ext_cmdline: allow external ui to draw cmdline

runtime/doc/msgpack_rpc.txt

@@ -260,12 +260,23 @@ a dictionary with these (optional) keys:
 				colors.
 				Set to false to use terminal color codes (at
 				most 256 different colors).
+
 	`ext_popupmenu`		Externalize the popupmenu. |ui-ext-popupmenu|
 	`ext_tabline`		Externalize the tabline. |ui-ext-tabline|
 				Externalized widgets will not be drawn by
 				Nvim; only high-level data will be published
 				in new UI event kinds.
 
+	`popupmenu_external`:	Instead of drawing the completion popupmenu on
+				the grid, Nvim will send higher-level events to
+				the ui and let it draw the popupmenu.
+				Defaults to false.
+	cmdline_external:	Instead of drawing the cmdline on
+				the grid, Nvim will send higher-level events to
+				the ui and let it draw the cmdline.
+				Defaults to false.
+
+
 Nvim will then send msgpack-rpc notifications, with the method name "redraw"
 and a single argument, an array of screen updates (described below).  These
 should be processed in order. Preferably the user should only be able to see
@@ -441,5 +452,27 @@ states might be represented as separate modes.
 	curtab:	  Current Tabpage
 	tabs:	  List of Dicts [{ "tab": Tabpage, "name": String }, ...]
 
+["cmdline_enter"]
+	Enter the cmdline.
+
+["cmdline_leave"]
+	Leave the cmdline.
+
+["cmdline_firstc", firstc]
+        The first character of the command, which could be : / ? etc. With
+	the firstc, you know wheither it's a command or a search.
+
+["cmdline", content, pos]
+	When cmdline_external is set to true, nvim will not draw the cmdline
+	on the grad, instead nvim will send ui events of the cmdline content
+	and cursor position to the remote ui. The content is the full content
+	that should be displayed in the cmdline, and the pos is the position
+	of the cursor that in the cmdline. This event will be triggered when
+	you type in the cmdline.
+
+["cmdline_pos", pos]
+	When you move your cursor, nvim will send out this event which tells
+	you the current position of the cursor in the cmdline.
+
 ==============================================================================
  vim:tw=78:ts=8:noet:ft=help:norl:

src/nvim/ex_getln.c

@@ -185,6 +185,8 @@ static int cmd_showtail;                /* Only show path tail in lists ? */
 
 static int new_cmdpos;          /* position set by set_cmdline_pos() */
 
+static bool cmdline_external = false;
+
 /*
  * Type used by call_user_expand_func
  */
@@ -281,7 +283,9 @@ static uint8_t *command_line_enter(int firstc, long count, int indent)
   if (!cmd_silent) {
     s->i = msg_scrolled;
     msg_scrolled = 0;           // avoid wait_return message
-    gotocmdline(true);
+    if (!cmdline_external) {
+      gotocmdline(true);
+    }
     msg_scrolled += s->i;
     redrawcmdprompt();          // draw prompt or indent
     set_cmdspos();
@@ -1828,7 +1832,16 @@ getcmdline (
     int indent               // indent for inside conditionals
 )
 {
-  return command_line_enter(firstc, count, indent);
+  if (cmdline_external) {
+    Array args = ARRAY_DICT_INIT;
+    ui_event("cmdline_enter", args);
+  }
+  char_u *p = command_line_enter(firstc, count, indent);
+  if (cmdline_external) {
+    Array args = ARRAY_DICT_INIT;
+    ui_event("cmdline_leave", args);
+  }
+  return p;
 }
 
 /// Get a command line with a prompt
@@ -2589,6 +2602,14 @@ static void draw_cmdline(int start, int len)
     return;
   }
 
