Run text rendering tests on OpenType.js

Hi all, I’ve started a project for testing text rendering systems; the project is hosted/copyrighted by Unicode. Although this test suite is still very much in its infancy, you might still find it useful. Feel free to change its test framework so it runs node.js + OpenType.js on the test suite when passing --engine=OpenType.js; your pull requests would be very welcome. Also, don’t hesitate to extend the test coverage if you want; you’d help other projects too. https://github.com/icu-project/text-rendering-tests

[brawer]

Friendly ping, since this would have found https://github.com/nodebox/opentype.js/issues/273 much earlier. So here’s an offer. If somebody implements a command line tool in Node that can be called like this:

some-command --testcase=SomeID/1 --font=path/to/testfont.otf --render="Jj"

so the tool writes an SVG file to standard output, like the following output for --testcase=SomeID/1, --font pointing to this test font, and --render="Jj":

<?xml version="1.0" encoding="UTF-8"?>
<svg version="1.1"
    xmlns="http://www.w3.org/2000/svg"
    xmlns:xlink="http://www.w3.org/1999/xlink"
    viewBox="0 -455 535 1383">
  <symbol id="SomeID/1.J" overflow="visible"><path d="M125,184 L125,599 L57,599 Q41,599 41,613 Q41,620 46,637 L48,645 L261,645 Q265,639 265,629 Q265,618 258,609 L181,601 L181,201 Q181,77 140,0 Q99,-76 -4,-142 Q-22,-127 -29,-107 Q59,-40 92,23 Q125,87 125,184 Z"/></symbol>
  <symbol id="SomeID/1.j" overflow="visible"><path d="M100,134 L100,453 L19,453 Q16,461 16,467 Q16,476 22,486 L126,505 Q143,496 154,483 L154,151 Q154,27 113,-49 Q72,-126 -31,-192 Q-49,-179 -55,-158 Q35,-92 67,-30 Q100,31 100,134 Z M157,632 Q157,590 112,590 Q67,590 67,632 Q67,674 112,674 Q157,674 157,632 Z"/></symbol>
  <use xlink:href="#SomeID/1.J" x="0" y="0"/>
  <use xlink:href="#SomeID/1.j" x="296" y="0"/>
</svg>

If you do that, I’ll make the necessary changes to the Unicode text rendering test suite so it calls your tool for --engine=OpenType.js. Then, we’ll get test reports like this for free.

For the test cases with variable fonts, the test suite also passes an argument --variation=M1:0.2;wght:721.5. This means that axis M1 should be set to 0.2 and axis wght to 721.5. Since OpenType.js doesn’t yet implement variable fonts, you could just ignore the --variation argument for now.

[fdb]

I’ve added a bin/test-render script that creates the SVG file in the correct format.

I’ve also looked at integrating it into text-rendering-tests, and it shouldn’t be too hard. I’ll try to submit a PR tomorrow.