fix(marks): truncate double-width inline virt_text consistently (#32560)

- Fix wrong cursor position with 'listchars' "precedes".
- Always show the '<' truncation character.

src/nvim/drawline.c

@@ -930,28 +930,22 @@ static void handle_inline_virtual_text(win_T *wp, winlinevars_T *wlv, ptrdiff_t
       if (wlv->skip_cells > 0) {
         int virt_text_width = (int)mb_string2cells(wlv->p_extra);
         if (virt_text_width > wlv->skip_cells) {
-          int cells_to_skip = wlv->skip_cells;
+          int skip_cells_remaining = wlv->skip_cells;
           // Skip cells in the text.
-          while (cells_to_skip > 0) {
+          while (skip_cells_remaining > 0) {
+            int cells = utf_ptr2cells(wlv->p_extra);
+            if (cells > skip_cells_remaining) {
+              break;
+            }
             int c_len = utfc_ptr2len(wlv->p_extra);
-            cells_to_skip -= utf_ptr2cells(wlv->p_extra);
+            skip_cells_remaining -= cells;
             wlv->p_extra += c_len;
             wlv->n_extra -= c_len;
             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->skipped_cells += wlv->skip_cells - skip_cells_remaining;
-          wlv->skip_cells = 0;
+          wlv->skip_cells = skip_cells_remaining;
         } else {
           // The whole text is left of the window, drop
           // it and advance to the next one.
@@ -1076,6 +1070,9 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, int col_rows, s
   bool in_multispace = false;           // in multiple consecutive spaces
   int multispace_pos = 0;               // position in lcs-multispace string
 
+  int n_extra_next = 0;                 // n_extra to use after current extra chars
+  int extra_attr_next = -1;             // extra_attr to use after current extra chars
+
   bool search_attr_from_match = false;  // if search_attr is from :match
   bool has_decor = false;               // this buffer has decoration
 
@@ -1950,7 +1947,6 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, int col_rows, s
         if (wlv.col >= grid->cols - 1 && schar_cells(mb_schar) == 2) {
           mb_c = '>';
           mb_l = 1;
-          (void)mb_l;
           mb_schar = schar_from_ascii(mb_c);
           multi_attr = win_hl_attr(wp, HLF_AT);
 
@@ -1963,30 +1959,58 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, int col_rows, s
           wlv.n_extra -= mb_l;
           wlv.p_extra += mb_l;
         }
+
+        // If a double-width char doesn't fit at the left side display a '<'.
+        if (wlv.filler_todo <= 0 && wlv.skip_cells > 0 && mb_l > 1) {
+          if (wlv.n_extra > 0) {
+            n_extra_next = wlv.n_extra;
+            extra_attr_next = wlv.extra_attr;
+          }
+          wlv.n_extra = 1;
+          wlv.sc_extra = schar_from_ascii(MB_FILLER_CHAR);
+          wlv.sc_final = NUL;
+          mb_schar = schar_from_ascii(' ');
+          mb_c = ' ';
+          mb_l = 1;
+          (void)mb_l;
+          wlv.n_attr++;
+          wlv.extra_attr = win_hl_attr(wp, HLF_AT);
+        }
       }
 
-      // Only restore search_attr and area_attr after "n_extra" in
-      // the next screen line is also done.
       if (wlv.n_extra <= 0) {
-        if (search_attr == 0) {
+        // Only restore search_attr and area_attr when there is no "n_extra" to show.
-          search_attr = saved_search_attr;
+        if (n_extra_next <= 0) {
-          saved_search_attr = 0;
+          if (search_attr == 0) {
-        }
+            search_attr = saved_search_attr;
-        if (area_attr == 0 && *ptr != NUL) {
+            saved_search_attr = 0;
-          area_attr = saved_area_attr;
+          }
-          saved_area_attr = 0;
+          if (area_attr == 0 && *ptr != NUL) {
-        }
+            area_attr = saved_area_attr;
-        if (decor_attr == 0) {
+            saved_area_attr = 0;
-          decor_attr = saved_decor_attr;
+          }
-          saved_decor_attr = 0;
+          if (decor_attr == 0) {
-        }
+            decor_attr = saved_decor_attr;
-
+            saved_decor_attr = 0;
-        if (wlv.extra_for_extmark) {
+          }
-          // wlv.extra_attr should be used at this position but not
+          if (wlv.extra_for_extmark) {
-          // any further.
+            // wlv.extra_attr should be used at this position but not any further.
+            wlv.reset_extra_attr = true;
+            extra_attr_next = -1;
+          }
+          wlv.extra_for_extmark = false;
+        } else {
+          assert(wlv.sc_extra != NUL || wlv.sc_final != NUL);
+          assert(wlv.p_extra != NULL);
+          wlv.sc_extra = NUL;
+          wlv.sc_final = NUL;
+          wlv.n_extra = n_extra_next;
+          n_extra_next = 0;
+          // wlv.extra_attr should be used at this position, but extra_attr_next
+          // should be used after that.
           wlv.reset_extra_attr = true;
+          assert(extra_attr_next >= 0);
         }
-        wlv.extra_for_extmark = false;
       }
     } else if (wlv.filler_todo > 0) {
       // Wait with reading text until filler lines are done. Still need to
@@ -2563,14 +2587,19 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, int col_rows, s
       wp->w_valid |= VALID_WCOL|VALID_WROW|VALID_VIRTCOL;
     }
 
