html: Parse a comma-separated list of faces in the <font> tag (#32622)

This change parses a comma-separated list of faces in the `<font>` tag
and also moves the parsing code from `stylo` to Servo. This means that
the servo-specific code can be removed from stylo decreasing the
differences between Gecko and Servo's version of `stylo`.

components/script/dom/element.rs

@@ -751,19 +751,18 @@ impl<'dom> LayoutElementHelpers<'dom> for LayoutDom<'dom, Element> {
             ));
         }
 
-        let font_family = if let Some(this) = self.downcast::<HTMLFontElement>() {
+        let font_face = if let Some(this) = self.downcast::<HTMLFontElement>() {
             this.get_face()
         } else {
             None
         };
 
-        if let Some(font_family) = font_family {
-            // FIXME(emilio): This in Gecko parses a whole family list.
+        if let Some(font_face) = font_face {
             hints.push(from_declaration(
                 shared_lock,
                 PropertyDeclaration::FontFamily(font_family::SpecifiedValue::Values(
                     computed::font::FontFamilyList {
-                        list: Box::new([computed::font::SingleFontFamily::from_atom(font_family)]),
+                        list: HTMLFontElement::parse_face_attribute(font_face).into_boxed_slice(),
                     },
                 )),
             ));

components/script/dom/htmlfontelement.rs

@@ -2,6 +2,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
+use cssparser::match_ignore_ascii_case;
 use dom_struct::dom_struct;
 use html5ever::{local_name, namespace_url, ns, LocalName, Prefix};
 use js::rust::HandleObject;
@@ -9,6 +10,9 @@ use servo_atoms::Atom;
 use style::attr::AttrValue;
 use style::color::AbsoluteColor;
 use style::str::{read_numbers, HTML_SPACE_CHARACTERS};
+use style::values::computed::font::{
+    FamilyName, FontFamilyNameSyntax, GenericFontFamily, SingleFontFamily,
+};
 
 use crate::dom::attr::Attr;
 use crate::dom::bindings::codegen::Bindings::HTMLFontElementBinding::HTMLFontElementMethods;
@@ -50,6 +54,38 @@ impl HTMLFontElement {
             proto,
         )
     }
+
+    pub(crate) fn parse_face_attribute(face_value: Atom) -> Vec<SingleFontFamily> {
+        face_value
+            .to_string()
+            .split(",")
+            .map(|string| Self::parse_single_face_value_from_string(string.trim()))
+            .collect()
+    }
+
+    fn parse_single_face_value_from_string(string: &str) -> SingleFontFamily {
+        match_ignore_ascii_case! { string,
+            "serif" => return SingleFontFamily::Generic(GenericFontFamily::Serif),
+            "sans-serif" => return SingleFontFamily::Generic(GenericFontFamily::SansSerif),
+            "cursive" => return SingleFontFamily::Generic(GenericFontFamily::Cursive),
+            "fantasy" => return SingleFontFamily::Generic(GenericFontFamily::Fantasy),
+            "monospace" => return SingleFontFamily::Generic(GenericFontFamily::Monospace),
+            "system-ui" => return SingleFontFamily::Generic(GenericFontFamily::SystemUi),
+            _ => {}
+        }
+
+        let name = string.to_owned().replace(['\'', '"'], "");
+        let syntax = if name == string {
+            FontFamilyNameSyntax::Identifiers
+        } else {
+            FontFamilyNameSyntax::Quoted
+        };
+
+        SingleFontFamily::FamilyName(FamilyName {
+            name: name.into(),
+            syntax,
+        })
+    }
 }
 
 impl HTMLFontElementMethods for HTMLFontElement {

tests/wpt/mozilla/meta/MANIFEST.json

@@ -7576,6 +7576,19 @@
       {}
      ]
     ],
+    "font-element-comma-separated.html": [
+     "db7e13f2ca3db0ebd3c610c3c25b052749b85e30",
+     [
+      null,
+      [
+       [
+        "/_mozilla/mozilla/font-element-comma-separated-ref.html",
+        "=="
+       ]
+      ],
+      {}
+     ]
+    ],
     "fullscreen": {
      "reftests": {
       "fullscreen-baseline.html": [
@@ -10436,6 +10449,10 @@
      "6783d72a6629f4938df8126dc5114d936eaaa48f",
      []
     ],
+    "font-element-comma-separated-ref.html": [
+     "97efe2b83d5f78bdac0d4aa951b63342fb1fa1cf",
+     []
+    ],
     "form_submit_about_frame.html": [
      "7beb90f1ab7bce0b162050180c4a44380940aed8",
      []

tests/wpt/mozilla/tests/mozilla/font-element-comma-separated-ref.html

@@ -0,0 +1,16 @@
+<!DOCTYPE html>
+<html>
+<head>
+    <meta charset="utf-8">
+    <title>The &lt;font&gt; element should support a comma separated list of font family names</title>
+    <link rel="author" title="Martin Robinson" href="mrobinson@igalia.com">
+    <link rel="stylesheet" type="text/css" href="/fonts/ahem.css">
+</head>
+
+<body>
+    The elements below should be rendered with the Ahem font and show as a black rectangles.
+    <br/>
+    <span style="font-family: 'Ahem', serif;">XXXX</font>
+    <br/>
+    <span style="font-family: 'Ahem', serif;">XXXX</font>
+</body>

tests/wpt/mozilla/tests/mozilla/font-element-comma-separated.html

@@ -0,0 +1,17 @@
+<!DOCTYPE html>
+<html>
+<head>
+    <meta charset="utf-8">
+    <title>The &lt;font&gt; element should support a comma separated list of font family names</title>
+    <link rel="author" title="Martin Robinson" href="mrobinson@igalia.com">
+    <link rel="match" href="font-element-comma-separated-ref.html">
+    <link rel="stylesheet" type="text/css" href="/fonts/ahem.css">
+</head>
+
+<body>
+    The elements below should be rendered with the Ahem font and show as a black rectangles.
+    <br/>
+    <font face="Ahem, serif">XXXX</font>
+    <br/>
+    <font face="'Ahem', serif">XXXX</font>
+</body>