We welcome pull requests to KaTeX. If you'd like to add a new symbol, or try to tackle adding a larger feature, keep reading. If you have any questions, or want help solving a problem, feel free to stop by our gitter channel.
If you'd like to contribute, try contributing new symbols or functions that KaTeX doesn't currently support. The wiki has a page which lists all of the supported functions as well as a page that describes how to examine TeX commands and where to find rules which can be quite useful when adding new commands. There's also a user-contributed preview page showing how KaTeX would render a series of symbols/functions (including the ones MathJax listed in their documentation and the extra ones supported by KaTeX). You can check them to see if we don't support a function you like, or try your function in the interactive demo at http://khan.github.io/KaTeX/.
There are many individual symbols that KaTeX doesn't yet support. Read through the symbols.js file for more information on how to add a symbol.
To figure out the unicode symbol for the symbol you are trying to add, try using the symbol in MathJax to see what unicode symbol it outputs. An interactive MathJax shell can be found here.
To figure out what group your symbol falls into, look through the symbols list
to find other symbols of a similar kind. (e.g. if you were adding \neq, look
for =). If you cannot find anything similar, or are unsure, you can try using
your symbol in TeX surrounded by other different kinds of symbols, and seeing
whether your spacing matches the spacing that TeX produces.
Once your symbol works, check the JavaScript console to make sure you don't get a message like "Can't find character metrics for _" when you render your symbol. If you do, check out extract_ttfs.py.
New functions should be added in src/functions using
defineFunction from defineFunction.js. Read the
comments in this file to get started. Look at
phantom.js and
delimsizing.js as examples of how to use
defineFunction. Notice how delimsizing.js groups several related functions
together in a single call to defineFunction.
The new method of defining functions combines methods that were previously spread out over three different files functions.js, buildHTML.js, buildMathML.js into a single file. The goal is to have all functions use this new system.
Local testing can be done by running the node server in server.js. Run
npm install to install dependencies, and then npm start to start the server.
This will host an interactive editor at http://localhost:7936/ to play around with and test changes.
The JavaScript parser and some of the HTML and MathML tree
builders are tested with Jest. These tests can be run using node with
npm run jest. If you need to debug the tests see
https://facebook.github.io/jest/docs/troubleshooting.html
The interactive editor can also be used for debugging tests in the browser by copy/pasting the test case to be debugged into the editor. The permalink option can come in really useful when doing repeated runs of the same test case.
The Jest tests should be run after every change, even the addition of small symbols. However, Travis will run these tests when you submit a pull request, in case you forget.
If you make any changes to Parser.js, add Jest tests to ensure they work.
To ensure the final output looks good, we screenshot different expressions. These tests can be run by using the Screenshotter docker.
The screenshot tests should be run if you add anything more significant than individual symbols. These tests are not automatically run, so please remember! If the new images are different (meaning they are not byte-by-byte the same as the old ones), inspect them visually. If there are no visible changes, that is okay. If things change in a way consistent with your additions, explain what changed and why. Otherwise, figure out what is causing the changes and fix it!
If you add a feature that is dependent on the final output looking the way you created it, add a screenshot test. See ss_data.yaml.
You can use our texcmp tool to compare the outputs of a screenshot test as generated by KaTeX and LaTeX. It's often useful to attach the resulting "visual diff" to your pull request with a new feature.
KaTeX supports all major browsers, including IE 9 and newer. Unfortunately, it is hard to test new changes in many browsers. If you can, please test your changes in as many browsers as possible. In particular, if you make CSS changes, try to test in IE 9, using modern.ie VMs.
Code
- 4 spaces for indentation
- 80 character line length
- commas last
- declare variables in the outermost scope that they are used
- camelCase for variables in JavaScript
- snake_case for variables in Python
In general, try to make your code blend in with the surrounding code.
- link back to the original issue(s) whenever possible
- new commands should be added to the wiki
- commits should be squashed before merging
- large pull requests should be broken into separate pull requests (or multiple logically cohesive commits), if possible
In order to contribute to KaTeX, you must first sign the CLA, found at www.khanacademy.org/r/cla
KaTeX is licenced under the MIT License.