summaryrefslogtreecommitdiffhomepage
path: root/docs/content/en/templates/render-hooks.md
blob: 57c2efa06897938c5260abfc63f72cb0901b45b4 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
---
title: "Markdown Render Hooks"
linkTitle: "Render Hooks"
description: "Render Hooks allow custom templates to override markdown rendering functionality."
date: 2017-03-11
categories: [templates]
keywords: [markdown]
toc: true
menu:
  docs:
    title: "Markdown Render Hooks"
    parent: "templates"
    weight: 20
---

{{< new-in "0.62.0" >}} Note that this is only supported with the [Goldmark](#goldmark) renderer.


You can override certain parts of the default Markdown rendering to HTML by creating templates with base names `render-{kind}` in `layouts/_default/_markup`.

You can also create type/section specific hooks in `layouts/[type/section]/_markup`, e.g.: `layouts/blog/_markup`.{{< new-in "0.71.0" >}}

The hook kinds currently supported are:

* `image`
* `link`
* `heading` {{< new-in "0.71.0" >}}
* `codeblock`{{< new-in "0.83.0" >}}

You can define [Output-Format-](/templates/output-formats) and [language-](/content-management/multilingual/)specific templates if needed. Your `layouts` folder may look like this:

```goat { class="black f7" }
layouts
└── _default
    └── _markup
        ├── render-image.html
        ├── render-image.rss.xml
        └── render-link.html
        └── render-codeblock.html
        └── render-codeblock-bash.html
```

Some use cases for the above:

* Resolve link references using `.GetPage`. This would make links portable as you could translate `./my-post.md` (and similar constructs that would work on GitHub) into `/blog/2019/01/01/my-post/` etc.
* Add `target=_blank` to external links.
* Resolve and [process](/content-management/image-processing/) images.
* Add [header links](https://remysharp.com/2014/08/08/automatic-permalinks-for-blog-posts).

## Render Hooks for Headings, Links and Images

The `render-link` and `render-image` templates will receive this context:

Page
: The [Page](/variables/page/) being rendered.

Destination
: The URL.

Title
: The title attribute.

Text
: The rendered (HTML) link text.

PlainText
: The plain variant of the above.

The `render-heading` template will receive this context:

Page
: The [Page](/variables/page/) being rendered.

Level
: The header level (1--6)

Anchor
: An auto-generated html id unique to the header within the page

Text
: The rendered (HTML) text.

PlainText
: The plain variant of the above.

Attributes (map) {{< new-in "0.82.0" >}}
: A map of attributes (e.g. `id`, `class`)

### Link with title Markdown example:

```md
[Text](https://www.gohugo.io "Title")
```

Here is a code example for how the render-link.html template could look:

{{< code file="layouts/_default/_markup/render-link.html" >}}
<a href="{{ .Destination | safeURL }}"{{ with .Title}} title="{{ . }}"{{ end }}{{ if strings.HasPrefix .Destination "http" }} target="_blank" rel="noopener"{{ end }}>{{ .Text | safeHTML }}</a>
{{< /code >}}

### Image Markdown example:

```md
![Text](https://d33wubrfki0l68.cloudfront.net/c38c7334cc3f23585738e40334284fddcaf03d5e/2e17c/images/hugo-logo-wide.svg "Title")
```

Here is a code example for how the render-image.html template could look:

{{< code file="layouts/_default/_markup/render-image.html" >}}
<p class="md__image">
  <img src="{{ .Destination | safeURL }}" alt="{{ .Text }}" {{ with .Title}} title="{{ . }}"{{ end }} />
</p>
{{< /code >}}

### Heading link example

Given this template file

{{< code file="layouts/_default/_markup/render-heading.html" >}}
<h{{ .Level }} id="{{ .Anchor | safeURL }}">{{ .Text | safeHTML }} <a href="#{{ .Anchor | safeURL }}">¶</a></h{{ .Level }}>
{{< /code >}}

And this markdown

```md
### Section A
```

The rendered html will be

```html
<h3 id="section-a">Section A <a href="#section-a">¶</a></h3>
```

## Render Hooks for Code Blocks

{{< new-in "0.93.0" >}}

You can add a hook template for either all code blocks or for a specific type/language (`bash` in the example below):

```goat { class="black f7" }
layouts
└── _default
    └── _markup
        └── render-codeblock.html
        └── render-codeblock-bash.html
```

The default behaviour for these code blocks is to do [Code Highlighting](/content-management/syntax-highlighting/#highlighting-in-code-fences), but since you can pass attributes to these code blocks, they can be used for almost anything. One example would be the built-in [GoAT Diagrams](/content-management/diagrams/#goat-diagrams-ascii) or this [Mermaid Diagram Code Block Hook](/content-management/diagrams/#mermaid-diagrams) example.

The context (the ".") you receive in a code block template contains:

Type (string)
: The type of code block. This will be the programming language, e.g. `bash`, when doing code highlighting.

Attributes (map)
: Attributes passed in from Markdown (e.g. `{ attrName1=attrValue1 attrName2="attr Value 2" }`).

Options (map)
: Chroma highlighting processing options. This will only be filled if `Type` is a known [Chroma Lexer](/content-management/syntax-highlighting/#list-of-chroma-highlighting-languages).

Inner (string)
: The text between the code fences.

Ordinal (integer)
: Zero-based ordinal for all code blocks in the current document.

Page
: The owning `Page`.

Position
: Useful in error logging as it prints the filename and position (linenumber, column), e.g. `{{ errorf "error in code block: %s" .Position }}`.