3 files changed, 119 insertions, 5 deletions

diff --git a/src/nvim/api/buffer.c b/src/nvim/api/buffer.c
index 8d82d22040..67f4f92bf6 100644
--- a/src/nvim/api/buffer.c
+++ b/src/nvim/api/buffer.c
@@ -1200,8 +1200,7 @@ static Array extmark_to_array(ExtmarkInfo extmark, bool id, bool add_dict)
 /// @param ns_id  Namespace id from |nvim_create_namespace()|
 /// @param id  Extmark id
 /// @param opts  Optional parameters. Keys:
-///          - limit:  Maximum number of marks to return
-///          - details Whether to include the details dict
+///          - details: Whether to include the details dict
 /// @param[out] err   Error details, if any
 /// @return (row, col) tuple or empty list () if extmark id was absent
 ArrayOf(Integer) nvim_buf_get_extmark_by_id(Buffer buffer, Integer ns_id,
@@ -1400,6 +1399,13 @@ Array nvim_buf_get_extmarks(Buffer buffer, Integer ns_id,
 ///                   callbacks. The mark will only be used for the current
 ///                   redraw cycle, and not be permantently stored in the
 ///                   buffer.
+///               - right_gravity : boolean that indicates the direction
+///                   the extmark will be shifted in when new text is inserted
+///                   (true for right, false for left).  defaults to true.
+///               - end_right_gravity : boolean that indicates the direction
+///                   the extmark end position (if it exists) will be shifted
+///                   in when new text is inserted (true for right, false
+///                   for left). Defaults to false.
 /// @param[out]  err   Error details, if any
 /// @return Id of the created/updated extmark
 Integer nvim_buf_set_extmark(Buffer buffer, Integer ns_id,
@@ -1440,6 +1446,10 @@ Integer nvim_buf_set_extmark(Buffer buffer, Integer ns_id,
   DecorPriority priority = DECOR_PRIORITY_BASE;
   colnr_T col2 = 0;
   VirtText virt_text = KV_INITIAL_VALUE;
+  bool right_gravity = true;
+  bool end_right_gravity = false;
+  bool end_gravity_set = false;
+
   for (size_t i = 0; i < opts.size; i++) {
     String k = opts.items[i].key;
     Object *v = &opts.items[i].value;
@@ -1522,12 +1532,35 @@ Integer nvim_buf_set_extmark(Buffer buffer, Integer ns_id,
         goto error;
       }
       priority = (DecorPriority)v->data.integer;
+    } else if (strequal("right_gravity", k.data)) {
+      if (v->type != kObjectTypeBoolean) {
+        api_set_error(err, kErrorTypeValidation,
+                      "right_gravity must be a boolean");
+        goto error;
+      }
+      right_gravity = v->data.boolean;
+    } else if (strequal("end_right_gravity", k.data)) {
+      if (v->type != kObjectTypeBoolean) {
+        api_set_error(err, kErrorTypeValidation,
+                      "end_right_gravity must be a boolean");
+        goto error;
+      }
+      end_right_gravity = v->data.boolean;
+      end_gravity_set = true;
     } else {
       api_set_error(err, kErrorTypeValidation, "unexpected key: %s", k.data);
       goto error;
     }
   }
 
+  // Only error out if they try to set end_right_gravity without
+  // setting end_col or end_line
+  if (line2 == -1 && col2 == 0 && end_gravity_set) {
+    api_set_error(err, kErrorTypeValidation,
+                  "cannot set end_right_gravity "
+                  "without setting end_line or end_col");
+  }
+
   if (col2 >= 0) {
     if (line2 >= 0 && line2 < buf->b_ml.ml_line_count) {
       len = STRLEN(ml_get_buf(buf, (linenr_T)line2 + 1, false));
@@ -1572,7 +1605,8 @@ Integer nvim_buf_set_extmark(Buffer buffer, Integer ns_id,
     }
 
     id = extmark_set(buf, (uint64_t)ns_id, id, (int)line, (colnr_T)col,
-                     line2, col2, decor, kExtmarkNoUndo);
+                     line2, col2, decor, right_gravity,
+                     end_right_gravity, kExtmarkNoUndo);
   }
 
   return (Integer)id;
@@ -1687,7 +1721,7 @@ Integer nvim_buf_add_highlight(Buffer buffer,
   extmark_set(buf, ns_id, 0,
               (int)line, (colnr_T)col_start,
               end_line, (colnr_T)col_end,
-              decor_hl(hl_id), kExtmarkNoUndo);
+              decor_hl(hl_id), true, false, kExtmarkNoUndo);
   return src_id;
 }
 
