perf: only redraw concealed line if cursor has moved horizontally

Building upon #17889, this moves conceal redrawing logic into move.c, so
that concealed line is only redrawn if cursor has moved horizontally.

src/nvim/edit.c

@@ -1480,8 +1480,6 @@ bool edit(int cmdchar, bool startln, long count)
 /// @param ready not busy with something
 static void ins_redraw(bool ready)
 {
- bool conceal_cursor_moved = false;
-
  if (char_avail()) {
  return;
  }
@@ -1504,7 +1502,6 @@ static void ins_redraw(bool ready)
  update_curswant();
  ins_apply_autocmds(EVENT_CURSORMOVEDI);
  }
- conceal_cursor_moved = true;
  curwin->w_last_cursormoved = curwin->w_cursor;
  }
 
@@ -1560,11 +1557,6 @@ static void ins_redraw(bool ready)
  curbuf->b_changed_invalid = false;
  }
 
- if (curwin->w_p_cole > 0 && conceal_cursor_line(curwin)
- && conceal_cursor_moved) {
- redrawWinline(curwin, curwin->w_cursor.lnum);
- }
-
  pum_check_clear();
  if (must_redraw) {
  update_screen(0);

src/nvim/move.c

@@ -96,19 +96,20 @@ static void comp_botline(win_T *wp)
 }
 
 /// Redraw when w_cline_row changes and 'relativenumber' or 'cursorline' is set.
+/// Also when concealing is on and 'concealcursor' is not active.
 void redraw_for_cursorline(win_T *wp)
  FUNC_ATTR_NONNULL_ALL
 {
- if ((wp->w_p_rnu || win_cursorline_standout(wp))
- && (wp->w_valid & VALID_CROW) == 0
- && !pum_visible()) {
+ if ((wp->w_valid & VALID_CROW) == 0 && !pum_visible()
+ && (wp->w_p_rnu || win_cursorline_standout(wp))) {
  // win_line() will redraw the number column and cursorline only.
  redraw_later(wp, VALID);
  }
 }
 
 /// Redraw when w_virtcol changes and 'cursorcolumn' is set or 'cursorlineopt'
 /// contains "screenline".
+/// Also when concealing is on and 'concealcursor' is active.
 static void redraw_for_cursorcolumn(win_T *wp)
  FUNC_ATTR_NONNULL_ALL
 {
@@ -121,6 +122,12 @@ static void redraw_for_cursorcolumn(win_T *wp)
  redraw_later(wp, VALID);
  }
  }
+ // If the cursor moves horizontally when 'concealcursor' is active, then the
+ // current line needs to be redrawn in order to calculate the correct
+ // cursor position.
+ if ((wp->w_valid & VALID_VIRTCOL) == 0 && wp->w_p_cole > 0 && conceal_cursor_line(wp)) {
+ redrawWinline(wp, wp->w_cursor.lnum);
+ }
 }
 
 /*

src/nvim/normal.c

@@ -1288,13 +1288,6 @@ static void normal_redraw(NormalState *s)
  update_topline(curwin);
  validate_cursor();
 
- // If the cursor moves horizontally when 'concealcursor' is active, then the
- // current line needs to be redrawn in order to calculate the correct
- // cursor position.
- if (curwin->w_p_cole > 0 && conceal_cursor_line(curwin)) {
- redrawWinline(curwin, curwin->w_cursor.lnum);
- }
-
  if (VIsual_active) {
  update_curbuf(INVERTED); // update inverted part
  } else if (must_redraw) {

test/functional/ui/syntax_conceal_spec.lua

@@ -3,6 +3,7 @@ local Screen = require('test.functional.ui.screen')
 local clear, feed, command = helpers.clear, helpers.feed, helpers.command
 local eq = helpers.eq
 local insert = helpers.insert
+local poke_eventloop = helpers.poke_eventloop
 
 describe('Screen', function()
  local screen
@@ -911,7 +912,57 @@ describe('Screen', function()
  {0:~ }|
  |
  ]]}
- eq(grid_lines, {{2, 0, {{'c', 0, 3}}}})
+ eq({{2, 0, {{'c', 0, 3}}}}, grid_lines)
+ end)
+
+ it('K_EVENT should not cause extra redraws with concealcursor #13196', function()
+ command('set conceallevel=1')
+ command('set concealcursor=nv')
+ command('set redrawdebug+=nodelta')
+
+ insert([[
+ aaa
+ bbb
+ ccc
+ ]])
+ screen:expect{grid=[[
+ aaa |
+ bbb |
+ ccc |
+ ^ |
+ {0:~ }|
+ {0:~ }|
+ {0:~ }|
+ {0:~ }|
+ {0:~ }|
+ |
+ ]]}
+
+ -- XXX: hack to get notifications, and check only a single line is
+ -- updated. Could use next_msg() also.
+ local orig_handle_grid_line = screen._handle_grid_line
+ local grid_lines = {}
+ function screen._handle_grid_line(self, grid, row, col, items)
+ table.insert(grid_lines, {row, col, items})
+ orig_handle_grid_line(self, grid, row, col, items)
+ end
+ feed('k')
+ screen:expect{grid=[[
+ aaa |
+ bbb |
+ ^ccc |
+ |
+ {0:~ }|
+ {0:~ }|
+ {0:~ }|
+ {0:~ }|
+ {0:~ }|
+ |
+ ]]}
+ eq({{2, 0, {{'c', 0, 3}}}}, grid_lines)
+ poke_eventloop() -- causes K_EVENT key
+ screen:expect_unchanged()
+ eq({{2, 0, {{'c', 0, 3}}}}, grid_lines)
  end)
 
  -- Copy of Test_cursor_column_in_concealed_line_after_window_scroll in