Match inline font fragment geometry

crates/obscura-render/src/dom.rs

@@ -224,6 +224,11 @@ impl OverflowClip {
 /// Per-element border boxes after layout, in viewport coordinates.
 pub struct DomLayout {
     pub rects: HashMap<NodeId, Rect>,
+    /// Per-line border-box fragments for ordinary non-replaced inline
+    /// elements. `rects` retains their union for `getBoundingClientRect()`;
+    /// this list is the source for background/border painting and
+    /// `getClientRects()` as wrapping support is extended.
+    pub inline_fragments: HashMap<NodeId, Vec<Rect>>,
     pub styles: HashMap<NodeId, crate::LayoutStyle>,
     /// Computed custom properties in force for each element. Values are
     /// reference-counted because the overwhelmingly common case is inheritance
@@ -262,6 +267,11 @@ pub struct DomLayout {
     /// have no DOM node of their own.
     #[cfg(feature = "paint")]
     pub run_ifc_items: HashMap<NodeId, Vec<usize>>,
+    /// Webfont-shaped items backing the general per-word fallback. Unlike
+    /// `run_ifc_items`, these remain keyed by their real DOM text node so they
+    /// can paint in exact tree order at each independently wrapped Taffy box.
+    #[cfg(feature = "paint")]
+    pub word_ifc_items: HashMap<NodeId, Vec<usize>>,
     /// Anonymous in-flow boxes generated by `::before`/`::after`. These have
     /// no DOM node of their own, but unlike the legacy text-only fast path
     /// they participate in layout with their pseudo style's real box model.
@@ -1019,6 +1029,7 @@ fn sync_positioned_pseudo_percentage_padding(
 struct IfcRegistry {
     whole: HashMap<NodeId, usize>,
     runs: HashMap<NodeId, Vec<usize>>,
+    word_items: HashMap<NodeId, Vec<usize>>,
     generated: Vec<GeneratedBoxBuild>,
     /// Specified column widths per table grid node, from `<col>` elements and
     /// colspan-1 cells: `(px, percent)` per column index. Consumed by the
@@ -2035,6 +2046,7 @@ fn layout_dom_once(
         .find(|id| tree.get_node(*id).map(|n| n.is_element()).unwrap_or(false));
 
     let mut rects = HashMap::new();
+    let mut inline_fragments = HashMap::new();
     let mut text_runs = HashMap::new();
     // Final absolute rects of anonymous inline-run leaves, keyed by the
     // engine item index (they have no DOM id to key `rects` by).
@@ -3866,6 +3878,8 @@ fn layout_dom_once(
                 &generated_nodes,
                 &mut generated_rects,
             );
+            inline_fragments =
+                synthesize_ordinary_inline_fragments(&mut rects, &styles, &engine);
             synthesize_row_rects(tree, &mut rects);
         }
     }
@@ -3959,6 +3973,23 @@ fn layout_dom_once(
             }
         }
     }
+    // General word-fallback items are shaped with the same loaded font system
+    // as full IFCs but retain one independently wrapped Taffy rect per token.
+    // Their source is a real text node, so clipping/translation follows that
+    // node while each item is pinned to its anonymous leaf.
+    #[cfg(feature = "paint")]
+    for (text_node, items) in &ifc_items.word_items {
+        let clip = clip_rects
+            .get(text_node)
+            .copied()
+            .flatten()
+            .map(|clip| clip.viewport_rect(viewport));
+        for &idx in items {
+            if let Some(rect) = anon_rects.get(&idx) {
+                engine.finalize(idx, (rect.x, rect.y), rect.width, clip);
+            }
+        }
+    }
 
     let generated_boxes = ifc_items
         .generated
@@ -3976,6 +4007,7 @@ fn layout_dom_once(
     (
         DomLayout {
             rects,
+            inline_fragments,
             styles,
             custom_properties,
             clip_rects,
@@ -3987,6 +4019,8 @@ fn layout_dom_once(
             ifc_items: ifc_items.whole,
             #[cfg(feature = "paint")]
             run_ifc_items: ifc_items.runs,
+            #[cfg(feature = "paint")]
+            word_ifc_items: ifc_items.word_items,
             generated_boxes,
         },
         signature,
@@ -3995,6 +4029,54 @@ fn layout_dom_once(
     )
 }
 
