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>

11 files changed, 197 insertions, 166 deletions

diff --git a/Documentation/Doxyfile.in b/Documentation/Doxyfile.in
index 3d94623a..a9596c2a 100644
--- a/Documentation/Doxyfile.in
+++ b/Documentation/Doxyfile.in
@@ -865,11 +865,11 @@ EXCLUDE_PATTERNS       =
 # Note that the wildcards are matched against the file with absolute path, so to
 # exclude all test directories use the pattern */test/*
 
-EXCLUDE_SYMBOLS        = libcamera::SignalBase \
-                         libcamera::SlotArgs \
-                         libcamera::SlotBase \
-                         libcamera::SlotMember \
-                         libcamera::SlotStatic \
+EXCLUDE_SYMBOLS        = libcamera::BoundMemberMethod \
+                         libcamera::BoundMethodArgs \
+                         libcamera::BoundMethodBase \
+                         libcamera::BoundStaticMethod \
+                         libcamera::SignalBase \
                          std::*
 
 # The EXAMPLE_PATH tag can be used to specify one or more files or directories
diff --git a/include/libcamera/bound_method.h b/include/libcamera/bound_method.h
new file mode 100644
index 00000000..38c44b92
--- /dev/null
+++ b/include/libcamera/bound_method.h
@@ -0,0 +1,131 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2019, Google Inc.
+ *
+ * bound_method.h - Method bind and invocation
+ */
+#ifndef __LIBCAMERA_BOUND_METHOD_H__
+#define __LIBCAMERA_BOUND_METHOD_H__
+
+#include <tuple>
+#include <type_traits>
+
+namespace libcamera {
+
+class Object;
+template<typename... Args>
+class Signal;
+class SignalBase;
+
+class BoundMethodBase
+{
+public:
+	BoundMethodBase(void *obj, Object *object)
+		: obj_(obj), object_(object) {}
+	virtual ~BoundMethodBase() {}
+
+	template<typename T, typename std::enable_if<!std::is_same<Object, T>::value>::type * = nullptr>
+	bool match(T *obj) { return obj == obj_; }
+	bool match(Object *object) { return object == object_; }
+
+	void disconnect(SignalBase *signal);
+
+	void activatePack(void *pack);
+	virtual void invokePack(void *pack) = 0;
+
+protected:
+	void *obj_;
+	Object *object_;
+};
+
+template<typename... Args>
+class BoundMethodArgs : public BoundMethodBase
+{
+private:
+#ifndef __DOXYGEN__
+	/*
+	 * This is a cheap partial implementation of std::integer_sequence<>
+	 * from C++14.
+	 */
+	template<int...>
+	struct sequence {
+	};
+
+	template<int N, int... S>
+	struct generator : generator<N-1, N-1, S...> {
+	};
+
+	template<int... S>
+	struct generator<0, S...> {
+		typedef sequence<S...> type;
+	};
+#endif
+
+	using PackType = std::tuple<typename std::remove_reference<Args>::type...>;
+
+	template<int... S>
+	void invokePack(void *pack, sequence<S...>)
+	{
+		PackType *args = static_cast<PackType *>(pack);
+		invoke(std::get<S>(*args)...);
+		delete args;
+	}
+
+public:
+	BoundMethodArgs(void *obj, Object *object)
+		: BoundMethodBase(obj, object) {}
+
+	void invokePack(void *pack) override
+	{
+		invokePack(pack, typename generator<sizeof...(Args)>::type());
+	}
+
+	virtual void activate(Args... args) = 0;
+	virtual void invoke(Args... args) = 0;
+};
+
+template<typename T, typename... Args>
+class BoundMemberMethod : public BoundMethodArgs<Args...>
+{
+public:
+	using PackType = std::tuple<typename std::remove_reference<Args>::type...>;
+
+	BoundMemberMethod(T *obj, Object *object, void (T::*func)(Args...))
+		: BoundMethodArgs<Args...>(obj, object), func_(func) {}
+
+	void activate(Args... args)
+	{
+		if (this->object_)
+			BoundMethodBase::activatePack(new PackType{ args... });
+		else
+			(static_cast<T *>(this->obj_)->*func_)(args...);
+	}
+
+	void invoke(Args... args)
+	{
+		(static_cast<T *>(this->obj_)->*func_)(args...);
+	}
+
+private:
+	friend class Signal<Args...>;
+	void (T::*func_)(Args...);
+};
+
+template<typename... Args>
+class BoundStaticMethod : public BoundMethodArgs<Args...>
+{
+public:
+	BoundStaticMethod(void (*func)(Args...))
+		: BoundMethodArgs<Args...>(nullptr, nullptr), func_(func) {}
+
+	void activate(Args... args) { (*func_)(args...); }
+	void invoke(Args... args) {}
+
+private:
+	friend class Signal<Args...>;
+	void (*func_)(Args...);
+};
+
+}; /* namespace libcamera */
+
+#endif /* __LIBCAMERA_BOUND_METHOD_H__ */
diff --git a/include/libcamera/meson.build b/include/libcamera/meson.build
index 920eb5fc..a8a38a9b 100644
--- a/include/libcamera/meson.build
+++ b/include/libcamera/meson.build
@@ -1,4 +1,5 @@
 libcamera_api = files([
+    'bound_method.h',
     'buffer.h',
     'camera.h',
     'camera_manager.h',
diff --git a/include/libcamera/object.h b/include/libcamera/object.h
index 3d08d69a..e3b39cf5 100644
--- a/include/libcamera/object.h
+++ b/include/libcamera/object.h
@@ -10,13 +10,14 @@
 #include <list>
 #include <memory>
 
