fix(column): rebuild status column when sign column is invalidated (#22690)

* fix(column): rebuild status column when sign column is invalidated

Problem:    When implementing a custom sign column through
            `'statuscolumn'`, the status column is not properly rebuilt
            when the sign column width changes.
Solution:   Force a rebuild of the status column when the sign column
            width is invalidated.

* test(column): 'statuscolumn' has correct width when (un)placing signs

4 files changed, 63 insertions, 4 deletions

diff --git a/src/nvim/buffer.c b/src/nvim/buffer.c
index cedbadbaf3..9a757960af 100644
--- a/src/nvim/buffer.c
+++ b/src/nvim/buffer.c
@@ -4109,6 +4109,7 @@ void buf_signcols_del_check(buf_T *buf, linenr_T line1, linenr_T line2)
 
   if (!buf->b_signcols.sentinel) {
     buf->b_signcols.valid = false;
+    invalidate_statuscol(NULL, buf);
     return;
   }
 
@@ -4117,6 +4118,7 @@ void buf_signcols_del_check(buf_T *buf, linenr_T line1, linenr_T line2)
   if (sent >= line1 && sent <= line2) {
     // Only invalidate when removing signs at the sentinel line.
     buf->b_signcols.valid = false;
+    invalidate_statuscol(NULL, buf);
   }
 }
 
@@ -4132,6 +4134,7 @@ void buf_signcols_add_check(buf_T *buf, sign_entry_T *added)
 
   if (!added || !buf->b_signcols.sentinel) {
     buf->b_signcols.valid = false;
+    invalidate_statuscol(NULL, buf);
     return;
   }
 
diff --git a/src/nvim/option.c b/src/nvim/option.c
index 5fe6e18155..02b32b1fe5 100644
--- a/src/nvim/option.c
+++ b/src/nvim/option.c
@@ -2176,10 +2176,8 @@ static char *set_bool_option(const int opt_idx, char *const varp, const int valu
     if (curwin->w_p_spell) {
       errmsg = did_set_spelllang(curwin);
     }
-  } else if ((int *)varp == &curwin->w_p_nu && *curwin->w_p_stc != NUL) {
-    // When 'statuscolumn' is set and 'number' is changed:
-    curwin->w_nrwidth_line_count = 0;    // make sure width is reset
-    curwin->w_statuscol_line_count = 0;  // make sure width is re-estimated
+  } else if ((int *)varp == &curwin->w_p_nu) {  // 'number'
+    invalidate_statuscol(curwin, NULL);
   }
 
   if ((int *)varp == &curwin->w_p_arab) {
@@ -5519,6 +5517,9 @@ int win_signcol_configured(win_T *wp, int *is_fixed)
   if (*scl == 'n'
       && (*(scl + 1) == 'o' || (*(scl + 1) == 'u'
                                 && (wp->w_p_nu || wp->w_p_rnu)))) {
+    if (*wp->w_p_stc != NUL) {
+      buf_signcols(wp->w_buffer, 0);
+    }
     return 0;
   }
 
diff --git a/src/nvim/statusline.c b/src/nvim/statusline.c
index ca92953b05..a54618205e 100644
--- a/src/nvim/statusline.c
+++ b/src/nvim/statusline.c
@@ -909,6 +909,25 @@ int build_statuscol_str(win_T *wp, linenr_T lnum, long relnum, statuscol_T *stcp
   return width;
 }
 
+/// Force a reset and re-estimation of the status column width.
+///
+/// @param wp  The window for which to reset the status column (can be NULL if "buf" is not)
+/// @param buf  The buffer for which to reset the status column (can be NULL)
+void invalidate_statuscol(win_T *wp, buf_T *buf)
+{
+  if (buf != NULL) {
+    FOR_ALL_WINDOWS_IN_TAB(win, curtab) {
+      if (*win->w_p_stc != NUL && win->w_buffer == buf) {
+        win->w_nrwidth_line_count = 0;
+        win->w_statuscol_line_count = 0;
+      }
+    }
+  } else if (*wp->w_p_stc != NUL) {
+    wp->w_nrwidth_line_count = 0;    // make sure width is reset
+    wp->w_statuscol_line_count = 0;  // make sure width is re-estimated
+  }
+}
+
 /// Build a string from the status line items in "fmt".
 /// Return length of string in screen cells.
 ///
diff --git a/test/functional/ui/statuscolumn_spec.lua b/test/functional/ui/statuscolumn_spec.lua
index d9385ef221..0a253455ad 100644
--- a/test/functional/ui/statuscolumn_spec.lua
+++ b/test/functional/ui/statuscolumn_spec.lua
@@ -557,4 +557,40 @@ describe('statuscolumn', function()
                                                            |
     ]])
   end)
+
+  it("has correct width with custom sign column when (un)placing signs", function()
+    screen:try_resize(screen._width, 6)
+    exec_lua([[
+      vim.cmd.norm('gg')
+      vim.o.signcolumn = 'no'
+      vim.fn.sign_define('sign', { text = 'ss' })
+      _G.StatusCol = function()
+        local s = vim.fn.sign_getplaced(1)[1].signs
+        local sign = ''
+        if #s > 0 then
+          sign = vim.v.lnum == 5 and 'ss' or '  '
+        end
+        return vim.v.lnum .. '%=' .. sign
+      end
+      vim.o.statuscolumn = "%!v:lua.StatusCol()"
+      vim.fn.sign_place(0, '', 'sign', 1, { lnum = 5 })
+    ]])
+    screen:expect([[
+      1   ^aaaaa                                            |
+      2   aaaaa                                            |
+      3   aaaaa                                            |
+      4   aaaaa                                            |
+      5 ssaaaaa                                            |
+                                                           |
+    ]])
+    command('sign unplace 1')
+    screen:expect([[
+      1 ^aaaaa                                              |
+      2 aaaaa                                              |
+      3 aaaaa                                              |
+      4 aaaaa                                              |
+      5 aaaaa                                              |
+                                                           |
+    ]])
+  end)
 end)