Type: Hebrew and Arabic text laid out right to left (bidi), aligned by its direction

- Unicode bidi (unicode-bidi, unicode-script, unicode-general-category):
  each paragraph's direction from its first strong character, Hebrew and
  Arabic shaped right to left, embedded Latin and numbers keep theirs,
  lines wrapped in logical order and reordered per line by whole
  clusters; source text, undo and style ranges stay logical.
- Caret, hit testing, selection and the arrow keys follow the visual
  order.
- New text aligns automatically: right-to-left paragraphs right, others
  left (Justify::Auto, text.setStyle {justify: "auto"}); the Paragraph
  panel highlights the resolved alignment and has an Automatic alignment
  toggle. Explicit alignments, and older documents', are kept.
- SVG export outlines bidirectional text (with a warning) until it can
  be written as directional live text.

crates/engine/src/cmd/typecmd.rs

@@ -75,7 +75,7 @@ pub fn specs() -> Vec<CommandSpec> {
             "Character",
             [],
             None,
-            "{ids?|id?, font?, style?, size?: pt, leading?: pt|\"auto\", tracking?: 1/1000 em, justify?: \"left\"|\"center\"|\"right\"|\"justifyAll\", fill?: colour, features?: [\"dlig\", \"-liga\", …] OpenType}",
+            "{ids?|id?, font?, style?, size?: pt, leading?: pt|\"auto\", tracking?: 1/1000 em, justify?: \"auto\"|\"left\"|\"center\"|\"right\"|\"justifyAll\", fill?: colour, features?: [\"dlig\", \"-liga\", …] OpenType}",
             has_doc,
             set_style
         ),
@@ -190,6 +190,7 @@ fn set_text(s: &mut Session, p: &Value) -> Result<Value> {
 
 fn justify_param(v: &str) -> Option<Justify> {
     Some(match v.to_ascii_lowercase().as_str() {
+        "auto" => Justify::Auto,
         "left" => Justify::Left,
         "center" => Justify::Center,
         "right" => Justify::Right,
@@ -216,7 +217,7 @@ fn set_style(s: &mut Session, p: &Value) -> Result<Value> {
     };
     let tracking = num_param(p, "tracking");
     let justify = match str_param(p, "justify") {
-        Some(j) => Some(justify_param(j).ok_or_else(|| bad(C, "justify must be left|center|right|justifyAll"))?),
+        Some(j) => Some(justify_param(j).ok_or_else(|| bad(C, "justify must be auto|left|center|right|justifyAll"))?),
         None => None,
     };
     let fill = match p.get("fill") {

crates/engine/src/cmd/typemenu.rs

@@ -275,6 +275,7 @@ fn to_area(s: &mut Session, p: &Value) -> Result<Value> {
             let (sl, sr) = match t.para.justify {
                 Justify::Center | Justify::JustifyCenter => (slack * 0.5, slack * 0.5),
                 Justify::Right | Justify::JustifyRight => (slack, 0.0),
+                Justify::Auto if lay.lines.first().is_some_and(|l| l.rtl) => (slack, 0.0),
                 _ => (0.0, slack),
             };
             let frame = Rect::new(b.x0 - sl, top, b.x1 + sr, b.y1.max(top + 1.0));
@@ -330,6 +331,7 @@ fn to_point(s: &mut Session, p: &Value) -> Result<Value> {
             let ox = match t.para.justify {
                 Justify::Center | Justify::JustifyCenter => (x0 + x1) * 0.5,
                 Justify::Right | Justify::JustifyRight => x1,
+                Justify::Auto if lay.lines.first().is_some_and(|l| l.rtl) => x1,
                 _ => x0,
             };
             t.kind = TextKind::Point;

