From 8f0d2915007c30990004e7ba2a9298c0951332d8 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Sun, 17 Nov 2024 12:37:27 +0530
Subject: [PATCH] Delete chars with multicell tests

---
 kitty/screen.c           |  9 +++---
 kitty_tests/multicell.py | 63 ++++++++++++++++++++++++++++++++++++++--
 2 files changed, 65 insertions(+), 7 deletions(-)

diff --git a/kitty/screen.c b/kitty/screen.c
index ccfec1045..45e52393b 100644
--- a/kitty/screen.c
+++ b/kitty/screen.c
@@ -721,9 +721,9 @@ nuke_incomplete_single_line_multicell_chars_in_range(
     for (index_type x = start; x < limit; x++) {
         if (cpu_cells[x].is_multicell) {
             MultiCellData mcd = cell_multicell_data(cpu_cells + x, self->text_cache);
-            index_type last_x = x + mcd.width;
-            if (last_x > limit) nuke_in_line(cpu_cells, gpu_cells, x, limit, replace_with_spaces ? ' ': 0);
-            x = last_x + 1;
+            index_type mcd_x_limit = x + mcd.width - cpu_cells[x].x;
+            if (cpu_cells[x].x || mcd_x_limit > limit) nuke_in_line(cpu_cells, gpu_cells, x, MIN(mcd_x_limit, limit), replace_with_spaces ? ' ': 0);
+            x = mcd_x_limit;
         }
     }
 }
@@ -2410,14 +2410,13 @@ remove_characters(Screen *self, index_type at, index_type num, index_type y, boo
     // and x=at + num - 1 are deleted
     nuke_multiline_char_intersecting_with(self, at, self->columns, y, y + 1, replace_with_spaces);
     nuke_split_multicell_char_at_left_boundary(self, at, y, replace_with_spaces);
-    nuke_split_multicell_char_at_right_boundary(self, at + num - 1, y, replace_with_spaces);
     CPUCell *cp; GPUCell *gp;
     linebuf_init_cells(self->linebuf, y, &cp, &gp);
     // left shift
     for (index_type i = at; i < self->columns - num; i++) {
         cp[i] = cp[i+num]; gp[i] = gp[i+num];
     }
-    nuke_split_multicell_char_at_right_boundary(self, at + num - 1, y, replace_with_spaces);
+    nuke_incomplete_single_line_multicell_chars_in_range(self, at, self->columns, y, replace_with_spaces);
 }
 
 void
diff --git a/kitty_tests/multicell.py b/kitty_tests/multicell.py
index 9a167422c..77f5c8551 100644
--- a/kitty_tests/multicell.py
+++ b/kitty_tests/multicell.py
@@ -80,8 +80,10 @@ def test_multicell(self: TestMulticell) -> None:
             y = s.cursor.y
         self.ae(text, line_text(y))
 
-    # Test basic multicell drawing
     s = self.create_screen(cols=6, lines=6)
+
+    # Test basic multicell drawing
+    s.reset()
     ac(0, 0, is_multicell=False)
     multicell(s, 'a')
     ac(0, 0, is_multicell=True, width=1, scale=1, subscale=0, x=0, y=0, text='a', explicitly_set=True, cursor=(1, 0))
@@ -133,7 +135,7 @@ def test_multicell(self: TestMulticell) -> None:
             ac(x, 4, text=' ')
     big_a(0, 0), big_a(1, 1), big_a(2, 2), big_a(5, 1)
 
-    # Test insert chars with multicell
+    # Test insert chars with multicell (aka right shift)
     s.reset()
     s.draw('a')
     s.cursor.x = 0
@@ -166,6 +168,7 @@ def test_multicell(self: TestMulticell) -> None:
     s.cursor.x = 0
     s.insert_characters(1)
     assert_line('\0\0\0\0\0\0')
+    # multiline
     s.reset()
     s.draw('a')
     multicell(s, 'b', scale=2)
@@ -182,3 +185,59 @@ def test_multicell(self: TestMulticell) -> None:
     assert_line('a_\0\0\0\0')
     assert_line('__\0\0\0\0', 1)
 
+    # Test delete chars with multicell (aka left shift)
+    s.reset()
+    multicell(s, 'a', width=2)
+    s.cursor.x = 0
+    s.delete_characters(1)
+    assert_line('\0\0\0\0\0\0')
+    s.reset()
+    multicell(s, 'a', width=2)
+    s.cursor.x = 1
+    s.delete_characters(1)
+    assert_line('\0\0\0\0\0\0')
+    s.reset()
+    s.draw('ab')
+    multicell(s, 'a', width=2)
+    s.cursor.x = 0
+    s.delete_characters(2)
+    assert_line('a_\0\0\0\0')
+    s.reset()
+    s.draw('a'), multicell(s, 'b', width=2), s.draw('c')
+    s.cursor.x = 0
+    s.delete_characters(1)
+    assert_line('b_c\0\0\0')
+    s.reset()
+    s.draw('a'), multicell(s, 'b', width=2), s.draw('c')
+    s.cursor.x = 0
+    s.delete_characters(1)
+    assert_line('b_c\0\0\0')
+    s.reset(), s.draw('a'), multicell(s, 'b', width=2), s.draw('c')
+    s.cursor.x = 0
+    s.delete_characters(2)
+    assert_line('\0c\0\0\0\0')
+    s.reset(), s.draw('a'), multicell(s, 'b', width=2), s.draw('c')
+    s.cursor.x = 1
+    s.delete_characters(1)
+    assert_line('a\0c\0\0\0')
+    s.reset(), s.draw('a'), multicell(s, 'b', width=2), s.draw('c')
+    s.cursor.x = 2
+    s.delete_characters(1)
+    assert_line('a\0c\0\0\0')
+
+    # multiline
+    s.reset()
+    s.draw('a'), multicell(s, 'b', scale=2), s.draw('c')
+    assert_line('ab_c\0\0')
+    assert_line('\0__\0\0\0', 1)
+    s.cursor.x, s.cursor.y = 0, 0
+    s.delete_characters(1)
+    assert_line('\0\0c\0\0\0')
+    assert_line('\0\0\0\0\0\0', 1)
+    s.reset()
+    multicell(s, 'a', scale=2)
+    s.cursor.x = 3
+    s.delete_characters(1)
+    assert_line('a_\0\0\0\0')
+    assert_line('__\0\0\0\0', 1)
+