fix(redraw): make redrawdebug=nodelta handle all the cases

Before only win_line lines were considered. this applies nodelta
to all screen elements. Causes some failures, which might indeed
indicate excessive redraws.

7 files changed, 43 insertions, 21 deletions

diff --git a/src/nvim/decoration.c b/src/nvim/decoration.c
index 778f9293fb..5a1708a57c 100644
--- a/src/nvim/decoration.c
+++ b/src/nvim/decoration.c
@@ -75,12 +75,11 @@ void decor_redraw(buf_T *buf, int row1, int row2, Decoration *decor)
   }
 
   if (decor && decor_virt_pos(*decor)) {
-    redraw_buf_line_later(buf, row1 + 1);
+    redraw_buf_line_later(buf, row1 + 1, false);
   }
 
   if (decor && kv_size(decor->virt_lines)) {
-    redraw_buf_line_later(buf, MIN(buf->b_ml.ml_line_count,
-                                   row1 + 1 + (decor->virt_lines_above?0:1)));
+    redraw_buf_line_later(buf, row1 + 1 + (decor->virt_lines_above?0:1), true);
   }
 }
 
diff --git a/src/nvim/drawline.c b/src/nvim/drawline.c
index 25ea2e1000..5c3fa3d3b0 100644
--- a/src/nvim/drawline.c
+++ b/src/nvim/drawline.c
@@ -2638,6 +2638,7 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, bool nochange,
       // When the window is too narrow draw all "@" lines.
       if (draw_state != WL_LINE && filler_todo <= 0) {
         win_draw_end(wp, '@', ' ', true, row, wp->w_grid.rows, HLF_AT);
+        set_empty_rows(wp, row);
         row = endrow;
       }
 
diff --git a/src/nvim/drawscreen.c b/src/nvim/drawscreen.c
index fb98e3effc..c95f3f3550 100644
--- a/src/nvim/drawscreen.c
+++ b/src/nvim/drawscreen.c
@@ -1018,6 +1018,9 @@ win_update_start:
   bool scrolled_down = false;   // true when scrolled down when w_topline got smaller a bit
   bool top_to_mod = false;      // redraw above mod_top
 
+  int bot_scroll_start = 999;   // first line that needs to be redrawn due to
+                                // scrolling. only used for EOB
+
   int row;                      // current window row to display
   linenr_T lnum;                // current buffer lnum to display
   int idx;                      // current index in w_lines[]
@@ -1195,6 +1198,7 @@ win_update_start:
       mod_bot = MAXLNUM;
     }
   }
+
   wp->w_redraw_top = 0;  // reset for next time
   wp->w_redraw_bot = 0;
 
@@ -1265,6 +1269,7 @@ win_update_start:
           // If not the last window, delete the lines at the bottom.
           // win_ins_lines may fail when the terminal can't do it.
           win_scroll_lines(wp, 0, i);
+          bot_scroll_start = 0;
           if (wp->w_lines_valid != 0) {
             // Need to update rows that are new, stop at the
             // first one that scrolled down.
@@ -1325,6 +1330,7 @@ win_update_start:
         if (row > 0) {
           win_scroll_lines(wp, 0, -row);
           bot_start = wp->w_grid.rows - row;
+          bot_scroll_start = bot_start;
         }
         if ((row == 0 || bot_start < 999) && wp->w_lines_valid != 0) {
           // Skip the lines (below the deleted lines) that are still
@@ -1702,6 +1708,7 @@ win_update_start:
           // need to redraw until the end of the window.
           // Inserting/deleting lines has no use.
           bot_start = 0;
+          bot_scroll_start = 0;
         } else {
           // Able to count old number of rows: Count new window
           // rows, and may insert/delete lines
@@ -1732,6 +1739,7 @@ win_update_start:
             } else {
               win_scroll_lines(wp, row, xtra_rows);
               bot_start = wp->w_grid.rows + xtra_rows;
+              bot_scroll_start = bot_start;
             }
           } else if (xtra_rows > 0) {
             // May scroll text down.  If there is not enough
@@ -1741,6 +1749,7 @@ win_update_start:
               mod_bot = MAXLNUM;
             } else {
               win_scroll_lines(wp, row + old_rows, xtra_rows);
+              bot_scroll_start = 0;
               if (top_end > row + old_rows) {
                 // Scrolled the part at the top that requires
                 // updating down.
@@ -1930,6 +1939,7 @@ win_update_start:
       wp->w_botline = lnum;
     } else {
       win_draw_end(wp, '@', ' ', true, srow, wp->w_grid.rows, HLF_AT);
+      set_empty_rows(wp, srow);
       wp->w_botline = lnum;
     }
   } else {
@@ -1950,8 +1960,18 @@ win_update_start:
     // Make sure the rest of the screen is blank.
     // write the "eob" character from 'fillchars' to rows that aren't part
     // of the file.
-    win_draw_end(wp, wp->w_p_fcs_chars.eob, ' ', false, row, wp->w_grid.rows,
+    // TODO(bfredl): just keep track of the valid EOB area from last redraw?
+    int lastline = bot_scroll_start;
+    if (mid_end >= row) {
+      lastline = MIN(lastline, mid_start);
+    }
+    if (mod_bot > buf->b_ml.ml_line_count + 1) {
+      lastline = 0;
+    }
+
+    win_draw_end(wp, wp->w_p_fcs_chars.eob, ' ', false, MAX(lastline, row), wp->w_grid.rows,
                  HLF_EOB);
+    set_empty_rows(wp, row);
   }
 
