render: load preloaded web fonts

crates/obscura-render/Cargo.toml

@@ -11,7 +11,7 @@ default = []
 # Rasterize the laid-out tree to a pixmap (tiny-skia) with text (cosmic-text
 # shaping + line breaking, ab_glyph fallback) and images.
 # Off by default; the layout core (getBoundingClientRect etc.) works without it.
-paint = ["dep:tiny-skia", "dep:ab_glyph", "dep:cosmic-text", "dep:image", "dep:ureq", "dep:base64", "dep:resvg", "dep:usvg", "dep:url"]
+paint = ["dep:tiny-skia", "dep:ab_glyph", "dep:cosmic-text", "dep:image", "dep:ureq", "dep:base64", "dep:resvg", "dep:usvg", "dep:url", "dep:wuff"]
 
 [dependencies]
 taffy = { workspace = true }
@@ -32,6 +32,7 @@ resvg = { version = "0.47", default-features = false, features = ["text", "raste
 usvg = { version = "0.47", default-features = false, optional = true }
 url = { workspace = true, optional = true }
 cssparser = "0.34"
+wuff = { version = "0.2.7", optional = true }
 [lib]
 path = "src/lib.rs"
 

crates/obscura-render/src/dom.rs

@@ -392,6 +392,17 @@ pub fn layout_dom_with_images(
     tree: &DomTree,
     viewport: (f32, f32),
     intrinsic: &HashMap<NodeId, (f32, f32)>,
+) -> DomLayout {
+    layout_dom_with_resources(tree, viewport, intrinsic, &[])
+}
+
+/// Like [`layout_dom_with_images`], with decoded OpenType web-font data loaded
+/// into the shaping database for this render pass.
+pub fn layout_dom_with_resources(
+    tree: &DomTree,
+    viewport: (f32, f32),
+    intrinsic: &HashMap<NodeId, (f32, f32)>,
+    fonts: &[Vec<u8>],
 ) -> DomLayout {
     let timing = std::env::var("OBSCURA_RENDER_TIMING").is_ok();
 
@@ -449,7 +460,7 @@ pub fn layout_dom_with_images(
     let mut taffy_tree: TaffyTree<usize> = TaffyTree::new();
     let mut id_map: HashMap<taffy::NodeId, NodeId> = HashMap::new();
     let mut words: HashMap<taffy::NodeId, (NodeId, String)> = HashMap::new();
-    let mut engine = crate::inline::TextEngine::new();
+    let mut engine = crate::inline::TextEngine::new_with_fonts(fonts);
     let mut ifc_items = IfcRegistry::default();
 
     // The document node itself is not an element; lay out from the first

crates/obscura-render/src/inline.rs

@@ -12,7 +12,7 @@
 //! Fonts are loaded from embedded bytes only, never the OS, so layout is
 //! byte-for-byte deterministic across hosts (the whole engine's guarantee).
 
-use std::sync::Arc;
+use std::{collections::HashMap, sync::Arc};
 
 use cosmic_text::{Align, Attrs, Buffer, Color, Family, FontSystem, Metrics, Shaping, Style, SwashCache, Weight, Wrap};
 
@@ -77,6 +77,24 @@ fn resolve_font_family(fam: Option<&str>) -> &'static str {
     }
     FAMILY
 }
+
+fn resolve_loaded_font_family(
+    fam: Option<&str>,
+    loaded: &HashMap<String, Arc<str>>,
+) -> Arc<str> {
+    if let Some(stack) = fam {
+        for token in stack.split(',') {
+            let name = token
+                .trim()
+                .trim_matches(|c| c == '"' || c == '\'')
+                .trim();
+            if let Some(family) = loaded.get(&name.to_ascii_lowercase()) {
+                return Arc::clone(family);
+            }
+        }
+    }
+    Arc::from(resolve_font_family(fam))
+}
 /// Resolve `line-height: normal` from the selected face's horizontal header.
 ///
 /// Chromium's FreeType-backed Linux path grid-fits the ascent, descent, and
@@ -148,6 +166,7 @@ pub struct InlineItem {
 /// [`crate::DomLayout`] so paint can rasterize the shaped glyphs.
 pub struct TextEngine {
     font_system: FontSystem,
+    loaded_families: HashMap<String, Arc<str>>,
     swash: SwashCache,
     items: Vec<InlineItem>,
     replaced: Vec<ReplacedItem>,
@@ -215,6 +234,10 @@ impl Default for TextEngine {
 
