xC/xP: finalize and implement Event.PING

xC-proto

@@ -8,11 +8,12 @@ struct CommandMessage {
 	u32 command_seq;
 	union CommandData switch (enum Command {
 		HELLO,
-		PING,
 		ACTIVE,
-		BUFFER_COMPLETE,
 		BUFFER_INPUT,
 		BUFFER_ACTIVATE,
+		PING_RESPONSE,
+		PING,
+		BUFFER_COMPLETE,
 		BUFFER_LOG,
 	} command) {
 	case HELLO:
@@ -20,19 +21,24 @@ struct CommandMessage {
 		// If the version check succeeds, the client will receive
 		// an initial stream of BUFFER_UPDATE, BUFFER_LINE,
 		// and finally a BUFFER_ACTIVATE message.
-	case PING:
-		void;
 	case ACTIVE:
 		void;
-	case BUFFER_COMPLETE:
-		string buffer_name;
-		string text;
-		u32 position;
 	case BUFFER_INPUT:
 		string buffer_name;
 		string text;
 	case BUFFER_ACTIVATE:
 		string buffer_name;
+	case PING_RESPONSE:
+		u32 event_seq;
+
+	// Only these commands may produce Event.RESPONSE, as below,
+	// but any command may produce an error.
+	case PING:
+		void;
+	case BUFFER_COMPLETE:
+		string buffer_name;
+		string text;
+		u32 position;
 	case BUFFER_LOG:
 		string buffer_name;
 	} data;
@@ -129,6 +135,8 @@ struct EventMessage {
 	case RESPONSE:
 		u32 command_seq;
 		union ResponseData switch (Command command) {
+		case PING:
+			void;
 		case BUFFER_COMPLETE:
 			u32 start;
 			string completions<>;

xC.c

@@ -3189,6 +3189,16 @@ relay_prepare_error (struct app_context *ctx, uint32_t seq, const char *message)
 	e->error = str_from_cstr (message);
 }
 
+static struct relay_event_data_response *
+relay_prepare_response (struct app_context *ctx, uint32_t seq)
+{
+	struct relay_event_message *m = relay_prepare (ctx);
+	struct relay_event_data_response *e = &m->data.response;
+	e->event = RELAY_EVENT_RESPONSE;
+	e->command_seq = seq;
+	return e;
+}
+
 // --- Terminal output ---------------------------------------------------------
 
 /// Default colour pair
@@ -15267,12 +15277,8 @@ client_process_buffer_complete (struct client *c, uint32_t seq,
 		goto out_internal;
 	}
 
-	struct relay_event_data_response *e =
+	struct relay_event_data_response *e = relay_prepare_response (c->ctx, seq);
-		&relay_prepare (c->ctx)->data.response;
-	e->event = RELAY_EVENT_RESPONSE;
-	e->command_seq = seq;
 	e->data.command = RELAY_COMMAND_BUFFER_COMPLETE;
-
 	struct relay_response_data_buffer_complete *resp =
 		&e->data.buffer_complete;
 	resp->start = start;
@@ -15291,10 +15297,7 @@ static void
 client_process_buffer_log
 	(struct client *c, uint32_t seq, struct buffer *buffer)
 {
-	struct relay_event_data_response *e =
+	struct relay_event_data_response *e = relay_prepare_response (c->ctx, seq);
-		&relay_prepare (c->ctx)->data.response;
-	e->event = RELAY_EVENT_RESPONSE;
-	e->command_seq = seq;
 	e->data.command = RELAY_COMMAND_BUFFER_LOG;
 
 	char *path = buffer_get_log_path (buffer);
@@ -15357,7 +15360,8 @@ client_process_message (struct client *c,
 		client_resync (c);
 		break;
 	case RELAY_COMMAND_PING:
-		relay_prepare_ping (c->ctx);
+		relay_prepare_response (c->ctx, m->command_seq)
+			->data.command = RELAY_COMMAND_PING;
 		relay_send (c);
 		break;
 	case RELAY_COMMAND_ACTIVE:

xP/public/xP.js

@@ -85,7 +85,8 @@ class RelayRpc extends EventTarget {
 			if (typeof e.event !== 'string')
 				throw "Invalid event tag"
 
-			this.dispatchEvent(new CustomEvent(e.event, {detail: e}))
+			this.dispatchEvent(new CustomEvent(
+				e.event, {detail: {eventSeq: message.eventSeq, ...e}}))
 
 			// Minor abstraction layering violation.
 			m.redraw()
@@ -153,6 +154,10 @@ rpc.addEventListener('close', event => {
 	m.redraw()
 })
 
+rpc.addEventListener('Ping', event => {
+	rpc.send({command: 'PingResponse', eventSeq: event.detail.eventSeq})
+})
+
 rpc.addEventListener('BufferUpdate', event => {
 	let e = event.detail, b = buffers.get(e.bufferName)
 	if (b === undefined) {