refactor(options): use schar_T representation for fillchars and listchars

A bit big, but practically it was a lot simpler to change over all
fillchars and all listchars at once, to not need to maintain two
parallel implementations.

This is mostly an internal refactor, but it also removes an arbitrary
limitation: that 'fillchars' and 'listchars' values can only be
single-codepoint characters. Now any character which fits into a single
screen cell can be used.

1 files changed, 24 insertions, 29 deletions

diff --git a/src/nvim/drawscreen.c b/src/nvim/drawscreen.c
index 9dec2ce1e3..12f06e13cc 100644
--- a/src/nvim/drawscreen.c
+++ b/src/nvim/drawscreen.c
@@ -546,7 +546,7 @@ int update_screen(void)
 
   // might need to clear space on default_grid for the message area.
   if (type == UPD_NOT_VALID && clear_cmdline && !ui_has(kUIMessages)) {
-    grid_fill(&default_grid, Rows - (int)p_ch, Rows, 0, Columns, ' ', ' ', 0);
+    grid_clear(&default_grid, Rows - (int)p_ch, Rows, 0, Columns, 0);
   }
 
   ui_comp_set_screen_valid(true);
@@ -1297,9 +1297,8 @@ static void draw_vsep_win(win_T *wp)
 
   // draw the vertical separator right of this window
   int hl = win_hl_attr(wp, HLF_C);
-  int c = wp->w_p_fcs_chars.vert;
-  grid_fill(&default_grid, wp->w_winrow, W_ENDROW(wp),
-            W_ENDCOL(wp), W_ENDCOL(wp) + 1, c, ' ', hl);
+  schar_T c = wp->w_p_fcs_chars.vert;
+  grid_fill(&default_grid, wp->w_winrow, W_ENDROW(wp), W_ENDCOL(wp), W_ENDCOL(wp) + 1, c, c, hl);
 }
 
 /// Draw the horizontal separator below window "wp"
@@ -1311,9 +1310,8 @@ static void draw_hsep_win(win_T *wp)
 
   // draw the horizontal separator below this window
   int hl = win_hl_attr(wp, HLF_C);
-  int c = wp->w_p_fcs_chars.horiz;
-  grid_fill(&default_grid, W_ENDROW(wp), W_ENDROW(wp) + 1,
-            wp->w_wincol, W_ENDCOL(wp), c, c, hl);
+  schar_T c = wp->w_p_fcs_chars.horiz;
+  grid_fill(&default_grid, W_ENDROW(wp), W_ENDROW(wp) + 1, wp->w_wincol, W_ENDCOL(wp), c, c, hl);
 }
 
 /// Get the separator connector for specified window corner of window "wp"
@@ -1321,21 +1319,19 @@ static schar_T get_corner_sep_connector(win_T *wp, WindowCorner corner)
 {
   // It's impossible for windows to be connected neither vertically nor horizontally
   // So if they're not vertically connected, assume they're horizontally connected
-  int c;
   if (vsep_connected(wp, corner)) {
     if (hsep_connected(wp, corner)) {
-      c = wp->w_p_fcs_chars.verthoriz;
+      return wp->w_p_fcs_chars.verthoriz;
     } else if (corner == WC_TOP_LEFT || corner == WC_BOTTOM_LEFT) {
-      c = wp->w_p_fcs_chars.vertright;
+      return wp->w_p_fcs_chars.vertright;
     } else {
-      c = wp->w_p_fcs_chars.vertleft;
+      return wp->w_p_fcs_chars.vertleft;
     }
   } else if (corner == WC_TOP_LEFT || corner == WC_TOP_RIGHT) {
-    c = wp->w_p_fcs_chars.horizdown;
+    return wp->w_p_fcs_chars.horizdown;
   } else {
-    c = wp->w_p_fcs_chars.horizup;
+    return wp->w_p_fcs_chars.horizup;
   }
-  return schar_from_char(c);
 }
 
