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

1 files changed, 19 insertions, 0 deletions

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.
 ///