[cscore] Add polled support to listener

Change Java VideoListener to use polling.

cscore/src/main/native/cpp/Notifier.h

@@ -6,9 +6,11 @@
 #define CSCORE_NOTIFIER_H_
 
 #include <functional>
+#include <utility>
 
-#include <wpi/SafeThread.h>
+#include <wpi/CallbackManager.h>
 
+#include "Handle.h"
 #include "cscore_cpp.h"
 
 namespace cs {
@@ -16,7 +18,40 @@ namespace cs {
 class SinkImpl;
 class SourceImpl;
 
-class Notifier {
+namespace impl {
+
+struct ListenerData : public wpi::CallbackListenerData<
+                          std::function<void(const RawEvent& event)>> {
+  ListenerData() = default;
+  ListenerData(std::function<void(const RawEvent& event)> callback_,
+               int eventMask_)
+      : CallbackListenerData(std::move(callback_)), eventMask(eventMask_) {}
+  ListenerData(unsigned int pollerUid_, int eventMask_)
+      : CallbackListenerData(pollerUid_), eventMask(eventMask_) {}
+
+  int eventMask;
+};
+
+class NotifierThread
+    : public wpi::CallbackThread<NotifierThread, RawEvent, ListenerData> {
+ public:
+  bool Matches(const ListenerData& /*listener*/, const RawEvent& /*data*/) {
+    return true;
+  }
+
+  void SetListener(RawEvent* data, unsigned int listener_uid) {
+    data->listener = Handle(listener_uid, Handle::kListener);
+  }
+
+  void DoCallback(std::function<void(const RawEvent& event)> callback,
+                  const RawEvent& data) {
+    callback(data);
+  }
+};
+
+}  // namespace impl
+
+class Notifier : public wpi::CallbackManager<Notifier, impl::NotifierThread> {
   friend class NotifierTest;
 
  public:
@@ -24,16 +59,10 @@ class Notifier {
   ~Notifier();
 
   void Start();
-  void Stop();
 
-  static bool destroyed() { return s_destroyed; }
-
-  void SetOnStart(std::function<void()> on_start) { m_on_start = on_start; }
-  void SetOnExit(std::function<void()> on_exit) { m_on_exit = on_exit; }
-
-  int AddListener(std::function<void(const RawEvent& event)> callback,
-                  int eventMask);
-  void RemoveListener(int uid);
+  unsigned int Add(std::function<void(const RawEvent& event)> callback,
+                   int eventMask);
+  unsigned int AddPolled(unsigned int pollerUid, int eventMask);
 
   // Notification events
   void NotifySource(const wpi::Twine& name, CS_Source source,
@@ -54,14 +83,6 @@ class Notifier {
                           const wpi::Twine& valueStr);
   void NotifyNetworkInterfacesChanged();
   void NotifyTelemetryUpdated();
-
- private:
-  class Thread;
-  wpi::SafeThreadOwner<Thread> m_owner;
-
-  std::function<void()> m_on_start;
-  std::function<void()> m_on_exit;
-  static bool s_destroyed;
 };
 
 }  // namespace cs