Fix #8741

docs/changelog.rst

@@ -128,6 +128,8 @@ Detailed list of changes
 
 - Fix a regression in 0.40.0 that broke rendering of VS15 variation selectors in some circumstances (:iss:`8731`)
 
+- Fix a regression in 0.40.0 that broke serialization of tab characters as ANSI text (:iss:`8741`)
+
 0.42.1 [2025-05-17]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 

kitty/line.c

@@ -111,10 +111,11 @@ multicell_is_continuation_of_previous(const CPUCell *prev, const CPUCell *curr)
     return prev->width == curr->width && !curr->natural_width;
 }
 
-static void
+static index_type
 text_in_cell_ansi(ANSILineState *s, const CPUCell *c, TextCache *tc, bool skip_multiline_non_zero_lines) {
+    index_type num_cells_to_skip_for_tab = 0;
     if (c->is_multicell) {
-        if (c->x || (skip_multiline_non_zero_lines && c->y)) return;
+        if (c->x || (skip_multiline_non_zero_lines && c->y)) return num_cells_to_skip_for_tab;
         if (s->current_multicell_state) {
             if (!multicell_is_continuation_of_previous(s->current_multicell_state, c)) {
                 close_multicell(s);
@@ -134,18 +135,15 @@ text_in_cell_ansi(ANSILineState *s, const CPUCell *c, TextCache *tc, bool skip_m
         switch (s->output_buf->buf[pos]) {
             case 0: s->output_buf->buf[pos] = ' '; break;
             case '\t': {
-                unsigned num_cells_to_skip_for_tab = 0, n = s->output_buf->len - pos;
+                index_type n = s->output_buf->len - pos;
-                if (n - pos > 1) {
+                if (n > 1) {
                     num_cells_to_skip_for_tab = s->output_buf->buf[s->output_buf->len - n + 1];
                     s->output_buf->len -= n - 1;
                 }
-                const CPUCell *next = c + 1;
-                while (num_cells_to_skip_for_tab && pos + 1 < s->limit && cell_is_char(next, ' ')) {
-                    num_cells_to_skip_for_tab--; pos++; next++;
-                }
             } break;
         }
     }
+    return num_cells_to_skip_for_tab;
 }
 
 
@@ -596,8 +594,13 @@ line_as_ansi(Line *self, ANSILineState *s, index_type start_at, index_type stop_
             if (*sgr) write_sgr_to_ansi_buf(s, sgr);
         }
 
-        text_in_cell_ansi(s, self->cpu_cells + s->pos, self->text_cache, skip_multiline_non_zero_lines);
+        index_type num_cells_to_skip_for_tab = text_in_cell_ansi(
+            s, self->cpu_cells + s->pos, self->text_cache, skip_multiline_non_zero_lines);
         s->prev_gpu_cell = cell;
+        const CPUCell *next = self->cpu_cells + s->pos + 1;
+        while (num_cells_to_skip_for_tab && s->pos + 1 < s->limit && cell_is_char(next, ' ')) {
+            num_cells_to_skip_for_tab--; s->pos++; next++;
+        }
     }
     close_multicell(s);
     return s->escape_code_written;

kitty_tests/datatypes.py

@@ -535,8 +535,6 @@ class TestDataTypes(BaseTest):
                 if saved[k] is not None:
                     os.environ[k] = saved[k]
 
-
-
     def test_historybuf(self):
         lb = filled_line_buf()
         hb = HistoryBuf(5, 5)

kitty_tests/screen.py

@@ -105,6 +105,14 @@ class TestScreen(BaseTest):
         self.ae(str(s.line(4)), 'a\u0306b1\u030623')
         self.ae((s.cursor.x, s.cursor.y), (2, 4))
 
+        # Test drawing of tabs
+        s = self.create_screen(cols=32)
+        txt = 'a\tb'
+        s.draw(txt)
+        ln = s.line(0)
+        self.ae(txt, ln.as_ansi())
+
+
     def test_rep(self):
         s = self.create_screen()
         s.draw('a')