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 the #katex room on freenode.
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. You can check there 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.
Most functions are handled in the functions.js file. Read the comments in there to get started. If the function you want to add has similar output to an existing function, see if you can add a new line to that file to get it to work.
If your function isn't similar to an existing function, you'll need to add a
line to functions.js as well as adding an output function in
buildHTML.js and buildMathML.js.
Local testing can be done by running the node server in server.js. Run make setup to install dependencies, and then make serve 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 tree
builder is tested with Jasmine. These tests can be run either using node with
make test, or in the browser by visiting
http://localhost:7936/test/test.html.
The Jasmine 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 Jasmine 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.json.
KaTeX supports all major browsers, including IE 8 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 8, 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
In general, try to make your code blend in with the surrounding code.
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.