ibus: the InputContext interface as a table

onmsg matched the member name, then handleplain matched four of the
names again after checking their empty signature, and the handlers that
take arguments each re-checked theirs with a message of their own.  One
table of member, signature, and handler does the matching and the
checking once; the handlers read arguments a signature has already
vouched for.

ibus.c

@@ -630,13 +630,9 @@ handlekey(DBusConnection *c, DBusMessage *m, Ictx *ctx)
 	char commit[Maxutf], preedit[Maxutf];
 	int restart;
 
-	if(!dbus_message_get_args(m, nil,
+	dbus_message_get_args(m, nil, DBUS_TYPE_UINT32, &sym,
-		DBUS_TYPE_UINT32, &sym,
+		DBUS_TYPE_UINT32, &code, DBUS_TYPE_UINT32, &state,
-		DBUS_TYPE_UINT32, &code,
+		DBUS_TYPE_INVALID);
-		DBUS_TYPE_UINT32, &state,
-		DBUS_TYPE_INVALID))
-		return handleerror(c, m, DBUS_ERROR_INVALID_ARGS,
-			"ProcessKeyEvent expects three unsigned integers");
 	if(!processkey(ctx, sym, state, &res))
 		return replybool(c, m, 0);
 	stoutf(&res.commit, commit, sizeof commit);
@@ -722,10 +718,7 @@ handlecap(DBusConnection *c, DBusMessage *m, Ictx *ctx)
 	char preedit[Maxutf];
 	u32int old;
 
-	if(!dbus_message_get_args(m, nil, DBUS_TYPE_UINT32, &cap,
+	dbus_message_get_args(m, nil, DBUS_TYPE_UINT32, &cap, DBUS_TYPE_INVALID);
-	   DBUS_TYPE_INVALID))
-		return handleerror(c, m, DBUS_ERROR_INVALID_ARGS,
-			"SetCapabilities expects one unsigned integer");
 	old = ctx->cap;
 	ctx->cap = cap;
 	if(ctx->focused){
@@ -865,32 +858,35 @@ handlecursor(DBusConnection *c, DBusMessage *m, Ictx *ctx)
 {
 	dbus_int32_t x, y, w, h;
 
-	if(!dbus_message_get_args(m, nil,
+	dbus_message_get_args(m, nil, DBUS_TYPE_INT32, &x, DBUS_TYPE_INT32, &y,
-		DBUS_TYPE_INT32, &x, DBUS_TYPE_INT32, &y,
+		DBUS_TYPE_INT32, &w, DBUS_TYPE_INT32, &h, DBUS_TYPE_INVALID);
-		DBUS_TYPE_INT32, &w, DBUS_TYPE_INT32, &h,
-		DBUS_TYPE_INVALID))
-		return handleerror(c, m, DBUS_ERROR_INVALID_ARGS,
-			"SetCursorLocation expects four integers");
 	setcursor(ctx, x, y, h);
 	return reply(c, m, DBUS_TYPE_INVALID, nil);
 }
 
-/* Argument-free InputContext calls, checked for an empty signature. */
+/* SetEngine: there is one engine, so any name is fine. */
 static DBusHandlerResult
-handleplain(DBusConnection *c, DBusMessage *m, Ictx *ctx, const char *member)
+handleok(DBusConnection *c, DBusMessage *m, Ictx*)
 {
-	if(!dbus_message_has_signature(m, ""))
+	return reply(c, m, DBUS_TYPE_INVALID, nil);
-		return handleerror(c, m, DBUS_ERROR_INVALID_ARGS,
-			"this call takes no arguments");
-	if(strcmp(member, "FocusIn") == 0)
-		return handlefocusin(c, m, ctx);
-	if(strcmp(member, "FocusOut") == 0)
-		return handlefocusout(c, m, ctx);
-	if(strcmp(member, "Reset") == 0)
-		return handlereset(c, m, ctx);
-	return handledestroy(c, m, ctx);
 }
 
+/* The InputContext interface: member, argument signature, handler. */
+static struct {
+	char	*member;
+	char	*sig;
+	DBusHandlerResult (*fn)(DBusConnection*, DBusMessage*, Ictx*);
+} ictab[] = {
+	{"ProcessKeyEvent", "uuu", handlekey},
+	{"FocusIn", "", handlefocusin},
+	{"FocusOut", "", handlefocusout},
+	{"Reset", "", handlereset},
+	{"Destroy", "", handledestroy},
+	{"SetCursorLocation", "iiii", handlecursor},
+	{"SetCapabilities", "u", handlecap},
+	{"SetEngine", "s", handleok},
+};
+
 /*
  * One handler for everything a client sends: the tiny slice of the bus
  * that libibus needs, then the InputContext interface.  Unhandled calls
@@ -901,6 +897,7 @@ onmsg(DBusConnection *c, DBusMessage *m, void*)
 {
 	const char *iface, *member, *path;
 	Ictx *ctx;
+	int i;
 
 	if(dbus_message_get_type(m) != DBUS_MESSAGE_TYPE_METHOD_CALL)
 		return DBUS_HANDLER_RESULT_NOT_YET_HANDLED;
@@ -953,22 +950,13 @@ onmsg(DBusConnection *c, DBusMessage *m, void*)
 		if(ctx == nil)
 			return handleerror(c, m, DBUS_ERROR_UNKNOWN_OBJECT,
 				"unknown input context");
-		if(strcmp(member, "ProcessKeyEvent") == 0)
+		for(i = 0; i < nelem(ictab); i++){
-			return handlekey(c, m, ctx);
+			if(strcmp(member, ictab[i].member) != 0)
-		if(strcmp(member, "FocusIn") == 0 ||
+				continue;
-		   strcmp(member, "FocusOut") == 0 ||
+			if(!dbus_message_has_signature(m, ictab[i].sig))
-		   strcmp(member, "Reset") == 0 ||
-		   strcmp(member, "Destroy") == 0)
-			return handleplain(c, m, ctx, member);
-		if(strcmp(member, "SetCursorLocation") == 0)
-			return handlecursor(c, m, ctx);
-		if(strcmp(member, "SetCapabilities") == 0)
-			return handlecap(c, m, ctx);
-		if(strcmp(member, "SetEngine") == 0){
-			if(!dbus_message_has_signature(m, "s"))
 				return handleerror(c, m, DBUS_ERROR_INVALID_ARGS,
-					"SetEngine expects one engine name");
+					"bad arguments");
-			return reply(c, m, DBUS_TYPE_INVALID, nil);
+			return ictab[i].fn(c, m, ctx);
 		}
 	}
 	return DBUS_HANDLER_RESULT_NOT_YET_HANDLED;