 impl TextEngine {
     pub fn new() -> Self {
+        Self::new_with_fonts(&[])
+    }
+
+    pub fn new_with_fonts(fonts: &[Vec<u8>]) -> Self {
         // Build a database from our four embedded faces only. Never call
         // load_system_fonts: a host's font set would make layout differ
         // machine to machine and add a multi-millisecond startup scan.
@@ -227,10 +250,24 @@ impl TextEngine {
         ] {
             db.load_font_source(cosmic_text::fontdb::Source::Binary(Arc::new(bytes)));
         }
+        for bytes in fonts {
+            db.load_font_source(cosmic_text::fontdb::Source::Binary(Arc::new(
+                bytes.clone(),
+            )));
+        }
+        let mut loaded_families = HashMap::new();
+        for face in db.faces() {
+            for (name, _) in &face.families {
+                loaded_families
+                    .entry(name.to_ascii_lowercase())
+                    .or_insert_with(|| Arc::from(name.as_str()));
+            }
+        }
         db.set_sans_serif_family(FAMILY);
         let font_system = FontSystem::new_with_locale_and_db("en-US".to_string(), db);
         TextEngine {
             font_system,
+            loaded_families,
             swash: SwashCache::new(),
             items: Vec::new(),
             replaced: Vec::new(),
@@ -256,9 +293,21 @@ impl TextEngine {
         }
         let base = styles.get(&id)?;
         let mut collector = Collector { last_was_space: true, clip_fills: Vec::new() };
-        let ctx = base_span_ctx(base, &mut collector);
+        let ctx = base_span_ctx(
+            base,
+            resolve_loaded_font_family(base.font_family.as_deref(), &self.loaded_families),
+            &mut collector,
+        );
         let mut spans: Vec<(String, SpanAttrs)> = Vec::new();
-        collect_spans(tree, id, styles, ctx, &mut spans, &mut collector);
+        collect_spans(
+            tree,
+            id,
+            styles,
+            ctx,
+            &mut spans,
+            &mut collector,
+            &self.loaded_families,
+        );
         self.push_shaped_item(base, spans, collector.clip_fills)
     }
 
@@ -287,10 +336,22 @@ impl TextEngine {
         }
         let base = styles.get(&parent)?;
         let mut collector = Collector { last_was_space: true, clip_fills: Vec::new() };
-        let ctx = base_span_ctx(base, &mut collector);
+        let ctx = base_span_ctx(
+            base,
+            resolve_loaded_font_family(base.font_family.as_deref(), &self.loaded_families),
+            &mut collector,
+        );
         let mut spans: Vec<(String, SpanAttrs)> = Vec::new();
         for &cid in run {
-            collect_node_spans(tree, cid, styles, ctx, &mut spans, &mut collector);
+            collect_node_spans(
+                tree,
+                cid,
+                styles,
+                ctx.clone(),
+                &mut spans,
+                &mut collector,
+                &self.loaded_families,
+            );
         }
         self.push_shaped_item(base, spans, collector.clip_fills)
     }
@@ -452,13 +513,13 @@ struct SpanAttrs {
     italic: bool,
     underline: bool,
     color: [u8; 4],
-    family: &'static str,
+    family: Arc<str>,
     clip_fill: Option<usize>,
 }
 
 impl SpanAttrs {
     fn to_attrs(&self) -> Attrs<'_> {
-        let mut a = Attrs::new().family(Family::Name(self.family));
+        let mut a = Attrs::new().family(Family::Name(self.family.as_ref()));
         a = a.weight(if self.bold { Weight::BOLD } else { Weight::NORMAL });
         a = a.style(if self.italic { Style::Italic } else { Style::Normal });
         // Clip-text glyphs must be shaped with an opaque fill so their coverage
@@ -473,14 +534,14 @@ impl SpanAttrs {
 }
 
