fix(marks): handle double-with inline virt_text with 'nowrap' (#32476)

src/nvim/drawline.c

@@ -909,25 +909,39 @@ static void handle_inline_virtual_text(win_T *wp, winlinevars_T *wlv, ptrdiff_t
       // If the text didn't reach until the first window
       // column we need to skip cells.
       if (wlv->skip_cells > 0) {
-        // FIXME: this should use virt_text_width instead
+        int virt_text_width = (int)mb_string2cells(wlv->p_extra);
-        int virt_text_len = wlv->n_attr;
+        if (virt_text_width > wlv->skip_cells) {
-        if (virt_text_len > wlv->skip_cells) {
+          int cells_to_skip = wlv->skip_cells;
-          int len = mb_charlen2bytelen(wlv->p_extra, wlv->skip_cells);
+          // Skip cells in the text.
-          wlv->n_extra -= len;
+          while (cells_to_skip > 0) {
-          wlv->p_extra += len;
+            int clen = utf_ptr2len(wlv->p_extra);
-          wlv->n_attr -= wlv->skip_cells;
+            cells_to_skip -= utf_ptr2cells(wlv->p_extra);
+            wlv->p_extra += clen;
+            wlv->n_extra -= clen;
+            wlv->n_attr--;
+          }
+          // If a double-width char doesn't fit, pad with space.
+          if (cells_to_skip < 0) {
+            int pad_len = -cells_to_skip;
+            char *padded = get_extra_buf((size_t)(wlv->n_extra + pad_len) + 1);
+            memset(padded, ' ', (size_t)pad_len);
+            xmemcpyz(padded + pad_len, wlv->p_extra, (size_t)wlv->n_extra);
+            wlv->p_extra = padded;
+            wlv->n_extra += pad_len;
+            wlv->n_attr += pad_len;
+          }
           // Skipped cells needed to be accounted for in vcol.
           wlv->skipped_cells += wlv->skip_cells;
           wlv->skip_cells = 0;
         } else {
-          // the whole text is left of the window, drop
+          // The whole text is left of the window, drop
-          // it and advance to the next one
+          // it and advance to the next one.
-          wlv->skip_cells -= virt_text_len;
+          wlv->skip_cells -= virt_text_width;
           // Skipped cells needed to be accounted for in vcol.
-          wlv->skipped_cells += virt_text_len;
+          wlv->skipped_cells += virt_text_width;
           wlv->n_attr = 0;
           wlv->n_extra = 0;
-          // go to the start so the next virtual text chunk can be selected.
+          // Go to the start so the next virtual text chunk can be selected.
           continue;
         }
       }

src/nvim/mbyte.c

@@ -2251,24 +2251,6 @@ int mb_charlen(const char *str)
   return count;
 }
 
-int mb_charlen2bytelen(const char *str, int charlen)
-{
-  const char *p = str;
-  int count = 0;
-
-  if (p == NULL) {
-    return 0;
-  }
-
-  for (int i = 0; *p != NUL && i < charlen; i++) {
-    int b = utfc_ptr2len(p);
-    p += b;
-    count += b;
-  }
-
-  return count;
-}
-
 /// Like mb_charlen() but for a string with specified length.
 int mb_charlen_len(const char *str, int len)
 {

test/functional/ui/decorations_spec.lua

@@ -3375,6 +3375,86 @@ describe('decorations: inline virtual text', function()
     ]]}
   end)
 
+  it('draws correctly with no wrap and multibyte virtual text', function()
+    insert('12345678')
+    command('set nowrap')
+    api.nvim_buf_set_extmark(0, ns, 0, 2, {
+      virt_text = { { 'αβγ口=', 'Special' }, { '口', 'Special' } },
+      virt_text_pos = 'inline',
+    })
+    screen:expect([[
+      12{10:αβγ口=口}34567^8                                  |
+      {1:~                                                 }|
+                                                        |
+    ]])
+    feed('zl')
+    screen:expect([[
+      2{10:αβγ口=口}34567^8                                   |
+      {1:~                                                 }|
+                                                        |
+    ]])
+    feed('zl')
+    screen:expect([[
+      {10:αβγ口=口}34567^8                                    |
+      {1:~                                                 }|
+                                                        |
+    ]])
+    feed('zl')
+    screen:expect([[
+      {10:βγ口=口}34567^8                                     |
+      {1:~                                                 }|
+                                                        |
+    ]])
+    feed('zl')
+    screen:expect([[
+      {10:γ口=口}34567^8                                      |
+      {1:~                                                 }|
+                                                        |
+    ]])
+    feed('zl')
+    screen:expect([[
+      {10:口=口}34567^8                                       |
+      {1:~                                                 }|
+                                                        |
+    ]])
+    feed('zl')
+    screen:expect([[
+      {10: =口}34567^8                                        |
+      {1:~                                                 }|
+                                                        |
+    ]])
+    feed('zl')
+    screen:expect([[
+      {10:=口}34567^8                                         |
+      {1:~                                                 }|
+                                                        |
+    ]])
+    feed('zl')
+    screen:expect([[
+      {10:口}34567^8                                          |
+      {1:~                                                 }|
+                                                        |
+    ]])
+    feed('zl')
+    screen:expect([[
+      {10: }34567^8                                           |
+      {1:~                                                 }|
+                                                        |
+    ]])
+    feed('zl')
+    screen:expect([[
+      34567^8                                            |
+      {1:~                                                 }|
+                                                        |
+    ]])
+    feed('zl')
+    screen:expect([[
+      4567^8                                             |
+      {1:~                                                 }|
+                                                        |
+    ]])
+  end)
+
   it('tabs are the correct length with no wrap following virtual text', function()
     command('set nowrap')
     feed('itest<TAB>a<ESC>')