fix(dimstyle): preview respects per-end arrowheads

DimensionPreview drew identical generic triangles regardless of dimblk/dimblk1/dimblk2. It now resolves each end through the shared arrow_from_block_name mapping (widened to pub(crate)) and draws per-end glyphs, keeping DIMTSZ tick precedence. Tests: arrow_name_mapping_covers_preview_kinds pins the shared contract; 2 preview_arrow_tests pin per-end resolution (RED first). Full suite: 1989 passed / 0 failed / 25 ignored.

src/scene/convert/tessellate.rs

@@ -2781,7 +2781,10 @@ pub(crate) fn arrow_from_block_with_deferred_hatch(
         .unwrap_or_else(|| arrow_from_block_name(None, dimasz))
 }
 
-fn arrow_from_block_name(name: Option<&str>, dimasz: f32) -> ArrowKind {
+/// Canonical block-name → arrow-kind mapping shared by the renderer and the
+/// dimstyle preview so both agree on what a named arrowhead looks like.
+/// Unknown / empty names fall back to the standard filled triangle.
+pub(crate) fn arrow_from_block_name(name: Option<&str>, dimasz: f32) -> ArrowKind {
     name.and_then(|name| builtin_arrow_from_block_name(name, dimasz))
         .unwrap_or(ArrowKind::Triangle {
             size: dimasz,
@@ -3453,6 +3456,36 @@ pub(crate) fn normalized_or(v: Vec3, fallback: Vec3) -> Vec3 {
 mod tests {
     use super::*;
 
+    #[test]
+    fn arrow_name_mapping_covers_preview_kinds() {
+        // Pins the shared name→kind contract the dimstyle preview relies on.
+        assert!(matches!(
+            arrow_from_block_name(Some("OPEN"), 1.0),
+            ArrowKind::Open { .. }
+        ));
+        assert!(matches!(
+            arrow_from_block_name(Some("DOT"), 1.0),
+            ArrowKind::Dot { filled: true, .. }
+        ));
+        assert!(matches!(
+            arrow_from_block_name(Some("ARCHTICK"), 1.0),
+            ArrowKind::Tick { .. }
+        ));
+        assert!(matches!(
+            arrow_from_block_name(Some("NONE"), 1.0),
+            ArrowKind::None
+        ));
+        // Unknown / empty names fall back to the standard filled triangle.
+        assert!(matches!(
+            arrow_from_block_name(Some("NOPE"), 1.0),
+            ArrowKind::Triangle { filled: true, .. }
+        ));
+        assert!(matches!(
+            arrow_from_block_name(None, 1.0),
+            ArrowKind::Triangle { filled: true, .. }
+        ));
+    }
+
     #[test]
     fn test_split_mixed_polyline_straight_lines_have_taper_widths() {
         let tg_line = TangentGeom::Line {

src/ui/style/dimstyle.rs

@@ -1,6 +1,7 @@
 //! Dimension Style Manager window — fills the entire OS window.
 
 use crate::app::{ColorPickTarget, DsField, Message};
+use crate::scene::convert::tessellate::{arrow_from_block_name, ArrowKind};
 use iced::widget::{
     button, canvas, checkbox, column, container, row, scrollable, text, text_input, Space,
 };
@@ -171,11 +172,32 @@ struct DimensionPreview {
     dim2: bool,
     tick: bool,
     arrow_size: f32,
+    arrow1: ArrowKind,
+    arrow2: ArrowKind,
     text_above: bool,
     basic: bool,
     text: String,
 }
 
+/// Resolve the staged arrowhead block names to per-end preview kinds: the
+/// shared `dimblk` when Dimsah is off, the per-end blocks when on — the same
+/// selection the renderer makes. `dimasz` is the preview arrow size so
+/// size-scaled kinds (SMALL, DOTSMALL) keep their proportions.
+fn preview_arrow_kinds(
+    dimsah: bool,
+    dimblk: &str,
+    dimblk1: &str,
+    dimblk2: &str,
+    dimasz: f32,
+) -> (ArrowKind, ArrowKind) {
+    let kind = |name: &str| arrow_from_block_name(Some(name), dimasz);
+    if dimsah {
+        (kind(dimblk1), kind(dimblk2))
+    } else {
+        (kind(dimblk), kind(dimblk))
+    }
+}
+
 impl canvas::Program<Message> for DimensionPreview {
     type State = ();
 