 /// Inherited inline context threaded down the subtree while collecting spans.
-#[derive(Clone, Copy)]
+#[derive(Clone)]
 struct SpanCtx {
     color: [u8; 4],
     bold: bool,
     italic: bool,
     underline: bool,
     transform: TextTransform,
-    family: &'static str,
+    family: Arc<str>,
     clip_fill: Option<usize>,
 }
 
@@ -502,7 +563,11 @@ struct Collector {
 /// shape the glyphs in opaque white so their coverage renders, then recolor
 /// them from the background at paint time; otherwise transparent text stays
 /// transparent (and invisible), unchanged.
-fn base_span_ctx(base: &LayoutStyle, collector: &mut Collector) -> SpanCtx {
+fn base_span_ctx(
+    base: &LayoutStyle,
+    family: Arc<str>,
+    collector: &mut Collector,
+) -> SpanCtx {
     let clip_fill = clip_text_fill(base).map(|fill| {
         let index = collector.clip_fills.len();
         collector.clip_fills.push(fill);
@@ -514,7 +579,7 @@ fn base_span_ctx(base: &LayoutStyle, collector: &mut Collector) -> SpanCtx {
         italic: base.font_style_italic.unwrap_or(false),
         underline: base.underline.unwrap_or(false),
         transform: base.text_transform.unwrap_or(TextTransform::None),
-        family: resolve_font_family(base.font_family.as_deref()),
+        family,
         clip_fill,
     }
 }
@@ -526,9 +591,18 @@ fn collect_spans(
     ctx: SpanCtx,
     out: &mut Vec<(String, SpanAttrs)>,
     c: &mut Collector,
+    loaded_families: &HashMap<String, Arc<str>>,
 ) {
     for cid in tree.children(id) {
-        collect_node_spans(tree, cid, styles, ctx, out, c);
+        collect_node_spans(
+            tree,
+            cid,
+            styles,
+            ctx.clone(),
+            out,
+            c,
+            loaded_families,
+        );
     }
 }
 
@@ -543,6 +617,7 @@ fn collect_node_spans(
     ctx: SpanCtx,
     out: &mut Vec<(String, SpanAttrs)>,
     c: &mut Collector,
+    loaded_families: &HashMap<String, Arc<str>>,
 ) {
     let Some(node) = tree.get_node(cid) else { return };
     match &node.data {
@@ -552,7 +627,7 @@ fn collect_node_spans(
                 italic: ctx.italic,
                 underline: ctx.underline,
                 color: ctx.color,
-                family: ctx.family,
+                family: Arc::clone(&ctx.family),
                 clip_fill: ctx.clip_fill,
             };
             push_text(contents, ctx.transform, &attrs, out, c);
@@ -569,7 +644,7 @@ fn collect_node_spans(
                     italic: ctx.italic,
                     underline: ctx.underline,
                     color: ctx.color,
-                    family: ctx.family,
+                    family: Arc::clone(&ctx.family),
                     clip_fill: ctx.clip_fill,
                 }));
                 c.last_was_space = true;
@@ -597,11 +672,21 @@ fn collect_node_spans(
                 transform: style.and_then(|s| s.text_transform).unwrap_or(ctx.transform),
                 family: style
                     .and_then(|s| s.font_family.as_deref())
-                    .map(|f| resolve_font_family(Some(f)))
-                    .unwrap_or(ctx.family),
+                    .map(|family| {
+                        resolve_loaded_font_family(Some(family), loaded_families)
+                    })
+                    .unwrap_or_else(|| Arc::clone(&ctx.family)),
                 clip_fill,
             };
-            collect_spans(tree, cid, styles, child, out, c);
+            collect_spans(
+                tree,
+                cid,
+                styles,
+                child,
+                out,
+                c,
+                loaded_families,
+            );
         }
     }
 }

crates/obscura-render/src/lib.rs

@@ -20,7 +20,7 @@ pub mod style;
 pub use style::compute_style;
 
 pub mod dom;
-pub use dom::{layout_dom, layout_dom_with_images, DomLayout};
+pub use dom::{layout_dom, layout_dom_with_images, layout_dom_with_resources, DomLayout};
 