-    // Don't override visual selection highlighting.
+    // Use "wlv.extra_attr", but don't override visual selection highlighting.
     if (wlv.n_attr > 0 && !search_attr_from_match) {
       wlv.char_attr = hl_combine_attr(wlv.char_attr, wlv.extra_attr);
       if (wlv.reset_extra_attr) {
         wlv.reset_extra_attr = false;
-        wlv.extra_attr = 0;
+        if (extra_attr_next >= 0) {
-        // search_attr_from_match can be restored now that the extra_attr has been applied
+          wlv.extra_attr = extra_attr_next;
-        search_attr_from_match = saved_search_attr_from_match;
+          extra_attr_next = -1;
+        } else {
+          wlv.extra_attr = 0;
+          // search_attr_from_match can be restored now that the extra_attr has been applied
+          search_attr_from_match = saved_search_attr_from_match;
+        }
       }
     }
 
@@ -2584,14 +2613,20 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, int col_rows, s
         && wlv.skip_cells <= 0
         && mb_schar != NUL) {
       lcs_prec_todo = NUL;
-      // TODO(zeertzjq): handle the n_extra > 0 case
+      if (schar_cells(mb_schar) > 1) {
-      if (schar_cells(mb_schar) > 1 && wlv.n_extra == 0) {
         // Double-width character being overwritten by the "precedes"
         // character, need to fill up half the character.
         wlv.sc_extra = schar_from_ascii(MB_FILLER_CHAR);
         wlv.sc_final = NUL;
+        if (wlv.n_extra > 0) {
+          assert(wlv.p_extra != NULL);
+          n_extra_next = wlv.n_extra;
+          extra_attr_next = wlv.extra_attr;
+          wlv.n_attr = MAX(wlv.n_attr + 1, 2);
+        } else {
+          wlv.n_attr = 2;
+        }
         wlv.n_extra = 1;
-        wlv.n_attr = 2;
         wlv.extra_attr = win_hl_attr(wp, HLF_AT);
       }
       mb_schar = wp->w_p_lcs_chars.prec;

test/functional/ui/decorations_spec.lua

@@ -3368,17 +3368,24 @@ describe('decorations: inline virtual text', function()
     command("set nowrap")
     api.nvim_buf_set_extmark(0, ns, 0, 2, { virt_text = { { string.rep('X', 55), 'Special' } }, virt_text_pos = 'inline' })
     feed('$')
-    screen:expect{grid=[[
+    screen:expect([[
       {10:XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX}cdefgh^i|
       {1:~                                                 }|
                                                         |
-    ]]}
+    ]])
+    command('set list listchars+=precedes:!')
+    screen:expect([[
+      {1:!}{10:XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX}cdefgh^i|
+      {1:~                                                 }|
+                                                        |
+    ]])
   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, {
+      hl_mode = 'replace',
       virt_text = { { 'α口β̳γ̲=', 'Special' }, { '❤️', 'Special' } },
       virt_text_pos = 'inline',
     })
@@ -3405,9 +3412,33 @@ describe('decorations: inline virtual text', function()
       {1:~                                                 }|
                                                         |
     ]])
+    feed('V')
+    screen:expect([[
+      {10:口β̳γ̲=❤️}{7:34567}^8                                     |
+      {1:~                                                 }|
+      {8:-- VISUAL LINE --}                                 |
+    ]])
+    command('set list listchars+=precedes:!')
+    screen:expect([[
+      {1:!<}{10:β̳γ̲=❤️}{7:34567}^8                                     |
+      {1:~                                                 }|
+      {8:-- VISUAL LINE --}                                 |
+    ]])
     feed('zl')
     screen:expect([[
-      {10: β̳γ̲=❤️}34567^8                                      |
+      {1:!}{10:β̳γ̲=❤️}{7:34567}^8                                      |
+      {1:~                                                 }|
+      {8:-- VISUAL LINE --}                                 |
+    ]])
+    command('set nolist')
+    screen:expect([[
+      {1:<}{10:β̳γ̲=❤️}{7:34567}^8                                      |
+      {1:~                                                 }|
+      {8:-- VISUAL LINE --}                                 |
+    ]])
+    feed('<Esc>')
+    screen:expect([[
+      {1:<}{10:β̳γ̲=❤️}34567^8                                      |
       {1:~                                                 }|
                                                         |
     ]])
@@ -3435,9 +3466,21 @@ describe('decorations: inline virtual text', function()
       {1:~                                                 }|
                                                         |
     ]])
+    command('set list')
+    screen:expect([[
+      {1:!<}34567^8                                          |
+      {1:~                                                 }|
+                                                        |
+    ]])
     feed('zl')
     screen:expect([[
-      {10: }34567^8                                           |
+      {1:!}34567^8                                           |
+      {1:~                                                 }|
+                                                        |
+    ]])
+    command('set nolist')
+    screen:expect([[
+      {1:<}34567^8                                           |
       {1:~                                                 }|
                                                         |
     ]])