xC: normalize BSD Editline's history behaviour

Now it's a realistically useful frontend.

NEWS

@@ -8,6 +8,8 @@ Unreleased
 
  * xC: improved pager integration capabilities
 
+ * xC: normalized editline's history behaviour, making it a viable frontend
+
  * xC: made it show WALLOPS messages, as PRIVMSG for the server buffer
 
  * xD: implemented WALLOPS, choosing to make it target even non-operators

README.adoc

@@ -77,9 +77,6 @@ Runtime dependencies: openssl +
 Additionally for 'xC': curses, libffi, lua >= 5.3 (optional),
                        readline >= 6.0 or libedit >= 2013-07-12
 
-Avoid libedit if you can, in general it works but at the moment history is
-acting up and I have no clue about fixing it.
-
  $ git clone --recursive https://git.janouch.name/p/xK.git
  $ mkdir xK/build
  $ cd xK/build

xC.adoc

@@ -114,8 +114,7 @@ _/usr/share/xC/plugins/_::
 
 Bugs
 ----
-The editline (libedit) frontend is more of a proof of concept that mostly seems
-to work but exhibits bugs that are not our fault.
+The editline (libedit) frontend may exhibit some unexpected behaviour.
 
 Reporting bugs
 --------------

xC.c

@@ -761,6 +761,7 @@ struct input_el
 {
 	struct input super;                 ///< Parent class
 	EditLine *editline;                 ///< The EditLine object
+	FILE *null;                         ///< Output redirect
 
 	bool active;                        ///< Are we a thing?
 	char *prompt;                       ///< The prompt we use
@@ -778,12 +779,12 @@ input_el__redisplay (void *input)
 	// See rl_redisplay(), however NetBSD editline's map.c v1.54 breaks VREPRINT
 	// so we bind redisplay somewhere else in app_editline_init()
 	struct input_el *self = input;
-	char x[] = { 'q' & 31, 0 };
-	el_push (self->editline, x);
+	wchar_t x[] = { L'q' & 31, 0 };
+	el_wpush (self->editline, x);
 
 	// We have to do this or it gets stuck and nothing is done
-	int count = 0;
-	(void) el_wgets (self->editline, &count);
+	int dummy_count = 0;
+	(void) el_wgets (self->editline, &dummy_count);
 }
 
 static char *
@@ -1026,18 +1027,50 @@ input_el__restore (struct input_el *self)
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 
+// XXX: Editline keeping its own history position (look for "eventno" there).
+//   Invoking ed-next-history through our bind from app_editline_init() seems
+//   like the only viable hack to get consistent history behaviour.
+static void
+input_el__bottom (struct input_el *self)
+{
+	// First, we need to redirect output to avoid ringing the terminal bell.
+	FILE *out = NULL;
+	el_wget (self->editline, EL_GETFP, 1, &out);
+	el_wset (self->editline, EL_SETFP, 1, self->null);
+
+	// Invoke hist_get() to make the history pointer's cursor match "eventno".
+	int down = 1, dummy_count = 0;
+	el_wpush (self->editline, L"\x1bn");
+	(void) el_wgets (self->editline, &dummy_count);
+
+	// It doesn't seem like we can just retrieve the position.
+	HistEventW ev;
+	while (!history_w (self->current->history, &ev, H_PREV))
+		down++;
+	while (down--)
+	{
+		el_wpush (self->editline, L"\x1bn");
+		(void) el_wgets (self->editline, &dummy_count);
+	}
+
+	el_wset (self->editline, EL_SETFP, 1, out);
+}
+
 static void
 input_el_buffer_switch (void *input, input_buffer_t input_buffer)
 {
 	struct input_el *self = input;
 	struct input_el_buffer *buffer = input_buffer;
+	if (!self->active)
+		return;
 
 	if (self->current)
 		input_el__save_buffer (self, self->current);
 
-	input_el__restore_buffer (self, buffer);
-	el_wset (self->editline, EL_HIST, history, buffer->history);
 	self->current = buffer;
+	el_wset (self->editline, EL_HIST, history, buffer->history);
+	input_el__bottom (self);
+	input_el__restore_buffer (self, buffer);
 }
 
 static void
@@ -1111,7 +1144,7 @@ input_el_on_tty_readable (void *input)
 	if (!buf || count-- <= 0)
 		return;
 
-	if (count == 0 && buf[0] == ('D' - 0x40) /* hardcoded VEOF in editline */)
+	if (count == 0 && buf[0] == ('D' - 0x40) /* hardcoded VEOF in el_wgets() */)
 	{
 		el_deletestr (self->editline, 1);
 		input_el__redisplay (self);
@@ -1131,6 +1164,7 @@ input_el_destroy (void *input)
 		free (iter->help);
 		ffi_closure_free (iter);
 	}
+	fclose (self->null);
 	free (self->prompt);
 	free (self);
 }
@@ -1144,6 +1178,7 @@ input_el_new (void)
 {
 	struct input_el *self = xcalloc (1, sizeof *self);
 	self->super.vtable = &input_el_vtable;
+	self->null = fopen ("/dev/null", "w");
 	return &self->super;
 }
 
@@ -13908,13 +13943,10 @@ on_editline_return (EditLine *editline, int key)
 	wchar_t *line = calloc (sizeof *info->buffer, len + 1);
 	memcpy (line, info->buffer, sizeof *info->buffer * len);
 
-	// XXX: Editline seems to remember its position in history,
-	//   so it's not going to work as you'd expect it to
 	if (*line)
 	{
 		HistEventW ev;
 		history_w (self->current->history, &ev, H_ENTER, line);
-		print_debug ("history: %d %ls", ev.num, ev.str);
 	}
 	free (line);
 
@@ -13926,6 +13958,7 @@ on_editline_return (EditLine *editline, int key)
 
 	el_cursor (editline, len - point);
 	el_wdeletestr (editline, len);
+	input_el__bottom (self);
 	return CC_REFRESH;
 }