xC: fully synchronize input history with frontends

The missing parts were:

 - frontends to client
 - client to frontends after the initial sync
 - frontend to other frontends

xC.c

@@ -228,11 +228,13 @@ struct input_vtable
 	/// Create a new input buffer
 	input_buffer_t (*buffer_new) (void *input);
 	/// Destroy an input buffer
-	void (*buffer_destroy) (void *input, input_buffer_t buffer);
+	void (*buffer_destroy) (void *input, input_buffer_t);
 	/// Switch to a different input buffer
-	void (*buffer_switch) (void *input, input_buffer_t buffer);
+	void (*buffer_switch) (void *input, input_buffer_t);
 	/// Return all history lines in the locale encoding
-	struct strv (*buffer_history) (void *input, input_buffer_t buffer);
+	struct strv (*buffer_get_history) (void *input, input_buffer_t);
+	/// Add a history line in the locale encoding
+	void (*buffer_add_history) (void *input, input_buffer_t, const char *);
 
 	/// Register a function that can be bound to character sequences
 	void (*register_fn) (void *input,
@@ -260,7 +262,8 @@ struct input_vtable
 #define INPUT_VTABLE(XX)                                                       \
 	XX (start) XX (stop) XX (prepare) XX (destroy)                             \
 	XX (hide) XX (show) XX (get_prompt) XX (set_prompt) XX (ding)              \
-	XX (buffer_new) XX (buffer_destroy) XX (buffer_switch) XX (buffer_history) \
+	XX (buffer_new) XX (buffer_destroy) XX (buffer_switch)                     \
+	XX (buffer_get_history) XX (buffer_add_history)                            \
 	XX (register_fn) XX (bind) XX (bind_control) XX (bind_meta)                \
 	XX (get_line) XX (clear_line) XX (insert)                                  \
 	XX (on_tty_resized) XX (on_tty_readable)
@@ -564,6 +567,7 @@ input_rl_buffer_switch (void *input, input_buffer_t input_buffer)
 {
 	struct input_rl *self = input;
 	struct input_rl_buffer *buffer = input_buffer;
+
 	// There could possibly be occurences of the current undo list in some
 	// history entry.  We either need to free the undo list, or move it
 	// somewhere else to load back later, as the buffer we're switching to
@@ -587,8 +591,9 @@ input_rl_buffer_switch (void *input, input_buffer_t input_buffer)
 }
 
 static struct strv
-input_rl_buffer_history (void *input, input_buffer_t input_buffer)
+input_rl_buffer_get_history (void *input, input_buffer_t input_buffer)
 {
+	(void) input;
 	struct input_rl_buffer *buffer = input_buffer;
 	HIST_ENTRY **p =
 		buffer->history ? buffer->history->entries : history_list();
@@ -598,6 +603,25 @@ input_rl_buffer_history (void *input, input_buffer_t input_buffer)
 	return v;
 }
 
+static void
+input_rl_buffer_add_history (void *input, input_buffer_t input_buffer,
+	const char *line)
+{
+	(void) input;
+	struct input_rl_buffer *buffer = input_buffer;
+
+	// For inactive buffers, we'd have to either alloc_history_entry(),
+	// construe a timestamp, and manually insert it into saved HISTORY_STATEs,
+	// or temporarily switch histories.
+	if (!buffer->history)
+	{
+		bool at_end = history_offset == history_length;
+		add_history (line);
+		if (at_end)
+			next_history ();
+	}
+}
+
 static void
 input_rl__buffer_destroy_wo_history (struct input_rl_buffer *self)
 {
@@ -1069,13 +1093,15 @@ input_el_buffer_switch (void *input, input_buffer_t input_buffer)
 
 	self->current = buffer;
 	el_wset (self->editline, EL_HIST, history, buffer->history);
+	// We only know how to reset the history position to be at the end.
 	input_el__start_over (self);
 	input_el__restore_buffer (self, buffer);
 }
 
 static struct strv
-input_el_buffer_history (void *input, input_buffer_t input_buffer)
+input_el_buffer_get_history (void *input, input_buffer_t input_buffer)
 {
+	(void) input;
 	struct input_el_buffer *buffer = input_buffer;
 	struct strv v = strv_make ();
 	HistEventW ev;
@@ -1096,6 +1122,26 @@ input_el_buffer_history (void *input, input_buffer_t input_buffer)
 	return v;
 }
 
