libcamera: bound_method: Decouple from Signal implementation

To make the BoundMethod classes more generic, replace direct access to
private member from Signal classes with accessors or helper functions.
This allows removal of friend statements from the BoundMethod classes.

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

include/libcamera/bound_method.h

@@ -13,9 +13,6 @@
 namespace libcamera {
 
 class Object;
-template<typename... Args>
-class Signal;
-class SignalBase;
 
 class BoundMethodBase
 {
@@ -28,7 +25,7 @@ public:
 	bool match(T *obj) { return obj == obj_; }
 	bool match(Object *object) { return object == object_; }
 
-	void disconnect(SignalBase *signal);
+	Object *object() const { return object_; }
 
 	void activatePack(void *pack);
 	virtual void invokePack(void *pack) = 0;
@@ -93,6 +90,8 @@ public:
 	BoundMemberMethod(T *obj, Object *object, void (T::*func)(Args...))
 		: BoundMethodArgs<Args...>(obj, object), func_(func) {}
 
+	bool match(void (T::*func)(Args...)) const { return func == func_; }
+
 	void activate(Args... args)
 	{
 		if (this->object_)
@@ -107,7 +106,6 @@ public:
 	}
 
 private:
-	friend class Signal<Args...>;
 	void (T::*func_)(Args...);
 };
 
@@ -118,11 +116,12 @@ public:
 	BoundStaticMethod(void (*func)(Args...))
 		: BoundMethodArgs<Args...>(nullptr, nullptr), func_(func) {}
 
+	bool match(void (*func)(Args...)) const { return func == func_; }
+
 	void activate(Args... args) { (*func_)(args...); }
 	void invoke(Args... args) {}
 
 private:
-	friend class Signal<Args...>;
 	void (*func_)(Args...);
 };