Fix #8794

docs/changelog.rst

@@ -126,7 +126,7 @@ Detailed list of changes
 - Wayland GNOME: Fix incorrect OS Window tracking because GNOME has started
   activating windows on non-current workspaces (:iss:`8716`)
 
-- 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 rendering of VS15 variation selectors in some circumstances (:iss:`8731`, :iss:`8794`)
 
 - Fix a regression in 0.40.0 that broke serialization of tab characters as ANSI text (:iss:`8741`)
 

kitty/screen.c

@@ -866,7 +866,7 @@ halve_multicell_width(Screen *self, index_type x_, index_type y_) {
     int y_max_limit = MIN(self->lines, y_ + cp[x_].scale);
     for (int y = y_min_limit + 1; y < y_max_limit; y++) {
         Line *line = range_line_(self, y); cp = line->cpu_cells; gp = line->gpu_cells;
-        for (index_type x = 0; x < half_x_limit; x++) cp[x].width = new_width;
+        for (index_type x = x_; x < half_x_limit; x++) cp[x].width = new_width;
         for (index_type x = half_x_limit; x < x_limit; x++) {
             cp[x] = (CPUCell){0}; clear_sprite_position(gp[x]);
         }

kitty_tests/screen.py

@@ -710,12 +710,24 @@ class TestScreen(BaseTest):
         self.ae(s.text_for_selection(), ('a\u00adb',))
 
     def test_variation_selectors(self):
+        s = self.create_screen(cols=8)
+        def widths(text, *widths):
+            s.reset()
+            s.draw(text)
+            def w(x):
+                c = s.cpu_cells(0, x)
+                return (c['mcd'] or {'width': 1})['width']
+            actual = tuple(w(x) for x in range(len(widths)))
+            self.ae(widths, actual)
+        widths('\u4e00\u4e00\u26ab\ufe0e', 2, 2, 2, 2, 1)
+
         s = self.create_screen()
         def tt(text_to_draw):
             s.reset()
             s.draw(text_to_draw)
             self.ae(str(s.line(0)), text_to_draw)
         tt('abc\U0001f44d\ufe0ed')
+
         def t(*a):
             s.reset()
             for i in range(0, len(a), 2):