+/// Convert Taffy's ordinary-inline line surrogate into the element's actual
+/// visual fragment box.
+///
+/// The surrogate remains at CSS line-height so it contributes the correct
+/// line advance. The fragment uses the selected face's grid-fitted ascent plus
+/// descent, expanded by block-axis padding and border. Those decorations
+/// protrude into the leading and never feed back into the line height.
+fn synthesize_ordinary_inline_fragments(
+    rects: &mut HashMap<NodeId, Rect>,
+    styles: &HashMap<NodeId, crate::LayoutStyle>,
+    engine: &crate::inline::TextEngine,
+) -> HashMap<NodeId, Vec<Rect>> {
+    let mut fragments = HashMap::new();
+    let mut unions = Vec::new();
+    for (&id, style) in styles {
+        if !style.ignores_used_box_sizes() {
+            continue;
+        }
+        let Some(flow_rect) = rects.get(&id).copied() else {
+            continue;
+        };
+        let font_height = engine.inline_font_box_height(style).max(0.0);
+        let line_height = engine.selected_line_height(style).max(0.0);
+        // Taffy's surrogate may be taller than this element's own strut when
+        // a nested inline enlarges the line. Center the element's logical
+        // line-height inside that allocation before removing its leading.
+        let logical_top = flow_rect.y + (flow_rect.height - line_height) / 2.0;
+        let fragment = Rect {
+            x: flow_rect.x,
+            y: logical_top + (line_height - font_height) / 2.0
+                - style.padding.top
+                - style.border.top,
+            width: flow_rect.width,
+            height: font_height
+                + style.padding.top
+                + style.padding.bottom
+                + style.border.top
+                + style.border.bottom,
+        };
+        fragments.insert(id, vec![fragment]);
+        unions.push((id, fragment));
+    }
+    for (id, union) in unions {
+        rects.insert(id, union);
+    }
+    fragments
+}
+
 fn container_snapshot(
     tree: &DomTree,
     layout: &DomLayout,
@@ -5736,7 +5818,15 @@ fn build_any(
         .map(|n| matches!(n.data, obscura_dom::tree::NodeData::Text { .. }))
         .unwrap_or(false);
     if is_text {
-        return build_text_words(tree, id, taffy_tree, styles, words);
+        return build_text_words(
+            tree,
+            id,
+            taffy_tree,
+            styles,
+            words,
+            engine,
+            ifc_items,
+        );
     }
     // `display: contents` removes the element's own box; its children lay out as
     // if they were direct children of its parent (CSS Display 3). Splice them
@@ -5975,6 +6065,8 @@ fn build_text_words(
     taffy_tree: &mut TaffyTree<usize>,
     styles: &HashMap<NodeId, crate::LayoutStyle>,
     words: &mut HashMap<taffy::NodeId, (NodeId, String)>,
+    engine: &mut crate::inline::TextEngine,
+    ifc_items: &mut IfcRegistry,
 ) -> Vec<taffy::NodeId> {
     let Some(node) = tree.get_node(id) else { return Vec::new() };
     let obscura_dom::tree::NodeData::Text { contents } = &node.data else { return Vec::new() };
@@ -6011,8 +6103,22 @@ fn build_text_words(
             letter_spacing = p_style.letter_spacing.unwrap_or(0.0);
         }
     }
-    display_text = transform_word_leaf_text(&display_text, transform);
+    if let Some(style) = node.parent.and_then(|parent| styles.get(&parent)) {
+        let shaped = build_shaped_word_leaves(
+            id,
+            &display_text,
+            style,
+            taffy_tree,
+            words,
+            engine,
+            ifc_items,
+        );
+        if !shaped.is_empty() {
+            return shaped;
+        }
+    }
 
+    display_text = transform_word_leaf_text(&display_text, transform);
     build_word_leaves(
         id,
         &display_text,
@@ -6026,6 +6132,70 @@ fn build_text_words(
     )
 }
 
