This is a very early draft for a test suite for text rendering.
It is not easy to correctly display text, so we founded this project to help implementations to get this right. Currently, the test suite is still very much in its infancy, so please don’t be disappointed if you don’t find much. Of course you are more than welcome to help; just send a pull request.
$ git clone --recursive https://github.com/unicode-org/text-rendering-tests.git
$ cd text-rendering-tests
$ python check.py --output=report.html --engine=FreeStackCurrently, the test suite supports only two OpenType implementations:
-
With
--engine=FreeStack, the tests are run on the free/libre open-source text rendering stack with FreeType, HarfBuzz, FriBidi, and Raqm. These libraries are used by Linux, Android, ChromeOS, and many other systems. -
With
--engine=CoreText, the tests are run on Apple’s CoreText. This option will work only if you run the test suite on MacOS X.
If you’d like to test another OpenType implementation, please go ahead.
When you pass --output=report.html, the test suite will generate a
test report that explains what was tested, which tests have passed,
and which ones have failed. By clicking the following links, you can
also just look at the reports
for FreeStack
and CoreText without running the test suite yourself.
The test cases are defined in the testcases directory. It contains HTML snippets which describe each test, and define the rendering parameters together with the expected result.
For each test case, the check.py script parses the HTML snippet to
extract the rendering parameters. Then, it runs a sub-process (written
in C++ and Objective C) that writes the observed rendering in SVG
format to Standard Output. Finally, the script checks whether the
expected rendering matches the observed result. Currently, “matching”
is implemented by iterating over SVG paths, allowing for maximally
1 font design unit of difference.
Your contributions are very welcome; simply send pull requests via GitHub. A bot will ask you (on the GitHub review thread) to accept Unicode’s Contributor License Agreement by clicking on a web form. Alternatively, if you prefer paper, you can also send a signed paper copy of the agreement to Unicode.