+static void
+input_el_buffer_add_history (void *input, input_buffer_t input_buffer,
+	const char *line)
+{
+	(void) input;
+	struct input_el_buffer *buffer = input_buffer;
+
+	// When currently iterating history, this makes editline's internal
+	// history pointer wrongly point to a newer entry.
+	size_t len = mbstowcs (NULL, line, 0);
+	if (len++ != (size_t) -1)
+	{
+		wchar_t *wc = xcalloc (len, sizeof *wc);
+		wc[mbstowcs (wc, line, len)] = 0;
+		HistEventW ev;
+		(void) history_w (buffer->history, &ev, H_ENTER, wc);
+		free (wc);
+	}
+}
+
 static void
 input_el_buffer_destroy (void *input, input_buffer_t input_buffer)
 {
@@ -2899,12 +2945,15 @@ relay_send (struct client *c)
 }
 
 static void
-relay_broadcast (struct app_context *ctx)
+relay_broadcast_except (struct app_context *ctx, struct client *exception)
 {
 	LIST_FOR_EACH (struct client, c, ctx->clients)
-		relay_send (c);
+		if (c != exception)
+			relay_send (c);
 }
 
+#define relay_broadcast(ctx) relay_broadcast_except ((ctx), NULL)
+
 static struct relay_event_message *
 relay_prepare (struct app_context *ctx)
 {
@@ -3131,16 +3180,13 @@ relay_prepare_buffer_activate (struct app_context *ctx, struct buffer *buffer)
 
 static void
 relay_prepare_buffer_input (struct app_context *ctx, struct buffer *buffer,
-	const char *locale_input)
+	const char *input)
 {
 	struct relay_event_message *m = relay_prepare (ctx);
 	struct relay_event_data_buffer_input *e = &m->data.buffer_input;
 	e->event = RELAY_EVENT_BUFFER_INPUT;
 	e->buffer_name = str_from_cstr (buffer->name);
-	char *input = iconv_xstrdup (ctx->term_to_utf8,
-		(char *) locale_input, -1, NULL);
 	e->text = str_from_cstr (input);
-	free (input);
 }
 
 static void
@@ -15305,12 +15351,18 @@ on_pending_input (struct app_context *ctx)
 	poller_idle_reset (&ctx->input_event);
 	for (size_t i = 0; i < ctx->pending_input.len; i++)
 	{
-		char *input = iconv_xstrdup
-			(ctx->term_to_utf8, ctx->pending_input.vector[i], -1, NULL);
-		if (input)
-			process_input (ctx, ctx->current_buffer, input);
-		else
+		char *input = iconv_xstrdup (ctx->term_to_utf8,
+			ctx->pending_input.vector[i], -1, NULL);
+		if (!input)
+		{
 			print_error ("character conversion failed for: %s", "user input");
+			continue;
+		}
+
+		relay_prepare_buffer_input (ctx, ctx->current_buffer, input);
+		relay_broadcast (ctx);
+
+		process_input (ctx, ctx->current_buffer, input);
 		free (input);
 	}
 	strv_reset (&ctx->pending_input);
@@ -15362,11 +15414,21 @@ static void
 client_resync_buffer_input (struct client *c, struct buffer *buffer)
 {
 	struct strv history =
-		CALL_ (c->ctx->input, buffer_history, buffer->input_data);
+		CALL_ (c->ctx->input, buffer_get_history, buffer->input_data);
 	for (size_t i = 0; i < history.len; i++)
 	{
-		relay_prepare_buffer_input (c->ctx, buffer, history.vector[i]);
+		char *input = iconv_xstrdup (c->ctx->term_to_utf8,
+			history.vector[i], -1, NULL);
+		if (!input)
+		{
+			print_error ("character conversion failed for: %s",
+				"user input history");
+			continue;
+		}
+
+		relay_prepare_buffer_input (c->ctx, buffer, input);
 		relay_send (c);
+		free (input);
 	}
 	strv_free (&history);
 }
@@ -15462,6 +15524,20 @@ out:
 	relay_send (c);
 }
 
+static void
+client_process_buffer_input
+	(struct client *c, struct buffer *buffer, const char *input)
+{
+	char *mb = iconv_xstrdup (c->ctx->term_from_utf8, (char *) input, -1, NULL);
+	CALL_ (c->ctx->input, buffer_add_history, buffer->input_data, mb);
+	free (mb);
+
+	relay_prepare_buffer_input (c->ctx, buffer, input);
+	relay_broadcast_except (c->ctx, c);
+
+	process_input (c->ctx, buffer, input);
+}
+
 static void
 client_process_buffer_log
 	(struct client *c, uint32_t seq, struct buffer *buffer)
@@ -15544,7 +15620,7 @@ client_process_message (struct client *c,
 		buffer_activate (c->ctx, buffer);
 		break;
 	case RELAY_COMMAND_BUFFER_INPUT:
-		process_input (c->ctx, buffer, m->data.buffer_input.text.str);
+		client_process_buffer_input (c, buffer, m->data.buffer_input.text.str);
 		break;
 	case RELAY_COMMAND_BUFFER_TOGGLE_UNIMPORTANT:
 		buffer_toggle_unimportant (c->ctx, buffer);