+#include <libcamera/bound_method.h>
+
 namespace libcamera {
 
 class Message;
 template<typename... Args>
 class Signal;
 class SignalBase;
-class SlotBase;
 class Thread;
 
 class Object
@@ -36,7 +37,7 @@ protected:
 private:
 	template<typename... Args>
 	friend class Signal;
-	friend class SlotBase;
+	friend class BoundMethodBase;
 	friend class Thread;
 
 	void connect(SignalBase *signal);
diff --git a/include/libcamera/signal.h b/include/libcamera/signal.h
index 8f6db700..3b6de30f 100644
--- a/include/libcamera/signal.h
+++ b/include/libcamera/signal.h
@@ -8,127 +8,14 @@
 #define __LIBCAMERA_SIGNAL_H__
 
 #include <list>
-#include <tuple>
 #include <type_traits>
 #include <vector>
 
+#include <libcamera/bound_method.h>
 #include <libcamera/object.h>
 
 namespace libcamera {
 
-template<typename... Args>
-class Signal;
-class SignalBase;
-
-class SlotBase
-{
-public:
-	SlotBase(void *obj, Object *object)
-		: obj_(obj), object_(object) {}
-	virtual ~SlotBase() {}
-
-	template<typename T, typename std::enable_if<!std::is_same<Object, T>::value>::type * = nullptr>
-	bool match(T *obj) { return obj == obj_; }
-	bool match(Object *object) { return object == object_; }
-
-	void disconnect(SignalBase *signal);
-
-	void activatePack(void *pack);
-	virtual void invokePack(void *pack) = 0;
-
-protected:
-	void *obj_;
-	Object *object_;
-};
-
-template<typename... Args>
-class SlotArgs : public SlotBase
-{
-private:
-#ifndef __DOXYGEN__
-	/*
-	 * This is a cheap partial implementation of std::integer_sequence<>
-	 * from C++14.
-	 */
-	template<int...>
-	struct sequence {
-	};
-
-	template<int N, int... S>
-	struct generator : generator<N-1, N-1, S...> {
-	};
-
-	template<int... S>
-	struct generator<0, S...> {
-		typedef sequence<S...> type;
-	};
-#endif
-
-	using PackType = std::tuple<typename std::remove_reference<Args>::type...>;
-
-	template<int... S>
-	void invokePack(void *pack, sequence<S...>)
-	{
-		PackType *args = static_cast<PackType *>(pack);
-		invoke(std::get<S>(*args)...);
-		delete args;
-	}
-
-public:
-	SlotArgs(void *obj, Object *object)
-		: SlotBase(obj, object) {}
-
-	void invokePack(void *pack) override
-	{
-		invokePack(pack, typename generator<sizeof...(Args)>::type());
-	}
-
-	virtual void activate(Args... args) = 0;
-	virtual void invoke(Args... args) = 0;
-};
-
-template<typename T, typename... Args>
-class SlotMember : public SlotArgs<Args...>
-{
-public:
-	using PackType = std::tuple<typename std::remove_reference<Args>::type...>;
-
-	SlotMember(T *obj, Object *object, void (T::*func)(Args...))
-		: SlotArgs<Args...>(obj, object), func_(func) {}
-
-	void activate(Args... args)
-	{
-		if (this->object_)
-			SlotBase::activatePack(new PackType{ args... });
-		else
-			(static_cast<T *>(this->obj_)->*func_)(args...);
-	}
-
-	void invoke(Args... args)
-	{
-		(static_cast<T *>(this->obj_)->*func_)(args...);
-	}
-
-private:
-	friend class Signal<Args...>;
-	void (T::*func_)(Args...);
-};
-
-template<typename... Args>
-class SlotStatic : public SlotArgs<Args...>
-{
-public:
-	SlotStatic(void (*func)(Args...))
-		: SlotArgs<Args...>(nullptr, nullptr), func_(func) {}
-
-	void activate(Args... args) { (*func_)(args...); }
-	void invoke(Args... args) {}
-
-private:
-	friend class Signal<Args...>;
-	void (*func_)(Args...);
-};
-
 class SignalBase
 {
 public:
@@ -136,7 +23,7 @@ public:
 	void disconnect(T *obj)
 	{
 		for (auto iter = slots_.begin(); iter != slots_.end(); ) {
-			SlotBase *slot = *iter;
+			BoundMethodBase *slot = *iter;
 			if (slot->match(obj)) {
 				iter = slots_.erase(iter);
 				delete slot;
@@ -148,7 +35,7 @@ public:
 
