PlantUML-Pywal

A locally hosted PlantUML server that uses system colors

Purpose

I use markdown-preview.nvim, which is a great plugin for writing markdown in neovim and previewing it live in your browser.

In my vim.reaper config, I have a custom stylesheet that allows the markdown preview to be styled based on your system colors.

Now, I have extended this feature into PlantUML. For me, this solves two problems:

• Reduce reliance on public PlantUML servers
• Allow customization of generated images

Usage

This PlantUML server runs in a docker container, and starts up in less than a second.

Obviously you can go to the port itself (in my case localhost:4928) and plug in UML there. But these images won't look quite in context unless viewed through another application using the system theme, such as neovim or a PDF viewer like zathura.

In order for the docker container to be aware of the new color file upon theme change, it must be restarted. I accomplish this with a hook in my chameleon config

hooks:
  plantUML:
    command: "docker-compose -f docker-compose.yaml restart plantuml"
    directory: "/home/me/Projects/PlantUML-Pywal/"

EDIT: The container may not require a restart at all

With markdown-preview

I have the following settings for my markdown-preview.nvim configuration:

let g:mkdp_preview_options = {
    \ 'mkit': {},
    \ 'katex': {},
    \ 'uml': {'server': 'http://localhost:4928'},
    \ 'maid': {},
    \ 'disable_sync_scroll': 0,
    \ 'sync_scroll_type': 'middle',
    \ 'hide_yaml_meta': 1,
    \ 'sequence_diagrams': {},
    \ 'flowchart_diagrams': {},
    \ 'content_editable': v:false,
    \ 'disable_filename': 0
    \ }

Note that the uml option has it's server variable pointed at our docker container. To switch back to the default public server, simply delete this line or dictionary item.

Once we are inside our markdown file, we have to "include" the pywal style. This can be done like so.

@startuml
!include /include/plantuml.puml

< content here>

@enduml

Note that the config file created by pywal is mounted to include/plantuml.puml, so we are simply referencing that.

Now, no matter what system I am on, the diagrams I preview in my markdown will be appropriately colored.

Credit to Puml Themes for the theme template which got me started.