Merge pull request #6565 from dotCooCoo/fix/glyph-alternate-noop-ligature

Glyphs: gid null inside a ligature reports the ligature

crates/engine/src/cmd/textedit.rs

@@ -1321,6 +1321,16 @@ fn set_glyph_alternate(s: &mut Session, p: &Value) -> Result<Value> {
         }
     }
     if held == choice && (choice.is_none() || alone) {
+        // The text is left as it is, so the glyph is the one the unchanged text draws. The probe
+        // splits a run that holds an earlier character's choice, and the split can break a ligature
+        // that takes in this character.
+        let drawn = match &choice {
+            None if probe.runs != t.runs => {
+                let lay = vectorcraft_text::layout(vectorcraft_text::FontDb::global(), &t);
+                drawn_glyph(&plain, &lay, ch, &bytes, &face).or_else(|| shaped_alone(&t, ch, &bytes, &face).1).unwrap_or(default)
+            }
+            _ => drawn,
+        };
         return Ok(json!({"id": id.0, "start": bytes.start, "end": bytes.end, "gid": drawn}));
     }
     s.edit("Glyphs", |d, _| {

crates/engine/src/tests/textedit.rs

@@ -3511,6 +3511,31 @@ fn a_glyph_choice_taken_away_reports_the_glyph_drawn() {
     assert_eq!(chosen(&mut s, caps, 1), json!(drawn));
 }
 
+/// A run that holds a choice for its first character and goes on past it, as a file may have,
+/// draws Source Serif 4's fi ligature for the f and the i after that character. `gid: null` for the
+/// i leaves the text as it is and reports the ligature, as `text.glyphAlternates` does.
+#[test]
+fn a_glyph_choice_taken_away_inside_a_ligature_reports_the_ligature() {
+    let db = vectorcraft_text::FontDb::global();
+    let face = db.face("Source Serif 4", "Regular").expect("the bundled face");
+    let mut s = session();
+    let r = s.execute("text.create", &json!({"x": 100, "y": 100, "text": "xfin", "size": 40, "font": "Source Serif 4"})).unwrap();
+    let id = NodeId(r["id"].as_u64().unwrap());
+    let mut runs = obj(&s, id).runs;
+    runs[0].style.glyph_alternate = Some(face.choice('x', face.glyph_for('x')));
+    let doc = std::sync::Arc::make_mut(&mut s.doc_mut().unwrap().doc);
+    let Some(NodeKind::Text(text)) = doc.node_mut(id).map(|n| &mut n.kind) else { panic!("text") };
+    text.runs = runs.clone();
+    let ligature = vectorcraft_text::layout(db, &obj(&s, id)).glyphs.iter().find(|g| g.byte == 1 && g.len == 2).expect("f + i is one glyph").gid;
+    let chosen = s.execute("text.glyphAlternates", &json!({"id": id.0, "start": 2})).unwrap()["chosen"].clone();
+    assert_eq!(chosen, json!(ligature));
+    let undo = s.doc().unwrap().history.undo.len();
+    let r = s.execute("text.setGlyphAlternate", &json!({"id": id.0, "start": 2, "gid": null})).unwrap();
+    assert_eq!(r["gid"], chosen, "the ligature drawn for the i");
+    assert_eq!(s.doc().unwrap().history.undo.len(), undo, "no edit");
+    assert_eq!(obj(&s, id).runs, runs, "the runs are kept");
+}
+
 /// A fallback face draws Ka with the vowel sign I in one cluster, the vowel sign first. The glyph
 /// reported for Ka is the fallback face's glyph for Ka, laid out or overflowing, not the vowel
 /// sign's.