feat(marks): add conceal_lines to nvim_buf_set_extmark()

Implement an extmark property that conceals lines vertically.

runtime/doc/api.txt

@@ -2698,6 +2698,10 @@ nvim_buf_set_extmark({buffer}, {ns_id}, {line}, {col}, {opts})
                     When a character is supplied it is used as |:syn-cchar|.
                     "hl_group" is used as highlight for the cchar if provided,
                     otherwise it defaults to |hl-Conceal|.
+                  • conceal_lines: string which should be empty. When
+                    provided, lines in the range are not drawn at all
+                    (according to 'conceallevel'); the next unconcealed line
+                    is drawn instead.
                   • spell: boolean indicating that spell checking should be
                     performed within this extmark
                   • ui_watched: boolean that indicates the mark should be

runtime/doc/news.txt

@@ -202,13 +202,14 @@ API
 • |nvim_echo()| `err` field to print error messages and `chunks` accepts
   highlight group IDs.
 • |nvim_open_win()| `relative` field can be set to "laststatus" and "tabline".
-• |nvim_buf_set_extmark()| new field `virt_lines_overflow` accepts value `scroll` to
+• Additions to |nvim_buf_set_extmark()|:
-  enable horizontal scrolling for virtual lines with 'nowrap'.
+  • `conceal_lines` field to conceal an entire line.
-  right aligned text that truncates before covering up buffer text.
+  • `hl_group` field can be an array of layered groups.
-• |nvim_buf_set_extmark()| `hl_group` field can be an array of layered groups.
+  • `virt_text_pos` field accepts value `eol_right_align` to allow for right
+    aligned text that truncates before covering up buffer text.
+  • `virt_lines_overflow` field accepts value `scroll` to enable horizontal
+    scrolling for virtual lines with 'nowrap'.
 • |vim.hl.range()| now has a optional `timeout` field which allows for a timed highlight
-• |nvim_buf_set_extmark()| `virt_text_pos` field accepts value `eol_right_align` to
-  allow for right aligned text that truncates before covering up buffer text.
 
 DEFAULTS
 

runtime/lua/vim/_meta/api.lua

@@ -685,6 +685,10 @@ function vim.api.nvim_buf_line_count(buffer) end
 ---     When a character is supplied it is used as `:syn-cchar`.
 ---     "hl_group" is used as highlight for the cchar if provided,
 ---     otherwise it defaults to `hl-Conceal`.
+--- - conceal_lines: string which should be empty. When
+---     provided, lines in the range are not drawn at all
+---     (according to 'conceallevel'); the next unconcealed line
+---     is drawn instead.
 --- - spell: boolean indicating that spell checking should be
 ---     performed within this extmark
 --- - ui_watched: boolean that indicates the mark should be drawn

runtime/lua/vim/_meta/api_keysets.lua

@@ -266,6 +266,7 @@ error('Cannot require a meta file')
 --- @field line_hl_group? integer|string
 --- @field cursorline_hl_group? integer|string
 --- @field conceal? string
+--- @field conceal_lines? string
 --- @field spell? boolean
 --- @field ui_watched? boolean
 --- @field undo_restore? boolean

src/nvim/api/extmark.c

@@ -492,6 +492,10 @@ Array nvim_buf_get_extmarks(Buffer buffer, Integer ns_id, Object start, Object e
 ///                   When a character is supplied it is used as |:syn-cchar|.
 ///                   "hl_group" is used as highlight for the cchar if provided,
 ///                   otherwise it defaults to |hl-Conceal|.
+///               - conceal_lines: string which should be empty. When
+///                   provided, lines in the range are not drawn at all
+///                   (according to 'conceallevel'); the next unconcealed line
+///                   is drawn instead.
 ///               - spell: boolean indicating that spell checking should be
 ///                   performed within this extmark
 ///               - ui_watched: boolean that indicates the mark should be drawn
@@ -607,15 +611,23 @@ Integer nvim_buf_set_extmark(Buffer buffer, Integer ns_id, Integer line, Integer
   if (HAS_KEY(opts, set_extmark, conceal)) {
     hl.flags |= kSHConceal;
     has_hl = true;
-    String c = opts->conceal;
+    if (opts->conceal.size > 0) {
-    if (c.size > 0) {
       int ch;
-      hl.conceal_char = utfc_ptr2schar(c.data, &ch);
+      hl.conceal_char = utfc_ptr2schar(opts->conceal.data, &ch);
-      if (!hl.conceal_char || !vim_isprintc(ch)) {
+      VALIDATE(hl.conceal_char && vim_isprintc(ch), "%s", "conceal char has to be printable", {
-        api_set_error(err, kErrorTypeValidation, "conceal char has to be printable");
         goto error;
+      });
     }
   }
+
+  if (HAS_KEY(opts, set_extmark, conceal_lines)) {
+    hl.flags |= kSHConcealLines;
+    has_hl = true;
+    if (opts->conceal_lines.size > 0) {
+      VALIDATE(*opts->conceal_lines.data == NUL, "%s", "conceal_lines has to be an empty string", {
+        goto error;
+      });
+    }
   }
 
   if (HAS_KEY(opts, set_extmark, virt_text)) {
@@ -863,6 +875,10 @@ Integer nvim_buf_set_extmark(Buffer buffer, Integer ns_id, Integer line, Integer
       }
     }
 
+    if (hl.flags & kSHConcealLines) {
+      decor_flags |= MT_FLAG_DECOR_CONCEAL_LINES;
+    }
+
     DecorInline decor = DECOR_INLINE_INIT;
     if (decor_alloc || decor_indexed != DECOR_ID_INVALID || url != NULL
         || schar_high(hl.conceal_char)) {

src/nvim/api/keysets_defs.h

@@ -53,6 +53,7 @@ typedef struct {
   HLGroupID line_hl_group;
   HLGroupID cursorline_hl_group;
   String conceal;
+  String conceal_lines;
   Boolean spell;
   Boolean ui_watched;
   Boolean undo_restore;

src/nvim/buffer_defs.h

@@ -813,6 +813,7 @@ typedef struct {
   uint16_t wl_size;             // height in screen lines
   char wl_valid;                // true values are valid for text in buffer
   char wl_folded;               // true when this is a range of folded lines
+  linenr_T wl_foldend;          // last buffer line number for folded line
   linenr_T wl_lastlnum;         // last buffer line number for logical line
 } wline_T;
 

src/nvim/change.c

@@ -205,9 +205,10 @@ static void changed_lines_invalidate_win(win_T *wp, linenr_T lnum, colnr_T col,
         } else if (xtra != 0) {
           // line below change
           wp->w_lines[i].wl_lnum += xtra;
+          wp->w_lines[i].wl_foldend += xtra;
           wp->w_lines[i].wl_lastlnum += xtra;
         }
-      } else if (wp->w_lines[i].wl_lastlnum >= lnum) {
+      } else if (wp->w_lines[i].wl_foldend >= lnum) {
         // change somewhere inside this range of folded lines,
         // may need to be redrawn
         wp->w_lines[i].wl_valid = false;

src/nvim/decoration.c

@@ -22,6 +22,7 @@
 #include "nvim/marktree.h"
 #include "nvim/memory.h"
 #include "nvim/memory_defs.h"
+#include "nvim/move.h"
 #include "nvim/option_vars.h"
 #include "nvim/pos_defs.h"
 #include "nvim/sign.h"
@@ -124,6 +125,15 @@ void decor_redraw_sh(buf_T *buf, int row1, int row2, DecorSignHighlight sh)
       redraw_buf_range_later(buf, row1 + 1, row2 + 1);
     }
   }
+  if (sh.flags & kSHConcealLines) {
+    FOR_ALL_WINDOWS_IN_TAB(wp, curtab) {
+      // TODO(luukvbaal): redraw only unconcealed lines, and scroll lines below
+      // it up or down. Also when opening/closing a fold.
+      if (wp->w_buffer == buf) {
+        changed_window_setting(wp);
+      }
+    }
+  }
   if (sh.flags & kSHUIWatched) {
     redraw_buf_line_later(buf, row1 + 1, false);
   }
@@ -830,6 +840,56 @@ next_mark:
   return attr;
 }
 
