From 9e68cc559a38e0c82c79a8bbe703174f04cbbe20 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Wed, 30 Nov 2016 21:50:54 +0530
Subject: [PATCH] Implement CBT

---
 kitty/control-codes.h |  2 ++
 kitty/data-types.h    |  2 ++
 kitty/parser.c        |  2 ++
 kitty/screen.c        | 16 ++++++++++++++++
 4 files changed, 22 insertions(+)

diff --git a/kitty/control-codes.h b/kitty/control-codes.h
index 84be1313f..0813282d6 100644
--- a/kitty/control-codes.h
+++ b/kitty/control-codes.h
@@ -225,6 +225,8 @@
 // *Horizontal position adjust*: Same as :data:`CHA`.
 #define HPA '`'
 
+// Back tab
+#define CBT 'Z'
 
 // Misc sequences
 // ----------------
diff --git a/kitty/data-types.h b/kitty/data-types.h
index 6a55e62c4..8ff3748a7 100644
--- a/kitty/data-types.h
+++ b/kitty/data-types.h
@@ -353,6 +353,8 @@ void screen_reverse_index(Screen *self);
 void screen_index(Screen *self);
 void screen_reset(Screen *self);
 void screen_set_tab_stop(Screen *self);
+void screen_tab(Screen *self);
+void screen_backtab(Screen *self, unsigned int);
 void screen_clear_tab_stop(Screen *self, unsigned int how);
 void screen_set_mode(Screen *self, unsigned int mode);
 void screen_reset_mode(Screen *self, unsigned int mode);
diff --git a/kitty/parser.c b/kitty/parser.c
index 545fda3bd..333f6289c 100644
--- a/kitty/parser.c
+++ b/kitty/parser.c
@@ -410,6 +410,8 @@ dispatch_csi(Screen *screen, PyObject DUMP_UNUSED *dump_callback) {
             CALL_CSI_HANDLER1(screen_cursor_to_column, 1); 
         case VPA: 
             CALL_CSI_HANDLER1(screen_cursor_to_line, 1); 
+        case CBT:
+            CALL_CSI_HANDLER1(screen_backtab, 1); 
         case CUP:  
         case HVP: 
             CALL_CSI_HANDLER2(screen_cursor_position, 1, 1); 
diff --git a/kitty/screen.c b/kitty/screen.c
index 006935690..4bed1b344 100644
--- a/kitty/screen.c
+++ b/kitty/screen.c
@@ -430,6 +430,22 @@ screen_tab(Screen *self) {
     }
 }
 
+void 
+screen_backtab(Screen *self, unsigned int count) {
+    // Move back count tabs
+    if (!count) count = 1;
+    unsigned int before = self->cursor->x;
+    int i;
+    while (count > 0 && self->cursor->x > 0) {
+        count--;
+        for (i = self->cursor->x - 1; i >= 0; i--) {
+            if (self->tabstops[i]) { self->cursor->x = i; break; }
+        }
+        if (i <= 0) self->cursor->x = 0;
+    }
+    if (before != self->cursor->x) tracker_cursor_changed(self->change_tracker);
+}
+
 void 
 screen_clear_tab_stop(Screen *self, unsigned int how) {
     switch(how) {