 /// Draw separator connecting characters on the corners of window "wp"
@@ -2384,7 +2380,7 @@ static void win_update(win_T *wp)
       // Last line isn't finished: Display "@@@" in the last screen line.
       grid_line_start(&wp->w_grid, wp->w_grid.rows - 1);
       grid_line_fill(0, MIN(wp->w_grid.cols, 3), wp->w_p_fcs_chars.lastline, at_attr);
-      grid_line_fill(3, wp->w_grid.cols, ' ', at_attr);
+      grid_line_fill(3, wp->w_grid.cols, schar_from_ascii(' '), at_attr);
       grid_line_flush();
       set_empty_rows(wp, srow);
       wp->w_botline = lnum;
@@ -2399,7 +2395,8 @@ static void win_update(win_T *wp)
       set_empty_rows(wp, srow);
       wp->w_botline = lnum;
     } else {
-      win_draw_end(wp, wp->w_p_fcs_chars.lastline, ' ', true, srow, wp->w_grid.rows, HLF_AT);
+      win_draw_end(wp, wp->w_p_fcs_chars.lastline, schar_from_ascii(' '), true, srow,
+                   wp->w_grid.rows, HLF_AT);
       set_empty_rows(wp, srow);
       wp->w_botline = lnum;
     }
@@ -2432,7 +2429,8 @@ static void win_update(win_T *wp)
       lastline = 0;
     }
 
-    win_draw_end(wp, wp->w_p_fcs_chars.eob, ' ', false, MAX(lastline, row), wp->w_grid.rows,
+    win_draw_end(wp, wp->w_p_fcs_chars.eob, schar_from_ascii(' '), false, MAX(lastline, row),
+                 wp->w_grid.rows,
                  HLF_EOB);
     set_empty_rows(wp, row);
   }
@@ -2519,10 +2517,9 @@ void win_scroll_lines(win_T *wp, int row, int line_count)
   }
 }
 
-/// Call grid_fill() with columns adjusted for 'rightleft' if needed.
+/// Call grid_clear() with columns adjusted for 'rightleft' if needed.
 /// Return the new offset.
-static int win_fill_end(win_T *wp, int c1, int c2, int off, int width, int row, int endrow,
-                        int attr)
+static int win_clear_end(win_T *wp, int off, int width, int row, int endrow, int attr)
 {
   int nn = off + width;
   const int endcol = wp->w_grid.cols;
@@ -2532,9 +2529,9 @@ static int win_fill_end(win_T *wp, int c1, int c2, int off, int width, int row,
   }
 
   if (wp->w_p_rl) {
-    grid_fill(&wp->w_grid, row, endrow, endcol - nn, endcol - off, c1, c2, attr);
+    grid_clear(&wp->w_grid, row, endrow, endcol - nn, endcol - off, attr);
   } else {
-    grid_fill(&wp->w_grid, row, endrow, off, nn, c1, c2, attr);
+    grid_clear(&wp->w_grid, row, endrow, off, nn, attr);
   }
 
   return nn;
@@ -2543,7 +2540,8 @@ static int win_fill_end(win_T *wp, int c1, int c2, int off, int width, int row,
 /// Clear lines near the end of the window and mark the unused lines with "c1".
 /// Use "c2" as filler character.
 /// When "draw_margin" is true, then draw the sign/fold/number columns.
-void win_draw_end(win_T *wp, int c1, int c2, bool draw_margin, int row, int endrow, hlf_T hl)
+void win_draw_end(win_T *wp, schar_T c1, schar_T c2, bool draw_margin, int row, int endrow,
+                  hlf_T hl)
 {
   assert(hl >= 0 && hl < HLF_COUNT);
   int n = 0;
@@ -2552,19 +2550,16 @@ void win_draw_end(win_T *wp, int c1, int c2, bool draw_margin, int row, int endr
     // draw the fold column
     int fdc = compute_foldcolumn(wp, 0);
     if (fdc > 0) {
-      n = win_fill_end(wp, ' ', ' ', n, fdc, row, endrow,
-                       win_hl_attr(wp, HLF_FC));
+      n = win_clear_end(wp, n, fdc, row, endrow, win_hl_attr(wp, HLF_FC));
     }
     // draw the sign column
     int count = wp->w_scwidth;
     if (count > 0) {
-      n = win_fill_end(wp, ' ', ' ', n, SIGN_WIDTH * count, row,
-                       endrow, win_hl_attr(wp, HLF_SC));
+      n = win_clear_end(wp, n, SIGN_WIDTH * count, row, endrow, win_hl_attr(wp, HLF_SC));
     }
     // draw the number column
     if ((wp->w_p_nu || wp->w_p_rnu) && vim_strchr(p_cpo, CPO_NUMCOL) == NULL) {
-      n = win_fill_end(wp, ' ', ' ', n, number_width(wp) + 1, row, endrow,
-                       win_hl_attr(wp, HLF_N));
+      n = win_clear_end(wp, n, number_width(wp) + 1, row, endrow, win_hl_attr(wp, HLF_N));
     }
   }