fix(components): resolve default sizes against the node font-size

crates/rustmotion-components/src/box_builder.rs

@@ -1495,7 +1495,9 @@ fn apply_intrinsic_overrides(component: &Component, css: &mut CssStyle) {
                 css.width = Some(CSize::Length(CLP::Px(c.width)));
             }
             if css.height.is_none() {
-                let font_size = c.style.font_size_px_or(16.0);
+                let font_size = c
+                    .style
+                    .font_size_px_ctx(&crate::intrinsic::measure_time_font_size_ctx(0.0), 16.0);
                 let line_height = font_size * 1.3;
                 let n = c.items.len() as f32;
                 let h = n * line_height + (n - 1.0).max(0.0) * c.gap;
@@ -1640,7 +1642,9 @@ fn apply_intrinsic_overrides(component: &Component, css: &mut CssStyle) {
             // box is fit exactly to the unwrapped text width, the painter's
             // own `wrap_text(text, font, Some(text_area_w))` never has a
             // reason to wrap, so painted output matches this box exactly.
-            let font_size = t.style.font_size_px_or(16.0);
+            let font_size = t
+                .style
+                .font_size_px_ctx(&crate::intrinsic::measure_time_font_size_ctx(0.0), 16.0);
             let family = t.style.font_family_or("Inter");
             let text_w = measure_text_line_width(&t.text, font_size, family, false);
             let h_pad = 12.0; // callout.rs's own `let padding = 12.0;`
@@ -1660,7 +1664,10 @@ fn apply_intrinsic_overrides(component: &Component, css: &mut CssStyle) {
             // Same shape as Callout above; padding value borrowed from
             // callout.rs since tooltip.rs's own paint() centers text in the
             // body with no defined constant of its own.
-            let font_size = t.style.font_size_px_or(t.font_size);
+            let font_size = t.style.font_size_px_ctx(
+                &crate::intrinsic::measure_time_font_size_ctx(0.0),
+                t.font_size,
+            );
             let family = t.style.font_family_or("Inter");
             let text_w = measure_text_line_width(&t.text, font_size, family, false);
             let h_pad = 12.0;
@@ -1685,7 +1692,9 @@ fn apply_intrinsic_overrides(component: &Component, css: &mut CssStyle) {
             // formula (h_pad = font_size*1.2 per side, `gap` before/after/
             // between every pill) using the same public fields and the same
             // `measure_text_with_fallback` call it makes internally.
-            let font_size = p.style.font_size_px_or(14.0);
+            let font_size = p
+                .style
+                .font_size_px_ctx(&crate::intrinsic::measure_time_font_size_ctx(0.0), 14.0);
             let family = p.style.font_family_or("Inter");
             let h_pad = font_size * 1.2;
             let n = p.items.len() as f32;
@@ -1713,7 +1722,10 @@ fn apply_intrinsic_overrides(component: &Component, css: &mut CssStyle) {
             // height ratio both of those same real usages share:
             // `font_size: 24` paired with `style.height: 48`, i.e.
             // `2 × font_size`.
-            let font_size = m.style.font_size_px_or(m.font_size);
+            let font_size = m.style.font_size_px_ctx(
+                &crate::intrinsic::measure_time_font_size_ctx(0.0),
+                m.font_size,
+            );
             apply_default_size(css, 800.0, font_size * 2.0);
         }
         Stepper(s) => {

crates/rustmotion-components/tests/audit_ws_i.rs

@@ -0,0 +1,67 @@
+//! Regression tests for workstream I of the 2026-09 audit (components and
+//! the CSS cascade).
+//!
+//! - `apply_intrinsic_overrides`'s default-size branches resolved
+//!   `font-size` through the context-free `font_size_px_or`, which returns
+//!   `0.0` for a relative unit (`rem`/`vw`/`vh`) instead of resolving it —
+//!   collapsing `marquee`/`list`/`callout`/`tooltip`/`pill_nav` to a 0px box.
+//! - `cascade::inherit_from` computes inherited `color`/`font-*` but
+//!   nothing on the render path ever reads the result — every painter reads
+//!   its own component's un-cascaded `style` field instead.
+//! - `TableIntrinsic` measures content-fitted per-column widths, but
+//!   the painter splits the box evenly across columns regardless.
+
+use rustmotion_components::box_builder::{build_scene_with_anim, BuildAnimationCtx};
+use rustmotion_components::{ChildComponent, Component, PositionMode};
+use rustmotion_core::css::taffy_bridge::ConversionContext;
+use rustmotion_core::engine::layout_pass::run_layout;
+
+fn single_child_scene(json: serde_json::Value) -> ChildComponent {
+    let component: Component = serde_json::from_value(json).expect("deserialize component");
+    ChildComponent {
+        component,
+        position: Some(PositionMode::Absolute { x: 0.0, y: 0.0 }),
+        x: None,
+        y: None,
+        z_index: None,
+        bleed: false,
+    }
+}
+
+// ─── default sizes must resolve against the node's font-size ───────────────
+
+#[test]
+fn marquee_with_relative_font_size_gets_a_positive_height() {
+    // Reproduction: `font_size_px_or` returns 0.0 for any relative unit
+    // (`.px()` can't resolve `%`/`em`/`rem`/`vw`/`vh`). Five sites in
+    // `apply_intrinsic_overrides` still called it — Marquee among them —
+    // so a marquee declaring `"font-size": "2rem"` and no explicit height
+    // used to collapse `apply_default_size(css, 800.0, 0.0)` to a 0px-tall
+    // box, and `paint_pass`'s `height <= 0.0` guard then skipped it
+    // entirely: the marquee never appeared on screen.
+    let child = single_child_scene(serde_json::json!({
+        "type": "marquee",
+        "content": "BREAKING NEWS",
+        "style": { "font-size": "2rem" }
+    }));
+    let children = vec![child];
+
+    let built = build_scene_with_anim(
+        &children,
+        (1920.0, 1080.0),
+        BuildAnimationCtx {
+            time: 0.0,
+            scenario_time: 0.0,
+            scene_duration: 1.0,
+            fps: 30,
+        },
+    );
+    let layout = run_layout(&built.root, (1920.0, 1080.0), &ConversionContext::default());
+    let marquee_id = built.root.children[0].id;
+    let l = layout.get(marquee_id).expect("marquee laid out");
+    assert!(
+        l.height > 0.0,
+        "marquee at font-size: 2rem must lay out with a positive height, got {}",
+        l.height
+    );
+}