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//! Metadata contains information about the page. This includes information
//! about styles, scripts and data to help software (search engines, browsers,
//! etc.) use and render the page. Metadata for styles and scripts may be
//! defined in the page or link to another file that has the information.
html_element! {
/// The [HTML `<base> element`][mdn] specifies the base URL to use for all relative URLs
/// contained within a document. There can be only one `<base>` element in a document.
///
/// If either of its inherent attributes are specified, this element must come before other
/// elements with attributes whose values are URLs, such as <link>’s href attribute.
///
/// [mdn]: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/base
<base>
categories {
Metadata
}
attributes {
/// The base URL to be used throughout the document for relative URLs. Absolute and relative
/// URLs are allowed.
href
/// A keyword or author-defined name of the default browsing context to display the result
/// when links or forms cause navigation, for `<a>` or `<form>` elements without an explicit
/// target attribute. The attribute value targets a browsing context (such as a tab, window,
/// or `<iframe>`).
///
/// The following keywords have special meanings:
///
/// * `_self`: Load the result into the same browsing context as the current one. (This is
/// the default.)
/// * `_blank`: Load the result into a new, unnamed browsing context.
/// * `_parent`: Load the result into the parent browsing context of the current one. (If
/// the current page is inside a frame.) If there is no parent, behaves the same way as
/// _self.
/// * `_top`: Load the result into the topmost browsing context (that is, the browsing
/// context that is an ancestor of the current one, and has no parent). If there is no
/// parent, behaves the same way as _self.
target
}
}
html_element! {
/// The [HTML `<head>` element][mdn] contains machine-readable information ([metadata]) about
/// the document, like its [title], [scripts], and [style sheets].
///
/// [mdn]: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/head
/// [metadata]: https://developer.mozilla.org/en-US/docs/Glossary/metadata
/// [title]: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/title
/// [scripts]: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/script
/// [style sheets]: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/style
<head>
children {
categories {
Metadata
}
}
}
html_element! {
/// The [HTML External Resource Link element (`<link>`)][mdn] specifies relationships between
/// the current document and an external resource. This element is most commonly used to link to
/// [stylesheets], but is also used to establish site icons (both "favicon" style icons and
/// icons for the home screen and apps on mobile devices) among other things.
///
/// [mdn]: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/link
/// [stylesheets]: https://developer.mozilla.org/en-US/docs/Glossary/CSS
<link>
categories {
Metadata,
// if `itemprop` is present:
Flow, Phrasing
}
attributes {
/// This attribute is only used when rel="preload" or rel="prefetch" has been set on the
/// `<link>` element. It specifies the type of content being loaded by the `<link>`, which is
/// necessary for request matching, application of correct content security policy, and
/// setting of correct Accept request header. Furthermore, rel="preload" uses this as a
/// signal for request prioritization. The table below lists the valid values for this
/// attribute and the elements or resources they apply to.
///
/// | Value | Applies To |
/// | -------- | ------------------------------------------------------------------------- |
/// | audio | `<audio>` elements |
/// | document | `<iframe>` and `<frame>` elements |
/// | embed | `<embed>` elements |
/// | fetch | fetch, XHR (also requires `<link>` to contain the crossorigin attribute.) |
/// | font | CSS @font-face |
/// | image | `<img>` and `<picture>` elements with srcset or imageset attributes, |
/// | | SVG `<image>` elements, CSS *-image rules |
/// | object | `<object>` elements |
/// | script | `<script>` elements, Worker importScripts |
/// | style | `<link rel=stylesheet>` elements, CSS @import |
/// | track | `<track>` elements |
/// | video | `<video>` elements |
/// | worker | Worker, SharedWorker |
as_
/// This enumerated attribute indicates whether CORS must be used when fetching the
/// resource. CORS-enabled images can be reused in the `<canvas>` element without being
/// tainted. The allowed values are:
///
/// * `anonymous`: A cross-origin request (i.e. with an Origin HTTP header) is performed,
/// but no credential is sent (i.e. no cookie, X.509 certificate, or HTTP Basic
/// authentication). If the server does not give credentials to the origin site (by not
/// setting the Access-Control-Allow-Origin HTTP header) the resource will be tainted and
/// its usage restricted.
/// * `use-credentials`: A cross-origin request (i.e. with an Origin HTTP header) is
/// performed along with a credential sent (i.e. a cookie, certificate, and/or HTTP Basic
/// authentication is performed). If the server does not give credentials to the origin
/// site (through Access-Control-Allow-Credentials HTTP header), the resource will be
/// tainted and its usage restricted.
///
/// If the attribute is not present, the resource is fetched without a CORS request (i.e.
/// without sending the Origin HTTP header), preventing its non-tainted usage. If invalid,
/// it is handled as if the enumerated keyword anonymous was used.
crossorigin
/// For rel="stylesheet" only, the disabled Boolean attribute indicates whether or not the
/// described stylesheet should be loaded and applied to the document. If disabled is
/// specified in the HTML when it is loaded, the stylesheet will not be loaded during page
/// load. Instead, the stylesheet will be loaded on-demand, if and when the disabled
/// attribute is changed to false or removed.
///
/// Once the stylesheet has been loaded, however, changes made to the value of the disabled
/// property no longer have any relationship to the value of the StyleSheet.disabled
/// property. Changing the value of this property instead simply enables and disables the
/// stylesheet form being applied to the document.
///
/// This differs from StyleSheet's disabled property; changing it to true removes the
/// stylesheet from the document's document.styleSheets list, and doesn't automatically
/// reload the stylesheet when it's toggled back to false.
disabled
/// This attribute specifies the URL of the linked resource. A URL can be absolute or
/// relative.
href
/// This attribute indicates the language of the linked resource. It is purely advisory.