 #[cfg(feature = "paint")]
 mod paint;

crates/obscura-render/src/paint.rs

@@ -11,7 +11,7 @@ use ab_glyph::{Font, FontRef, PxScale, ScaleFont};
 
 static FONT_BYTES: &[u8] = include_bytes!("../assets/liberation-sans.ttf");
 
-use crate::layout_dom_with_images;
+use crate::layout_dom_with_resources;
 
 /// Render `tree` at `viewport` (width, height) in CSS pixels to a Pixmap, or
 /// None if the viewport is zero-sized. `base_url`, when given, resolves the
@@ -33,7 +33,8 @@ pub fn paint_dom(tree: &DomTree, viewport: (f32, f32), base_url: Option<&str>) -
     // and never paint). This seeds the same cache the paint pass reads, so
     // each URL is still fetched at most once.
     let intrinsic = collect_image_intrinsics(tree, base_url, &mut image_cache);
-    let mut laid = layout_dom_with_images(tree, viewport, &intrinsic);
+    let fonts = collect_web_fonts(tree, base_url);
+    let mut laid = layout_dom_with_resources(tree, viewport, &intrinsic, &fonts);
     // Nodes that live inside an inline `<svg>` we rasterized as one document;
     // their painting is owned by that raster, so they are skipped in both the
     // box/text loop below and the inline-formatting loop after it (an svg
@@ -757,13 +758,12 @@ fn fetch_bytes(
     base_url: Option<&str>,
     cache: &mut std::collections::HashMap<String, Option<Vec<u8>>>,
 ) -> Option<Vec<u8>> {
-    if let Some(rest) = src.strip_prefix("data:image/") {
+    if let Some(rest) = src.strip_prefix("data:") {
         let comma_idx = rest.find(',')?;
         let (meta, data) = (&rest[..comma_idx], &rest[comma_idx + 1..]);
-        // Inline SVGs are very commonly authored as data:image/svg+xml;utf8,
-        // (or with no encoding label at all, which is equivalent): plain,
-        // percent-escaped text, not base64. Only decode as base64 when the
-        // URI actually says so.
+        // Data-backed SVGs and web fonts may be base64 or percent-escaped.
+        // Decode from the encoding label rather than assuming every data URI
+        // is base64.
         return if meta.contains("base64") {
             use base64::Engine;
             base64::engine::general_purpose::STANDARD.decode(data).ok()
@@ -805,6 +805,257 @@ fn fetch_bytes(
         .clone()
 }
 
