Import documentation

Co-Authored-By: Martin Haug <mhaug@live.de>

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+---
+description: All concepts needed to style your document with Typst.
+---
+
+# Styling
+Typst includes a flexible styling system that automatically applies styling of
+your choice to your document. With _set rules,_ you can configure basic
+properties of elements. This way, you create most common styles. However, there
+might not be a built-in property for everything you wish to do. For this reason,
+Typst further supports _show rules_ that can completely redefine the appearance
+of elements.
+
+## Set rules { #set-rules }
+With set rules, you can customize the appearance of elements. They are written
+as a [function call]($type/function) to the respective function preceded by the
+`{set}` keyword (or `[#set]` in markup). Only settable parameters must be
+provided as arguments. Refer to each function's documentation for a list of
+settable parameters. In the example below, we use two set rules to change the
+[font family]($func/text.family) and
+[heading numbering]($func/heading.numbering) style.
+
+```example
+#set text("Latin Modern Roman")
+#set heading(numbering: "I.")
+
+= Introduction
+With set rules, you can style
+your document.
+```
+
+A top level set rule stays in effect until the end of the file. When nested
+inside of a block, it is only in effect until the end of that block. With a
+block, you can thus restrict the effect of a rule to a particular segment of
+your document. Below, we use a content block to scope the list styling to one
+particular list.
+
+```example
+This list is affected:
+#[#set list(marker: [--])
+ - Dash]
+
+This one is not:
+- Bullet
+```
+
+Sometimes, you'll want to apply a set rule conditionally. For this, you can use
+a _set-if_ rule.
+
+```example
+#let task(body, critical: false) = {
+  set text(red) if critical
+  [- #body]
+}
+
+#task(critical: true)[Food today?]
+#task(critical: false)[Work deadline]
+```
+
+## Show rules { #show-rules }
+With show rules, you can deeply customize the look of a type of element. The
+most basic form of show rule is a _show-set rule._ Such a rule is written as the
+`{show}` keyword followed by a function name, a colon and then a set rule. This
+lets the set rule only apply to the selected element. In the example below,
+headings become dark blue while all other text stays black.
+
+```example
+#show heading: set text(navy)
+
+= This is navy-blue
+But this stays black.
+```
+
+With show-set rules you can mix and match properties from different functions to
+achieve many different effects. But they still limit you to what is predefined
+in Typst. For maximum flexibility, you can instead write a show rule that
+defines how to format an element from scratch. To write such a show rule,
+replace the set rule behind the colon with an arbitrary
+[function]($type/function). This functions receives the element in question and
+can return arbitrary content. Different
+[fields]($scripting/#fields) are available on the element passed
+to the function. Below, we define a show rule that formats headings for a
+fantasy encyclopedia.
+
+```example
+#set heading(numbering: "(I)")
+#show heading: it => block[
+  #set align(center)
+  #set text("Inria Serif")
+  \~ _#it.title;_
+      #it.numbers \~
+]
+
+= Dragon
+With a base health of 15, the
+dragon is the most powerful
+creature.
+
+= Manticore
+While less powerful than the
+dragon, the manticore gets
+extra style points.
+```
+
+Like set rules, show rules are in effect until the end of the current block or
+file.
+
+Instead of a function, the right-hand side of a show rule can also take a
+literal string or content block that should be directly substituted for the
+element. And apart from a function, the left-hand side of a show rule can also
+take a number of other _selectors_ that define what to apply the transformation
+to:
+
+- **Everything:** `{show rest => ..}` \
+  Transform everything after the show rule. This is useful to apply a more
+  complex layout to your whole document without wrapping everything in a giant
+  function call.
+
+- **Text:** `{show "Text": ..}` \
+  Style, transform or replace text.
+
+- **Regex:** `{show regex("\w+"): ..}` \
+  Select and transform text with a regular expression for even more flexibility.
+  See the documentation of the [`regex` function]($func/regex) for details.
+
+- **Function with fields:** `{show heading.where(level: 1): ..}` \
+  Transform only elements that have the specified fields. For example, you might
+  want to only change the style of level-1 headings.
+
+- **Label:** `{show <intro>: ..}` \
+  Select and transform elements that have the specified label.
+  See the documentation of the [`label` function]($func/label) for more details.
+
+```example
+#set text("Noto Serif")
+#show "Project": smallcaps
+#show "badly": "great"
+
+We started Project in 2019
+and are still working on it.
+Project is progressing badly.
+```