+/// Webfont-aware counterpart to [`build_word_leaves`].
+///
+/// The general flex-wrap fallback still needs one independently placeable
+/// Taffy leaf per word. Shape each visible token through the render pass's
+/// retained `TextEngine`, then reuse that same item at paint time. This keeps
+/// loaded faces, variable axes, optical sizing, transforms, and glyph
+/// rasterization identical to the full inline-formatting-context path.
+fn build_shaped_word_leaves(
+    source_id: NodeId,
+    text: &str,
+    style: &crate::LayoutStyle,
+    taffy_tree: &mut TaffyTree<usize>,
+    words: &mut HashMap<taffy::NodeId, (NodeId, String)>,
+    engine: &mut crate::inline::TextEngine,
+    ifc_items: &mut IfcRegistry,
+) -> Vec<taffy::NodeId> {
+    let mut leaves = Vec::new();
+    for token in tokenize_with_spaces(text) {
+        if token.trim().is_empty() {
+            continue;
+        }
+        // A token normally retains one trailing collapsed space. Shape it as
+        // preformatted content so the item keeps that advance instead of the
+        // paragraph path trimming collapsible trailing whitespace.
+        let mut token_style = style.clone();
+        token_style.white_space = Some(crate::WhiteSpace::Pre);
+        let Some(item) = engine.push_generated_text(&token, &token_style) else {
+            // Returning no leaves makes the caller use the deterministic
+            // layout-only/static-font fallback for the whole text node.
+            return Vec::new();
+        };
+        let (width, height) = engine.measure_word(item);
+        let taffy_style = taffy::Style {
+            size: taffy::Size {
+                width: taffy::Dimension::length(width.max(0.0)),
+                height: taffy::Dimension::length(height.max(0.0)),
+            },
+            ..Default::default()
+        };
+        let Ok(leaf) = taffy_tree.new_leaf_with_context(taffy_style, item) else {
+            return Vec::new();
+        };
+        words.insert(
+            leaf,
+            (
+                source_id,
+                transform_word_leaf_text(
+                    &token,
+                    style
+                        .text_transform
+                        .unwrap_or(crate::TextTransform::None),
+                ),
+            ),
+        );
+        ifc_items
+            .word_items
+            .entry(source_id)
+            .or_default()
+            .push(item);
+        leaves.push(leaf);
+    }
+    leaves
+}
+
 fn transform_word_leaf_text(text: &str, transform: crate::TextTransform) -> String {
     match transform {
         crate::TextTransform::None => text.to_string(),
@@ -10985,6 +11155,101 @@ mod tests {
         );
     }
 