@@ -218,23 +240,107 @@ impl canvas::Program<Message> for DimensionPreview {
         }
 
         let size = self.arrow_size.clamp(5.0, 14.0);
-        for (tip_x, sign) in [(x1, 1.0_f32), (x2, -1.0_f32)] {
+        // Per-end arrowheads: each end draws its own resolved kind so split
+        // (Dimsah) configurations read correctly. A global DIMTSZ tick still
+        // overrides both ends, matching AutoCAD precedence.
+        let tick_path = |tip_x: f32, tick_size: f32| {
+            canvas::Path::line(
+                Point::new(tip_x - tick_size * 0.55, y + tick_size * 0.75),
+                Point::new(tip_x + tick_size * 0.55, y - tick_size * 0.75),
+            )
+        };
+        for (kind, tip_x, sign) in [(&self.arrow1, x1, 1.0_f32), (&self.arrow2, x2, -1.0_f32)] {
             if self.tick {
                 frame.stroke(
-                    &line(
-                        Point::new(tip_x - size * 0.55, y + size * 0.75),
-                        Point::new(tip_x + size * 0.55, y - size * 0.75),
-                    ),
+                    &tick_path(tip_x, size),
                     canvas::Stroke::default().with_color(guide).with_width(1.6),
                 );
-            } else {
-                let arrow = canvas::Path::new(|path| {
-                    path.move_to(Point::new(tip_x, y));
-                    path.line_to(Point::new(tip_x + sign * size, y - size * 0.42));
-                    path.line_to(Point::new(tip_x + sign * size, y + size * 0.42));
-                    path.close();
-                });
-                frame.fill(&arrow, guide);
+                continue;
+            }
+            match kind {
+                ArrowKind::None => {}
+                ArrowKind::Triangle { size, filled, size_mul } => {
+                    let s = size * size_mul;
+                    let arrow = canvas::Path::new(|path| {
+                        path.move_to(Point::new(tip_x, y));
+                        path.line_to(Point::new(tip_x + sign * s, y - s * 0.42));
+                        path.line_to(Point::new(tip_x + sign * s, y + s * 0.42));
+                        path.close();
+                    });
+                    if *filled {
+                        frame.fill(&arrow, guide);
+                    } else {
+                        frame.stroke(&arrow, canvas::Stroke::default().with_color(guide).with_width(1.4));
+                    }
+                }
+                ArrowKind::Open { size, half_angle } => {
+                    let (sin, cos) = half_angle.sin_cos();
+                    for side in [-1.0_f32, 1.0_f32] {
+                        frame.stroke(
+                            &line(
+                                Point::new(tip_x, y),
+                                Point::new(tip_x + sign * size * cos, y + side * size * sin),
+                            ),
+                            canvas::Stroke::default().with_color(guide).with_width(1.4),
+                        );
+                    }
+                }
+                ArrowKind::Dot { size, filled } => {
+                    let dot = canvas::Path::circle(Point::new(tip_x + sign * size * 0.5, y), size * 0.5);
+                    if *filled {
+                        frame.fill(&dot, guide);
+                    } else {
+                        frame.stroke(&dot, canvas::Stroke::default().with_color(guide).with_width(1.4));
+                    }
+                }
+                ArrowKind::Tick { size } => {
+                    frame.stroke(
+                        &tick_path(tip_x, *size),
+                        canvas::Stroke::default().with_color(guide).with_width(1.6),
+                    );
+                }
+                ArrowKind::Box_ { size, filled } => {
+                    let half = size * 0.45;
+                    let square = canvas::Path::rectangle(
+                        Point::new(tip_x + sign * half - half, y - half),
+                        iced::Size::new(half * 2.0, half * 2.0),
+                    );
+                    if *filled {
+                        frame.fill(&square, guide);
+                    } else {
+                        frame.stroke(&square, canvas::Stroke::default().with_color(guide).with_width(1.4));
+                    }
+                }
+                // Datum/Origin have dedicated CAD geometry; the preview keeps
+                // the schematic triangle/dot respectively.
+                ArrowKind::Datum { size, filled } => {
+                    let arrow = canvas::Path::new(|path| {
+                        path.move_to(Point::new(tip_x, y));
+                        path.line_to(Point::new(tip_x + sign * size, y - size * 0.42));
+                        path.line_to(Point::new(tip_x + sign * size, y + size * 0.42));
+                        path.close();
+                    });
+                    if *filled {
+                        frame.fill(&arrow, guide);
+                    } else {
+                        frame.stroke(&arrow, canvas::Stroke::default().with_color(guide).with_width(1.4));
+                    }
+                }
+                ArrowKind::Origin { size } => {
+                    let dot = canvas::Path::circle(Point::new(tip_x + sign * size * 0.5, y), size * 0.4);
+                    frame.stroke(&dot, canvas::Stroke::default().with_color(guide).with_width(1.4));
+                }
+                // Custom DWG block geometry cannot render in the schematic
+                // preview; fall back to the standard filled triangle.
+                ArrowKind::Custom { .. } => {
+                    let arrow = canvas::Path::new(|path| {
+                        path.move_to(Point::new(tip_x, y));
+                        path.line_to(Point::new(tip_x + sign * size, y - size * 0.42));
+                        path.line_to(Point::new(tip_x + sign * size, y + size * 0.42));
+                        path.close();
+                    });
+                    frame.fill(&arrow, guide);
+                }
             }
         }
 
