Subsystems: stub code for smart add+remove

Groups track their state, which will enable them to correctly transition
added and removed children in the future. Only stubbed for now, to avoid
breakage on the FG side.

simgear/structure/subsystem_mgr.cxx

@@ -157,6 +157,7 @@ SGSubsystemMgr* SGSubsystem::get_manager() const
 std::string SGSubsystem::nameForState(State s)
 {
     switch (s) {
+    case State::INVALID: return "invalid";
     case State::INIT: return "init";
     case State::REINIT: return "reinit";
     case State::POSTINIT: return "post-init";
@@ -216,11 +217,13 @@ SGSubsystemGroup::~SGSubsystemGroup ()
 void
 SGSubsystemGroup::init ()
 {
+    assert(_state == State::BIND);
     forEach([this](SGSubsystem* s){
         this->notifyWillChange(s, State::INIT);
         s->init();
         this->notifyDidChange(s, State::INIT);
     });
+    _state = State::INIT;
 }
 
 SGSubsystem::InitStatus
@@ -233,11 +236,13 @@ SGSubsystemGroup::incrementalInit()
 
     // termination test
     if (_initPosition >= static_cast<int>(_members.size())) {
+        _state = State::INIT;
         return INIT_DONE;
     }
   
     if (_initPosition < 0) {
         // first call
+        assert(_state == State::BIND);
         _initPosition = 0;
         notifyWillChange(_members.front()->subsystem, State::INIT);
     }
@@ -279,11 +284,13 @@ void SGSubsystemGroup::reverseForEach(std::function<void(SGSubsystem*)> f)
 void
 SGSubsystemGroup::postinit ()
 {
+    assert(_state == State::INIT);
     forEach([this](SGSubsystem* s){
         this->notifyWillChange(s, State::POSTINIT);
         s->postinit();
         this->notifyDidChange(s, State::POSTINIT);
     });
+    _state = State::POSTINIT;
 }
 
 void
@@ -304,6 +311,7 @@ SGSubsystemGroup::shutdown ()
         s->shutdown();
         this->notifyDidChange(s, State::SHUTDOWN);
     });
+    _state = State::SHUTDOWN;
     _initPosition = -1;
 }
 
@@ -315,6 +323,7 @@ SGSubsystemGroup::bind ()
         s->bind();
         this->notifyDidChange(s, State::BIND);
     });
+    _state = State::BIND;
 }
 
 void
@@ -325,6 +334,7 @@ SGSubsystemGroup::unbind ()
         s->unbind();
         this->notifyDidChange(s, State::UNBIND);
     });
+    _state = State::UNBIND;
 }
 
 void
@@ -420,6 +430,16 @@ SGSubsystemGroup::set_subsystem (const string &name, SGSubsystem * subsystem,
     member->min_step_sec = min_step_sec;
     subsystem->set_group(this);
     notifyDidChange(subsystem, State::ADD);
+    
+    if (_state != State::INVALID) {
+        SG_LOG(SG_GENERAL, SG_DEV_WARN, "TODO: implement SGSubsystemGroup transition when adding after init");
+        // transition to the correct state
+        // bind
+        
+        // init
+        
+        // post-init
+    }
 }
 
 void
@@ -457,6 +477,16 @@ SGSubsystemGroup::remove_subsystem(const string &name)
     if (it != _members.end()) {
         // found it, great
         const auto sub = (*it)->subsystem;
+        
+        if (_state != State::INVALID) {
+            // transition out correctly
+            SG_LOG(SG_GENERAL, SG_DEV_WARN, "TODO: implement SGSubsystemGroup transition when removing before shutdown");
+
+            // shutdown
+            
+            // unbind
+        }
+        
         notifyWillChange(sub, State::REMOVE);
         delete *it;
         _members.erase(it);

simgear/structure/subsystem_mgr.hxx

@@ -288,7 +288,8 @@ public:
     SGSubsystemGroup* get_group() const;
     
     enum class State {
-        ADD,
+        INVALID = -1,
+        ADD = 0,
         BIND,
         INIT,
         POSTINIT,
@@ -401,6 +402,9 @@ private:
     using MemberVec = std::vector<Member*>;
     MemberVec _members;
 
+    // track the state of this group, so we can transition added/removed
+    // members correctly
+    SGSubsystem::State _state = SGSubsystem::State::INVALID;
     double _fixedUpdateTime;
     double _updateTimeRemainder;
 

simgear/structure/subsystem_test.cxx

@@ -30,7 +30,8 @@ public:
     void bind() override
     {
         auto node = get_manager()->root_node();
-        node->setIntValue("mysub/foo", 42);
+        if (node)
+            node->setIntValue("mysub/foo", 42);
     }
     
     void update(double dt) override
@@ -54,7 +55,8 @@ public:
     void bind() override
     {
         auto node = get_manager()->root_node();
-        node->setIntValue("anothersub/bar", 172);
+        if (node)
+            node->setIntValue("anothersub/bar", 172);
     }
     
     void update(double dt) override
@@ -246,6 +248,7 @@ void testSubGrouping()
     // lookup of the group should also work
     SG_CHECK_EQUAL(manager->get_subsystem<InstrumentGroup>(), instruments);
     
+    manager->bind();
     manager->init();
     
     SG_VERIFY(instruments->wasInited);
@@ -304,6 +307,7 @@ void testIncrementalInit()
     instruments->set_subsystem(radio1);
     instruments->set_subsystem(radio2);
     
+    manager->bind();
     for ( ; ; ) {
         auto status = manager->incrementalInit();
         if (status == SGSubsystemMgr::INIT_DONE)
@@ -347,6 +351,7 @@ void testSuspendResume()
     instruments->set_subsystem(radio1);
     instruments->set_subsystem(radio2);
     
+    manager->bind();
     manager->init();
     manager->update(1.0);