Implement 'backwards tab'

This escape sequence isn't officially documented anywhere, but is
supported by xterm and gnome-vte.

1 files changed, 13 insertions, 6 deletions

diff --git a/src/term/mod.rs b/src/term/mod.rs
index 227e90d2..6cbd07d7 100644
--- a/src/term/mod.rs
+++ b/src/term/mod.rs
@@ -696,12 +696,10 @@ impl Term {
 
         let grid = Grid::new(num_lines, num_cols, &template);
 
-        let mut tabs = IndexRange::from(Column(0)..grid.num_cols())
+        let tabs = IndexRange::from(Column(0)..grid.num_cols())
             .map(|i| (*i as usize) % TAB_SPACES == 0)
             .collect::<Vec<bool>>();
 
-        tabs[0] = false;
-
         let alt = grid.clone();
         let scroll_region = Line(0)..grid.num_lines();
 
@@ -1039,8 +1037,6 @@ impl Term {
             .map(|i| (*i as usize) % TAB_SPACES == 0)
             .collect::<Vec<bool>>();
 
-        self.tabs[0] = false;
-
         if num_lines > old_lines {
             // Make sure bottom of terminal is clear
             let template = self.empty_cell;
@@ -1531,7 +1527,18 @@ impl ansi::Handler for Term {
 
     #[inline]
     fn move_backward_tabs(&mut self, count: i64) {
-        trace!("[unimplemented] move_backward_tabs: {}", count);
+        trace!("move_backward_tabs: {}", count);
+
+        for _ in 0..count {
+            let mut col = self.cursor.point.col;
+            for i in (0..(col.0)).rev() {
+                if self.tabs[i as usize] {
+                    col = index::Column(i);
+                    break;
+                }
+            }
+            self.cursor.point.col = col;
+        }
     }
 
     #[inline]