 protected:
 	friend class Object;
-	std::list<SlotBase *> slots_;
+	std::list<BoundMethodBase *> slots_;
 };
 
 template<typename... Args>
@@ -158,7 +45,7 @@ public:
 	Signal() {}
 	~Signal()
 	{
-		for (SlotBase *slot : slots_) {
+		for (BoundMethodBase *slot : slots_) {
 			slot->disconnect(this);
 			delete slot;
 		}
@@ -170,7 +57,7 @@ public:
 	{
 		Object *object = static_cast<Object *>(obj);
 		object->connect(this);
-		slots_.push_back(new SlotMember<T, Args...>(obj, object, func));
+		slots_.push_back(new BoundMemberMethod<T, Args...>(obj, object, func));
 	}
 
 	template<typename T, typename std::enable_if<!std::is_base_of<Object, T>::value>::type * = nullptr>
@@ -179,17 +66,17 @@ public:
 #endif
 	void connect(T *obj, void (T::*func)(Args...))
 	{
-		slots_.push_back(new SlotMember<T, Args...>(obj, nullptr, func));
+		slots_.push_back(new BoundMemberMethod<T, Args...>(obj, nullptr, func));
 	}
 
 	void connect(void (*func)(Args...))
 	{
-		slots_.push_back(new SlotStatic<Args...>(func));
+		slots_.push_back(new BoundStaticMethod<Args...>(func));
 	}
 
 	void disconnect()
 	{
-		for (SlotBase *slot : slots_)
+		for (BoundMethodBase *slot : slots_)
 			delete slot;
 		slots_.clear();
 	}
@@ -204,15 +91,15 @@ public:
 	void disconnect(T *obj, void (T::*func)(Args...))
 	{
 		for (auto iter = slots_.begin(); iter != slots_.end(); ) {
-			SlotArgs<Args...> *slot = static_cast<SlotArgs<Args...> *>(*iter);
+			BoundMethodArgs<Args...> *slot = static_cast<BoundMethodArgs<Args...> *>(*iter);
 			/*
 			 * If the object matches the slot, the slot is
 			 * guaranteed to be a member slot, so we can safely
-			 * cast it to SlotMember<T, Args...> and access its
+			 * cast it to BoundMemberMethod<T, Args...> and access its
 			 * func_ member.
 			 */
 			if (slot->match(obj) &&
-			    static_cast<SlotMember<T, Args...> *>(slot)->func_ == func) {
+			    static_cast<BoundMemberMethod<T, Args...> *>(slot)->func_ == func) {
 				iter = slots_.erase(iter);
 				delete slot;
 			} else {
@@ -224,9 +111,9 @@ public:
 	void disconnect(void (*func)(Args...))
 	{
 		for (auto iter = slots_.begin(); iter != slots_.end(); ) {
-			SlotArgs<Args...> *slot = *iter;
+			BoundMethodArgs<Args...> *slot = *iter;
 			if (slot->match(nullptr) &&
-			    static_cast<SlotStatic<Args...> *>(slot)->func_ == func) {
+			    static_cast<BoundStaticMethod<Args...> *>(slot)->func_ == func) {
 				iter = slots_.erase(iter);
 				delete slot;
 			} else {
@@ -241,9 +128,9 @@ public:
 		 * Make a copy of the slots list as the slot could call the
 		 * disconnect operation, invalidating the iterator.
 		 */
-		std::vector<SlotBase *> slots{ slots_.begin(), slots_.end() };
-		for (SlotBase *slot : slots)
-			static_cast<SlotArgs<Args...> *>(slot)->activate(args...);
+		std::vector<BoundMethodBase *> slots{ slots_.begin(), slots_.end() };
+		for (BoundMethodBase *slot : slots)
+			static_cast<BoundMethodArgs<Args...> *>(slot)->activate(args...);
 	}
 };
 
