Export target docs (#5812)

Co-authored-by: Martin Haug <3874949+reknih@users.noreply.github.com>

18 files changed, 381 insertions, 6 deletions

diff --git a/docs/reference/export/html.md b/docs/reference/export/html.md
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+<div class="info-box">
+
+Typst's HTML export is currently under active development. The feature is still
+very incomplete and only available for experimentation behind a feature flag. Do
+not use this feature for production use cases. In the CLI, you can experiment
+with HTML export by passing `--features html` or setting the `TYPST_FEATURES`
+environment variables to `html`. In the web app, HTML export is not available at
+this time. Visit the [tracking issue](https://github.com/typst/typst/issues/5512)
+to follow progress on HTML export and learn more about planned features.
+</div>
+
+HTML files describe a document structurally. The aim of Typst's HTML export is
+to capture the structure of an input document and produce semantically rich HTML
+that retains this structure. The resulting HTML should be accessible,
+human-readable, and editable by hand and downstream tools.
+
+PDF, PNG, and SVG export, in contrast, all produce _visual_ representations of a
+fully-laid out document. This divergence in the formats' intents means that
+Typst cannot simply produce perfect HTML for your existing Typst documents. It
+cannot always know what the best semantic HTML representation of your content
+is.
+
+Instead, it gives _you_ full control: You can check the current export format
+through the [`target`] function and when it is set to HTML, generate [raw HTML
+elements]($html.elem). The primary intended use of these elements is in
+templates and show rules. This way, the document's contents can be fully
+agnostic to the export target and content can be shared between PDF and HTML
+export.
+
+Currently, Typst will always output a single HTML file. Support for outputting
+directories with multiple HTML documents and assets, as well as support for
+outputting fragments that can be integrated into other HTML documents is
+planned.
+
+Typst currently does not output CSS style sheets, instead focussing on emitting
+semantic markup. You can of course write your own CSS styles and still benefit
+from sharing your _content_ between PDF and HTML. For the future, we plan to
+give you the option of automatically emitting CSS, taking more of your existing
+set rules into account.
+
+# Exporting as HTML
+## Command Line
+Pass `--format html` to the `compile` or `watch` subcommand or provide an output
+file name that ends with `.html`. Note that you must also pass `--features html`
+or set `TYPST_FEATURES=html` to enable this experimental export target.
+
+When using `typst watch`, Typst will spin up a live-reloading HTTP server. You
+can configure it as follows:
+
+- Pass `--port` to change the port. (Defaults to the first free port in the
+  range 3000-3005.)
+- Pass `--no-reload` to disable injection of a live reload script. (The HTML
+  that is written to disk isn't affected either way.)
+- Pass `--no-serve` to disable the server altogether.
+
+## Web App
+Not currently available.
+
+# HTML-specific functionality
+Typst exposes HTML-specific functionality in the global `html` module. See below
+for the definitions it contains.
diff --git a/docs/reference/export/pdf.md b/docs/reference/export/pdf.md
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+PDF files focus on accurately describing documents visually, but also have
+facilities for annotating their structure. This hybrid approach makes
+them a good fit for document exchange: They render exactly the same on every
+device, but also support extraction of a document's content and structure (at
+least to an extent). Unlike PNG files, PDFs are not bound to a specific
+resolution. Hence, you can view them at any size without incurring a loss of
+quality.
+
+# PDF standards
+The International Standards Organization (ISO) has published the base PDF
+standard and various standards that extend it to make PDFs more suitable for
+specific use-cases. By default, Typst exports PDF 1.7 files. Adobe Acrobat 8 and
+later as well as all other commonly used PDF viewers are compatible with this
+PDF version.
+
+## PDF/A
+Typst optionally supports emitting PDF/A-conformant files. PDF/A files are
+geared towards maximum compatibility with current and future PDF tooling. They
+do not rely on difficult-to-implement or proprietary features and contain
+exhaustive metadata. This makes them suitable for long-term archival.