+/// Fetch the Latin/ASCII face from each authored `@font-face` rule and decode
+/// WOFF/WOFF2 into the sfnt bytes consumed by fontdb/cosmic-text. Unicode-range
+/// filtering is load-bearing for performance: generated font packages commonly
+/// emit six or seven script subsets per face, while an English page needs only
+/// the subset containing ASCII.
+fn collect_web_fonts(tree: &DomTree, base_url: Option<&str>) -> Vec<Vec<u8>> {
+    let mut cache = std::collections::HashMap::new();
+    let mut seen = std::collections::HashSet::new();
+    let mut fonts = Vec::new();
+
+    // Critical web fonts are normally preloaded from the document with a URL
+    // already resolved relative to the HTML. Prefer that browser-authored list:
+    // CSS gathered from external stylesheets is flattened into <style> text in
+    // the live DOM, where a relative src no longer carries its stylesheet URL.
+    let mut preloads = Vec::new();
+    for nid in tree.descendants(tree.document()) {
+        let Some(node) = tree.get_node(nid) else { continue };
+        if node
+            .as_element()
+            .map(|element| element.local.as_ref() != "link")
+            .unwrap_or(true)
+        {
+            continue;
+        }
+        let rel = node.get_attribute("rel").unwrap_or("");
+        let as_value = node.get_attribute("as").unwrap_or("");
+        if rel
+            .split_ascii_whitespace()
+            .any(|token| token.eq_ignore_ascii_case("preload"))
+            && as_value.eq_ignore_ascii_case("font")
+        {
+            if let Some(href) = node.get_attribute("href") {
+                preloads.push(href.to_string());
+            }
+        }
+    }
+    for src in preloads.iter().take(16) {
+        if !seen.insert(src.clone()) {
+            continue;
+        }
+        if let Some(decoded) = fetch_and_decode_font(src, base_url, &mut cache) {
+            fonts.push(decoded);
+        }
+    }
+    if !preloads.is_empty() {
+        return fonts;
+    }
+
+    for nid in tree.descendants(tree.document()) {
+        let Some(node) = tree.get_node(nid) else { continue };
+        if node
+            .as_element()
+            .map(|element| element.local.as_ref() != "style")
+            .unwrap_or(true)
+        {
+            continue;
+        }
+        let css = tree.text_content(nid);
+        for face in font_face_blocks(&css) {
+            if !font_face_covers_ascii(face) {
+                continue;
+            }
+            let Some(src) = font_face_urls(face).into_iter().next() else {
+                continue;
+            };
+            if !seen.insert(src.clone()) {
+                continue;
+            }
+            // Bound pathological pages without penalizing normal generated
+            // font packages (family x weight x style usually stays under 20).
+            if fonts.len() >= 12 {
+                return fonts;
+            }
+            if let Some(decoded) = fetch_and_decode_font(&src, base_url, &mut cache) {
+                fonts.push(decoded);
+            }
+        }
+    }
+    fonts
+}
+
+fn fetch_and_decode_font(
+    src: &str,
+    base_url: Option<&str>,
+    cache: &mut std::collections::HashMap<String, Option<Vec<u8>>>,
+) -> Option<Vec<u8>> {
+    let compressed = fetch_bytes(src, base_url, cache)?;
+    if compressed.len() > 8 * 1024 * 1024 {
+        return None;
+    }
+    let decoded = match compressed.get(..4) {
+        Some(b"wOF2") => wuff::decompress_woff2(&compressed).ok(),
+        Some(b"wOFF") => wuff::decompress_woff1(&compressed).ok(),
+        // TrueType/OpenType collections and raw sfnt fonts already have the
+        // representation fontdb expects.
+        Some(b"\0\x01\0\0" | b"OTTO" | b"ttcf") => Some(compressed),
+        _ => None,
+    }?;
+    (decoded.len() <= 32 * 1024 * 1024).then_some(decoded)
+}
+
+fn font_face_blocks(css: &str) -> Vec<&str> {
+    let lower = css.to_ascii_lowercase();
+    let mut out = Vec::new();
+    let mut cursor = 0;
+    while let Some(relative) = lower[cursor..].find("@font-face") {
+        let at = cursor + relative;
+        let Some(open_relative) = lower[at..].find('{') else {
+            break;
+        };
+        let open = at + open_relative;
+        let mut depth = 1i32;
+        let mut quote = None;
+        let mut escaped = false;
+        let mut close = None;
+        for (offset, ch) in css[open + 1..].char_indices() {
+            if escaped {
+                escaped = false;
+                continue;
+            }
+            if ch == '\\' {
+                escaped = true;
+                continue;
+            }
+            if let Some(active) = quote {
+                if ch == active {
+                    quote = None;
+                }
+                continue;
+            }
+            if matches!(ch, '"' | '\'') {
+                quote = Some(ch);
+                continue;
+            }
+            match ch {
+                '{' => depth += 1,
+                '}' => {
+                    depth -= 1;
+                    if depth == 0 {
+                        close = Some(open + 1 + offset);
