fix(status): handle unprintable chars in the statusline

5 files changed, 60 insertions, 30 deletions

diff --git a/src/nvim/buffer.c b/src/nvim/buffer.c
index 5dcb10751f..129a8c6fb2 100644
--- a/src/nvim/buffer.c
+++ b/src/nvim/buffer.c
@@ -3311,7 +3311,7 @@ void maketitle(void)
         buf_p += MIN(size, SPACE_FOR_FNAME);
       } else {
         buf_p += transstr_buf((const char *)path_tail(curbuf->b_fname),
-                              buf_p, SPACE_FOR_FNAME + 1, true);
+                              -1, buf_p, SPACE_FOR_FNAME + 1, true);
       }
 
       switch (bufIsChanged(curbuf)
diff --git a/src/nvim/charset.c b/src/nvim/charset.c
index 5aec9ccf9d..c4c7c5f387 100644
--- a/src/nvim/charset.c
+++ b/src/nvim/charset.c
@@ -354,14 +354,15 @@ size_t transstr_len(const char *const s, bool untab)
 /// @param[in]  untab  remove tab characters
 ///
 /// @return length of the resulting string, without the NUL byte.
-size_t transstr_buf(const char *const s, char *const buf, const size_t len, bool untab)
+size_t transstr_buf(const char *const s, const ssize_t slen, char *const buf, const size_t buflen,
+                    bool untab)
   FUNC_ATTR_NONNULL_ALL
 {
   const char *p = s;
   char *buf_p = buf;
-  char *const buf_e = buf_p + len - 1;
+  char *const buf_e = buf_p + buflen - 1;
 
-  while (*p != NUL && buf_p < buf_e) {
+  while ((slen < 0 || (p - s) < slen) && *p != NUL && buf_p < buf_e) {
     const size_t l = (size_t)utfc_ptr2len(p);
     if (l > 1) {
       if (buf_p + l > buf_e) {
@@ -416,7 +417,7 @@ char *transstr(const char *const s, bool untab)
   // multi-byte characters.
   const size_t len = transstr_len(s, untab) + 1;
   char *const buf = xmalloc(len);
-  transstr_buf(s, buf, len, untab);
+  transstr_buf(s, -1, buf, len, untab);
   return buf;
 }
 
@@ -431,7 +432,7 @@ size_t kv_transstr(StringBuilder *str, const char *const s, bool untab)
   // multi-byte characters.
   const size_t len = transstr_len(s, untab);
   kv_ensure_space(*str, len + 1);
-  transstr_buf(s, str->items + str->size, len + 1, untab);
+  transstr_buf(s, -1, str->items + str->size, len + 1, untab);
   str->size += len;  // do not include NUL byte
   return len;
 }
diff --git a/src/nvim/grid.c b/src/nvim/grid.c
index 16ebbfbb90..efbeac4f3f 100644
--- a/src/nvim/grid.c
+++ b/src/nvim/grid.c
@@ -158,9 +158,9 @@ void grid_getbytes(ScreenGrid *grid, int row, int col, char *bytes, int *attrp)
 /// attributes 'attr', and update chars[] and attrs[].
 /// Note: only outputs within one row, message is truncated at grid boundary!
 /// Note: if grid, row and/or col is invalid, nothing is done.
-void grid_puts(ScreenGrid *grid, char *text, int row, int col, int attr)
+int grid_puts(ScreenGrid *grid, char *text, int row, int col, int attr)
 {
-  grid_puts_len(grid, text, -1, row, col, attr);
+  return grid_puts_len(grid, text, -1, row, col, attr);
 }
 
 static ScreenGrid *put_dirty_grid = NULL;
@@ -197,7 +197,7 @@ void grid_put_schar(ScreenGrid *grid, int row, int col, char *schar, int attr)
 
 /// like grid_puts(), but output "text[len]".  When "len" is -1 output up to
 /// a NUL.
-void grid_puts_len(ScreenGrid *grid, char *text, int textlen, int row, int col, int attr)
+int grid_puts_len(ScreenGrid *grid, char *text, int textlen, int row, int col, int attr)
 {
   size_t off;
   char *ptr = text;
@@ -218,7 +218,7 @@ void grid_puts_len(ScreenGrid *grid, char *text, int textlen, int row, int col,
   if (grid->chars == NULL
       || row >= grid->rows || row < 0
       || col >= grid->cols || col < 0) {
-    return;
+    return 0;
   }
 
   if (put_dirty_row == -1) {
@@ -230,6 +230,7 @@ void grid_puts_len(ScreenGrid *grid, char *text, int textlen, int row, int col,
     }
   }
   off = grid->line_offset[row] + (size_t)col;
+  int start_col = col;
 
   // When drawing over the right half of a double-wide char clear out the
   // left half.  Only needed in a terminal.
@@ -252,6 +253,12 @@ void grid_puts_len(ScreenGrid *grid, char *text, int textlen, int row, int col,
       ? utfc_ptr2char_len(ptr, u8cc, (int)((text + len) - ptr))
       : utfc_ptr2char(ptr, u8cc);
     int mbyte_cells = utf_char2cells(u8c);
+    if (mbyte_cells > 2) {
+      mbyte_cells = 1;
+      u8c = 0xFFFD;
+      u8cc[0] = 0;
+    }
+
     if (p_arshape && !p_tbidi && ARABIC_CHAR(u8c)) {
       // Do Arabic shaping.
       if (len >= 0 && (int)(ptr - text) + mbyte_blen >= len) {
@@ -336,6 +343,7 @@ void grid_puts_len(ScreenGrid *grid, char *text, int textlen, int row, int col,
   if (do_flush) {
     grid_puts_line_flush(true);
   }
+  return col - start_col;
 }
 
