libcamera: signal: Split Slot implementation to reusable classes

Move the Slot* classes to bound_method.{h,cpp} and rename them to
Bound*Method*. They will be reused to implement asynchronous method
invocation similar to cross-thread signal delivery.

This is only a move and rename, no functional changes are included.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>

src/libcamera/bound_method.cpp

@@ -0,0 +1,33 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2019, Google Inc.
+ *
+ * bound_method.cpp - Method bind and invocation
+ */
+
+#include <libcamera/bound_method.h>
+
+#include "message.h"
+#include "thread.h"
+#include "utils.h"
+
+namespace libcamera {
+
+void BoundMethodBase::disconnect(SignalBase *signal)
+{
+	if (object_)
+		object_->disconnect(signal);
+}
+
+void BoundMethodBase::activatePack(void *pack)
+{
+	if (Thread::current() == object_->thread()) {
+		invokePack(pack);
+	} else {
+		std::unique_ptr<Message> msg =
+			utils::make_unique<SignalMessage>(this, pack);
+		object_->postMessage(std::move(msg));
+	}
+}
+
+} /* namespace libcamera */