+
+The PDF/A Standard has multiple versions (_parts_ in ISO terminology) and most
+parts have multiple profiles that indicate the file's conformance level.
+Currently, Typst supports these PDF/A output profiles:
+
+- PDF/A-2b: The basic conformance level of ISO 19005-2. This version of PDF/A is
+  based on PDF 1.7 and results in self-contained, archivable PDF files.
+
+- PDF/A-3b: The basic conformance level of ISO 19005-3. This version of PDF/A is
+  based on PDF 1.7 and results in archivable PDF files that can contain
+  arbitrary other related files as [attachments]($pdf.embed). The only
+  difference between it and PDF/A-2b is the capability to embed
+  non-PDF/A-conformant files within.
+
+When choosing between exporting PDF/A and regular PDF, keep in mind that PDF/A
+files contain additional metadata, and that some readers will prevent the user
+from modifying a PDF/A file. Some features of Typst may be disabled depending on
+the PDF standard you choose.
+
+# Exporting as PDF
+## Command Line
+PDF is Typst's default export format. Running the `compile` or `watch`
+subcommand without specifying a format will create a PDF. When exporting to PDF,
+you have the following configuration options:
+
+- Which PDF standards Typst should enforce conformance with by specifying
+  `--pdf-standard` followed by one or multiple comma-separated standards. Valid
+  standards are `1.7`, `a-2b`, and `a-3b`. By default, Typst outputs
+  PDF-1.7-compliant files.
+
+- Which pages to export by specifying `--pages` followed by a comma-separated
+  list of numbers or dash-separated number ranges. Ranges can be half-open.
+  Example: `2,3,7-9,11-`.
+
+## Web App
+Click the quick download button at the top right to export a PDF with default
+settings. For further configuration, click "File" > "Export as" > "PDF" or click
+the downwards-facing arrow next to the quick download button and select "Export
+as PDF". When exporting to PDF, you have the following configuration options:
+
+- Which PDF standards Typst should enforce conformance with. By default, Typst
+  outputs PDF-1.7-compliant files. Valid additional standards are `A-2b` and
+  `A-3b`.
+
+- Which pages to export. Valid options are "All pages", "Current page", and
+  "Custom ranges". Custom ranges are a comma-separated list of numbers or
+  dash-separated number ranges. Ranges can be half-open. Example: `2,3,7-9,11-`.
+
+# PDF-specific functionality
+Typst exposes PDF-specific functionality in the global `pdf` module. See below
+for the definitions it contains.
diff --git a/docs/reference/export/png.md b/docs/reference/export/png.md
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+Instead of creating a PDF, Typst can also directly render pages to PNG raster
+graphics. PNGs are losslessly compressed images that can contain one page at a
+time. When exporting a multi-page document, Typst will emit multiple PNGs. PNGs
+are a good choice when you want to use Typst's output in an image editing
+software or when you can use none of Typst's other export formats.
+
+In contrast to Typst's other export formats, PNGs are bound to a specific
+resolution. When exporting to PNG, you can configure the resolution as pixels
+per inch (PPI). If the medium you view the PNG on has a finer resolution than
+the PNG you exported, you will notice a loss of quality. Typst calculates the
+resolution of your PNGs based on each page's physical dimensions and the PPI. If
+you need guidance for choosing a PPI value, consider the following:
+
+- A DPI value of 300 or 600 is typical for desktop printing.
+- Professional prints of detailed graphics can go up to 1200 PPI.
+- If your document is only viewed at a distance, e.g. a poster, you may choose a
+  smaller value than 300.
+- If your document is viewed on screens, a typical PPI value for a smartphone is
+  400-500.
+
+Because PNGs only contain a pixel raster, the text within cannot be extracted
+automatically (without OCR), for example by copy/paste or a screen reader. If
+you need the text to be accessible, export a PDF or HTML file instead.