+  if (cmdline_external) {
+    Array args = ARRAY_DICT_INIT;
+    ADD(args, STRING_OBJ(cstr_to_string((char *)(ccline.cmdbuff))));
+    ADD(args, INTEGER_OBJ(ccline.cmdpos));
+    ui_event("cmdline", args);
+    return;
+  }
+
   if (cmdline_star > 0) {
     for (int i = 0; i < len; i++) {
       msg_putchar('*');
@@ -2713,11 +2734,28 @@ void putcmdline(int c, int shift)
 {
   if (cmd_silent)
     return;
-  msg_no_more = TRUE;
-  msg_putchar(c);
-  if (shift)
-    draw_cmdline(ccline.cmdpos, ccline.cmdlen - ccline.cmdpos);
-  msg_no_more = FALSE;
+  if (!cmdline_external) {
+    msg_no_more = TRUE;
+    msg_putchar(c);
+    if (shift)
+      draw_cmdline(ccline.cmdpos, ccline.cmdlen - ccline.cmdpos);
+    msg_no_more = FALSE;
+  } else {
+      char_u *p;
+      if (ccline.cmdpos == ccline.cmdlen || shift) {
+        p = vim_strnsave(ccline.cmdbuff, ccline.cmdlen + 1);
+      } else {
+        p = vim_strsave(ccline.cmdbuff);
+      }
+      p[ccline.cmdpos] = c;
+      if (shift)
+        STRCPY(p + ccline.cmdpos + 1, ccline.cmdbuff + ccline.cmdpos);
+      Array args = ARRAY_DICT_INIT;
+      ADD(args, STRING_OBJ(cstr_to_string((char *)(p))));
+      ADD(args, INTEGER_OBJ(ccline.cmdpos));
+      ui_event("cmdline", args);
+      xfree(p);
+  }
   cursorcmd();
   ui_cursor_shape();
 }
@@ -3066,8 +3104,15 @@ static void redrawcmdprompt(void)
 
   if (cmd_silent)
     return;
-  if (ccline.cmdfirstc != NUL)
-    msg_putchar(ccline.cmdfirstc);
+  if (ccline.cmdfirstc != NUL) {
+    if (cmdline_external) {
+      Array args = ARRAY_DICT_INIT;
+      ADD(args, STRING_OBJ(cstr_to_string((char *)(&ccline.cmdfirstc))));
+      ui_event("cmdline_firstc", args);
+    } else {
+      msg_putchar(ccline.cmdfirstc);
+    }
+  }
   if (ccline.cmdprompt != NULL) {
     msg_puts_attr((const char *)ccline.cmdprompt, ccline.cmdattr);
     ccline.cmdindent = msg_col + (msg_row - cmdline_row) * Columns;
@@ -3087,6 +3132,11 @@ void redrawcmd(void)
   if (cmd_silent)
     return;
 
+  if (cmdline_external) {
+    draw_cmdline(0, ccline.cmdlen);
+    return;
+  }
+
   /* when 'incsearch' is set there may be no command line while redrawing */
   if (ccline.cmdbuff == NULL) {
     ui_cursor_goto(cmdline_row, 0);
@@ -3130,6 +3180,13 @@ static void cursorcmd(void)
   if (cmd_silent)
     return;
 
+  if (cmdline_external) {
+    Array args = ARRAY_DICT_INIT;
+    ADD(args, INTEGER_OBJ(ccline.cmdpos));
+    ui_event("cmdline_pos", args);
+    return;
+  }
+
   if (cmdmsg_rl) {
     msg_row = cmdline_row  + (ccline.cmdspos / (int)(Columns - 1));
     msg_col = (int)Columns - (ccline.cmdspos % (int)(Columns - 1)) - 1;
@@ -5974,3 +6031,8 @@ static void set_search_match(pos_T *t)
     coladvance((colnr_T)MAXCOL);
   }
 }
+
+void cmdline_set_external(bool external)
+{
+  cmdline_external = external;
+}

src/nvim/ui.c

@@ -30,6 +30,7 @@
 #include "nvim/os/input.h"
 #include "nvim/os/signal.h"
 #include "nvim/popupmnu.h"
+#include "nvim/ex_getln.h"
 #include "nvim/screen.h"
 #include "nvim/syntax.h"
 #include "nvim/window.h"
@@ -280,6 +281,7 @@ void ui_refresh(void)
 
   int save_p_lz = p_lz;
   p_lz = false;  // convince redrawing() to return true ...
+  cmdline_set_external(cmdline_external);
   screen_resize(width, height);
   p_lz = save_p_lz;