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org-roam/doc/templating.md
2020-05-07 16:33:42 +08:00

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Rather than creating blank files on `org-roam-insert` and
`org-roam-find-file`, it is may be desirable to prefill the file with
content. This may include:
- Time of creation
- File it was created from
- Clipboard content
- Any other data you may want to input manually
This requires a complex template insertion system, but fortunately,
Org ships with a powerful one: `org-capture`. However, org-capture was
not designed for such use. Org-roam abuses `org-capture` to some
extent, extending its syntax. To first understand how org-roam's
templating system works, it may be useful to look into org-capture.
Org-roam's templates can be customized by modifying the variable
`org-roam-capture-templates`.
## Org-roam Templates
The org-roam capture template extends org-capture's template with 2
additional properties:
1. `:file-name`: This is the file name template used when a new note
is created. Notes can be placed in sub-directories by prepending them to
the filename (`sub/file-name`)
2. `:head`: This is the template that is inserted on initial note
creation.
### Org-roam Template Expansion
Org-roam's template definitions also extend org-capture's template
syntax, to allow prefilling of strings. In many scenarios,
`org-roam-capture--capture` is passed a mapping between variables and strings.
For example, during `org-roam-insert`, a title is prompted for. If the
title doesn't already exist, we would like to create a new file,
without prompting for the title again.
Variables passed are expanded with the `${var}` syntax. For example,
during `org-roam-insert`, `${title}` is prefilled for expansion. Any
variables that do not contain strings, are prompted for values using
`completing-read`.
After doing this expansion, the org-capture's template expansion
system is used to fill up the rest of the template. You may read up
more on this on [org-capture's documentation
page](https://orgmode.org/manual/Template-expansion.html#Template-expansion).
For example, take the template: `"%<%Y%m%d%H%M%S>-${title}"`, with the title
`"Foo"`. The template is first expanded into `%<%Y%m%d%H%M%S>-Foo`. Then
org-capture expands `%<%Y%m%d%H%M%S>` with timestamp: e.g.
`20200213032037-Foo`.
All of the flexibility afforded by emacs and org-mode are
available. For example, if you want to encode a UTC timestamp in the
filename, you can take advantage of org-mode's `%(EXP)` template
expansion to call `format-time-string` directly to provide its third
argument to specify UTC.
``` emacs-lisp
("d" "default" plain (function org-roam--capture-get-point)
"%?"
:file-name "%(format-time-string \"%Y-%m-%d--%H-%M-%SZ--${slug}\" (current-time) t)"
:head "#+TITLE: ${title}\n"
:unnarrowed t)
```
Similarly, if you want to change how titles are transformed into
slugs, you can override `org-roam--title-to-slug`. For example, to use
hyphens instead of underscores:
``` emacs-lisp
(defun org-roam--title-to-slug (title)
"Convert TITLE to a filename-suitable slug. Uses hyphens rather than underscores."
(cl-flet* ((nonspacing-mark-p (char)
(eq 'Mn (get-char-code-property char 'general-category)))
(strip-nonspacing-marks (s)
(apply #'string (seq-remove #'nonspacing-mark-p
(ucs-normalize-NFD-string s))))
(cl-replace (title pair)
(replace-regexp-in-string (car pair) (cdr pair) title)))
(let* ((pairs `(("[^[:alnum:][:digit:]]" . "-") ;; convert anything not alphanumeric
("--*" . "-") ;; remove sequential underscores
("^-" . "") ;; remove starting underscore
("-$" . ""))) ;; remove ending underscore
(slug (-reduce-from #'cl-replace (strip-nonspacing-marks title) pairs)))
(s-downcase slug))))
```
This templating system is used throughout org-roam templates.
### Template examples
Here I walkthrough the default template, reproduced below.
```
("d" "default" plain (function org-roam--capture-get-point)
"%?"
:file-name "%<%Y%m%d%H%M%S>-${slug}"
:head "#+TITLE: ${title}\n"
:unnarrowed t)
```
1. The template has short key `"d"`. If you have only one template,
org-roam automatically chooses this template for you.
2. The template is given a description of `"default"`.
3. `plain` text is inserted. Other options include Org headings via
`entry`.
4. `(function org-roam--capture-get-point)` should not be changed.
5. `"%?"` is the template inserted on each call to `org-roam-capture--capture`.
This template means don't insert any content, but place the cursor
here.
6. `:file-name` is the file-name template for a new note, if it
doesn't yet exist. This creates a file at path that looks like
`/path/to/org-roam-directory/20200213032037-foo.org`.
7. `:head` contains the initial template to be inserted (once only),
at the beginning of the file. Here, the title global attribute is
inserted.
8. `:unnarrowed t` tells org-capture to show the contents for the
whole file, rather than narrowing to just the entry.
Other options you may want to learn about include `:immediate-finish`.