+static const uint32_t conceal_filter[kMTMetaCount] = {[kMTMetaConcealLines] = kMTFilterSelect };
+
+/// Called by draw, move and plines code to determine whether a line is concealed.
+/// Scans the marktree for conceal_line marks on "row", if necessary.
+///
+/// @param check_cursor If true, avoid an early return for an unconcealed cursorline.
+///                     Depending on the callsite, we still want to know whether the
+///                     cursor line would be concealed if it was not the cursorline.
+///
+/// @return whether "row" is concealed
+bool decor_conceal_line(win_T *wp, int row, bool check_cursor)
+{
+  if (wp->w_p_cole < 2 || !buf_meta_total(wp->w_buffer, kMTMetaConcealLines)
+      || (!check_cursor && wp == curwin && row + 1 == wp->w_cursor.lnum
+          && !conceal_cursor_line(wp))) {
+    return false;
+  }
+
+  // Scan the marktree for any conceal_line marks on this row.
+  MTPair pair;
+  MarkTreeIter itr[1];
+  marktree_itr_get_overlap(wp->w_buffer->b_marktree, row, 0, itr);
+  while (marktree_itr_step_overlap(wp->w_buffer->b_marktree, itr, &pair)) {
+    if (mt_conceal_lines(pair.start) && ns_in_win(pair.start.ns, wp)) {
+      return true;
+    }
+  }
+
+  marktree_itr_step_out_filter(wp->w_buffer->b_marktree, itr, conceal_filter);
+
+  while (itr->x) {
+    MTKey mark = marktree_itr_current(itr);
+    if (mark.pos.row > row) {
+      break;
+    }
+    if (mt_conceal_lines(mark) && ns_in_win(pair.start.ns, wp)) {
+      return true;
+    }
+    marktree_itr_next_filter(wp->w_buffer->b_marktree, itr, row + 1, 0, conceal_filter);
+  }
+  return false;
+}
+
+/// @return whether a window may have folded or concealed lines
+bool win_lines_concealed(win_T *wp)
+{
+  return hasAnyFolding(wp)
+         || (wp->w_p_cole >= 2 && buf_meta_total(wp->w_buffer, kMTMetaConcealLines));
+}
+
 int sign_item_cmp(const void *p1, const void *p2)
 {
   const SignItem *s1 = (SignItem *)p1;
@@ -850,7 +910,7 @@ int sign_item_cmp(const void *p1, const void *p2)
   return 0;
 }
 
-static const uint32_t sign_filter[4] = {[kMTMetaSignText] = kMTFilterSelect,
+static const uint32_t sign_filter[kMTMetaCount] = {[kMTMetaSignText] = kMTFilterSelect,
                                                    [kMTMetaSignHL] = kMTFilterSelect };
 
 /// Return the signs and highest priority sign attributes on a row.
@@ -873,7 +933,7 @@ void decor_redraw_signs(win_T *wp, buf_T *buf, int row, SignTextAttrs sattrs[],
   // TODO(bfredl): integrate with main decor loop.
   marktree_itr_get_overlap(buf->b_marktree, row, 0, itr);
   while (marktree_itr_step_overlap(buf->b_marktree, itr, &pair)) {
-    if (!mt_invalid(pair.start) && mt_decor_sign(pair.start)) {
+    if (!mt_invalid(pair.start) && mt_decor_sign(pair.start) && ns_in_win(pair.start.ns, wp)) {
       DecorSignHighlight *sh = decor_find_sign(mt_decor(pair.start));
       num_text += (sh->text[0] != NUL);
       kv_push(signs, ((SignItem){ sh, pair.start.id }));
@@ -940,7 +1000,7 @@ DecorSignHighlight *decor_find_sign(DecorInline decor)
   }
 }
 
-static const uint32_t signtext_filter[4] = {[kMTMetaSignText] = kMTFilterSelect };
+static const uint32_t signtext_filter[kMTMetaCount] = {[kMTMetaSignText] = kMTFilterSelect };
 
 /// Count the number of signs in a range after adding/removing a sign, or to
 /// (re-)initialize a range in "b_signcols.count".
@@ -1035,7 +1095,7 @@ bool decor_redraw_eol(win_T *wp, DecorState *state, int *eol_attr, int eol_col)
   return has_virt_pos;
 }
 
-static const uint32_t lines_filter[4] = {[kMTMetaLines] = kMTFilterSelect };
+static const uint32_t lines_filter[kMTMetaCount] = {[kMTMetaLines] = kMTFilterSelect };
 
 /// @param apply_folds Only count virtual lines that are not in folds.
 int decor_virt_lines(win_T *wp, int start_row, int end_row, int *num_below, VirtLines *lines,
@@ -1067,7 +1127,8 @@ int decor_virt_lines(win_T *wp, int start_row, int end_row, int *num_below, Virt
           int mrow = mark.pos.row;
           int draw_row = mrow + (above ? 0 : 1);
           if (draw_row >= start_row && draw_row < end_row
-              && (!apply_folds || !hasFolding(wp, mrow + 1, NULL, NULL))) {
+              && (!apply_folds || !(hasFolding(wp, mrow + 1, NULL, NULL)
+                                    || decor_conceal_line(wp, mrow, false)))) {
             virt_lines += (int)kv_size(vt->data.virt_lines);
             if (lines) {
               kv_splice(*lines, vt->data.virt_lines);
@@ -1137,6 +1198,10 @@ void decor_to_dict_legacy(Dict *dict, DecorInline decor, bool hl_name, Arena *ar
     PUT_C(*dict, "conceal", CSTR_TO_ARENA_OBJ(arena, buf));
   }
 
+  if (sh_hl.flags & kSHConcealLines) {
+    PUT_C(*dict, "conceal_lines", STRING_OBJ(cstr_as_string("")));
+  }
+
   if (sh_hl.flags & kSHSpellOn) {
     PUT_C(*dict, "spell", BOOLEAN_OBJ(true));
   } else if (sh_hl.flags & kSHSpellOff) {

src/nvim/decoration_defs.h

@@ -54,6 +54,7 @@ enum {
   kSHSpellOn = 16,
   kSHSpellOff = 32,
   kSHConceal = 64,
+  kSHConcealLines = 128,
 };
 
 typedef struct {

src/nvim/diff.c

@@ -24,6 +24,7 @@
 #include "nvim/change.h"
 #include "nvim/charset.h"
 #include "nvim/cursor.h"
+#include "nvim/decoration.h"
 #include "nvim/diff.h"
 #include "nvim/drawscreen.h"
 #include "nvim/errors.h"
@@ -2107,7 +2108,7 @@ int diff_check_with_linestatus(win_T *wp, linenr_T lnum, int *linestatus)
   }
 
   // A closed fold never has filler lines.
-  if (hasFolding(wp, lnum, NULL, NULL)) {
+  if (hasFolding(wp, lnum, NULL, NULL) || decor_conceal_line(wp, lnum - 1, false)) {
     return 0;
   }
 

src/nvim/drawline.c

@@ -1013,6 +1013,7 @@ static int get_rightmost_vcol(win_T *wp, const int *color_cols)
 /// @param endrow       last grid row to be redrawn
 /// @param col_rows     set to the height of the line when only updating the columns,
 ///                     otherwise set to 0
+/// @param concealed    only draw virtual lines belonging to the line above
 /// @param spv          'spell' related variables kept between calls for "wp"
 /// @param foldinfo     fold info for this line
 /// @param[in, out] providers  decoration providers active this line
@@ -1020,8 +1021,8 @@ static int get_rightmost_vcol(win_T *wp, const int *color_cols)
 ///                            or explicitly return `false`.
 ///
 /// @return             the number of last row the line occupies.
-int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, int col_rows, spellvars_T *spv,
+int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, int col_rows, bool concealed,
-             foldinfo_T foldinfo)
+             spellvars_T *spv, foldinfo_T foldinfo)
 {
   colnr_T vcol_prev = -1;             // "wlv.vcol" of previous character
   ScreenGrid *grid = &wp->w_grid;     // grid specific to the window
@@ -1122,14 +1123,14 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, int col_rows, s
   };
 
   buf_T *buf = wp->w_buffer;
-  const bool end_fill = (lnum == buf->b_ml.ml_line_count + 1);
+  // Not drawing text when line is concealed or drawing filler lines beyond last line.
+  const bool draw_text = !concealed && (lnum != buf->b_ml.ml_line_count + 1);
 
-  if (col_rows == 0) {
+  if (col_rows == 0 && draw_text) {
     // To speed up the loop below, set extra_check when there is linebreak,
     // trailing white space and/or syntax processing to be done.
     extra_check = wp->w_p_lbr;
-    if (syntax_present(wp) && !wp->w_s->b_syn_error && !wp->w_s->b_syn_slow
+    if (syntax_present(wp) && !wp->w_s->b_syn_error && !wp->w_s->b_syn_slow && !has_foldtext) {
-        && !has_foldtext && !end_fill) {
       // Prepare for syntax highlighting in this line.  When there is an
       // error, stop syntax highlighting.
       int save_did_emsg = did_emsg;
@@ -1146,9 +1147,7 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, int col_rows, s
       }
     }
 
-    if (!end_fill) {
     decor_providers_invoke_line(wp, lnum - 1);
-    }
 
     has_decor = decor_redraw_line(wp, lnum - 1, &decor_state);
 
@@ -1331,7 +1330,7 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, int col_rows, s
   int line_attr_save = wlv.line_attr;
   int line_attr_lowprio_save = wlv.line_attr_lowprio;
 
-  if (spv->spv_has_spell && col_rows == 0) {
+  if (spv->spv_has_spell && col_rows == 0 && draw_text) {
     // Prepare for spell checking.
     extra_check = true;
 
@@ -1357,7 +1356,6 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, int col_rows, s
       char *line = ml_get_buf(wp->w_buffer, lnum + 1);
       spell_cat_line(nextline + SPWORDLEN, line, SPWORDLEN);
     }
-    assert(!end_fill);
     char *line = ml_get_buf(wp->w_buffer, lnum);
 
     // If current line is empty, check first word in next line for capital.
@@ -1394,7 +1392,7 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, int col_rows, s
   }
 
   // current line
-  char *line = end_fill ? "" : ml_get_buf(wp->w_buffer, lnum);
+  char *line = draw_text ? ml_get_buf(wp->w_buffer, lnum) : "";
   // current position in "line"
   char *ptr = line;
 