+
+PNGs can have transparent backgrounds. By default, Typst will output a PNG with
+an opaque white background. You can make the background transparent using
+`[#set page(fill: none)]`. Learn more on the
+[`page` function's reference page]($page.fill).
+
+# Exporting as PNG
+## Command Line
+Pass `--format png` to the `compile` or `watch` subcommand or provide an output
+file name that ends with `.png`.
+
+If your document has more than one page, Typst will create multiple image files.
+The output file name must then be a template string containing at least one of
+- `[{p}]`, which will be replaced by the page number
+- `[{0p}]`, which will be replaced by the zero-padded page number (so that all
+  numbers have the same length)
+- `[{t}]`, which will be replaced by the total number of pages
+
+When exporting to PNG, you have the following configuration options:
+
+- Which resolution to render at by specifying `--ppi` followed by a number of
+  pixels per inch. The default is `144`.
+
+- Which pages to export by specifying `--pages` followed by a comma-separated
+  list of numbers or dash-separated number ranges. Ranges can be half-open.
+  Example: `2,3,7-9,11-`.
+
+## Web App
+Click "File" > "Export as" > "PNG" or click the downwards-facing arrow next to
+the quick download button and select "Export as PNG". When exporting to PNG, you
+have the following configuration options:
+
+- The resolution at which the pages should be rendered, as a number of pixels
+  per inch. The default is `144`.
+
+- Which pages to export. Valid options are "All pages", "Current page", and
+  "Custom ranges". Custom ranges are a comma-separated list of numbers or
+  dash-separated number ranges. Ranges can be half-open. Example: `2,3,7-9,11-`.
diff --git a/docs/reference/export/svg.md b/docs/reference/export/svg.md
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+Instead of creating a PDF, Typst can also directly render pages to scalable
+vector graphics (SVGs), which are the preferred format for embedding vector
+graphics in web pages. Like PDF files, SVGs display your document exactly how
+you have laid it out in Typst. Likewise, they share the benefit of not being
+bound to a specific resolution. Hence, you can print or view SVG files on any
+device without incurring a loss of quality. (Note that font printing quality may
+be better with a PDF.) In contrast to a PDF, an SVG cannot contain multiple
+pages. When exporting a multi-page document, Typst will emit multiple SVGs.
+
+SVGs can represent text in two ways: By embedding the text itself and rendering
+it with the fonts available on the viewer's computer or by embedding the shapes
+of each glyph in the font used to create the document. To ensure that the SVG
+file looks the same across all devices it is viewed on, Typst chooses the latter
+method. This means that the text in the SVG cannot be extracted automatically,
+for example by copy/paste or a screen reader. If you need the text to be
+accessible, export a PDF or HTML file instead.
+
+SVGs can have transparent backgrounds. By default, Typst will output an SVG with
+an opaque white background. You can make the background transparent using
+`[#set page(fill: none)]`. Learn more on the
+[`page` function's reference page]($page.fill).
+
+# Exporting as SVG
+## Command Line
+Pass `--format svg` to the `compile` or `watch` subcommand or provide an output
+file name that ends with `.svg`.
+
+If your document has more than one page, Typst will create multiple image files.
+The output file name must then be a template string containing at least one of
+- `[{p}]`, which will be replaced by the page number
+- `[{0p}]`, which will be replaced by the zero-padded page number (so that all
+  numbers have the same length)
+- `[{t}]`, which will be replaced by the total number of pages
+
+When exporting to SVG, you have the following configuration options:
+
+- Which pages to export by specifying `--pages` followed by a comma-separated
+  list of numbers or dash-separated number ranges. Ranges can be half-open.
+  Example: `2,3,7-9,11-`.