   kvi_destroy(line_providers);
@@ -2063,12 +2083,14 @@ void redraw_buf_later(buf_T *buf, int type)
   }
 }
 
-void redraw_buf_line_later(buf_T *buf,  linenr_T line)
+void redraw_buf_line_later(buf_T *buf, linenr_T line, bool force)
 {
   FOR_ALL_WINDOWS_IN_TAB(wp, curtab) {
-    if (wp->w_buffer == buf
-        && line >= wp->w_topline && line < wp->w_botline) {
-      redrawWinline(wp, line);
+    if (wp->w_buffer == buf) {
+      redrawWinline(wp, MIN(line, buf->b_ml.ml_line_count));
+      if (force && line > buf->b_ml.ml_line_count) {
+        wp->w_redraw_bot = line;
+      }
     }
   }
 }
diff --git a/src/nvim/grid.c b/src/nvim/grid.c
index 63bb945f73..2b73ff895d 100644
--- a/src/nvim/grid.c
+++ b/src/nvim/grid.c
@@ -175,7 +175,7 @@ void grid_put_schar(ScreenGrid *grid, int row, int col, char *schar, int attr)
 {
   assert(put_dirty_row == row);
   size_t off = grid->line_offset[row] + (size_t)col;
-  if (grid->attrs[off] != attr || schar_cmp(grid->chars[off], schar)) {
+  if (grid->attrs[off] != attr || schar_cmp(grid->chars[off], schar) || rdb_flags & RDB_NODELTA) {
     schar_copy(grid->chars[off], schar);
     grid->attrs[off] = attr;
 
@@ -280,7 +280,8 @@ void grid_puts_len(ScreenGrid *grid, char *text, int textlen, int row, int col,
     need_redraw = schar_cmp(grid->chars[off], buf)
                   || (mbyte_cells == 2 && grid->chars[off + 1][0] != 0)
                   || grid->attrs[off] != attr
-                  || exmode_active;
+                  || exmode_active
+                  || rdb_flags & RDB_NODELTA;
 