@@ -1405,7 +1403,7 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, int col_rows, s
   const schar_T lcs_eol = wp->w_p_lcs_chars.eol;  // 'eol' value
   schar_T lcs_prec_todo = wp->w_p_lcs_chars.prec;  // 'prec' until it's been used, then NUL
 
-  if (wp->w_p_list && !has_foldtext && !end_fill) {
+  if (wp->w_p_list && !has_foldtext && draw_text) {
     if (wp->w_p_lcs_chars.space
         || wp->w_p_lcs_chars.multispace != NULL
         || wp->w_p_lcs_chars.leadmultispace != NULL
@@ -1577,7 +1575,7 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, int col_rows, s
     }
   }
 
-  if (col_rows == 0 && !has_foldtext && !end_fill) {
+  if (col_rows == 0 && draw_text && !has_foldtext) {
     const int v = (int)(ptr - line);
     area_highlighting |= prepare_search_hl_line(wp, lnum, v,
                                                 &line, &screen_search_hl, &search_attr,
@@ -1645,7 +1643,7 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, int col_rows, s
         if (wp->w_redr_statuscol) {
           break;
         }
-        if (!end_fill) {
+        if (draw_text) {
           // Get the line again as evaluating 'statuscolumn' may free it.
           line = ml_get_buf(wp->w_buffer, lnum);
           ptr = line + v;
@@ -1681,7 +1679,7 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, int col_rows, s
             break;
           }
           wlv.filler_todo--;
-          if (wlv.filler_todo == 0 && (wp->w_botfill || end_fill)) {
+          if (wlv.filler_todo == 0 && (wp->w_botfill || !draw_text)) {
             break;
           }
           // win_line_start(wp, &wlv);
@@ -3072,8 +3070,8 @@ end_check:
       virt_line_index = -1;
       virt_line_flags = 0;
       // When the filler lines are actually below the last line of the
-      // file, don't draw the line itself, break here.
+      // file, or we are not drawing text for this line, break here.
-      if (wlv.filler_todo == 0 && (wp->w_botfill || end_fill)) {
+      if (wlv.filler_todo == 0 && (wp->w_botfill || !draw_text)) {
         break;
       }
     }

src/nvim/drawscreen.c

@@ -147,6 +147,11 @@ void conceal_check_cursor_line(void)
   }
 
   redrawWinline(curwin, curwin->w_cursor.lnum);
+
+  // Concealed line visibility toggled.
+  if (decor_conceal_line(curwin, curwin->w_cursor.lnum - 1, true)) {
+    changed_window_setting(curwin);
+  }
   // Need to recompute cursor column, e.g., when starting Visual mode
   // without concealing.
   curs_columns(curwin, true);
@@ -1621,7 +1626,7 @@ static void win_update(win_T *wp)
       }
     }
 
-    if (mod_top != 0 && hasAnyFolding(wp)) {
+    if (mod_top != 0 && win_lines_concealed(wp)) {
       // A change in a line can cause lines above it to become folded or
       // unfolded.  Find the top most buffer line that may be affected.
       // If the line was previously folded and displayed, get the first
@@ -1718,12 +1723,12 @@ static void win_update(win_T *wp)
                        && wp->w_topfill > wp->w_old_topfill))) {
       // New topline is above old topline: May scroll down.
       int j;
-      if (hasAnyFolding(wp)) {
+      if (win_lines_concealed(wp)) {
-        // count the number of lines we are off, counting a sequence
+        // Count the number of lines we are off, counting a sequence
-        // of folded lines as one
+        // of folded lines as one, and skip concealed lines.
         j = 0;
         for (linenr_T ln = wp->w_topline; ln < wp->w_lines[0].wl_lnum; ln++) {
-          j++;
+          j += !decor_conceal_line(wp, ln - 1, false);
           if (j >= wp->w_grid.rows - 2) {
             break;
           }
@@ -2101,6 +2106,31 @@ static void win_update(win_T *wp)
         top_to_mod = false;
       }
 
+      // When lines are folded, display one line for all of them.
+      // Otherwise, display normally (can be several display lines when
+      // 'wrap' is on).
+      foldinfo_T foldinfo = wp->w_p_cul && lnum == wp->w_cursor.lnum
+                            ? cursorline_fi : fold_info(wp, lnum);
+
+      // If the line is concealed and has no filler lines, go to the next line.
+      bool concealed = decor_conceal_line(wp, lnum - 1, false);
+      if (concealed) {
+        if (wp == curwin && lnum == curwin->w_cursor.lnum) {
+          conceal_cursor_used = conceal_cursor_line(curwin);
+        }
+        if (idx > 0) {
+          wp->w_lines[idx - 1].wl_lastlnum = lnum + foldinfo.fi_lines - 1;
+        }
+        if (lnum == mod_top && lnum < mod_bot) {
+          mod_top += foldinfo.fi_lines ? foldinfo.fi_lines : 1;
+        }
+        if (win_get_fill(wp, lnum) == 0) {
+          lnum += foldinfo.fi_lines ? foldinfo.fi_lines : 1;
+          spv.spv_capcol_lnum = 0;
+          continue;
+        }
+      }
+
       // When at start of changed lines: May scroll following lines
       // up or down to minimize redrawing.
       // Don't do this when the change continues until the end.
@@ -2150,8 +2180,10 @@ static void win_update(win_T *wp)
           // rows, and may insert/delete lines
           int j = idx;
           for (l = lnum; l < mod_bot; l++) {
+            linenr_T first = l;
+            int prev_rows = new_rows;
             if (hasFolding(wp, l, NULL, &l)) {
-              new_rows++;
+              new_rows += !decor_conceal_line(wp, first - 1, false);
             } else if (l == wp->w_topline) {
               int n = plines_win_nofill(wp, l, false) + wp->w_topfill
                       - adjust_plines_for_skipcol(wp);
@@ -2160,7 +2192,8 @@ static void win_update(win_T *wp)
             } else {
               new_rows += plines_win(wp, l, true);
             }
-            j++;
+            // Do not increment when height was 0 (for a concealed line).
+            j += (prev_rows != new_rows);
             if (new_rows > wp->w_grid.rows - row - 2) {
               // it's getting too much, must redraw the rest
               new_rows = 9999;
@@ -2242,12 +2275,6 @@ static void win_update(win_T *wp)
         }
       }
 
-      // When lines are folded, display one line for all of them.
-      // Otherwise, display normally (can be several display lines when
-      // 'wrap' is on).
-      foldinfo_T foldinfo = wp->w_p_cul && lnum == wp->w_cursor.lnum
-                            ? cursorline_fi : fold_info(wp, lnum);
-
       if (foldinfo.fi_lines == 0
           && idx < wp->w_lines_valid
           && wp->w_lines[idx].wl_valid
@@ -2267,11 +2294,11 @@ static void win_update(win_T *wp)
           syntax_end_parsing(wp, syntax_last_parsed + 1);
         }
 
-        bool display_buf_line = (foldinfo.fi_lines == 0 || *wp->w_p_fdt == NUL);
+        bool display_buf_line = !concealed && (foldinfo.fi_lines == 0 || *wp->w_p_fdt == NUL);
 
         // Display one line
         spellvars_T zero_spv = { 0 };
-        row = win_line(wp, lnum, srow, wp->w_grid.rows, 0,
+        row = win_line(wp, lnum, srow, wp->w_grid.rows, 0, concealed,
                        display_buf_line ? &spv : &zero_spv, foldinfo);
 
         if (display_buf_line) {
@@ -2282,11 +2309,13 @@ static void win_update(win_T *wp)
 
         if (foldinfo.fi_lines == 0) {
           wp->w_lines[idx].wl_folded = false;
+          wp->w_lines[idx].wl_foldend = lnum;
           wp->w_lines[idx].wl_lastlnum = lnum;
           did_update = DID_LINE;
         } else {
           foldinfo.fi_lines--;
           wp->w_lines[idx].wl_folded = true;
+          wp->w_lines[idx].wl_foldend = lnum + foldinfo.fi_lines;
           wp->w_lines[idx].wl_lastlnum = lnum + foldinfo.fi_lines;
           did_update = DID_FOLD;
         }
@@ -2313,12 +2342,13 @@ static void win_update(win_T *wp)
       // - 'number' is set and below inserted/deleted lines, or
       // - 'relativenumber' is set and cursor moved vertically,
       // the text doesn't need to be redrawn, but the number column does.
-      if ((wp->w_p_nu && mod_top != 0 && lnum >= mod_bot
+      if (((wp->w_p_nu && mod_top != 0 && lnum >= mod_bot
             && buf->b_mod_set && buf->b_mod_xlines != 0)
-          || (wp->w_p_rnu && wp->w_last_cursor_lnum_rnu != wp->w_cursor.lnum)) {
+           || (wp->w_p_rnu && wp->w_last_cursor_lnum_rnu != wp->w_cursor.lnum))
+          && !decor_conceal_line(wp, lnum - 1, true)) {
         foldinfo_T info = wp->w_p_cul && lnum == wp->w_cursor.lnum
                           ? cursorline_fi : fold_info(wp, lnum);
-        win_line(wp, lnum, srow, wp->w_grid.rows, wp->w_lines[idx].wl_size, &spv, info);
+        win_line(wp, lnum, srow, wp->w_grid.rows, wp->w_lines[idx].wl_size, false, &spv, info);
       }
 