+
+## Web App
+Click "File" > "Export as" > "SVG" or click the downwards-facing arrow next to
+the quick download button and select "Export as SVG". When exporting to SVG, you
+have the following configuration options:
+
+- Which pages to export. Valid options are "All pages", "Current page", and
+  "Custom ranges". Custom ranges are a comma-separated list of numbers or
+  dash-separated number ranges. Ranges can be half-open. Example: `2,3,7-9,11-`.
diff --git a/docs/reference/context.md b/docs/reference/language/context.md
index bdd520f5..bdd520f5 100644
--- a/docs/reference/context.md
+++ b/docs/reference/language/context.md
diff --git a/docs/reference/scripting.md b/docs/reference/language/scripting.md
index 5e0f1555..5e0f1555 100644
--- a/docs/reference/scripting.md
+++ b/docs/reference/language/scripting.md
diff --git a/docs/reference/styling.md b/docs/reference/language/styling.md
index b0b7ab71..b0b7ab71 100644
--- a/docs/reference/styling.md
+++ b/docs/reference/language/styling.md
diff --git a/docs/reference/syntax.md b/docs/reference/language/syntax.md
index fdc4d154..fdc4d154 100644
--- a/docs/reference/syntax.md
+++ b/docs/reference/language/syntax.md
diff --git a/docs/reference/library/data-loading.md b/docs/reference/library/data-loading.md
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+Data loading from external files.
+
+These functions help you with loading and embedding data, for example from the
+results of an experiment.
diff --git a/docs/reference/library/foundations.md b/docs/reference/library/foundations.md
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+Foundational types and functions.
+
+Here, you'll find documentation for basic data types like [integers]($int) and
+[strings]($str) as well as details about core computational functions.
diff --git a/docs/reference/library/introspection.md b/docs/reference/library/introspection.md
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+Interactions between document parts.
+
+This category is home to Typst's introspection capabilities: With the `counter`
+function, you can access and manipulate page, section, figure, and equation
+counters or create custom ones. Meanwhile, the `query` function lets you search
+for elements in the document to construct things like a list of figures or
+headers which show the current chapter title.
+
+Most of the functions are _contextual._ It is recommended to read the chapter on
+[context] before continuing here.
diff --git a/docs/reference/library/layout.md b/docs/reference/library/layout.md
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+Arranging elements on the page in different ways.
+
+By combining layout functions, you can create complex and automatic layouts.
diff --git a/docs/reference/library/math.md b/docs/reference/library/math.md
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+Typst has special [syntax]($syntax/#math) and library functions to typeset
+mathematical formulas. Math formulas can be displayed inline with text or as
+separate blocks. They will be typeset into their own block if they start and end
+with at least one space (e.g. `[$ x^2 $]`).
+
+# Variables
+In math, single letters are always displayed as is. Multiple letters, however,
+are interpreted as variables and functions. To display multiple letters
+verbatim, you can place them into quotes and to access single letter variables,
+you can use the [hash syntax]($scripting/#expressions).
+
+```example
+$ A = pi r^2 $
+$ "area" = pi dot "radius"^2 $
+$ cal(A) :=
+    { x in RR | x "is natural" } $
+#let x = 5
+$ #x < 17 $
+```
+
+# Symbols
+Math mode makes a wide selection of [symbols]($category/symbols/sym) like `pi`,
+`dot`, or `RR` available. Many mathematical symbols are available in different
+variants. You can select between different variants by applying
+[modifiers]($symbol) to the symbol. Typst further recognizes a number of
+shorthand sequences like `=>` that approximate a symbol. When such a shorthand
+exists, the symbol's documentation lists it.
+
+```example
+$ x < y => x gt.eq.not y $
+```
+
+# Line Breaks
+Formulas can also contain line breaks. Each line can contain one or multiple
+_alignment points_ (`&`) which are then aligned.
+
+```example
+$ sum_(k=0)^n k
+    &= 1 + ... + n \
+    &= (n(n+1)) / 2 $
+```
+
+# Function calls
+Math mode supports special function calls without the hash prefix. In these
+"math calls", the argument list works a little differently than in code:
+
+- Within them, Typst is still in "math mode". Thus, you can write math directly
+  into them, but need to use hash syntax to pass code expressions (except for
+  strings, which are available in the math syntax).
