vim-patch:9.0.0652: 'smoothscroll' not tested with 'number' and "n" in 'cpo'

Problem:    'smoothscroll' not tested with 'number' and "n" in 'cpo'.
Solution:   Add tests, fix uncovered problem.

b6aab8f44b

Co-authored-by: Bram Moolenaar <Bram@vim.org>

src/nvim/drawline.c

@@ -596,7 +596,8 @@ static void handle_lnum_col(win_T *wp, winlinevars_T *wlv, int num_signs, int si
                             int sign_num_attr, int sign_cul_attr)
 {
   if ((wp->w_p_nu || wp->w_p_rnu)
-      && (wlv->row == wlv->startrow + wlv->filler_lines
+      && ((wlv->row == wlv->startrow + wlv->filler_lines
+           && (wp->w_skipcol == 0 || wlv->row > wp->w_winrow))
           || vim_strchr(p_cpo, CPO_NUMCOL) == NULL)) {
     // If 'signcolumn' is set to 'number' and a sign is present
     // in "lnum", then display the sign instead of the line

src/nvim/drawscreen.c

@@ -1447,6 +1447,26 @@ static void win_update(win_T *wp, DecorProviders *providers)
 
   init_search_hl(wp, &screen_search_hl);
 
+  // Make sure skipcol is valid, it depends on various options and the window
+  // width.
+  if (wp->w_skipcol > 0) {
+    int w = 0;
+    int width1 = wp->w_width - win_col_off(wp);
+    int width2 = width1 + win_col_off2(wp);
+    int add = width1;
+
+    while (w < wp->w_skipcol) {
+      if (w > 0) {
+        add = width2;
+      }
+      w += add;
+    }
+    if (w != wp->w_skipcol) {
+      // always round down, the higher value may not be valid
+      wp->w_skipcol = w - add;
+    }
+  }
+
   // Force redraw when width of 'number' or 'relativenumber' column
   // changes.
   int nrwidth = (wp->w_p_nu || wp->w_p_rnu || *wp->w_p_stc) ? number_width(wp) : 0;