       // This line does not need to be drawn, advance to the next one.
@@ -2414,7 +2444,7 @@ redr_statuscol:
         // for ml_line_count+1 and only draw filler lines
         spellvars_T zero_spv = { 0 };
         foldinfo_T zero_foldinfo = { 0 };
-        row = win_line(wp, wp->w_botline, row, wp->w_grid.rows, 0, &zero_spv, zero_foldinfo);
+        row = win_line(wp, wp->w_botline, row, wp->w_grid.rows, 0, false, &zero_spv, zero_foldinfo);
         if (wp->w_redr_statuscol) {
           eof = false;
           goto redr_statuscol;

src/nvim/edit.c

@@ -17,6 +17,7 @@
 #include "nvim/change.h"
 #include "nvim/charset.h"
 #include "nvim/cursor.h"
+#include "nvim/decoration.h"
 #include "nvim/digraph.h"
 #include "nvim/drawscreen.h"
 #include "nvim/edit.h"
@@ -2586,15 +2587,15 @@ int oneleft(void)
   return OK;
 }
 
-/// Move the cursor up "n" lines in window "wp".
+/// Move the cursor up "n" lines in window "wp". Takes care of closed folds.
-/// Takes care of closed folds.
+/// Skips over concealed lines when "skip_conceal" is true.
-void cursor_up_inner(win_T *wp, linenr_T n)
+void cursor_up_inner(win_T *wp, linenr_T n, bool skip_conceal)
 {
   linenr_T lnum = wp->w_cursor.lnum;
 
   if (n >= lnum) {
     lnum = 1;
-  } else if (hasAnyFolding(wp)) {
+  } else if (win_lines_concealed(wp)) {
     // Count each sequence of folded lines as one logical line.
 
     // go to the start of the current fold
@@ -2603,6 +2604,7 @@ void cursor_up_inner(win_T *wp, linenr_T n)
     while (n--) {
       // move up one line
       lnum--;
+      n += skip_conceal && decor_conceal_line(wp, lnum - 1, true);
       if (lnum <= 1) {
         break;
       }
@@ -2628,7 +2630,7 @@ int cursor_up(linenr_T n, bool upd_topline)
   if (n > 0 && curwin->w_cursor.lnum <= 1) {
     return FAIL;
   }
-  cursor_up_inner(curwin, n);
+  cursor_up_inner(curwin, n, false);
 
   // try to advance to the column we want to be at
   coladvance(curwin, curwin->w_curswant);
@@ -2640,16 +2642,16 @@ int cursor_up(linenr_T n, bool upd_topline)
   return OK;
 }
 
-/// Move the cursor down "n" lines in window "wp".
+/// Move the cursor down "n" lines in window "wp". Takes care of closed folds.
-/// Takes care of closed folds.
+/// Skips over concealed lines when "skip_conceal" is true.
-void cursor_down_inner(win_T *wp, int n)
+void cursor_down_inner(win_T *wp, int n, bool skip_conceal)
 {
   linenr_T lnum = wp->w_cursor.lnum;
   linenr_T line_count = wp->w_buffer->b_ml.ml_line_count;
 
   if (lnum + n >= line_count) {
     lnum = line_count;
-  } else if (hasAnyFolding(wp)) {
+  } else if (win_lines_concealed(wp)) {
     linenr_T last;
 
     // count each sequence of folded lines as one logical line
@@ -2659,6 +2661,7 @@ void cursor_down_inner(win_T *wp, int n)
       } else {
         lnum++;
       }
+      n += skip_conceal && decor_conceal_line(wp, lnum - 1, true);
       if (lnum >= line_count) {
         break;
       }
@@ -2680,7 +2683,7 @@ int cursor_down(int n, bool upd_topline)
   if (n > 0 && lnum >= curwin->w_buffer->b_ml.ml_line_count) {
     return FAIL;
   }
-  cursor_down_inner(curwin, n);
+  cursor_down_inner(curwin, n, false);
 
   // try to advance to the column we want to be at
   coladvance(curwin, curwin->w_curswant);

src/nvim/fold.c

@@ -194,7 +194,7 @@ bool hasFoldingWin(win_T *const win, const linenr_T lnum, linenr_T *const firstp
     const int x = find_wl_entry(win, lnum);
     if (x >= 0) {
       first = win->w_lines[x].wl_lnum;
-      last = win->w_lines[x].wl_lastlnum;
+      last = win->w_lines[x].wl_foldend;
       had_folded = win->w_lines[x].wl_folded;
     }
   }
@@ -971,7 +971,7 @@ int find_wl_entry(win_T *win, linenr_T lnum)
       if (lnum < win->w_lines[i].wl_lnum) {
         return -1;
       }
-      if (lnum <= win->w_lines[i].wl_lastlnum) {
+      if (lnum <= win->w_lines[i].wl_foldend) {
         return i;
       }
     }

src/nvim/marktree.c

@@ -250,7 +250,7 @@ static inline void split_node(MarkTree *b, MTNode *x, const int i, MTKey next)
   refkey(b, x, i);
   x->n++;
 
-  uint32_t meta_inc[4];
+  uint32_t meta_inc[kMTMetaCount];
   meta_describe_key(meta_inc, x->key[i]);
   for (int m = 0; m < kMTMetaCount; m++) {
     // y used contain all of z and x->key[i], discount those
@@ -451,6 +451,7 @@ static void meta_describe_key_inc(uint32_t *meta_inc, MTKey *k)
     meta_inc[kMTMetaLines] += (k->flags & MT_FLAG_DECOR_VIRT_LINES) ? 1 : 0;
     meta_inc[kMTMetaSignHL] += (k->flags & MT_FLAG_DECOR_SIGNHL) ? 1 : 0;
     meta_inc[kMTMetaSignText] += (k->flags & MT_FLAG_DECOR_SIGNTEXT) ? 1 : 0;
+    meta_inc[kMTMetaConcealLines] += (k->flags & MT_FLAG_DECOR_CONCEAL_LINES) ? 1 : 0;
   }
 }
 
@@ -505,10 +506,10 @@ void marktree_put_key(MarkTree *b, MTKey k)
     r = s;
   }
 
-  uint32_t meta_inc[4];
+  uint32_t meta_inc[kMTMetaCount];
   meta_describe_key(meta_inc, k);
   marktree_putp_aux(b, r, k, meta_inc);
-  for (int m = 0; m < 4; m++) {
+  for (int m = 0; m < kMTMetaCount; m++) {
     b->meta_root[m] += meta_inc[m];
   }
   b->n_keys++;
@@ -579,7 +580,7 @@ uint64_t marktree_del_itr(MarkTree *b, MarkTreeIter *itr, bool rev)
   assert(x->level == 0);
   MTKey intkey = x->key[itr->i];
 
-  uint32_t meta_inc[4];
+  uint32_t meta_inc[kMTMetaCount];
   meta_describe_key(meta_inc, intkey);
   if (x->n > itr->i + 1) {
     memmove(&x->key[itr->i], &x->key[itr->i + 1],
@@ -776,7 +777,7 @@ uint64_t marktree_del_itr(MarkTree *b, MarkTreeIter *itr, bool rev)
 
 void marktree_revise_meta(MarkTree *b, MarkTreeIter *itr, MTKey old_key)
 {
-  uint32_t meta_old[4], meta_new[4];
+  uint32_t meta_old[kMTMetaCount], meta_new[kMTMetaCount];
   meta_describe_key(meta_old, old_key);
   meta_describe_key(meta_new, rawkey(itr));
 
@@ -1038,7 +1039,7 @@ static MTNode *merge_node(MarkTree *b, MTNode *p, int i)
     relative(p->key[i - 1].pos, &x->key[x->n].pos);
   }
 
-  uint32_t meta_inc[4];
+  uint32_t meta_inc[kMTMetaCount];
   meta_describe_key(meta_inc, x->key[x->n]);
 
   memmove(&x->key[x->n + 1], y->key, (size_t)y->n * sizeof(MTKey));
@@ -1128,9 +1129,9 @@ static void pivot_right(MarkTree *b, MTPos p_pos, MTNode *p, const int i)
   p->key[i] = x->key[x->n - 1];
   refkey(b, p, i);
 
-  uint32_t meta_inc_y[4];
+  uint32_t meta_inc_y[kMTMetaCount];
   meta_describe_key(meta_inc_y, y->key[0]);
-  uint32_t meta_inc_x[4];
+  uint32_t meta_inc_x[kMTMetaCount];
   meta_describe_key(meta_inc_x, p->key[i]);
 
   for (int m = 0; m < kMTMetaCount; m++) {
@@ -1214,9 +1215,9 @@ static void pivot_left(MarkTree *b, MTPos p_pos, MTNode *p, int i)
   p->key[i] = y->key[0];
   refkey(b, p, i);
 
-  uint32_t meta_inc_x[4];
+  uint32_t meta_inc_x[kMTMetaCount];
   meta_describe_key(meta_inc_x, x->key[x->n]);
-  uint32_t meta_inc_y[4];
+  uint32_t meta_inc_y[kMTMetaCount];
   meta_describe_key(meta_inc_y, p->key[i]);
   for (int m = 0; m < kMTMetaCount; m++) {
     p->meta[i][m] += meta_inc_x[m];
@@ -1619,8 +1620,13 @@ bool marktree_itr_next_filter(MarkTree *b, MarkTreeIter *itr, int stop_row, int
   return marktree_itr_check_filter(b, itr, stop_row, stop_col, meta_filter);
 }
 
