From a252cd526cd22bc2fc76c1eec9be75f1a2778978 Mon Sep 17 00:00:00 2001
From: Baptiste Parmantier <baptiste.parmantier.pro@gmail.com>
Date: Tue, 22 Sep 2026 11:04:34 +0200
Subject: [PATCH] fix(geometry): measure text overflow against the content box
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`bbox` here is `raw_bbox = bbox_of(layout)` (geometry.rs:272, 376-383), i.e. `layout.width` — the BORDER box. But `LegacyPaintDispatcher::dispatch` (crates/rustmotion-components/src/legacy_dispatch.rs) hands every non-codeblock painter a synthetic `BoxLayout { width: cw, height: ch, border/padding: zero }` taken from `layout.content_box()` and translates the canvas to the content-box origin. So `Text::paint` wraps and draws inside `cw`, not `layout.width`. A `white-space: nowrap` text with `style.padding: "0 24px"` in a 300px box has `cw = 252`; a natural line width of 280px paints 28px past the box's right edge, yet `280 > 300` is false and nothing is reported. The sibling check `check_content_overflows_box` (geometry.rs:848) does this correctly via `layout.content_box()` — the two checks disagree about which box text lives in, and the flagship `unwrappable_text_overflow` is the one that is wrong. The gap equals `padding.left + padding.right + border.left + border.right`.

Refs #220
---
 .../rustmotion/src/cli/commands/geometry.rs   | 51 ++++++++++++-------
 crates/rustmotion/tests/audit_ws_b.rs         | 51 +++++++++++++++++++
 2 files changed, 85 insertions(+), 17 deletions(-)

diff --git a/crates/rustmotion/src/cli/commands/geometry.rs b/crates/rustmotion/src/cli/commands/geometry.rs
index e1c10bf4..b502d461 100644
--- a/crates/rustmotion/src/cli/commands/geometry.rs
+++ b/crates/rustmotion/src/cli/commands/geometry.rs
@@ -300,7 +300,7 @@ fn walk(
                 check_unwrappable_text(
                     &child.component,
                     &child_path,
-                    &raw_bbox,
+                    layout,
                     viewport,
                     vi,
                     si,
@@ -791,10 +791,32 @@ fn measurer_and_nowrap(component: &Component) -> Option<(Box<dyn IntrinsicMeasur
     }
 }
 
