From f97789ade13a7c3ba27dac8078e1c38b14ff5eb4 Mon Sep 17 00:00:00 2001
From: MortenHusted <morten@hustedlochmann.dk>
Date: Sun, 18 Oct 2026 23:13:03 +0200
Subject: [PATCH] M7: CSS borders follow individual stroke sides

A layer with individual stroke sides (a header with only a bottom divider,
strokeSides [0, 0, 1, 0]) came out of the CSS, HTML, React and Leptos
code as `border: 1px solid ...` on all four sides, because the border
was written from the stroke weight alone. With individual sides it is now
a border-top/right/bottom/left for each side that has a weight, and a
side bound to a variable names it (border-top: var(--border-top, 3px)).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---
 crates/engine/src/codegen.rs                 | 24 +++++++++++++++++---
 crates/engine/src/inspect_behaviour_tests.rs | 20 ++++++++++++++++
 2 files changed, 41 insertions(+), 3 deletions(-)

diff --git a/crates/engine/src/codegen.rs b/crates/engine/src/codegen.rs
index 6dd80646..ac7c96fa 100644
--- a/crates/engine/src/codegen.rs
+++ b/crates/engine/src/codegen.rs
@@ -259,6 +259,25 @@ fn stroke_color(n: &Node) -> Option<Color> {
     n.strokes.iter().filter(|p| p.visible).find_map(|p| p.solid_color())
 }
 
+/// The CSS borders a solid stroke makes: one `border`, or with individual stroke sides a border
+/// on each side that has a weight.
+fn css_borders(doc: &Document, n: &Node, t: &mut Tokens) -> Vec<(String, String)> {
+    let Some(c) = stroke_color(n) else { return Vec::new() };
+    let Some(sides) = n.stroke.sides else {
+        let weight = tok(doc, n, &["strokeWeight"], format!("{}px", num(n.stroke.weight)), t);
+        return vec![("border".into(), format!("{weight} solid {}", tok(doc, n, &["stroke"], c.to_css(), t)))];
+    };
+    let color = tok(doc, n, &["stroke"], c.to_css(), t);
+    let named = ["top", "right", "bottom", "left"].into_iter().zip(crate::cmd::props::STROKE_SIDES);
+    named
+        .zip(sides)
+        .filter(|(_, weight)| *weight > 0.0)
+        .map(|((side, field), weight)| {
+            (format!("border-{side}"), format!("{} solid {color}", tok(doc, n, &[field], format!("{}px", num(weight)), t)))
+        })
+        .collect()
+}
+
 fn drop_shadow(n: &Node) -> Option<&Shadow> {
     n.effects.iter().filter(|e| e.visible).find_map(|e| match &e.kind {
         EffectKind::DropShadow(s) => Some(s),
@@ -452,9 +471,8 @@ pub(crate) fn css_decls(doc: &Document, n: &Node, t: &mut Tokens, hug: (bool, bo
             PaintKind::Pattern(_) => put("background", "url(pattern.png) repeat".into()),
         }
     }
-    if let Some(c) = stroke_color(n) {
-        let weight = tok(doc, n, &["strokeWeight"], px(n.stroke.weight), t);
-        put("border", format!("{weight} solid {}", tok(doc, n, &["stroke"], c.to_css(), t)));
+    for (key, value) in css_borders(doc, n, t) {
+        put(&key, value);
     }
     let shadows: Vec<String> = n
         .effects
diff --git a/crates/engine/src/inspect_behaviour_tests.rs b/crates/engine/src/inspect_behaviour_tests.rs
index a52cac86..c4bcc6be 100644
--- a/crates/engine/src/inspect_behaviour_tests.rs
+++ b/crates/engine/src/inspect_behaviour_tests.rs
@@ -214,6 +214,26 @@ fn css_for_common_layers() {
     }
 }
 
+/// Individual stroke sides are borders on those sides only: a header with a divider under it isn't
+/// boxed in, and a side bound to a variable names it.
+#[test]
+fn css_borders_follow_individual_stroke_sides() {
+    let mut s = Session::new();
+    let r = rect(&mut s, 0.0, 0.0, 100.0, 50.0, None);
+    set(&mut s, &[r], json!({"strokes": ["#000000"], "strokeWeight": 1, "strokeSides": [0, 0, 2, 0]}));
+    let c = css(&mut s, r);
+    assert!(c.contains("border-bottom: 2px solid #000000;"), "{c}");
+    assert!(!c.contains("border:") && !c.contains("border-top") && !c.contains("border-right") && !c.contains("border-left"), "{c}");
+
+    let col = ex(&mut s, "variable.createCollection", json!({"name": "Borders"}));
+    let col = col["id"].as_str().unwrap().to_string();
+    ex(&mut s, "variable.create", json!({"collection": col, "name": "border/top", "type": "number", "value": 3}));
+    ex(&mut s, "variable.bind", json!({"ids": [r], "field": "strokeTopWeight", "variable": "border/top"}));
+    let c = css(&mut s, r);
+    assert!(c.contains("border-top: var(--border-top, 3px) solid #000000;"), "{c}");
+    assert!(c.contains("border-bottom: 2px solid #000000;"), "{c}");
+}
+
 #[test]
 fn native_code_for_a_simple_layer() {
     let mut s = Session::new();