+    #[test]
+    fn ordinary_inline_fragment_uses_font_box_while_line_keeps_line_height() {
+        let tree = parse_html(
+            r#"<style>
+                html,body,p { margin:0 }
+                p { height:auto; font:16px/40px monospace }
+                code {
+                    position:relative;
+                    font:16px/40px monospace;
+                    padding-top:5px; padding-bottom:7px;
+                    border-top:2px solid; border-bottom:3px solid;
+                    margin-top:19px; margin-bottom:23px;
+                    background:red
+                }
+                #control { margin-top:0; margin-bottom:0 }
+            </style>
+            <p id="with-margin"><code id="token">token</code></p>
+            <p id="without-margin"><code id="control">token</code></p>"#,
+        );
+        let laid = layout_dom(&tree, (400.0, 200.0));
+        let host = tree.get_element_by_id("with-margin").unwrap();
+        let control_host = tree.get_element_by_id("without-margin").unwrap();
+        let token = tree.get_element_by_id("token").unwrap();
+        let control = tree.get_element_by_id("control").unwrap();
+        let style = &laid.styles[&token];
+        let raw_font_height = laid.text_engine.inline_font_box_height(style);
+        let expected_fragment_height = raw_font_height + 5.0 + 7.0 + 2.0 + 3.0;
+
+        assert_eq!(
+            laid.rects[&host].height, 40.0,
+            "block-axis inline padding/border must not increase line advance"
+        );
+        assert_eq!(laid.rects[&control_host].height, 40.0);
+        assert_eq!(laid.rects[&token].height, expected_fragment_height);
+        assert_eq!(laid.inline_fragments[&token], vec![laid.rects[&token]]);
+        assert_eq!(
+            laid.rects[&token].y - laid.rects[&host].y,
+            (40.0 - raw_font_height) / 2.0 - 5.0 - 2.0
+        );
+        assert_eq!(
+            laid.rects[&control].y - laid.rects[&control_host].y,
+            laid.rects[&token].y - laid.rects[&host].y,
+            "ordinary inline block-axis margins must not move its fragment"
+        );
+    }
+
+    #[test]
+    fn fallback_word_boxes_shape_and_paint_with_the_loaded_webfont() {
+        let tree = parse_html(
+            r#"<style>
+                html,body,p { margin:0 }
+                #token {
+                    position:relative;
+                    font-family:Fixture, sans-serif;
+                    font-size:40px;
+                    line-height:50px;
+                    background:red
+                }
+            </style>
+            <p><span id="token">WWWWiiii</span></p>"#,
+        );
+        let token = tree.get_element_by_id("token").unwrap();
+        let text = rendered_children(&tree, token)[0];
+        let fallback = layout_dom(&tree, (500.0, 150.0));
+        let loaded = layout_dom_with_web_fonts(
+            &tree,
+            (500.0, 150.0),
+            &HashMap::new(),
+            &[crate::inline::WebFont {
+                data: include_bytes!("../assets/liberation-serif.ttf").to_vec(),
+                family: Some("Fixture".to_string()),
+                weight: Some((400, 400)),
+                italic: Some(false),
+            }],
+        );
+
+        assert!(
+            loaded.word_ifc_items.get(&text).is_some_and(|items| !items.is_empty()),
+            "a decorated/relative inline fallback must retain shaped word items"
+        );
+        assert_ne!(
+            fallback.rects[&token].width, loaded.rects[&token].width,
+            "the loaded face's advances must drive fallback inline geometry"
+        );
+        assert_ne!(
+            fallback.rects[&token].height, loaded.rects[&token].height,
+            "the loaded face's raw ascent/descent must drive the visual fragment"
+        );
+        assert_eq!(
+            loaded.inline_fragments[&token],
+            vec![loaded.rects[&token]],
+            "the loaded-font fragment must be the geometry/paint source"
+        );
+    }
+
     #[test]
     fn positioned_pseudo_inherits_the_hosts_computed_font_metrics() {
         let tree = parse_html(

crates/obscura-render/src/inline.rs

@@ -300,6 +300,18 @@ fn normal_line_height(font_size: f32, metrics: FaceMetrics) -> f32 {
         + (metrics.line_gap * scale).round()
 }
 
+/// Grid-fitted font ascent plus descent, excluding both the face line gap and
+/// authored CSS `line-height`.
+///
+/// A non-replaced inline has two different vertical boxes. Its line
+/// participation uses [`used_line_height_with_metrics`], while its painted
+/// fragment/client rect uses this raw font box plus block-axis padding and
+/// border. Chromium and Gecko both fit ascent and descent independently.
+fn font_box_height(font_size: f32, metrics: FaceMetrics) -> f32 {
+    let scale = font_size / metrics.units_per_em.max(1.0);
+    (metrics.ascent * scale).round() + (metrics.descent * scale).round()
+}
+
 fn font_metrics(
     db: &cosmic_text::fontdb::Database,
     id: cosmic_text::fontdb::ID,
@@ -848,6 +860,32 @@ impl TextEngine {
     pub fn len(&self) -> usize {
         self.items.len()
     }
+
+    /// Raw selected-font box used by ordinary inline fragments. This is
+    /// deliberately not CSS `line-height`: leading belongs to the containing
+    /// line and must not enlarge backgrounds, borders, or DOM client rects.
+    pub(crate) fn inline_font_box_height(&self, style: &LayoutStyle) -> f32 {
+        let font = resolve_loaded_font(
+            style.font_family.as_deref(),
+            crate::style::used_font_weight(style),
+            style.font_style_italic.unwrap_or(false),
+            &self.loaded_families,
+        );
+        font_box_height(style.font_size.unwrap_or(16.0), font.metrics)
+    }
+
+    /// Used line-height for the same selected face. Kept beside
+    /// [`inline_font_box_height`](Self::inline_font_box_height) so layout can
+    /// distribute leading around the raw fragment using one font decision.
+    pub(crate) fn selected_line_height(&self, style: &LayoutStyle) -> f32 {
+        let font = resolve_loaded_font(
+            style.font_family.as_deref(),
+            crate::style::used_font_weight(style),
+            style.font_style_italic.unwrap_or(false),
+            &self.loaded_families,
+        );
+        used_line_height_for_font(style, &font)
+    }
     pub fn is_empty(&self) -> bool {
         self.items.is_empty()
     }
@@ -1158,6 +1196,32 @@ impl TextEngine {
         (width, height.max(item.forced_min_height))
     }
 
