fix: find decoration spans in bidi text

src/attrs.rs

@@ -276,6 +276,9 @@ pub struct GlyphDecorationData {
     pub underline_metrics: DecorationMetrics,
     /// Strikethrough offset and thickness from the font
     pub strikethrough_metrics: DecorationMetrics,
+    /// Font ascent in EM units (ascent / upem).
+    /// Used for overline positioning
+    pub ascent: f32,
 }
 
 /// Text attributes

src/render.rs

@@ -115,9 +115,8 @@ fn draw_decoration_span<R: Renderer>(
         let thickness = (deco.underline_metrics.thickness * font_size)
             .max(1.0)
             .ceil();
-        //TODO: this should be run.line_y - ascent, but we don't have per-glyph ascent
-        // in LayoutGlyph. Using line_top as an approximation for now.
-        let y = run.line_top;
+        // clamped so it doesn't go above the line top.
+        let y = (run.line_y - deco.ascent * font_size).max(run.line_top);
         renderer.rectangle(x_start as i32, y as i32, w, thickness as u32, color);
     }
 }

src/shape.rs

@@ -612,11 +612,15 @@ impl ShapeGlyph {
     }
 }
 
-fn decoration_metrics(font: &Font) -> (DecorationMetrics, DecorationMetrics) {
+fn decoration_metrics(font: &Font) -> (DecorationMetrics, DecorationMetrics, f32) {
     let metrics = font.metrics();
     let upem = metrics.units_per_em as f32;
     if upem == 0.0 {
-        return (DecorationMetrics::default(), DecorationMetrics::default());
+        return (
+            DecorationMetrics::default(),
+            DecorationMetrics::default(),
+            0.0,
+        );
     }
     (
         DecorationMetrics {
@@ -627,10 +631,11 @@ fn decoration_metrics(font: &Font) -> (DecorationMetrics, DecorationMetrics) {
             offset: metrics.strikeout.map_or(0.3, |d| d.offset / upem),
             thickness: metrics.strikeout.map_or(1.0 / 14.0, |d| d.thickness / upem),
         },
+        metrics.ascent / upem,
     )
 }
 
-/// span index used in VlRange to indicate this range is the ellipsis.
+/// span index used in `VlRange` to indicate this range is the ellipsis.
 const ELLIPSIS_SPAN: usize = usize::MAX;
 
 fn shape_ellipsis(
@@ -1046,7 +1051,7 @@ impl ShapeSpan {
                         .map(|font| decoration_metrics(&font))
                 });
 
-            if let Some((ul_metrics, st_metrics)) = primary_metrics {
+            if let Some((ul_metrics, st_metrics, ascent)) = primary_metrics {
                 // Track which sub-ranges of span_range are covered by explicit spans
                 let mut covered_end = span_range.start;
 
@@ -1068,6 +1073,7 @@ impl ShapeSpan {
                                     text_decoration: default_attrs.text_decoration,
                                     underline_metrics: ul_metrics,
                                     strikethrough_metrics: st_metrics,
+                                    ascent,
                                 },
                             ));
                         }
@@ -1082,6 +1088,7 @@ impl ShapeSpan {
                                 text_decoration: attrs.text_decoration,
                                 underline_metrics: ul_metrics,
                                 strikethrough_metrics: st_metrics,
+                                ascent,
                             },
                         ));
                     }
@@ -1097,6 +1104,7 @@ impl ShapeSpan {
                                 text_decoration: default_attrs.text_decoration,
                                 underline_metrics: ul_metrics,
                                 strikethrough_metrics: st_metrics,
+                                ascent,
                             },
                         ));
                     }
@@ -2081,7 +2089,7 @@ impl ShapeLine {
             .map_or(0.0, |s| s.words.iter().map(|w| w.width(font_size)).sum())
     }
 
-    /// Creates a VlRange for the ellipsis with the given BiDi level.
+    /// Creates a `VlRange` for the ellipsis with the give`BiDi`Di level.
     fn ellipsis_vlrange(&self, level: unicode_bidi::Level) -> VlRange {
         VlRange {
             span: ELLIPSIS_SPAN,
@@ -2091,7 +2099,7 @@ impl ShapeLine {
         }
     }
 
-    /// Determines the appropriate BiDi level for the ellipsis based on the
+    /// Determines the appropriate `BiDi` level for the ellipsis based on the
     /// adjacent ranges, following UAX#9 N1/N2 rules for neutral characters.
     fn ellipsis_level_between(
         &self,
@@ -2860,11 +2868,8 @@ impl ShapeLine {
                             }
                             glyphs.push(layout_glyph);
 
-                            // Advance (or reset) the decoration cursor to find
-                            // the span covering this glyph's byte position.
-                            // Resets for RTL/BiDi where byte order reverses.
-                            if deco_cursor < deco_spans.len()
-                                && glyph.start < deco_spans[deco_cursor].0.start
+                            if deco_cursor >= deco_spans.len()
+                                || glyph.start < deco_spans[deco_cursor].0.start
                             {
                                 deco_cursor = 0;
                             }

tests/images/text_decoration_bidi.png

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:7c856de2313bef83d36dd8776dfcba6f6312238d983f97603fc9a76fa53fea2c
-size 15386
+oid sha256:d83b58ede597fede243ebb042c31668c0847069a3843dc9b279c3624e1387728
+size 15146

tests/images/text_decoration_multiline_bidi.png

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:6e332dc9edc0d8c2fd6dd7d9361dc1441b4c979023e79571ac26b7f4f1f1b274
+size 15305

tests/text_decorations.rs

@@ -50,7 +50,6 @@ fn test_text_decorations() {
         .validate_text_rendering();
 }
 
-
 #[test]
 fn test_text_decorations_rtl() {
     let base = base_attrs();
@@ -125,3 +124,41 @@ fn test_text_decorations_bidi() {
         .canvas(600, 50)
         .validate_text_rendering();
 }
+
+/// Multiline Bidi test
+#[test]
+fn test_text_decorations_multiline_bidi() {
+    let base = base_attrs();
+    let red = Color::rgb(0xFF, 0x00, 0x00);
+    let cyan = Color::rgb(0x00, 0xFF, 0xFF);
+
+    DrawTestCfg::new("text_decoration_multiline_bidi")
+        .font_size(20., 26.)
+        .font_attrs(base.clone())
+        .rich_text(vec![
+            ("زیرخط ", base.clone().underline(UnderlineStyle::Single)),
+            ("Double ", base.clone().underline(UnderlineStyle::Double)),
+            ("خط ", base.clone().strikethrough()),
+            ("Over \n", base.clone().overline()),
+            (
+                "Red زیر خط ",
+                base.clone()
+                    .underline(UnderlineStyle::Single)
+                    .underline_color(red),
+            ),
+            (
+                "CyanSt ",
+                base.clone().strikethrough().strikethrough_color(cyan),
+            ),
+            (
+                "All",
+                base.clone()
+                    .underline(UnderlineStyle::Single)
+                    .strikethrough()
+                    .overline(),
+            ),
+            (" Plain", base),
+        ])
+        .canvas(400, 80)
+        .validate_text_rendering();
+}