 /// End a group of grid_puts_len calls and send the screen buffer to the UI
diff --git a/src/nvim/statusline.c b/src/nvim/statusline.c
index 6414b2bb74..c880de5060 100644
--- a/src/nvim/statusline.c
+++ b/src/nvim/statusline.c
@@ -152,8 +152,8 @@ void win_redr_status(win_T *wp)
 
     row = is_stl_global ? (Rows - (int)p_ch - 1) : W_ENDROW(wp);
     col = is_stl_global ? 0 : wp->w_wincol;
-    grid_puts(&default_grid, p, row, col, attr);
-    grid_fill(&default_grid, row, row + 1, len + col,
+    int width = grid_puts(&default_grid, p, row, col, attr);
+    grid_fill(&default_grid, row, row + 1, width + col,
               this_ru_col + col, fillchar, fillchar, attr);
 
     if (get_keymap_str(wp, "<%s>", NameBuff, MAXPATHL)
@@ -266,6 +266,7 @@ static void win_redr_custom(win_T *wp, bool draw_winbar, bool draw_ruler)
   int n;
   int fillchar;
   char buf[MAXPATHL];
+  char transbuf[MAXPATHL];
   char *stl;
   char *opt_name;
   int opt_scope = 0;
@@ -370,34 +371,25 @@ static void win_redr_custom(win_T *wp, bool draw_winbar, bool draw_ruler)
   // Make a copy, because the statusline may include a function call that
   // might change the option value and free the memory.
   stl = xstrdup(stl);
-  int width = build_stl_str_hl(ewp, buf, sizeof(buf), stl, opt_name, opt_scope,
-                               fillchar, maxwidth, &hltab, &tabtab, NULL);
+  build_stl_str_hl(ewp, buf, sizeof(buf), stl, opt_name, opt_scope,
+                   fillchar, maxwidth, &hltab, &tabtab, NULL);
 
   xfree(stl);
   ewp->w_p_crb = p_crb_save;
 
-  // Make all characters printable.
-  char *p = transstr(buf, true);
-  int len = (int)xstrlcpy(buf, p, sizeof(buf));
-  len = (size_t)len < sizeof(buf) ? len : (int)sizeof(buf) - 1;
-  xfree(p);
-
-  // fill up with "fillchar"
-  while (width < maxwidth && len < (int)sizeof(buf) - 1) {
-    len += utf_char2bytes(fillchar, buf + len);
-    width++;
-  }
-  buf[len] = NUL;
+  int len = (int)strlen(buf);
+  int start_col = col;
 
   // Draw each snippet with the specified highlighting.
   grid_puts_line_start(grid, row);
 
   int curattr = attr;
-  p = buf;
+  char *p = buf;
   for (n = 0; hltab[n].start != NULL; n++) {
     int textlen = (int)(hltab[n].start - p);
-    grid_puts_len(grid, p, textlen, row, col, curattr);
-    col += vim_strnsize(p, textlen);
+    // Make all characters printable.
+    size_t tsize = transstr_buf(p, textlen, transbuf, sizeof transbuf, true);
+    col += grid_puts_len(grid, transbuf, (int)tsize, row, col, curattr);
     p = hltab[n].start;
 
     if (hltab[n].userhl == 0) {
@@ -411,7 +403,12 @@ static void win_redr_custom(win_T *wp, bool draw_winbar, bool draw_ruler)
     }
   }
   // Make sure to use an empty string instead of p, if p is beyond buf + len.
-  grid_puts(grid, p >= buf + len ? "" : p, row, col, curattr);
+  size_t tsize = transstr_buf(p >= buf + len ? "" : p, -1, transbuf, sizeof transbuf, true);
+  col += grid_puts_len(grid, transbuf, (int)tsize, row, col, curattr);
+  int maxcol = start_col + maxwidth;
+
+  // fill up with "fillchar"
+  grid_fill(grid, row, row + 1, col, maxcol, fillchar, fillchar, curattr);
 
   grid_puts_line_flush(false);
 
diff --git a/test/functional/ui/multibyte_spec.lua b/test/functional/ui/multibyte_spec.lua
index d4e237bcb4..9f413f8bff 100644
--- a/test/functional/ui/multibyte_spec.lua
+++ b/test/functional/ui/multibyte_spec.lua
@@ -158,6 +158,7 @@ describe('multibyte rendering: statusline', function()
     screen:set_default_attr_ids({
       [1] = {bold = true, foreground = Screen.colors.Blue1},
       [2] = {bold = true, reverse = true},
+      [3] = {background = Screen.colors.Red, foreground = Screen.colors.Gray100};
     })
     screen:attach()
     command('set laststatus=2')
@@ -220,4 +221,27 @@ describe('multibyte rendering: statusline', function()
                                               |
     ]]}
   end)
+
+  it('unprintable chars in filename with default stl', function()
+    command("file 🧑‍💻")
+    -- TODO: this is wrong but avoids a crash
+    screen:expect{grid=[[
+      ^                                        |
+      {1:~                                       }|
+      {2:🧑�💻                                   }|
+                                              |
+    ]]}
+  end)
+
+  it('unprintable chars in filename with custom stl', function()
+    command('set statusline=xx%#ErrorMsg#%f%##yy')
+    command("file 🧑‍💻")
+    -- TODO: this is also wrong but also avoids a crash
+    screen:expect{grid=[[
+      ^                                        |
+      {1:~                                       }|
+      {2:xx}{3:🧑<200d>💻}{2:yy                          }|
+                                              |
+    ]]}
+  end)
 end)