+    /// Exact max-content size for one fallback word item. Paragraph IFCs keep
+    /// their historical integer-ceiled intrinsic width, but word boxes need
+    /// the selected webfont's fractional advance or every token accumulates a
+    /// pixel of horizontal drift against browser geometry.
+    pub(crate) fn measure_word(&mut self, idx: usize) -> (f32, f32) {
+        let TextEngine {
+            font_system, items, ..
+        } = self;
+        let Some(item) = items.get_mut(idx) else {
+            return (0.0, 0.0);
+        };
+        shape_with_text_indent(font_system, item, None);
+        let mut width = 0.0f32;
+        let mut height = 0.0f32;
+        for (line_index, run) in item.buffer.layout_runs().enumerate() {
+            let offset = if line_index == 0 {
+                item.first_line_offset
+            } else {
+                0.0
+            };
+            width = width.max((run.line_w + offset).max(0.0));
+            height = height.max(run.line_top + run.line_height);
+        }
+        (width, height.max(item.forced_min_height))
+    }
+
     /// Register a replaced element's intrinsic size as a taffy measure
     /// context. Percentage-sized image leaves still need their intrinsic
     /// max-content contribution while an auto-sized ancestor is measured.

crates/obscura-render/src/lib.rs

@@ -127,6 +127,37 @@ pub mod inline {
         ) -> Option<usize> {
             None
         }
+
+        /// Layout-only builds do not load page fonts. Preserve the same
+        /// line-vs-fragment contract with deterministic bundled metrics.
+        pub(crate) fn inline_font_box_height(&self, style: &crate::LayoutStyle) -> f32 {
+            style.font_size.unwrap_or(16.0)
+        }
+
+        pub(crate) fn selected_line_height(&self, style: &crate::LayoutStyle) -> f32 {
+            match style.line_height.unwrap_or(crate::LineHeight::Normal) {
+                crate::LineHeight::Normal => style.font_size.unwrap_or(16.0) * 1.2,
+                crate::LineHeight::Ratio(value) => style.font_size.unwrap_or(16.0) * value,
+                crate::LineHeight::Px(value) => value,
+                crate::LineHeight::Relative(crate::Dimension::Percent(value)) => {
+                    style.font_size.unwrap_or(16.0) * value
+                }
+                crate::LineHeight::Relative(crate::Dimension::Px(value)) => value,
+                crate::LineHeight::Relative(_) => style.font_size.unwrap_or(16.0),
+            }
+        }
+
+        pub(crate) fn push_generated_text(
+            &mut self,
+            _text: &str,
+            _style: &crate::LayoutStyle,
+        ) -> Option<usize> {
+            None
+        }
+
+        pub(crate) fn measure_word(&mut self, _idx: usize) -> (f32, f32) {
+            (0.0, 0.0)
+        }
     }
 }
 
@@ -1463,6 +1494,19 @@ pub(crate) fn to_taffy_style(style: &LayoutStyle) -> Style {
     s.margin = rect_auto(style.margin, style.margin_auto);
     s.padding = rect_lp_percent(style.padding, style.padding_percent);
     s.border = rect_lp(style.border);
+    if style.ignores_used_box_sizes() {
+        // Block-axis margins on an ordinary non-replaced inline neither move
+        // nor size its fragment. Padding and border do paint around the raw
+        // font box, but they protrude outside the CSS line-height rather than
+        // increasing line advance. Keep them in LayoutStyle for fragment
+        // synthesis/paint and remove them only from this Taffy line surrogate.
+        s.margin.top = taffy::LengthPercentageAuto::length(0.0);
+        s.margin.bottom = taffy::LengthPercentageAuto::length(0.0);
+        s.padding.top = taffy::LengthPercentage::length(0.0);
+        s.padding.bottom = taffy::LengthPercentage::length(0.0);
+        s.border.top = taffy::LengthPercentage::length(0.0);
+        s.border.bottom = taffy::LengthPercentage::length(0.0);
+    }
     s
 }
 