+/// natural (unwrapped) width vs the node's own CONTENT box, not its
+/// border box. `LegacyPaintDispatcher::dispatch` hands every non-codeblock
+/// painter (`Text`/`GradientText`/`Caption` included) a synthetic
+/// `BoxLayout` built from `layout.content_box()`, translated to the
+/// content-box origin — so the painter wraps and draws inside the content
+/// box, not the raw taffy layout box this walker reads. Comparing against
+/// the border box (as this used to) under-reports by exactly
+/// `padding.left + padding.right + border.left + border.right`, mirroring
+/// the same fix `check_content_overflows_box` already applies for the
+/// wrapped case.
+///
+/// Measured via the same cosmic-text–backed intrinsic the layout engine
+/// uses. Width is bounded by the node's own resolved content-box width
+/// (not `MaxContent`) so a `text-autofit: true` node can shrink to fit it —
+/// see `measurer_and_nowrap`'s `TextIntrinsic`/`GradientTextIntrinsic` arms
+/// and `CssStyle::text_autofit`'s doc comment. For a non-autofit node this
+/// changes nothing: `TextIntrinsic::measure` only reads the width
+/// constraint at all when `text_autofit` is on (see its early return), and
+/// `nowrap` already forces a single unwrapped line here regardless of what
+/// width is offered — so `natural_w` below is "natural" in the non-autofit
+/// case exactly as before, and "shrunk to fit, if that's enough" when the
+/// author declared it.
 fn check_unwrappable_text(
     component: &Component,
     path: &str,
-    bbox: &BBox,
+    layout: &BoxLayout,
     viewport: (u32, u32),
     vi: usize,
     si: usize,
@@ -806,22 +828,12 @@ fn check_unwrappable_text(
     if !nowrap {
         return;
     }
-    // Measure via the same cosmic-text–backed intrinsic the layout engine
-    // uses. Width is bounded by the node's own resolved `bbox.w` (not
-    // `MaxContent`) so a `text-autofit: true` node can shrink to fit it —
-    // see `measurer_and_nowrap`'s `TextIntrinsic`/`GradientTextIntrinsic`
-    // arms and `CssStyle::text_autofit`'s doc comment. For a non-autofit
-    // node this changes nothing: `TextIntrinsic::measure` only reads the
-    // width constraint at all when `text_autofit` is on (see its early
-    // return), and `nowrap` already forces a single unwrapped line here
-    // regardless of what width is offered — so `natural_w` below is
-    // "natural" in the non-autofit case exactly as before, and "shrunk to
-    // fit, if that's enough" when the author declared it.
+    let (cx, cy, cw, ch) = layout.content_box();
     let (natural_w, _) = intrinsic.measure(
         (None, None),
-        (AvailableSpace::Definite(bbox.w), AvailableSpace::MaxContent),
+        (AvailableSpace::Definite(cw), AvailableSpace::MaxContent),
     );
-    if natural_w > bbox.w + 0.5 {
+    if natural_w > cw + 0.5 {
         let kind = component_kind(component);
         out.push(GeometryViolation {
             view_index: vi,
@@ -830,11 +842,16 @@ fn check_unwrappable_text(
             component: kind.to_string(),
             axis: Axis::X,
             kind: ViolationKind::UnwrappableTextOverflow,
-            bbox: *bbox,
+            bbox: BBox {
+                x: cx,
+                y: cy,
+                w: cw,
+                h: ch,
+            },
             viewport,
             hint: format!(
                 "{kind} natural width is {natural_w:.0}px but only {:.0}px available — remove style.white-space: nowrap (or set it to normal) so it can wrap, or reduce style.font-size",
-                bbox.w
+                cw
             ),
         });
     }
diff --git a/crates/rustmotion/tests/audit_ws_b.rs b/crates/rustmotion/tests/audit_ws_b.rs
index 0d4923e0..7d550394 100644
--- a/crates/rustmotion/tests/audit_ws_b.rs
+++ b/crates/rustmotion/tests/audit_ws_b.rs
@@ -354,3 +354,54 @@ fn fix_leaves_relative_asset_paths_untouched() {
         "the actual violation --fix targeted must still be fixed: {fixed}"
     );
 }
+
+// ─── unwrappable_text_overflow must measure the CONTENT box ────────
+
+/// A nowrap text's own painter draws inside its CONTENT box
+/// (`LegacyPaintDispatcher` hands it `layout.content_box()`, not the raw
+/// layout box, for every component except `codeblock`) — so the geometry
+/// check must compare the natural line width against the content box too.
+/// Content box width here is 2000 - 1900 = 100px (950px of padding on each
+/// side); the border box is 2000px. Any real natural width for this
+/// string/font-size sits comfortably in between, so the violation fires if
+/// and only if the content box is used.
+#[test]
+fn unwrappable_text_overflow_is_measured_against_the_content_box() {
+    let scenario = ScratchFile::new("rm31-scenario");
+    let report = ScratchFile::new("rm31-report");
+    let json = r##"{
+        "video": { "width": 2400, "height": 1080 },
+        "scenes": [{
+            "duration": 1.0,
+            "children": [{
+                "type": "text",
+                "content": "Hello World Example",
+                "position": "absolute",
+                "x": 50, "y": 50,
+                "style": {
+                    "width": "2000px", "height": "300px",
+                    "padding": { "top": "20px", "right": "950px", "bottom": "20px", "left": "950px" },
+                    "white-space": "nowrap",
+                    "font-size": "48px",
+                    "color": "#ffffff"
+                }
+            }]
+        }]
+    }"##;
+    std::fs::write(&scenario.0, json).expect("write scenario");
+
+    let output = run_validate(&scenario.0, Some(&report.0), false, false);
+    let report_json = read_report(&report.0);
+    assert!(
+        !output.status.success(),
+        "the 100px content box (2000px border box minus 1900px of padding) is too narrow \
+         for this nowrap line; report={report_json}"
+    );
+    let violation = find_kind(&report_json, "unwrappable_text_overflow")
+        .expect("expected an unwrappable_text_overflow violation");
+    let width = violation["bbox"]["w"].as_f64().expect("bbox.w is a number");
+    assert!(
+        (width - 100.0).abs() < 1.0,
+        "violation bbox should be the 100px CONTENT box, not the 2000px border box: {report_json}"
+    );
+}