@@ -1127,13 +1233,23 @@ pub fn view_window<'a>(
             preview_text.push_str(&format!(" +{} −{}", vals.dimtp.trim(), vals.dimtm.trim()));
         }
     }
+    let arrow_size = vals.dimasz.trim().parse::<f32>().unwrap_or(1.0).abs() * 5.0 + 5.0;
+    let (arrow1, arrow2) = preview_arrow_kinds(
+        vals.dimsah,
+        &vals.dimblk_name,
+        &vals.dimblk1_name,
+        &vals.dimblk2_name,
+        arrow_size.clamp(5.0, 14.0),
+    );
     let preview = canvas(DimensionPreview {
         ext1: !vals.dimse1,
         ext2: !vals.dimse2,
         dim1: !vals.dimsd1,
         dim2: !vals.dimsd2,
         tick: vals.dimtsz.trim().parse::<f32>().unwrap_or(0.0) > 0.0,
-        arrow_size: vals.dimasz.trim().parse::<f32>().unwrap_or(1.0).abs() * 5.0 + 5.0,
+        arrow_size,
+        arrow1,
+        arrow2,
         text_above: vals.dimtad.trim() != "0",
         basic: vals.dimgap.trim().starts_with('-'),
         text: preview_text,
@@ -1231,3 +1347,25 @@ pub fn view_window<'a>(
         editor: right_panel.into(),
     })
 }
+
+#[cfg(test)]
+mod preview_arrow_tests {
+    // Preview must resolve each end independently: shared block when Dimsah
+    // is off, per-end blocks when on.
+    use super::preview_arrow_kinds;
+    use crate::scene::convert::tessellate::ArrowKind;
+
+    #[test]
+    fn shared_block_feeds_both_ends_when_dimsah_off() {
+        let (first, second) = preview_arrow_kinds(false, "OPEN", "DOT", "NONE", 10.0);
+        assert!(matches!(first, ArrowKind::Open { .. }));
+        assert!(matches!(second, ArrowKind::Open { .. }));
+    }
+
+    #[test]
+    fn per_end_blocks_feed_each_end_when_dimsah_on() {
+        let (first, second) = preview_arrow_kinds(true, "OPEN", "DOT", "NONE", 10.0);
+        assert!(matches!(first, ArrowKind::Dot { .. }));
+        assert!(matches!(second, ArrowKind::None));
+    }
+}