feat(marks): add conceal_lines to nvim_buf_set_extmark()

Implement an extmark property that conceals lines vertically.

2 files changed, 23 insertions, 6 deletions

diff --git a/src/nvim/api/extmark.c b/src/nvim/api/extmark.c
index ef09dbb0aa..e4bb9d6953 100644
--- a/src/nvim/api/extmark.c
+++ b/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
@@ -607,14 +611,22 @@ 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 (c.size > 0) {
+    if (opts->conceal.size > 0) {
       int ch;
-      hl.conceal_char = utfc_ptr2schar(c.data, &ch);
-      if (!hl.conceal_char || !vim_isprintc(ch)) {
-        api_set_error(err, kErrorTypeValidation, "conceal char has to be printable");
+      hl.conceal_char = utfc_ptr2schar(opts->conceal.data, &ch);
+      VALIDATE(hl.conceal_char && vim_isprintc(ch), "%s", "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;
+      });
     }
   }
 
@@ -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)) {
diff --git a/src/nvim/api/keysets_defs.h b/src/nvim/api/keysets_defs.h
index b3015911f9..b9bd8ea286 100644
--- a/src/nvim/api/keysets_defs.h
+++ b/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;