mermaid/docs/directives.md

Directives

Init directives

With this version, directives are supported. Technically there are two flavors of directive: init/initialize and everything else. The init/initialize directive is parsed early in the flow enough to be able to re-initialize mermaid with a new configuration object. Example:

%%{init: { 'logLevel': 'debug', 'theme': 'dark' } }%%
graph >
A-->B

will set the logLevel to debug and the theme to dark for a flowchart diagram.

Note: init or initialize are both acceptable as init directives. Also note that init directives are coalesced. This means:

%%{init: { 'logLevel': 'debug', 'theme': 'forest' } }%%
%%{initialize: { 'logLevel': 'fatal', "theme":'dark', 'startOnLoad': true } }%%
...

will result an init object looking like this:

{
  logLevel: 'fatal',
  theme: 'dark',
  startOnLoad: true
}

to be sent to mermaid.initialize(...)

Other directives

The other flavor of directive is everything else. In this category are any directives that follow the graph type declaration. Essentially, these directives will not be processed early in the flow like the init directive. Each individual graph type will handle these directives. As an example:

%%{init: { 'logLevel': 'debug', 'theme': 'dark' } }%%
sequenceDiagram
%%{config: { 'fontFamily': 'Menlo', 'fontSize': 18, 'fontWeight': 400} }%%
Alice->>Bob: Hi Bob
Bob->>Alice: Hi Alice

This will set the logLevel to debug and theme to dark for a sequence diagram. Then, during processing, the config for the sequence diagram is set by the config directive. This directive is handled in the sequenceDb.js. In this example, the fontFamily, fontSize, and fontWeight are all set for this sequence diagram.

Backwards Compatibility

Init directives and any other non-multiline directives should be backwards compatible because they will be treated as comments in prior versions of mermaid-js.

Multiline directives, however, will pose an issue and will render an error. This is unavoidable.

Wrapping

The %%{wrap}%% directive and the inline wrap: text hint have also been added for sequence diagrams. This has been explained in my previous comments and has not materially changed.