-const uint32_t meta_map[4] = { MT_FLAG_DECOR_VIRT_TEXT_INLINE, MT_FLAG_DECOR_VIRT_LINES,
+const uint32_t meta_map[kMTMetaCount] = {
-                               MT_FLAG_DECOR_SIGNHL, MT_FLAG_DECOR_SIGNTEXT };
+  MT_FLAG_DECOR_VIRT_TEXT_INLINE,
+  MT_FLAG_DECOR_VIRT_LINES,
+  MT_FLAG_DECOR_SIGNHL,
+  MT_FLAG_DECOR_SIGNTEXT,
+  MT_FLAG_DECOR_CONCEAL_LINES
+};
 static bool marktree_itr_check_filter(MarkTree *b, MarkTreeIter *itr, int stop_row, int stop_col,
                                       MetaFilter meta_filter)
 {
@@ -1860,9 +1866,9 @@ static void swap_keys(MarkTree *b, MarkTreeIter *itr1, MarkTreeIter *itr2, Damag
                                    itr2->i, itr1->i }));
     }
 
-    uint32_t meta_inc_1[4];
+    uint32_t meta_inc_1[kMTMetaCount];
     meta_describe_key(meta_inc_1, rawkey(itr1));
-    uint32_t meta_inc_2[4];
+    uint32_t meta_inc_2[kMTMetaCount];
     meta_describe_key(meta_inc_2, rawkey(itr2));
 
     if (memcmp(meta_inc_1, meta_inc_2, sizeof(meta_inc_1)) != 0) {
@@ -2373,7 +2379,7 @@ size_t marktree_check_node(MarkTree *b, MTNode *x, MTPos *last, bool *last_right
     *last = x->key[x->n - 1].pos;
   }
 
-  uint32_t meta_node[4];
+  uint32_t meta_node[kMTMetaCount];
   meta_describe_node(meta_node, x);
   for (int m = 0; m < kMTMetaCount; m++) {
     assert(meta_node_ref[m] == meta_node[m]);

src/nvim/marktree.h

@@ -33,6 +33,7 @@
 #define MT_FLAG_DECOR_SIGNHL (((uint16_t)1) << 10)
 #define MT_FLAG_DECOR_VIRT_LINES (((uint16_t)1) << 11)
 #define MT_FLAG_DECOR_VIRT_TEXT_INLINE (((uint16_t)1) << 12)
+#define MT_FLAG_DECOR_CONCEAL_LINES (((uint16_t)1) << 13)
 
 // These _must_ be last to preserve ordering of marks
 #define MT_FLAG_RIGHT_GRAVITY (((uint16_t)1) << 14)
@@ -42,8 +43,8 @@
                              | MT_FLAG_DECOR_SIGNHL | MT_FLAG_DECOR_VIRT_LINES \
                              | MT_FLAG_DECOR_VIRT_TEXT_INLINE)
 
-#define MT_FLAG_EXTERNAL_MASK (MT_FLAG_DECOR_MASK | MT_FLAG_NO_UNDO \
+#define MT_FLAG_EXTERNAL_MASK (MT_FLAG_DECOR_MASK | MT_FLAG_NO_UNDO | MT_FLAG_INVALIDATE \
-                               | MT_FLAG_INVALIDATE | MT_FLAG_INVALID)
+                               | MT_FLAG_INVALID | MT_FLAG_DECOR_CONCEAL_LINES)
 
 // this is defined so that start and end of the same range have adjacent ids
 #define MARKTREE_END_FLAG ((uint64_t)1)
@@ -107,6 +108,11 @@ static inline bool mt_decor_sign(MTKey key)
   return key.flags & (MT_FLAG_DECOR_SIGNTEXT | MT_FLAG_DECOR_SIGNHL);
 }
 
+static inline bool mt_conceal_lines(MTKey key)
+{
+  return key.flags & MT_FLAG_DECOR_CONCEAL_LINES;
+}
+
 static inline uint16_t mt_flags(bool right_gravity, bool no_undo, bool invalidate, bool decor_ext)
 {
   return (uint16_t)((right_gravity ? MT_FLAG_RIGHT_GRAVITY : 0)

src/nvim/marktree_defs.h

@@ -22,13 +22,12 @@ typedef struct {
 } MTPos;
 #define MTPos(r, c) ((MTPos){ .row = (r), .col = (c) })
 
-// Currently there are four counts, which makes for a uint32_t[4] per node
-// which makes for nice autovectorization into a single XMM or NEON register
 typedef enum {
   kMTMetaInline,
   kMTMetaLines,
   kMTMetaSignHL,
   kMTMetaSignText,
+  kMTMetaConcealLines,
   kMTMetaCount,  // sentinel, must be last
 } MetaIndex;
 

src/nvim/move.c

@@ -17,6 +17,7 @@
 #include "nvim/buffer.h"
 #include "nvim/buffer_defs.h"
 #include "nvim/cursor.h"
+#include "nvim/decoration.h"
 #include "nvim/diff.h"
 #include "nvim/drawscreen.h"
 #include "nvim/edit.h"
@@ -317,14 +318,13 @@ void update_topline(win_T *wp)
         halfheight = 2;
       }
       int64_t n;
-      if (hasAnyFolding(wp)) {
+      if (win_lines_concealed(wp)) {
         // Count the number of logical lines between the cursor and
         // topline + p_so (approximation of how much will be
         // scrolled).
         n = 0;
-        for (linenr_T lnum = wp->w_cursor.lnum;
+        for (linenr_T lnum = wp->w_cursor.lnum; lnum < wp->w_topline + *so_ptr; lnum++) {
-             lnum < wp->w_topline + *so_ptr; lnum++) {
+          n += !decor_conceal_line(wp, lnum, false);
-          n++;
           // stop at end of file or when we know we are far off
           assert(wp->w_buffer != 0);
           if (lnum >= wp->w_buffer->b_ml.ml_line_count || n >= halfheight) {
@@ -366,7 +366,7 @@ void update_topline(win_T *wp)
     assert(wp->w_buffer != 0);
     if (wp->w_botline <= wp->w_buffer->b_ml.ml_line_count) {
       if (wp->w_cursor.lnum < wp->w_botline) {
-        if ((wp->w_cursor.lnum >= wp->w_botline - *so_ptr || hasAnyFolding(wp))) {
+        if ((wp->w_cursor.lnum >= wp->w_botline - *so_ptr || win_lines_concealed(wp))) {
           lineoff_T loff;
 
           // Cursor is (a few lines) above botline, check if there are
@@ -398,13 +398,12 @@ void update_topline(win_T *wp)
       }
       if (check_botline) {
         int line_count = 0;
-        if (hasAnyFolding(wp)) {
+        if (win_lines_concealed(wp)) {
           // Count the number of logical lines between the cursor and
           // botline - p_so (approximation of how much will be
           // scrolled).
-          for (linenr_T lnum = wp->w_cursor.lnum;
+          for (linenr_T lnum = wp->w_cursor.lnum; lnum >= wp->w_botline - *so_ptr; lnum--) {
-               lnum >= wp->w_botline - *so_ptr; lnum--) {
+            line_count += !decor_conceal_line(wp, lnum - 1, false);
-            line_count++;
             // stop at end of file or when we know we are far off
             if (lnum <= 0 || line_count > wp->w_height_inner + 1) {
               break;
@@ -461,7 +460,7 @@ static int scrolljump_value(win_T *wp)
 static bool check_top_offset(win_T *wp)
 {
   int so = get_scrolloff_value(wp);
-  if (wp->w_cursor.lnum < wp->w_topline + so || hasAnyFolding(wp)) {
+  if (wp->w_cursor.lnum < wp->w_topline + so || win_lines_concealed(wp)) {
     lineoff_T loff;
     loff.lnum = wp->w_cursor.lnum;
     loff.fill = 0;
@@ -505,6 +504,13 @@ void check_cursor_moved(win_T *wp)
   if (wp->w_cursor.lnum != wp->w_valid_cursor.lnum) {
     wp->w_valid &= ~(VALID_WROW|VALID_WCOL|VALID_VIRTCOL
                      |VALID_CHEIGHT|VALID_CROW|VALID_TOPLINE);
+
+    // Concealed line visibility toggled.
+    if (wp->w_p_cole >= 2 && !conceal_cursor_line(wp)
+        && (decor_conceal_line(wp, wp->w_cursor.lnum - 1, true)
+            || decor_conceal_line(wp, wp->w_valid_cursor.lnum - 1, true))) {
+      changed_window_setting(wp);
+    }
     wp->w_valid_cursor = wp->w_cursor;
     wp->w_valid_leftcol = wp->w_leftcol;
     wp->w_valid_skipcol = wp->w_skipcol;
@@ -1351,13 +1357,14 @@ bool scrolldown(win_T *wp, linenr_T line_count, int byfold)
         // A sequence of folded lines only counts for one logical line
         linenr_T first;
         if (hasFolding(wp, wp->w_topline, &first, NULL)) {
-          done++;
+          done += !decor_conceal_line(wp, first - 1, false);
           if (!byfold) {
             todo -= wp->w_topline - first - 1;
           }
           wp->w_botline -= wp->w_topline - first;
           wp->w_topline = first;
         } else {
+          todo += decor_conceal_line(wp, wp->w_topline - 1, false);
           if (do_sms) {
             int size = linetabsize_eol(wp, wp->w_topline);
             if (size > width1) {
@@ -1400,12 +1407,8 @@ bool scrolldown(win_T *wp, linenr_T line_count, int byfold)
   while (wrow >= wp->w_height_inner && wp->w_cursor.lnum > 1) {
     linenr_T first;
     if (hasFolding(wp, wp->w_cursor.lnum, &first, NULL)) {
-      wrow--;
+      wrow -= !decor_conceal_line(wp, wp->w_cursor.lnum - 1, false);
-      if (first == 1) {
+      wp->w_cursor.lnum = MAX(first - 1, 1);
-        wp->w_cursor.lnum = 1;
-      } else {
-        wp->w_cursor.lnum = first - 1;
-      }
     } else {
       wrow -= plines_win(wp, wp->w_cursor.lnum--, true);
     }
@@ -1433,7 +1436,7 @@ bool scrollup(win_T *wp, linenr_T line_count, bool byfold)
   linenr_T botline = wp->w_botline;
   bool do_sms = wp->w_p_wrap && wp->w_p_sms;
 