+                        break;
+                    }
+                }
+                _ => {}
+            }
+        }
+        let Some(close) = close else { break };
+        out.push(&css[open + 1..close]);
+        cursor = close + 1;
+    }
+    out
+}
+
+fn font_face_declaration<'a>(face: &'a str, name: &str) -> Option<&'a str> {
+    split_css_top_level(face, ';').into_iter().find_map(|declaration| {
+        let (property, value) = declaration.split_once(':')?;
+        property.trim().eq_ignore_ascii_case(name).then_some(value.trim())
+    })
+}
+
+fn font_face_covers_ascii(face: &str) -> bool {
+    let Some(range) = font_face_declaration(face, "unicode-range") else {
+        return true;
+    };
+    range.split(',').any(|part| {
+        let token = part.trim().to_ascii_lowercase();
+        let Some(value) = token.strip_prefix("u+") else {
+            return false;
+        };
+        let (start, end) = if value.contains('?') {
+            (
+                u32::from_str_radix(&value.replace('?', "0"), 16).ok(),
+                u32::from_str_radix(&value.replace('?', "f"), 16).ok(),
+            )
+        } else if let Some((start, end)) = value.split_once('-') {
+            (
+                u32::from_str_radix(start, 16).ok(),
+                u32::from_str_radix(end, 16).ok(),
+            )
+        } else {
+            let point = u32::from_str_radix(value, 16).ok();
+            (point, point)
+        };
+        matches!((start, end), (Some(start), Some(end)) if start <= 0x7e && end >= 0x20)
+    })
+}
+
+fn font_face_urls(face: &str) -> Vec<String> {
+    let Some(src) = font_face_declaration(face, "src") else {
+        return Vec::new();
+    };
+    let lower = src.to_ascii_lowercase();
+    let mut out = Vec::new();
+    let mut cursor = 0;
+    while let Some(relative) = lower[cursor..].find("url(") {
+        let start = cursor + relative + 4;
+        let Some(end_relative) = src[start..].find(')') else {
+            break;
+        };
+        let end = start + end_relative;
+        let value = src[start..end]
+            .trim()
+            .trim_matches(|ch| ch == '"' || ch == '\'')
+            .trim();
+        if !value.is_empty() {
+            out.push(value.to_string());
+        }
+        cursor = end + 1;
+    }
+    out
+}
+
+fn split_css_top_level(value: &str, separator: char) -> Vec<&str> {
+    let mut out = Vec::new();
+    let mut start = 0;
+    let mut depth = 0i32;
+    let mut quote = None;
+    let mut escaped = false;
+    for (index, ch) in value.char_indices() {
+        if escaped {
+            escaped = false;
+            continue;
+        }
+        if ch == '\\' {
+            escaped = true;
+            continue;
+        }
+        if let Some(active) = quote {
+            if ch == active {
+                quote = None;
+            }
+            continue;
+        }
+        if matches!(ch, '"' | '\'') {
+            quote = Some(ch);
+            continue;
+        }
+        match ch {
+            '(' => depth += 1,
+            ')' => depth = (depth - 1).max(0),
+            ch if ch == separator && depth == 0 => {
+                out.push(&value[start..index]);
+                start = index + ch.len_utf8();
+            }
+            _ => {}
+        }
+    }
+    out.push(&value[start..]);
+    out
+}
+
 /// Fetch `url` with a descriptive User-Agent and a bounded timeout, retrying on
 /// rate-limit / transient errors with backoff. Real pages pull dozens of images
 /// from one CDN in a burst (a Wikipedia article references ~60); hosts like
@@ -2382,4 +2633,40 @@ mod tests {
         inject_external_sprites(&tree, svg, None, &mut markup, &mut cache, &mut sprite_cache);
         assert_eq!(markup, before, "same-document use must be untouched");
     }
+
+    #[test]
+    fn font_face_parser_selects_ascii_subset_and_preserves_functional_src() {
+        let css = r#"
+            @font-face {
+                font-family: "Example";
+                src: local("Example"), url("./example-cyrillic.woff2") format("woff2");
+                unicode-range: U+0400-04FF;
+            }
+            @font-face {
+                font-family: "Example";
+                src: url(data:font/woff2;base64,d09GMg==) format("woff2"),
+                     url("./example-latin.woff") format("woff");
+                unicode-range: U+??, U+2000-206F;
+            }
+        "#;
+        let faces = font_face_blocks(css);
+        assert_eq!(faces.len(), 2);
+        assert!(!font_face_covers_ascii(faces[0]));
+        assert!(font_face_covers_ascii(faces[1]));
+        assert_eq!(
+            font_face_urls(faces[1]),
+            vec![
+                "data:font/woff2;base64,d09GMg==".to_string(),
+                "./example-latin.woff".to_string(),
+            ]
+        );
+    }
+
+    #[test]
+    fn font_face_without_unicode_range_is_general_purpose() {
+        let css = r#"@font-face{font-family:Example;src:url(example.otf)}"#;
+        let face = font_face_blocks(css)[0];
+        assert!(font_face_covers_ascii(face));
+        assert_eq!(font_face_urls(face), vec!["example.otf"]);
+    }
 }