@@ -1796,7 +1830,8 @@ Integer nvim_buf_set_virtual_text(Buffer buffer,
   Decoration *decor = xcalloc(1, sizeof(*decor));
   decor->virt_text = virt_text;
 
-  extmark_set(buf, ns_id, 0, (int)line, 0, -1, -1, decor, kExtmarkNoUndo);
+  extmark_set(buf, ns_id, 0, (int)line, 0, -1, -1, decor, true,
+              false, kExtmarkNoUndo);
   return src_id;
 }
 
diff --git a/src/nvim/api/private/helpers.c b/src/nvim/api/private/helpers.c
index 8f224e8c78..7cee569989 100644
--- a/src/nvim/api/private/helpers.c
+++ b/src/nvim/api/private/helpers.c
@@ -1645,6 +1645,43 @@ bool api_object_to_bool(Object obj, const char *what,
   }
 }
 
+HlMessage parse_hl_msg(Array chunks, Error *err)
+{
+  HlMessage hl_msg = KV_INITIAL_VALUE;
+  for (size_t i = 0; i < chunks.size; i++) {
+    if (chunks.items[i].type != kObjectTypeArray) {
+      api_set_error(err, kErrorTypeValidation, "Chunk is not an array");
+      goto free_exit;
+    }
+    Array chunk = chunks.items[i].data.array;
+    if (chunk.size == 0 || chunk.size > 2
+        || chunk.items[0].type != kObjectTypeString
+        || (chunk.size == 2 && chunk.items[1].type != kObjectTypeString)) {
+      api_set_error(err, kErrorTypeValidation,
+                    "Chunk is not an array with one or two strings");
+      goto free_exit;
+    }
+
+    String str = copy_string(chunk.items[0].data.string);
+
+    int attr = 0;
+    if (chunk.size == 2) {
+      String hl = chunk.items[1].data.string;
+      if (hl.size > 0) {
+        int hl_id = syn_check_group((char_u *)hl.data, (int)hl.size);
+        attr = hl_id > 0 ? syn_id2attr(hl_id) : 0;
+      }
+    }
+    kv_push(hl_msg, ((HlMessageChunk){ .text = str, .attr = attr }));
+  }
+
+  return hl_msg;
+
+free_exit:
+  clear_hl_msg(&hl_msg);
+  return hl_msg;
+}
+
 const char *describe_ns(NS ns_id)
 {
   String name;
diff --git a/src/nvim/api/vim.c b/src/nvim/api/vim.c
index 1e972e01be..09895a2119 100644
--- a/src/nvim/api/vim.c
+++ b/src/nvim/api/vim.c
@@ -990,6 +990,48 @@ void nvim_set_option(uint64_t channel_id, String name, Object value, Error *err)
   set_option_to(channel_id, NULL, SREQ_GLOBAL, name, value, err);
 }
 
+/// Echo a message.
+///
+/// @param chunks  A list of [text, hl_group] arrays, each representing a
+///                text chunk with specified highlight. `hl_group` element
+///                can be omitted for no highlight.
+/// @param history  if true, add to |message-history|.
+/// @param opts  Optional parameters. Reserved for future use.
+void nvim_echo(Array chunks, Boolean history, Dictionary opts, Error *err)
+  FUNC_API_SINCE(7)
+{
+  HlMessage hl_msg = parse_hl_msg(chunks, err);
+  if (ERROR_SET(err)) {
+    goto error;
+  }
+
+  if (opts.size > 0) {
+    api_set_error(err, kErrorTypeValidation, "opts dict isn't empty");
+    goto error;
+  }
+
+  no_wait_return++;
+  msg_start();
+  msg_clr_eos();
+  bool need_clear = false;
+  for (uint32_t i = 0; i < kv_size(hl_msg); i++) {
+    HlMessageChunk chunk = kv_A(hl_msg, i);
+    msg_multiline_attr((const char *)chunk.text.data, chunk.attr,
+                       false, &need_clear);
+  }
+  if (history) {
+    msg_ext_set_kind("echomsg");
+    add_hl_msg_hist(hl_msg);
+  } else {
+    msg_ext_set_kind("echo");
+  }
+  no_wait_return--;
+  msg_end();
+
+error:
+  clear_hl_msg(&hl_msg);
+}
+
 /// Writes a message to the Vim output buffer. Does not append "\n", the
 /// message is buffered (won't display) until a linefeed is written.
 ///