     if (need_redraw) {
       // When at the end of the text and overwriting a two-cell
@@ -412,8 +413,7 @@ void grid_fill(ScreenGrid *grid, int start_row, int end_row, int start_col, int
     size_t lineoff = grid->line_offset[row];
     for (col = start_col; col < end_col; col++) {
       size_t off = lineoff + (size_t)col;
-      if (schar_cmp(grid->chars[off], sc)
-          || grid->attrs[off] != attr) {
+      if (schar_cmp(grid->chars[off], sc) || grid->attrs[off] != attr || rdb_flags & RDB_NODELTA) {
         schar_copy(grid->chars[off], sc);
         grid->attrs[off] = attr;
         if (dirty_first == INT_MAX) {
@@ -605,7 +605,8 @@ void grid_put_linebuf(ScreenGrid *grid, int row, int coloff, int endcol, int cle
     while (col < clear_width) {
       if (grid->chars[off_to][0] != ' '
           || grid->chars[off_to][1] != NUL
-          || grid->attrs[off_to] != bg_attr) {
+          || grid->attrs[off_to] != bg_attr
+          || rdb_flags & RDB_NODELTA) {
         grid->chars[off_to][0] = ' ';
         grid->chars[off_to][1] = NUL;
         grid->attrs[off_to] = bg_attr;
diff --git a/src/nvim/screen.c b/src/nvim/screen.c
index cdfb1e9ee1..1af93f061c 100644
--- a/src/nvim/screen.c
+++ b/src/nvim/screen.c
@@ -155,8 +155,6 @@ void win_draw_end(win_T *wp, int c1, int c2, bool draw_margin, int row, int endr
   } else {
     grid_fill(&wp->w_grid, row, endrow, n, wp->w_grid.cols, c1, c2, attr);
   }
-
-  set_empty_rows(wp, row);
 }
 
 /// Compute the width of the foldcolumn.  Based on 'foldcolumn' and how much
diff --git a/src/nvim/sign.c b/src/nvim/sign.c
index 5ce9ee4546..6f13dd2f06 100644
--- a/src/nvim/sign.c
+++ b/src/nvim/sign.c
@@ -557,7 +557,7 @@ static linenr_T buf_delsign(buf_T *buf, linenr_T atlnum, int id, char *group)
         sign_group_unref((char *)sign->se_group->sg_name);
       }
       xfree(sign);
-      redraw_buf_line_later(buf, lnum);
+      redraw_buf_line_later(buf, lnum, false);
       // Check whether only one sign needs to be deleted
       // If deleting a sign with a specific identifier in a particular
       // group or deleting any sign at a particular line number, delete
@@ -1062,7 +1062,7 @@ static int sign_place(int *sign_id, const char *sign_group, const char *sign_nam
     lnum = buf_change_sign_type(buf, *sign_id, (char *)sign_group, sp->sn_typenr, prio);
   }
   if (lnum > 0) {
-    redraw_buf_line_later(buf, lnum);
+    redraw_buf_line_later(buf, lnum, false);
 
     // When displaying signs in the 'number' column, if the width of the
     // number column is less than 2, then force recomputing the width.
@@ -1093,7 +1093,7 @@ static int sign_unplace(int sign_id, char *sign_group, buf_T *buf, linenr_T atln
     if (lnum == 0) {
       return FAIL;
     }
-    redraw_buf_line_later(buf, lnum);
+    redraw_buf_line_later(buf, lnum, false);
   }
 
   // When all the signs in a buffer are removed, force recomputing the
diff --git a/test/functional/ui/syntax_conceal_spec.lua b/test/functional/ui/syntax_conceal_spec.lua
index f790597140..e8798ddd93 100644
--- a/test/functional/ui/syntax_conceal_spec.lua
+++ b/test/functional/ui/syntax_conceal_spec.lua
@@ -947,7 +947,7 @@ describe('Screen', function()
       {0:~                                                    }|
                                                            |
     ]]}
-    eq({{2, 0, {{'c', 0, 3}}}}, grid_lines)
+    eq({{2, 0, {{'c', 0, 3}, {' ', 0, 50}}}, {3, 0, {{' ', 0, 53}}}}, grid_lines)
   end)
 
   it('K_EVENT should not cause extra redraws with concealcursor #13196', function()
@@ -994,10 +994,11 @@ describe('Screen', function()
       {0:~                                                    }|
                                                            |
     ]]}
-    eq({{2, 0, {{'c', 0, 3}}}}, grid_lines)
+    eq({{2, 0, {{'c', 0, 3}, {' ', 0, 50}}}}, grid_lines)
+    grid_lines = {}
     poke_eventloop()  -- causes K_EVENT key
     screen:expect_unchanged()
-    eq({{2, 0, {{'c', 0, 3}}}}, grid_lines)
+    eq({}, grid_lines) -- no redraw was done
   end)
 
   -- Copy of Test_cursor_column_in_concealed_line_after_window_scroll in