-  if (do_sms || (byfold && hasAnyFolding(wp)) || win_may_fill(wp)) {
+  if (do_sms || (byfold && win_lines_concealed(wp)) || win_may_fill(wp)) {
     int width1 = wp->w_width_inner - win_col_off(wp);
     int width2 = width1 + win_col_off2(wp);
     int size = 0;
@@ -1448,6 +1451,7 @@ bool scrollup(win_T *wp, linenr_T line_count, bool byfold)
     // the line, then advance to the next line.
     // folding: count each sequence of folded lines as one logical line.
     for (int todo = line_count; todo > 0; todo--) {
+      todo += decor_conceal_line(wp, wp->w_topline - 1, false);
       if (wp->w_topfill > 0) {
         wp->w_topfill--;
       } else {
@@ -1504,10 +1508,8 @@ bool scrollup(win_T *wp, linenr_T line_count, bool byfold)
 
   check_topfill(wp, false);
 
-  if (hasAnyFolding(wp)) {
   // Make sure w_topline is at the first of a sequence of folded lines.
   hasFolding(wp, wp->w_topline, &wp->w_topline, NULL);
-  }
 
   wp->w_valid &= ~(VALID_WROW|VALID_CROW|VALID_BOTLINE);
   if (wp->w_cursor.lnum < wp->w_topline) {
@@ -1710,8 +1712,8 @@ static void topline_back_winheight(win_T *wp, lineoff_T *lp, int winheight)
     if (lp->lnum < 1) {
       lp->height = MAXCOL;
     } else if (hasFolding(wp, lp->lnum, &lp->lnum, NULL)) {
-      // Add a closed fold
+      // Add a closed fold unless concealed.
-      lp->height = 1;
+      lp->height = !decor_conceal_line(wp, lp->lnum - 1, false);
     } else {
       lp->height = plines_win_nofill(wp, lp->lnum, winheight);
     }
@@ -1740,8 +1742,8 @@ static void botline_forw(win_T *wp, lineoff_T *lp)
     if (lp->lnum > wp->w_buffer->b_ml.ml_line_count) {
       lp->height = MAXCOL;
     } else if (hasFolding(wp, lp->lnum, NULL, &lp->lnum)) {
-      // Add a closed fold
+      // Add a closed fold unless concealed.
-      lp->height = 1;
+      lp->height = !decor_conceal_line(wp, lp->lnum - 1, false);
     } else {
       lp->height = plines_win_nofill(wp, lp->lnum, true);
     }
@@ -1793,9 +1795,8 @@ void scroll_cursor_top(win_T *wp, int min_scroll, int always)
   // Check if the lines from "top" to "bot" fit in the window.  If they do,
   // set new_topline and advance "top" and "bot" to include more lines.
   while (top > 0) {
-    int i = hasFolding(wp, top, &top, NULL)
+    int i = plines_win_nofill(wp, top, true);
-            ? 1  // count one logical line for a sequence of folded lines
+    hasFolding(wp, top, &top, NULL);
-            : plines_win_nofill(wp, top, true);
     if (top < wp->w_topline) {
       scrolled += i;
     }
@@ -1807,12 +1808,7 @@ void scroll_cursor_top(win_T *wp, int min_scroll, int always)
 
     used += i;
     if (extra + i <= off && bot < wp->w_buffer->b_ml.ml_line_count) {
-      if (hasFolding(wp, bot, NULL, &bot)) {
+      used += plines_win_full(wp, bot, &bot, NULL, true, true);
-        // count one logical line for a sequence of folded lines
-        used++;
-      } else {
-        used += plines_win(wp, bot, true);
-      }
     }
     if (used > wp->w_height_inner) {
       break;
@@ -2273,7 +2269,7 @@ void cursor_correct(win_T *wp)
   linenr_T cln = wp->w_cursor.lnum;  // Cursor Line Number
   if (cln >= wp->w_topline + above_wanted
       && cln < wp->w_botline - below_wanted
-      && !hasAnyFolding(wp)) {
+      && !win_lines_concealed(wp)) {
     return;
   }
 
@@ -2298,19 +2294,12 @@ void cursor_correct(win_T *wp)
   int below = wp->w_filler_rows;  // screen lines below botline
   while ((above < above_wanted || below < below_wanted) && topline < botline) {
     if (below < below_wanted && (below <= above || above >= above_wanted)) {
-      if (hasFolding(wp, botline, &botline, NULL)) {
+      below += plines_win_full(wp, botline, &botline, NULL, true, true);
-        below++;
-      } else {
-        below += plines_win(wp, botline, true);
-      }
       botline--;
     }
     if (above < above_wanted && (above < below || below >= below_wanted)) {
-      if (hasFolding(wp, topline, NULL, &topline)) {
-        above++;
-      } else {
       above += plines_win_nofill(wp, topline, true);
-      }
+      hasFolding(wp, topline, NULL, &topline);
 
       // Count filler lines below this line as context.
       if (topline < botline) {
@@ -2464,7 +2453,8 @@ int pagescroll(Direction dir, int count, bool half)
     int curscount = count;
     // Adjust count so as to not reveal end of buffer lines.
     if (dir == FORWARD
-        && (curwin->w_topline + curwin->w_height_inner + count > buflen || hasAnyFolding(curwin))) {
+        && (curwin->w_topline + curwin->w_height_inner + count > buflen
+            || win_lines_concealed(curwin))) {
       int n = plines_correct_topline(curwin, curwin->w_topline, NULL, false, NULL);
       if (n - count < curwin->w_height_inner && curwin->w_topline < buflen) {
         n += plines_m_win(curwin, curwin->w_topline + 1, buflen, curwin->w_height_inner + count);
@@ -2482,13 +2472,14 @@ int pagescroll(Direction dir, int count, bool half)
       curwin->w_curswant = prev_curswant;
     }
 
-    // Move the cursor the same amount of screen lines.
+    // Move the cursor the same amount of screen lines, skipping over
+    // concealed lines as those were not included in "curscount".
     if (curwin->w_p_wrap) {
-      nv_screengo(&oa, dir, curscount);
+      nv_screengo(&oa, dir, curscount, true);
     } else if (dir == FORWARD) {
-      cursor_down_inner(curwin, curscount);
+      cursor_down_inner(curwin, curscount, true);
     } else {
-      cursor_up_inner(curwin, curscount);
+      cursor_up_inner(curwin, curscount, true);
     }
   } else {
     // Scroll [count] times 'window' or current window height lines.

src/nvim/normal.c

@@ -24,6 +24,7 @@
 #include "nvim/charset.h"
 #include "nvim/cmdhist.h"
 #include "nvim/cursor.h"
+#include "nvim/decoration.h"
 #include "nvim/diff.h"
 #include "nvim/digraph.h"
 #include "nvim/drawscreen.h"
@@ -2486,7 +2487,7 @@ bool find_decl(char *ptr, size_t len, bool locally, bool thisblock, int flags_ar
 /// 'dist' must be positive.
 ///
 /// @return  true if able to move cursor, false otherwise.
-bool nv_screengo(oparg_T *oap, int dir, int dist)
+bool nv_screengo(oparg_T *oap, int dir, int dist, bool skip_conceal)
 {
   int linelen = linetabsize(curwin, curwin->w_cursor.lnum);
   bool retval = true;
@@ -2548,7 +2549,7 @@ bool nv_screengo(oparg_T *oap, int dir, int dist)
             retval = false;
             break;
           }
-          cursor_up_inner(curwin, 1);
+          cursor_up_inner(curwin, 1, skip_conceal);
 
           linelen = linetabsize(curwin, curwin->w_cursor.lnum);
           if (linelen > width1) {
@@ -2573,7 +2574,7 @@ bool nv_screengo(oparg_T *oap, int dir, int dist)
             retval = false;
             break;
           }
-          cursor_down_inner(curwin, 1);
+          cursor_down_inner(curwin, 1, skip_conceal);
           curwin->w_curswant %= width2;
 