/// Allowed values are determined by BCP47. Use this attribute only if the href attribute is
/// present.
hreflang
/// This attribute specifies the media that the linked resource applies to. Its value must
/// be a media type / media query. This attribute is mainly useful when linking to external
/// stylesheets — it allows the user agent to pick the best adapted one for the device it
/// runs on.
media
/// This attribute names a relationship of the linked document to the current document. The
/// attribute must be a space-separated list of link type values.
rel
/// This attribute defines the sizes of the icons for visual media contained in the
/// resource. It must be present only if the rel contains a value of icon or a non-standard
/// type such as Apple's apple-touch-icon. It may have the following values:
///
/// * `any`, meaning that the icon can be scaled to any size as it is in a vector format,
/// like image/svg+xml.
/// * a white-space separated list of sizes, each in the format <width in pixels>x<height in
/// pixels> or <width in pixels>X<height in pixels>. Each of these sizes must be contained
/// in the resource.
///
/// Note: Most icon formats are only able to store one single icon; therefore most of the
/// time the sizes attribute contains only one entry. MS's ICO format does, as well as
/// Apple's ICNS. ICO is more ubiquitous, so you should use this format if cross-browser
/// support is a concern (especially for old IE versions).
sizes
/// The title attribute has special semantics on the `<link>` element. When used on a
/// `<link rel="stylesheet">` it defines a preferred or an alternate stylesheet. Incorrectly
/// using it may cause the stylesheet to be ignored.
title
/// This attribute is used to define the type of the content linked to. The value of the
/// attribute should be a MIME type such as text/html, text/css, and so on. The common use
/// of this attribute is to define the type of stylesheet being referenced (such as
/// text/css), but given that CSS is the only stylesheet language used on the web, not only
/// is it possible to omit the type attribute, but is actually now recommended practice. It
/// is also used on rel="preload" link types, to make sure the browser only downloads file
/// types that it supports.
type_
}
}
html_element! {
/// The [HTML `<meta>` element][mdn] represents [metadata] that cannot be represented by other
/// HTML meta-related elements, like [`<base>`], [`<link>`], [`<script>`], [`<style>`] or
/// [`<title>`].
///
/// Note: the attribute `name` has a specific meaning for the `<meta>` element, and the
/// `itemprop` attribute must not be set on the same `<meta>` element that has any existing
/// name, `http-equiv` or `charset` attributes.
///
/// [mdn]: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/meta
/// [metadata]: https://developer.mozilla.org/en-US/docs/Glossary/Metadata
/// [`<base>`]: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/base
/// [`<link>`]: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/link
/// [`<script>`]: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/script
/// [`<style>`]: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/style
/// [`<title>`]: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/title
<meta>
categories {
Metadata,
// if `itemprop` is present:
Flow, Phrasing
}
attributes {
/// This attribute declares the document's character encoding. If the attribute is present,
/// its value must be an ASCII case-insensitive match for the string "utf-8".
charset
/// This attribute contains the value for the http-equiv or name attribute, depending on
/// which is used.
content
/// Defines a pragma directive. The attribute is named http-equiv(alent) because all the
/// allowed values are names of particular HTTP headers:
///
/// * `content-security-policy`: Allows page authors to define a content policy for the
/// current page. Content policies mostly specify allowed server origins and script
/// endpoints which help guard against cross-site scripting attacks.
/// * `content-type`: If specified, the content attribute must have the value
/// `text/html; charset=utf-8`. Note: Can only be used in documents served with a
/// text/html MIME type — not in documents served with an XML MIME type.
/// * `default-style`: Sets the name of the default CSS style sheet set.
/// * `x-ua-compatible`: If specified, the content attribute must have the value "IE=edge".
/// User agents are required to ignore this pragma.
/// * `refresh`: This instruction specifies:
/// * The number of seconds until the page should be reloaded - only if the content
/// attribute contains a positive integer.
/// * The number of seconds until the page should redirect to another - only if the
/// content attribute contains a positive integer followed by the string ';url=', and a
/// valid URL.
/// * Accessibility concerns: Pages set with a refresh value run the risk of having the
/// time interval being too short. People navigating with the aid of assistive
/// technology such as a screen reader may be unable to read through and understand the
/// page's content before being automatically redirected. The abrupt, unannounced
/// updating of the page content may also be disorienting for people experiencing low
/// vision conditions.
http_equiv
/// The name and content attributes can be used together to provide document metadata in
/// terms of name-value pairs, with the name attribute giving the metadata name, and the
/// content attribute giving the value.
///
/// See [standard metadata names] for details about the set of standard metadata names
/// defined in the HTML specification.
///
/// [standard metadata names]: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/meta/name
name
}
}
html_element! {
/// The [HTML `<style>` element][mdn] contains style information for a document, or part of a
/// document.
///
/// [mdn]: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/style
<style>
categories {
Metadata,
Flow // if the `scoped` attribute is present
}
attributes {
/// This attribute defines which media the style should be applied to. Its value is a media
/// query, which defaults to all if the attribute is missing.
media
/// A cryptographic nonce (number used once) used to whitelist inline styles in a style-src
/// Content-Security-Policy. The server must generate a unique nonce value each time it
/// transmits a policy. It is critical to provide a nonce that cannot be guessed as
/// bypassing a resource’s policy is otherwise trivial.
nonce
/// This attribute specifies alternative style sheet sets.
title
}
}
only_text_children! { <style> }
html_element! {
/// The [HTML Title element (`<title>`)][mdn] defines the document's title that is shown in a
/// [browser]'s title bar or a page's tab.
///
/// [mdn]: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/title
/// [browser]: https://developer.mozilla.org/en-US/docs/Glossary/Browser
<title>
categories {
Metadata
}
}
only_text_children! { <title> }