crates/obscura-render/src/paint.rs

@@ -479,11 +479,37 @@ impl PreparedRender {
             "line-height",
             match style.line_height.unwrap_or(crate::LineHeight::Normal) {
                 crate::LineHeight::Normal => "normal".to_string(),
-                crate::LineHeight::Ratio(value) => css_number(value),
-                crate::LineHeight::Px(value) => css_px(value),
-                crate::LineHeight::Relative(value) => dimension_css(value, "normal"),
+                _ => css_px(self.layout.text_engine.selected_line_height(style)),
             },
         );
+        out.insert(
+            "letter-spacing",
+            match style.letter_spacing.unwrap_or(0.0) {
+                value if value == 0.0 => "normal".to_string(),
+                value => css_px(value),
+            },
+        );
+        out.insert(
+            "white-space",
+            match style.white_space.unwrap_or_default() {
+                crate::WhiteSpace::Normal => "normal",
+                crate::WhiteSpace::NoWrap => "nowrap",
+                crate::WhiteSpace::Pre => "pre",
+                crate::WhiteSpace::PreWrap => "pre-wrap",
+                crate::WhiteSpace::PreLine => "pre-line",
+                crate::WhiteSpace::BreakSpaces => "break-spaces",
+            }
+            .to_string(),
+        );
+        out.insert(
+            "text-align",
+            match style.text_align {
+                Some(taffy::AlignItems::CENTER) => "center",
+                Some(taffy::AlignItems::FLEX_END | taffy::AlignItems::END) => "end",
+                _ => "start",
+            }
+            .to_string(),
+        );
 
         if style.ignores_used_box_sizes() {
             out.insert("width", dimension_css(style.width, "auto"));
@@ -677,6 +703,49 @@ impl PreparedRender {
         Some(rect)
     }
 
+    /// Every CSS border-box fragment in the current root viewport. Ordinary
+    /// inlines can have one fragment per line; all other boxes expose their
+    /// single border box. Keeping this separate from the bounding union is
+    /// required by CSSOM View's `getClientRects()`.
+    pub fn viewport_client_rects(
+        &self,
+        id: obscura_dom::tree::NodeId,
+        requested_scroll: (f32, f32),
+    ) -> Option<Vec<crate::Rect>> {
+        let source = self
+            .layout
+            .inline_fragments
+            .get(&id)
+            .cloned()
+            .or_else(|| self.layout.rects.get(&id).copied().map(|rect| vec![rect]))?;
+        let transform = self
+            .layout
+            .translates
+            .get(&id)
+            .copied()
+            .unwrap_or((0.0, 0.0));
+        let scroll = self.clamp_scroll(requested_scroll);
+        let movement = if self.viewport_fixed.contains(&id) {
+            transform
+        } else {
+            let sticky = self.sticky.translation_for(id, self.viewport, scroll);
+            (
+                transform.0 + sticky.0 - scroll.0,
+                transform.1 + sticky.1 - scroll.1,
+            )
+        };
+        Some(
+            source
+                .into_iter()
+                .map(|rect| crate::Rect {
+                    x: rect.x + movement.0,
+                    y: rect.y + movement.1,
+                    ..rect
+                })
+                .collect(),
+        )
+    }
+
     pub fn selected_image(
         &self,
         id: obscura_dom::tree::NodeId,
@@ -1183,7 +1252,16 @@ fn paint_laid_dom_scrolled(
         };
 
         if node.is_text() {
-            paint_text_node(tree, nid, laid, &scroll_state, &mut pixmap);
+            if let Some(items) = laid.word_ifc_items.get(&nid) {
+                let offset = scroll_state.translation_for(laid, nid);
+                let clip = scroll_state.shaped_text_clip_for(laid, nid);
+                for &item in items {
+                    laid.text_engine
+                        .paint_item_with_clip(item, &mut pixmap, offset, clip);
+                }
+            } else {
+                paint_text_node(tree, nid, laid, &scroll_state, &mut pixmap);
+            }
             for generated in &generated_after_at[paint_index] {
                 paint_in_flow_generated_box(
                     &mut pixmap,