           // Check if the cursor has moved below the number display
@@ -3616,12 +3617,11 @@ static void nv_scroll(cmdarg_T *cap)
     if (cap->count1 - 1 >= curwin->w_cursor.lnum) {
       curwin->w_cursor.lnum = 1;
     } else {
-      if (hasAnyFolding(curwin)) {
+      if (win_lines_concealed(curwin)) {
         // Count a fold for one screen line.
-        for (n = cap->count1 - 1; n > 0
+        for (n = cap->count1 - 1; n > 0 && curwin->w_cursor.lnum > curwin->w_topline; n--) {
-             && curwin->w_cursor.lnum > curwin->w_topline; n--) {
+          hasFolding(curwin, curwin->w_cursor.lnum, &curwin->w_cursor.lnum, NULL);
-          hasFolding(curwin, curwin->w_cursor.lnum,
+          n += decor_conceal_line(curwin, curwin->w_cursor.lnum, true);
-                     &curwin->w_cursor.lnum, NULL);
           if (curwin->w_cursor.lnum > curwin->w_topline) {
             curwin->w_cursor.lnum--;
           }
@@ -3634,8 +3634,7 @@ static void nv_scroll(cmdarg_T *cap)
     if (cap->cmdchar == 'M') {
       int used = 0;
       // Don't count filler lines above the window.
-      used -= win_get_fill(curwin, curwin->w_topline)
+      used -= win_get_fill(curwin, curwin->w_topline) - curwin->w_topfill;
-              - curwin->w_topfill;
       validate_botline(curwin);  // make sure w_empty_rows is valid
       int half = (curwin->w_height_inner - curwin->w_empty_rows + 1) / 2;
       for (n = 0; curwin->w_topline + n < curbuf->b_ml.ml_line_count; n++) {
@@ -3658,10 +3657,11 @@ static void nv_scroll(cmdarg_T *cap)
       }
     } else {  // (cap->cmdchar == 'H')
       n = cap->count1 - 1;
-      if (hasAnyFolding(curwin)) {
+      if (win_lines_concealed(curwin)) {
         // Count a fold for one screen line.
         lnum = curwin->w_topline;
-        while (n-- > 0 && lnum < curwin->w_botline - 1) {
+        while ((decor_conceal_line(curwin, lnum - 1, true) || n-- > 0)
+               && lnum < curwin->w_botline - 1) {
           hasFolding(curwin, lnum, NULL, &lnum);
           lnum++;
         }
@@ -5316,7 +5316,7 @@ static void nv_g_dollar_cmd(cmdarg_T *cap)
           curwin->w_cursor.col--;
         }
       }
-    } else if (nv_screengo(oap, FORWARD, cap->count1 - 1) == false) {
+    } else if (nv_screengo(oap, FORWARD, cap->count1 - 1, false) == false) {
       clearopbeep(oap);
     }
   } else {
@@ -5443,7 +5443,7 @@ static void nv_g_cmd(cmdarg_T *cap)
       oap->motion_type = kMTLineWise;
       i = cursor_down(cap->count1, oap->op_type == OP_NOP);
     } else {
-      i = nv_screengo(oap, FORWARD, cap->count1);
+      i = nv_screengo(oap, FORWARD, cap->count1, false);
     }
     if (!i) {
       clearopbeep(oap);
@@ -5457,7 +5457,7 @@ static void nv_g_cmd(cmdarg_T *cap)
       oap->motion_type = kMTLineWise;
       i = cursor_up(cap->count1, oap->op_type == OP_NOP);
     } else {
-      i = nv_screengo(oap, BACKWARD, cap->count1);
+      i = nv_screengo(oap, BACKWARD, cap->count1, false);
     }
     if (!i) {
       clearopbeep(oap);

src/nvim/plines.c

@@ -88,7 +88,7 @@ int linetabsize_eol(win_T *wp, linenr_T lnum)
          + ((wp->w_p_list && wp->w_p_lcs_chars.eol != NUL) ? 1 : 0);
 }
 
-static const uint32_t inline_filter[4] = {[kMTMetaInline] = kMTFilterSelect };
+static const uint32_t inline_filter[kMTMetaCount] = {[kMTMetaInline] = kMTFilterSelect };
 
 /// Prepare the structure passed to charsize functions.
 ///
@@ -757,6 +757,10 @@ int plines_win(win_T *wp, linenr_T lnum, bool limit_winheight)
 /// @param limit_winheight  when true limit to window height
 int plines_win_nofill(win_T *wp, linenr_T lnum, bool limit_winheight)
 {
+  if (decor_conceal_line(wp, lnum - 1, false)) {
+    return 0;
+  }
+
   if (!wp->w_p_wrap) {
     return 1;
   }
@@ -893,8 +897,14 @@ int plines_win_full(win_T *wp, linenr_T lnum, linenr_T *const nextp, bool *const
   if (foldedp != NULL) {
     *foldedp = folded;
   }
-  return ((folded ? 1 : plines_win_nofill(wp, lnum, limit_winheight)) +
+
-          (lnum == wp->w_topline ? wp->w_topfill : win_get_fill(wp, lnum)));
+  int filler_lines = lnum == wp->w_topline ? wp->w_topfill : win_get_fill(wp, lnum);
+
+  if (decor_conceal_line(wp, lnum - 1, false)) {
+    return filler_lines;
+  }
+
+  return (folded ? 1 : plines_win_nofill(wp, lnum, limit_winheight)) + filler_lines;
 }
 
 /// Return number of window lines a physical line range will occupy in window "wp".
@@ -971,8 +981,8 @@ int64_t win_text_height(win_T *const wp, const linenr_T start_lnum, const int64_
 
   if (start_vcol >= 0) {
     linenr_T lnum_next = lnum;
-    const bool folded = hasFolding(wp, lnum, &lnum, &lnum_next);
+    hasFolding(wp, lnum, &lnum, &lnum_next);
-    height_cur_nofill = folded ? 1 : plines_win_nofill(wp, lnum, false);
+    height_cur_nofill = plines_win_nofill(wp, lnum, false);
     height_sum_nofill += height_cur_nofill;
     const int64_t row_off = (start_vcol < width1 || width2 <= 0)
                             ? 0
@@ -983,9 +993,9 @@ int64_t win_text_height(win_T *const wp, const linenr_T start_lnum, const int64_
 
   while (lnum <= end_lnum) {
     linenr_T lnum_next = lnum;
-    const bool folded = hasFolding(wp, lnum, &lnum, &lnum_next);
+    hasFolding(wp, lnum, &lnum, &lnum_next);
     height_sum_fill += win_get_fill(wp, lnum);
-    height_cur_nofill = folded ? 1 : plines_win_nofill(wp, lnum, false);
+    height_cur_nofill = plines_win_nofill(wp, lnum, false);
     height_sum_nofill += height_cur_nofill;
     lnum = lnum_next + 1;
   }

src/nvim/window.c

@@ -6436,9 +6436,9 @@ void win_fix_scroll(bool resize)
 
         // Add difference in height and row to botline.
         if (diff > 0) {
-          cursor_down_inner(wp, diff);
+          cursor_down_inner(wp, diff, false);
         } else {
-          cursor_up_inner(wp, -diff);
+          cursor_up_inner(wp, -diff, false);
         }
 
         // Scroll to put the new cursor position at the bottom of the
@@ -6485,11 +6485,11 @@ static void win_fix_cursor(bool normal)
   linenr_T lnum = wp->w_cursor.lnum;
 
   wp->w_cursor.lnum = wp->w_topline;
-  cursor_down_inner(wp, so);
+  cursor_down_inner(wp, so, false);
   linenr_T top = wp->w_cursor.lnum;
 
   wp->w_cursor.lnum = wp->w_botline - 1;
-  cursor_up_inner(wp, so);
+  cursor_up_inner(wp, so, false);
   linenr_T bot = wp->w_cursor.lnum;
 
   wp->w_cursor.lnum = lnum;
@@ -6583,7 +6583,7 @@ void scroll_to_fraction(win_T *wp, int prev_height)
         hasFolding(wp, lnum, &lnum, NULL);
         if (lnum == 1) {
           // first line in buffer is folded
-          line_size = 1;
+          line_size = !decor_conceal_line(wp, lnum - 1, false);
           sline--;
           break;
         }

test/functional/api/extmark_spec.lua

@@ -1556,6 +1556,7 @@ describe('API/extmarks', function()
   it('can get details', function()
     set_extmark(ns, marks[1], 0, 0, {
       conceal = 'c',
+      conceal_lines = '',
       cursorline_hl_group = 'Statement',
       end_col = 0,
       end_right_gravity = true,
@@ -1585,6 +1586,7 @@ describe('API/extmarks', function()
       0,
       {
         conceal = 'c',
+        conceal_lines = '',
         cursorline_hl_group = 'Statement',
         end_col = 0,
         end_right_gravity = true,

