([length, w, 1]);
    color("white")
        translate([0, w / 2, 0.6])
            linear_extrude(1, convexity = 4)
                resize([length, 0], auto = true)
                    text("This is a Test", valign = "center");
}

Answer 2

If you use one of the Liberation fonts bundled with OpenSCAD or the fonts in the Microsoft Core Fonts pack, you can use my font measurement OpenSCAD library. E.g.:

use <fontmetrics.scad>;
length = measureText("This is a Test", font="Arial:style=Italic", size=20.);

The library is here. I used some Python scripts to extract metrics (including kerning pairs) from the ttf file, and you can use the scripts to add information about more fonts.