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template: overrides/main.html
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# Diagrams

Diagrams help to communicate complex relationships and interconnections between
different technical components, and are a great addition to project
documentation. Material for MkDocs integrates with [Mermaid.js], a very
popular and flexible solution for drawing diagrams.

  [Mermaid.js]: https://mermaid-js.github.io/mermaid/

## Configuration

[:octicons-tag-24: 8.2.0][Diagrams support] ·
:octicons-beaker-24: Experimental

This configuration enables native support for [Mermaid.js] diagrams. Material
for MkDocs will automatically initialize the JavaScript runtime when a page 
includes a `mermaid` code block:

``` yaml
markdown_extensions:
  - pymdownx.superfences:
      custom_fences:
        - name: mermaid
          class: mermaid
          format: !!python/name:pymdownx.superfences.fence_code_format
```

No further configuration is necessary. Advantages over a custom integration:

- [x] Works with [instant loading] without any additional effort
- [x] Diagrams automatically use fonts and colors defined in `mkdocs.yml`[^1]
- [x] Fonts and colors can be customized with [additional style sheets]
- [x] Support for both, light and dark color schemes – _try it on this page!_

  [^1]:
    While all [Mermaid.js] features should work out-of-the-box, Material for
    MkDocs will currently only adjust the fonts and colors for flowcharts,
    sequence diagrams, class diagams, state diagrams and entity relationship 
    diagrams. See the section on [other diagrams] for more informaton why this
    is currently not implemented for all diagrams.

  [Diagrams support]: https://github.com/squidfunk/mkdocs-material/releases/tag/8.2.0
  [instant loading]: ../setup/setting-up-navigation.md#instant-loading
  [additional style sheets]: ../customization.md#additional-css
  [other diagrams]: #other-diagrams

## Usage

### Using flowcharts

[Flowcharts] are diagrams that represent workflows or processes. The steps
are rendered as nodes of various kinds and are connected by edges, describing
the necessary order of steps:

```` markdown title="Flow chart"
``` mermaid
graph LR
  A[Start] --> B{Error?};
  B -->|Yes| C[Hmm...];
  C --> D[Debug];
  D --> B;
  B ---->|No| E[Yay!];
```
````

<div class="result" markdown>

``` mermaid
graph LR
  A[Start] --> B{Error?};
  B -->|Yes| C[Hmm...];
  C --> D[Debug];
  D --> B;
  B ---->|No| E[Yay!];
```

</div>

  [Flowcharts]: https://mermaid-js.github.io/mermaid/#/flowchart

### Using sequence diagrams

[Sequence diagrams] describe a specific scenario as sequential interactions 
between multiple objects or actors, including the messages that are exchanged
between those actors:

```` markdown title="Sequence diagram"
``` mermaid
sequenceDiagram
  Alice->>John: Hello John, how are you?
  loop Healthcheck
      John->>John: Fight against hypochondria
  end
  Note right of John: Rational thoughts!
  John-->>Alice: Great!
  John->>Bob: How about you?
  Bob-->>John: Jolly good!
```
````

<div class="result" markdown>

``` mermaid
sequenceDiagram
  Alice->>John: Hello John, how are you?
  loop Healthcheck
      John->>John: Fight against hypochondria
  end
  Note right of John: Rational thoughts!
  John-->>Alice: Great!
  John->>Bob: How about you?
  Bob-->>John: Jolly good!
```

</div>

  [Sequence diagrams]: https://mermaid-js.github.io/mermaid/#/sequenceDiagram

### Using state diagrams

[State diagrams] are a great tool to describe the behavior of a system,
decomposing it into a finite number of states, and transitions between those
states:

```` markdown title="State diagram"
``` mermaid
stateDiagram-v2
  state fork_state <<fork>>
    [*] --> fork_state
    fork_state --> State2
    fork_state --> State3

    state join_state <<join>>
    State2 --> join_state
    State3 --> join_state
    join_state --> State4
    State4 --> [*]
```
````

<div class="result" markdown>

``` mermaid
stateDiagram-v2
  state fork_state <<fork>>
    [*] --> fork_state
    fork_state --> State2
    fork_state --> State3

    state join_state <<join>>
    State2 --> join_state
    State3 --> join_state
    join_state --> State4
    State4 --> [*]
```

</div>

  [State diagrams]: https://mermaid-js.github.io/mermaid/#/stateDiagram

### Using class diagrams

[Class diagrams] are central to object oriented programing, describing the
structure of a system by modelling entities as classes and relationships between
them:

```` markdown title="Class diagram"
``` mermaid
classDiagram
  Person <|-- Student
  Person <|-- Professor
  Person : +String name
  Person : +String phoneNumber
  Person : +String emailAddress
  Person: +purchaseParkingPass()
  Address "1" <-- "0..1" Person:lives at
  class Student{
    +int studentNumber
    +int averageMark
    +isEligibleToEnrol()
    +getSeminarsTaken()
  }
  class Professor{
    +int salary
  }
  class Address{
    +String street
    +String city
    +String state
    +int postalCode
    +String country
    -validate()
    +outputAsLabel()  
  }
```
````

<div class="result" markdown>

``` mermaid
classDiagram
  Person <|-- Student
  Person <|-- Professor
  Person : +String name
  Person : +String phoneNumber
  Person : +String emailAddress
  Person: +purchaseParkingPass()
  Address "1" <-- "0..1" Person:lives at
  class Student{
    +int studentNumber
    +int averageMark
    +isEligibleToEnrol()
    +getSeminarsTaken()
  }
  class Professor{
    +int salary
  }
  class Address{
    +String street
    +String city
    +String state
    +int postalCode
    +String country
    -validate()
    +outputAsLabel()  
  }
```

</div>

  [Class diagrams]: https://mermaid-js.github.io/mermaid/#/classDiagram

### Using entity-relationship diagrams

An [entity-relationship diagram] is composed of entity types and specifies
relationships that exist between entities. It describes inter-related things in
a specific domain of knowledge:

```` markdown title="Entity-relationship diagram"
``` mermaid
erDiagram
  CUSTOMER ||--o{ ORDER : places
  ORDER ||--|{ LINE-ITEM : contains
  CUSTOMER }|..|{ DELIVERY-ADDRESS : uses
```
````

<div class="result" markdown>

``` mermaid
erDiagram
  CUSTOMER ||--o{ ORDER : places
  ORDER ||--|{ LINE-ITEM : contains
  CUSTOMER }|..|{ DELIVERY-ADDRESS : uses
```

</div>

  [entity-relationship diagram]: https://mermaid-js.github.io/mermaid/#/entityRelationshipDiagram

### Other diagram types

Besides the diagram types listed above, [Mermaid.js] provides support for
[pie charts], [gantt charts], [user journeys], [git graphs] and
[requirement diagrams], all of which are not officially supported by Material
for MkDocs. Those diagrams should still work as advertised by [Mermaid.js], but
we don't consider them a good choice, mostly as they don't work well on mobile.

  [pie charts]: https://mermaid-js.github.io/mermaid/#/pie
  [gantt charts]: https://mermaid-js.github.io/mermaid/#/gantt
  [user journeys]: https://mermaid-js.github.io/mermaid/#/user-journey
  [git graphs]: https://mermaid-js.github.io/mermaid/#/gitgraph
  [requirement diagrams]: https://mermaid-js.github.io/mermaid/#/requirementDiagram