test/functional/ui/decorations_spec.lua

@@ -2625,6 +2625,227 @@ describe('extmark decorations', function()
                                                         |
     ]])
   end)
+
+  it ('conceal_lines', function()
+    insert(example_text)
+    exec('set number conceallevel=3')
+    feed('ggj')
+    local not_concealed = {
+      grid = [[
+        {2:  1 }for _,item in ipairs(items) do                |
+        {2:  2 }^    local text, hl_id_cell, count = unpack(ite|
+        {2:    }m)                                            |
+        {2:  3 }    if hl_id_cell ~= nil then                 |
+        {2:  4 }        hl_id = hl_id_cell                    |
+        {2:  5 }    end                                       |
+        {2:  6 }    for _ = 1, (count or 1) do                |
+        {2:  7 }        local cell = line[colpos]             |
+        {2:  8 }        cell.text = text                      |
+        {2:  9 }        cell.hl_id = hl_id                    |
+        {2: 10 }        colpos = colpos+1                     |
+        {2: 11 }    end                                       |
+        {2: 12 }end                                           |
+        {1:~                                                 }|
+                                                          |
+      ]]
+    }
+    screen:expect(not_concealed)
+    api.nvim_buf_set_extmark(0, ns, 1, 0, { conceal_lines = "" })
+    screen:expect_unchanged()
+    feed('j')
+    local concealed = {
+      grid = [[
+        {2:  1 }for _,item in ipairs(items) do                |
+        {2:  3 }^    if hl_id_cell ~= nil then                 |
+        {2:  4 }        hl_id = hl_id_cell                    |
+        {2:  5 }    end                                       |
+        {2:  6 }    for _ = 1, (count or 1) do                |
+        {2:  7 }        local cell = line[colpos]             |
+        {2:  8 }        cell.text = text                      |
+        {2:  9 }        cell.hl_id = hl_id                    |
+        {2: 10 }        colpos = colpos+1                     |
+        {2: 11 }    end                                       |
+        {2: 12 }end                                           |
+        {1:~                                                 }|*3
+                                                          |
+      ]]
+    }
+    screen:expect(concealed)
+    feed('k')
+    screen:expect(not_concealed)
+    exec('set concealcursor=n')
+    screen:expect(concealed)
+    api.nvim_buf_set_extmark(0, ns, 3, 0, { conceal_lines = "" })
+    screen:expect({
+      grid = [[
+        {2:  1 }for _,item in ipairs(items) do                |
+        {2:  3 }^    if hl_id_cell ~= nil then                 |
+        {2:  5 }    end                                       |
+        {2:  6 }    for _ = 1, (count or 1) do                |
+        {2:  7 }        local cell = line[colpos]             |
+        {2:  8 }        cell.text = text                      |
+        {2:  9 }        cell.hl_id = hl_id                    |
+        {2: 10 }        colpos = colpos+1                     |
+        {2: 11 }    end                                       |
+        {2: 12 }end                                           |
+        {1:~                                                 }|*4
+                                                          |
+      ]]
+    })
+    feed('kjj')
+    screen:expect_unchanged()
+    api.nvim_buf_set_extmark(0, ns, 4, 0, { conceal_lines = "" })
+    feed('kjjjC')
+    screen:expect({
+      grid = [[
+        {2:  1 }for _,item in ipairs(items) do                |
+        {2:  3 }    if hl_id_cell ~= nil then                 |
+        {2:  5 }^                                              |
+        {2:  6 }    for _ = 1, (count or 1) do                |
+        {2:  7 }        local cell = line[colpos]             |
+        {2:  8 }        cell.text = text                      |
+        {2:  9 }        cell.hl_id = hl_id                    |
+        {2: 10 }        colpos = colpos+1                     |
+        {2: 11 }    end                                       |
+        {2: 12 }end                                           |
+        {1:~                                                 }|*4
+        {24:-- INSERT --}                                      |
+      ]]
+    })
+    feed('<esc>')
+    screen:expect({
+      grid = [[
+        {2:  1 }for _,item in ipairs(items) do                |
+        {2:  3 }    if hl_id_cell ~= nil then                 |
+        {2:  6 }^    for _ = 1, (count or 1) do                |
+        {2:  7 }        local cell = line[colpos]             |
+        {2:  8 }        cell.text = text                      |
+        {2:  9 }        cell.hl_id = hl_id                    |
+        {2: 10 }        colpos = colpos+1                     |
+        {2: 11 }    end                                       |
+        {2: 12 }end                                           |
+        {1:~                                                 }|*5
+                                                          |
+      ]]
+    })
+    feed('kji')
+    screen:expect({
+      grid = [[
+        {2:  1 }for _,item in ipairs(items) do                |
+        {2:  3 }    if hl_id_cell ~= nil then                 |
+        {2:  5 }^                                              |
+        {2:  6 }    for _ = 1, (count or 1) do                |
+        {2:  7 }        local cell = line[colpos]             |
+        {2:  8 }        cell.text = text                      |
+        {2:  9 }        cell.hl_id = hl_id                    |
+        {2: 10 }        colpos = colpos+1                     |
+        {2: 11 }    end                                       |
+        {2: 12 }end                                           |
+        {1:~                                                 }|*4
+        {24:-- INSERT --}                                      |
+      ]]
+    })
+    feed('conceal text')
+    screen:expect({
+      grid = [[
+        {2:  1 }for _,item in ipairs(items) do                |
+        {2:  3 }    if hl_id_cell ~= nil then                 |
+        {2:  5 }conceal text^                                  |
+        {2:  6 }    for _ = 1, (count or 1) do                |
+        {2:  7 }        local cell = line[colpos]             |
+        {2:  8 }        cell.text = text                      |
+        {2:  9 }        cell.hl_id = hl_id                    |
+        {2: 10 }        colpos = colpos+1                     |
+        {2: 11 }    end                                       |
+        {2: 12 }end                                           |
+        {1:~                                                 }|*4
+        {24:-- INSERT --}                                      |
+      ]]
+    })
+    feed('<esc>')
+    screen:expect({
+      grid = [[
+        {2:  1 }for _,item in ipairs(items) do                |
+        {2:  3 }    if hl_id_cell ~= nil then                 |
+        {2:  6 }    for _ =^ 1, (count or 1) do                |
+        {2:  7 }        local cell = line[colpos]             |
+        {2:  8 }        cell.text = text                      |
+        {2:  9 }        cell.hl_id = hl_id                    |
+        {2: 10 }        colpos = colpos+1                     |
+        {2: 11 }    end                                       |
+        {2: 12 }end                                           |
+        {1:~                                                 }|*5
+                                                          |
+      ]]
+    })
+    feed('ggzfj')
+    screen:expect({
+      grid = [[
+        {2:  1 }{33:^+--  2 lines: for _,item in ipairs(items) do··}|
+        {2:  3 }    if hl_id_cell ~= nil then                 |
+        {2:  6 }    for _ = 1, (count or 1) do                |
+        {2:  7 }        local cell = line[colpos]             |
+        {2:  8 }        cell.text = text                      |
+        {2:  9 }        cell.hl_id = hl_id                    |
+        {2: 10 }        colpos = colpos+1                     |
+        {2: 11 }    end                                       |
+        {2: 12 }end                                           |
+        {1:~                                                 }|*5
+                                                          |
+      ]]
+    })
+    feed('j')
+    screen:expect({
+      grid = [[
+        {2:  1 }{33:+--  2 lines: for _,item in ipairs(items) do··}|
+        {2:  3 }^    if hl_id_cell ~= nil then                 |
+        {2:  6 }    for _ = 1, (count or 1) do                |
+        {2:  7 }        local cell = line[colpos]             |
+        {2:  8 }        cell.text = text                      |
+        {2:  9 }        cell.hl_id = hl_id                    |
+        {2: 10 }        colpos = colpos+1                     |
+        {2: 11 }    end                                       |
+        {2: 12 }end                                           |
+        {1:~                                                 }|*5
+                                                          |
+      ]]
+    })
+    feed('ggzdjzfj')
+    screen:expect({
+      grid = [[
+        {2:  1 }for _,item in ipairs(items) do                |
+        {2:  6 }^    for _ = 1, (count or 1) do                |
+        {2:  7 }        local cell = line[colpos]             |
+        {2:  8 }        cell.text = text                      |
+        {2:  9 }        cell.hl_id = hl_id                    |
+        {2: 10 }        colpos = colpos+1                     |
+        {2: 11 }    end                                       |
+        {2: 12 }end                                           |
+        {1:~                                                 }|*6
+                                                          |
+      ]]
+    })
+    feed('jj')
+    screen:expect_unchanged()
+    -- Below virtual line belonging to line above concealed line is drawn.
+    api.nvim_buf_set_extmark(0, ns, 0, 0, { virt_lines = { { { 'line 1 below' } } } })
+    -- Above virtual line belonging to concealed line isn't.
+    api.nvim_buf_set_extmark(0, ns, 1, 0, {
+      virt_lines = { { { 'line 2 above' } } },
+      virt_lines_above = true
+    })
+    screen:expect([[
+      {2:  1 }for _,item in ipairs(items) do                |
+      {2:    }line 1 below                                  |
+      {2:  6 }^    for _ = 1, (count or 1) do                |
+      {2:  9 }        cell.hl_id = hl_id                    |
+      {2: 10 }        colpos = colpos+1                     |
+      {2: 11 }    end                                       |
+      {2: 12 }end                                           |
+      {1:~                                                 }|*7
+                                                        |
+    ]])
+  end)
 end)
 
 describe('decorations: inline virtual text', function()