forgejo/docs/content/doc/advanced/external-renderers.en-us.md
Johan Van de Wauw 08a905f614
Fix external renderers example (#12841)
* libffi-dev is required for building jupyter
* matplotlib can not be installed using wheels on the used version of alpine
  linux, which means it must be compiled and  a large number of other packages
  have to be installed as well.
  This is very inefficient: see eg.
  https://pythonspeed.com/articles/alpine-docker-python/

  Apart from that, matplotlib is actually not required for rendering
  notebook files in gitea and it will pull in other dependencies which take some
  time to build (ie numpy).
2020-09-14 18:11:11 -04:00

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---
date: "2018-11-23:00:00+02:00"
title: "External renderers"
slug: "external-renderers"
weight: 40
toc: true
draft: false
menu:
sidebar:
parent: "advanced"
name: "External renderers"
weight: 40
identifier: "external-renderers"
---
# Custom files rendering configuration
Gitea supports custom file renderings (i.e., Jupyter notebooks, asciidoc, etc.) through external binaries,
it is just a matter of:
* installing external binaries
* add some configuration to your `app.ini` file
* restart your Gitea instance
This supports rendering of whole files. If you want to render code blocks in markdown you would need to do something with javascript. See some examples on the [Customizing Gitea](../customizing-gitea) page.
## Installing external binaries
In order to get file rendering through external binaries, their associated packages must be installed.
If you're using a Docker image, your `Dockerfile` should contain something along this lines:
```
FROM gitea/gitea:{{< version >}}
[...]
COPY custom/app.ini /data/gitea/conf/app.ini
[...]
RUN apk --no-cache add asciidoctor freetype freetype-dev gcc g++ libpng libffi-dev python-dev py-pip python3-dev py3-pip py3-pyzmq
# install any other package you need for your external renderers
RUN pip3 install --upgrade pip
RUN pip3 install -U setuptools
RUN pip3 install jupyter docutils
# add above any other python package you may need to install
```
## `app.ini` file configuration
add one `[markup.XXXXX]` section per external renderer on your custom `app.ini`:
```
[markup.asciidoc]
ENABLED = true
FILE_EXTENSIONS = .adoc,.asciidoc
RENDER_COMMAND = "asciidoctor -s -a showtitle --out-file=- -"
; Input is not a standard input but a file
IS_INPUT_FILE = false
[markup.jupyter]
ENABLED = true
FILE_EXTENSIONS = .ipynb
RENDER_COMMAND = "jupyter nbconvert --stdout --to html --template basic "
IS_INPUT_FILE = true
[markup.restructuredtext]
ENABLED = true
FILE_EXTENSIONS = .rst
RENDER_COMMAND = rst2html.py
IS_INPUT_FILE = false
```
If your external markup relies on additional classes and attributes on the generated HTML elements, you might need to enable custom sanitizer policies. Gitea uses the [`bluemonday`](https://godoc.org/github.com/microcosm-cc/bluemonday) package as our HTML sanitizier. The example below will support [KaTeX](https://katex.org/) output from [`pandoc`](https://pandoc.org/).
```ini
[markup.sanitizer.TeX]
; Pandoc renders TeX segments as <span>s with the "math" class, optionally
; with "inline" or "display" classes depending on context.
ELEMENT = span
ALLOW_ATTR = class
REGEXP = ^\s*((math(\s+|$)|inline(\s+|$)|display(\s+|$)))+
[markup.markdown]
ENABLED = true
FILE_EXTENSIONS = .md,.markdown
RENDER_COMMAND = pandoc -f markdown -t html --katex
```
You must define `ELEMENT`, `ALLOW_ATTR`, and `REGEXP` in each section.
To define multiple entries, add a unique alphanumeric suffix (e.g., `[markup.sanitizer.1]` and `[markup.sanitizer.something]`).
Once your configuration changes have been made, restart Gitea to have changes take effect.
**Note**: Prior to Gitea 1.12 there was a single `markup.sanitiser` section with keys that were redefined for multiple rules, however,
there were significant problems with this method of configuration necessitating configuration through multiple sections.