diff --git a/src/libcamera/bound_method.cpp b/src/libcamera/bound_method.cpp
new file mode 100644
index 00000000..0a2d61a6
--- /dev/null
+++ b/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 */
diff --git a/src/libcamera/include/message.h b/src/libcamera/include/message.h
index 416fe74b..b4670c0e 100644
--- a/src/libcamera/include/message.h
+++ b/src/libcamera/include/message.h
@@ -11,8 +11,8 @@
 
 namespace libcamera {
 
+class BoundMethodBase;
 class Object;
-class SlotBase;
 class Thread;
 
 class Message
@@ -44,12 +44,12 @@ private:
 class SignalMessage : public Message
 {
 public:
-	SignalMessage(SlotBase *slot, void *pack)
-		: Message(Message::SignalMessage), slot_(slot), pack_(pack)
+	SignalMessage(BoundMethodBase *method, void *pack)
+		: Message(Message::SignalMessage), method_(method), pack_(pack)
 	{
 	}
 
-	SlotBase *slot_;
+	BoundMethodBase *method_;
 	void *pack_;
 };
 
diff --git a/src/libcamera/meson.build b/src/libcamera/meson.build
index 7d5d3c04..c5d8f116 100644
--- a/src/libcamera/meson.build
+++ b/src/libcamera/meson.build
@@ -1,4 +1,5 @@
 libcamera_sources = files([
+    'bound_method.cpp',
     'buffer.cpp',
     'camera.cpp',
     'camera_manager.cpp',
diff --git a/src/libcamera/message.cpp b/src/libcamera/message.cpp
index d44d2a4c..8d3376d8 100644
--- a/src/libcamera/message.cpp
+++ b/src/libcamera/message.cpp
@@ -114,12 +114,12 @@ Message::Type Message::registerMessageType()
 /**
  * \fn SignalMessage::SignalMessage()
  * \brief Construct a SignalMessage
- * \param[in] slot The slot that the signal targets
+ * \param[in] method The slot that the signal targets
  * \param[in] pack The signal arguments
  */
 
 /**
- * \var SignalMessage::slot_
+ * \var SignalMessage::method_
  * \brief The slot that the signal targets
  */
 
diff --git a/src/libcamera/object.cpp b/src/libcamera/object.cpp
index 61787fad..0adbc203 100644
--- a/src/libcamera/object.cpp
+++ b/src/libcamera/object.cpp
@@ -90,7 +90,7 @@ void Object::message(Message *msg)
 	switch (msg->type()) {
 	case Message::SignalMessage: {
 		SignalMessage *smsg = static_cast<SignalMessage *>(msg);
-		smsg->slot_->invokePack(smsg->pack_);
+		smsg->method_->invokePack(smsg->pack_);
 		break;
 	}
 
diff --git a/src/libcamera/signal.cpp b/src/libcamera/signal.cpp
index ab7dba50..6ee348ac 100644
--- a/src/libcamera/signal.cpp
+++ b/src/libcamera/signal.cpp
@@ -7,10 +7,6 @@
 
 #include <libcamera/signal.h>
 
-#include "message.h"
-#include "thread.h"
-#include "utils.h"
-
 /**
  * \file signal.h
  * \brief Signal & slot implementation
@@ -57,25 +53,6 @@ namespace libcamera {
  * passed through the signal will remain valid after the signal is emitted.
  */
 
-void SlotBase::disconnect(SignalBase *signal)
-{
-	if (object_)
-		object_->disconnect(signal);
-}
-
-void SlotBase::activatePack(void *pack)
-{
-	Object *obj = static_cast<Object *>(object_);
-
-	if (Thread::current() == obj->thread()) {
-		invokePack(pack);
-	} else {
-		std::unique_ptr<Message> msg =
-			utils::make_unique<SignalMessage>(this, pack);
-		obj->postMessage(std::move(msg));
-	}
-}
-
 /**
  * \fn Signal::connect(T *object, void(T::*func)(Args...))
  * \brief Connect the signal to a member function slot