crates/engine/src/tests_eyedropper.rs

@@ -100,9 +100,10 @@ fn type_picks_up_font_and_size() {
     assert!(width(&s, dst) > before, "laid out again at the new size");
     // Without character or paragraph attributes only the paints go.
     let dst2 = id_of(s.execute("text.create", &json!({"x": 10, "y": 500, "text": "Other"})).unwrap());
+    let preserved_alignment = style(&s, dst2).1;
     s.execute("appearance.copyFrom", &json!({"source": src.0, "pickUp": {"character": false, "paragraph": false}})).unwrap();
     let (st, justify) = style(&s, dst2);
-    assert_eq!((st.size, justify, st.fill.color().unwrap().to_hex()), (12.0, Justify::Left, "#00ff00".into()));
+    assert_eq!((st.size, justify, st.fill.color().unwrap().to_hex()), (12.0, preserved_alignment, "#00ff00".into()));
 }
 
 #[test]

crates/engine/src/tests_textedit.rs

@@ -506,3 +506,50 @@ fn vertical_text_creation_orientation_and_persistence() {
     let old: TextObject = serde_json::from_value(old).unwrap();
     assert!(!old.vertical);
 }
+
+#[test]
+fn rtl_edit_commands_and_undo_preserve_logical_source_and_style_ranges() {
+    let mut s = session();
+    let id = text(&mut s, "שלום Rust 123");
+    s.execute("text.editRange", &json!({"id": id.0, "start": 0, "end": 8, "insert": "مرحبا"})).unwrap();
+    let t = obj(&s, id);
+    assert_eq!(t.plain_text(), "مرحبا Rust 123");
+    let lay = vectorcraft_text::layout(vectorcraft_text::FontDb::global(), &t);
+    assert!(lay.glyphs.iter().any(|g| g.rtl));
+    s.execute("text.setRangeStyle", &json!({"id": id.0, "start": 0, "end": 10, "size": 30})).unwrap();
+    assert_eq!(obj(&s, id).runs[0].text, "مرحبا");
+    s.execute("edit.undo", &json!({})).unwrap();
+    s.execute("edit.undo", &json!({})).unwrap();
+    assert_eq!(obj(&s, id).plain_text(), "שלום Rust 123");
+}
+
+#[test]
+fn automatic_alignment_updates_during_edits_and_can_be_overridden() {
+    let mut s = session();
+    let id = text(&mut s, "English");
+    let db = vectorcraft_text::FontDb::global();
+    assert_eq!(obj(&s, id).para.justify, vectorcraft_doc::Justify::Auto);
+    for content in ["שלום", "مرحبا", "English"] {
+        let len = obj(&s, id).plain_text().len();
+        s.execute("text.editRange", &json!({"id": id.0, "start": 0, "end": len, "insert": content})).unwrap();
+        let t = obj(&s, id);
+        let l = vectorcraft_text::layout(db, &t);
+        if content == "English" {
+            assert_eq!(l.lines[0].x0, 0.0);
+        } else {
+            assert!(l.lines[0].x1.abs() < 1e-6);
+        }
+    }
+    s.execute("text.setStyle", &json!({"id": id.0, "justify": "center"})).unwrap();
+    s.execute("text.editRange", &json!({"id": id.0, "start": 0, "end": 7, "insert": "שלום"})).unwrap();
+    assert_eq!(obj(&s, id).para.justify, vectorcraft_doc::Justify::Center);
+    s.execute("text.setStyle", &json!({"id": id.0, "justify": "auto"})).unwrap();
+    let t = obj(&s, id);
+    assert!(vectorcraft_text::layout(db, &t).lines[0].x1.abs() < 1e-6);
+    let restored: TextObject = serde_json::from_value(serde_json::to_value(&t).unwrap()).unwrap();
+    assert_eq!(restored.para.justify, vectorcraft_doc::Justify::Auto);
+    // Legacy documents with explicit alignment retain that choice.
+    let mut legacy = serde_json::to_value(t).unwrap();
+    legacy["para"]["justify"] = json!("Left");
+    assert_eq!(serde_json::from_value::<TextObject>(legacy).unwrap().para.justify, vectorcraft_doc::Justify::Left);
+}