+- They support positional and named arguments, as well as argument spreading.
+- They don't support trailing content blocks.
+- They provide additional syntax for 2-dimensional argument lists. The semicolon
+  (`;`) merges preceding arguments separated by commas into an array argument.
+
+```example
+$ frac(a^2, 2) $
+$ vec(1, 2, delim: "[") $
+$ mat(1, 2; 3, 4) $
+$ mat(..#range(1, 5).chunks(2)) $
+$ lim_x =
+    op("lim", limits: #true)_x $
+```
+
+To write a verbatim comma or semicolon in a math call, escape it with a
+backslash. The colon on the other hand is only recognized in a special way if
+directly preceded by an identifier, so to display it verbatim in those cases,
+you can just insert a space before it.
+
+Functions calls preceded by a hash are normal code function calls and not
+affected by these rules.
+
+# Alignment
+When equations include multiple _alignment points_ (`&`), this creates blocks of
+alternatingly right- and left-aligned columns. In the example below, the
+expression `(3x + y) / 7` is right-aligned and `= 9` is left-aligned. The word
+"given" is also left-aligned because `&&` creates two alignment points in a row,
+alternating the alignment twice. `& &` and `&&` behave exactly the same way.
+Meanwhile, "multiply by 7" is right-aligned because just one `&` precedes it.
+Each alignment point simply alternates between right-aligned/left-aligned.
+
+```example
+$ (3x + y) / 7 &= 9 && "given" \
+  3x + y &= 63 & "multiply by 7" \
+  3x &= 63 - y && "subtract y" \
+  x &= 21 - y/3 & "divide by 3" $
+```
+
+# Math fonts
+You can set the math font by with a [show-set rule]($styling/#show-rules) as
+demonstrated below. Note that only special OpenType math fonts are suitable for
+typesetting maths.
+
+```example
+#show math.equation: set text(font: "Fira Math")
+$ sum_(i in NN) 1 + i $
+```
+
+# Math module
+All math functions are part of the `math` [module]($scripting/#modules), which
+is available by default in equations. Outside of equations, they can be accessed
+with the `math.` prefix.
diff --git a/docs/reference/library/model.md b/docs/reference/library/model.md
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+Document structuring.
+
+Here, you can find functions to structure your document and interact with that
+structure. This includes section headings, figures, bibliography management,
+cross-referencing and more.
diff --git a/docs/reference/library/symbols.md b/docs/reference/library/symbols.md
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+These two modules give names to symbols and emoji to make them easy to insert
+with a normal keyboard. Alternatively, you can also always directly enter
+Unicode symbols into your text and formulas. In addition to the symbols listed
+below, math mode defines `dif` and `Dif`. These are not normal symbol values
+because they also affect spacing and font style.
diff --git a/docs/reference/library/text.md b/docs/reference/library/text.md
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index 00000000..239c0b26
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+++ b/docs/reference/library/text.md
@@ -0,0 +1,3 @@
+Text styling.
+
+The [text function]($text) is of particular interest.
diff --git a/docs/reference/library/visualize.md b/docs/reference/library/visualize.md
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--- /dev/null
+++ b/docs/reference/library/visualize.md
@@ -0,0 +1,5 @@
+Drawing and data visualization.
+
+If you want to create more advanced drawings or plots, also have a look at the
+[CetZ](https://github.com/johannes-wolf/cetz) package as well as more
+specialized [packages]($universe) for your use case.
diff --git a/docs/reference/packages.md b/docs/reference/packages.md
deleted file mode 100644
index bfd1ef58..00000000
--- a/docs/reference/packages.md
+++ /dev/null
@@ -1,6 +0,0 @@
-Typst [packages]($scripting/#packages) encapsulate reusable building blocks
-and make them reusable across projects. Below is a list of Typst packages
-created by the community. Due to the early and experimental nature of Typst's
-package management, they all live in a `preview` namespace. Click on a package's
-name to view its documentation and use the copy button on the right to get a
-full import statement for it.