Fix vi motion with wide semantic escape chars

This patch fixes an issue where the semantic vi motion commands
`SemanticRight` and `SemanticLeft` were not behaving as expected when a
fullwidth character was used as a semantic character.

Closes #8314.

3 files changed, 52 insertions, 3 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index bbe0d2f4..c9faa35c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -18,6 +18,7 @@ Notable changes to the `alacritty_terminal` crate are documented in its
 
 - Mouse/Vi cursor hint highlighting broken on the terminal cursor line
 - Hint launcher opening arbitrary text, when terminal content changed while opening
+- `SemanticRight`/`SemanticLeft` vi motions breaking with wide semantic escape characters
 
 ## 0.14.0
 
diff --git a/alacritty_terminal/src/term/mod.rs b/alacritty_terminal/src/term/mod.rs
index 1f1e52c1..c2d77ec7 100644
--- a/alacritty_terminal/src/term/mod.rs
+++ b/alacritty_terminal/src/term/mod.rs
@@ -930,6 +930,11 @@ impl<T> Term<T> {
         &self.config.semantic_escape_chars
     }
 
+    #[cfg(test)]
+    pub(crate) fn set_semantic_escape_chars(&mut self, semantic_escape_chars: &str) {
+        self.config.semantic_escape_chars = semantic_escape_chars.into();
+    }
+
     /// Active terminal cursor style.
     ///
     /// While vi mode is active, this will automatically return the vi mode cursor style.
diff --git a/alacritty_terminal/src/vi_mode.rs b/alacritty_terminal/src/vi_mode.rs
index 7065544e..e23e9b80 100644
--- a/alacritty_terminal/src/vi_mode.rs
+++ b/alacritty_terminal/src/vi_mode.rs
@@ -265,14 +265,14 @@ fn semantic<T: EventListener>(
         }
     };
 
-    // Make sure we jump above wide chars.
-    point = term.expand_wide(point, direction);
-
     // Move to word boundary.
     if direction != side && !is_boundary(term, point, direction) {
         point = expand_semantic(point);
     }
 
+    // Make sure we jump above wide chars.
+    point = term.expand_wide(point, direction);
+
     // Skip whitespace.
     let mut next_point = advance(term, point, direction);
     while !is_boundary(term, point, direction) && is_space(term, next_point) {
@@ -283,6 +283,11 @@ fn semantic<T: EventListener>(
     // Assure minimum movement of one cell.
     if !is_boundary(term, point, direction) {
         point = advance(term, point, direction);
+
+        // Skip over wide cell spacers.
+        if direction == Direction::Left {
+            point = term.expand_wide(point, direction);
+        }
     }
 
     // Move to word boundary.
@@ -820,4 +825,42 @@ mod tests {
         cursor = cursor.scroll(&term, -20);
         assert_eq!(cursor.point, Point::new(Line(19), Column(0)));
     }
+
+    #[test]
+    fn wide_semantic_char() {
+        let mut term = term();
+        term.set_semantic_escape_chars("－");
+        term.grid_mut()[Line(0)][Column(0)].c = 'x';
+        term.grid_mut()[Line(0)][Column(1)].c = 'x';
+        term.grid_mut()[Line(0)][Column(2)].c = '－';
+        term.grid_mut()[Line(0)][Column(2)].flags.insert(Flags::WIDE_CHAR);
+        term.grid_mut()[Line(0)][Column(3)].c = ' ';
+        term.grid_mut()[Line(0)][Column(3)].flags.insert(Flags::WIDE_CHAR_SPACER);
+        term.grid_mut()[Line(0)][Column(4)].c = 'x';
+        term.grid_mut()[Line(0)][Column(5)].c = 'x';
+
+        // Test motion to the right.
+
+        let mut cursor = ViModeCursor::new(Point::new(Line(0), Column(0)));
+        cursor = cursor.motion(&mut term, ViMotion::SemanticRight);
+        assert_eq!(cursor.point, Point::new(Line(0), Column(2)));
+
+        let mut cursor = ViModeCursor::new(Point::new(Line(0), Column(2)));
+        cursor = cursor.motion(&mut term, ViMotion::SemanticRight);
+        assert_eq!(cursor.point, Point::new(Line(0), Column(4)));
+
+        // Test motion to the left.
+
+        let mut cursor = ViModeCursor::new(Point::new(Line(0), Column(5)));
+        cursor = cursor.motion(&mut term, ViMotion::SemanticLeft);
+        assert_eq!(cursor.point, Point::new(Line(0), Column(4)));
+
+        let mut cursor = ViModeCursor::new(Point::new(Line(0), Column(4)));
+        cursor = cursor.motion(&mut term, ViMotion::SemanticLeft);
+        assert_eq!(cursor.point, Point::new(Line(0), Column(2)));
+
+        let mut cursor = ViModeCursor::new(Point::new(Line(0), Column(2)));
+        cursor = cursor.motion(&mut term, ViMotion::SemanticLeft);
+        assert_eq!(cursor.point, Point::new(Line(0), Column(0)));
+    }
 }