HID-input: don’t crash when open fails

Important since hidraw devices need special permissions on Linux.

src/Input/FGEventInput.cxx

@@ -410,8 +410,12 @@ unsigned FGEventInput::AddDevice( FGInputDevice * inputDevice )
   inputDevice->Configure( deviceNode );
 
   try {	
-    inputDevice->Open();
+    bool ok = inputDevice->Open();
+      if (ok) {
           input_devices[ deviceNode->getIndex() ] = inputDevice;
+      } else {
+          throw sg_exception("Opening input device failed");
+      }
   }
   catch( ... ) {
     delete  inputDevice;

src/Input/FGEventInput.hxx

@@ -223,7 +223,7 @@ public:
     
   virtual ~FGInputDevice();
 
-  virtual void Open() = 0;
+  virtual bool Open() = 0;
   virtual void Close() = 0;
 
   virtual void Send( const char * eventName, double value ) = 0;

src/Input/FGHIDEventInput.cxx

@@ -219,7 +219,7 @@ public:
 
     virtual ~FGHIDDevice();
 
-    void Open() override;
+    bool Open() override;
     void Close() override;
     
     void update(double dt) override;
@@ -322,15 +322,17 @@ FGHIDDevice::FGHIDDevice(hid_device_info *devInfo, FGHIDEventInput *)
     
 FGHIDDevice::~FGHIDDevice()
 {
-    
+    if (_device) {
+        hid_close(_device);
+    }
 }
     
-void FGHIDDevice::Open()
+bool FGHIDDevice::Open()
 {
     _device = hid_open_path(_hidPath.c_str());
-    if (_device == 0) {
-        SG_LOG(SG_INPUT, SG_WARN, "Failed to open:" << _hidPath);
-        return;
+    if (_device == nullptr) {
+        SG_LOG(SG_INPUT, SG_WARN, "HID: Failed to open:" << _hidPath);
+        return false;
     }
     
     unsigned char reportDescriptor[1024];
@@ -354,6 +356,8 @@ void FGHIDDevice::Open()
        // SG_LOG(SG_INPUT, SG_INFO, "found item for event:" << v.first);
         reportItem.second->event = event;
     }
+    
+    return true;
 }
     
 void FGHIDDevice::scanCollection(hid_item* c)
@@ -475,11 +479,18 @@ void FGHIDDevice::scanItem(hid_item* item)
 
 void FGHIDDevice::Close()
 {
+    if (_device) {
         hid_close(_device);
+        _device = nullptr;
+    }
 }
 
 void FGHIDDevice::update(double dt)
 {
+    if (!_device) {
+        return;
+    }
+    
     uint8_t reportBuf[65];
     int readCount = 0;
     while (true) {
@@ -528,6 +539,10 @@ void writeBits(uint8_t* bytes, size_t bitOffset, size_t bitSize, int value)
     
 void FGHIDDevice::sendReport(Report* report) const
 {
+    if (!_device) {
+        return;
+    }
+    
     uint8_t reportBytes[65];
     size_t reportLength = 0;
     memset(reportBytes, 0, sizeof(reportBytes));
@@ -632,6 +647,10 @@ void FGHIDDevice::processInputReport(Report* report, unsigned char* data,
     
 void FGHIDDevice::SendFeatureReport(unsigned int reportId, const std::string& data)
 {
+    if (!_device) {
+        return;
+    }
+    
     uint8_t buf[65];
     size_t len = std::min(data.length() + 1, sizeof(buf));
     buf[0] = reportId;

src/Input/FGLinuxEventInput.cxx

@@ -286,9 +286,9 @@ static inline bool bitSet( unsigned char * buf, unsigned bit )
   return (buf[bit/sizeof(unsigned char)/8] >> (bit%(sizeof(unsigned char)*8))) & 1;
 }
 
-void FGLinuxInputDevice::Open()
+bool FGLinuxInputDevice::Open()
 {
-  if( fd != -1 ) return;
+  if( fd != -1 ) return true;
   if( (fd = ::open( devname.c_str(), O_RDWR )) == -1 ) { 
     throw std::exception();
   }
@@ -371,6 +371,8 @@ void FGLinuxInputDevice::Open()
       }
     }
   }
+
+  return true;
 }
 
 double FGLinuxInputDevice::Normalize( struct input_event & event ) 

src/Input/FGLinuxEventInput.hxx

@@ -45,10 +45,10 @@ public:
   FGLinuxInputDevice( std::string name, std::string devname, std::string aSerial );
   virtual ~FGLinuxInputDevice();
 
-  virtual void Open();
-  virtual void Close();
-  virtual void Send( const char * eventName, double value );
-  virtual const char * TranslateEventName( FGEventData & eventData );
+  bool Open() override;
+  void Close() override;
+  void Send( const char * eventName, double value ) override;
+  const char * TranslateEventName( FGEventData & eventData ) override;
 
   void SetDevname( const std::string & name );
   std::string GetDevname() const { return devname; }

src/Input/FGMacOSXEventInput.cxx

@@ -153,7 +153,7 @@ public:
 
     virtual ~FGMacOSXInputDevice();
 
-    void Open() override;
+    bool Open() override;
     void Close() override;
     
     virtual void update(double dt);
@@ -344,16 +344,21 @@ FGMacOSXInputDevice::~FGMacOSXInputDevice()
     CFRelease(_hid);
 }
 
-void FGMacOSXInputDevice::Open()
+bool FGMacOSXInputDevice::Open()
 {
+    IOReturn result = IOHIDDeviceOpen(_hid, kIOHIDOptionsTypeNone);
+    if (result != kIOReturnSuccess) {
+        return false;
+    }
     
-    IOHIDDeviceOpen(_hid, kIOHIDOptionsTypeNone);
     IOHIDDeviceScheduleWithRunLoop(_hid, CFRunLoopGetCurrent(), kCFRunLoopDefaultMode);
 
     // IOHIDQueueRegisterValueAvailableCallback(_queue, valueAvailableCallback, this);
 
     IOHIDQueueScheduleWithRunLoop(_queue, CFRunLoopGetCurrent(), kCFRunLoopDefaultMode);
     IOHIDQueueStart(_queue);
+    
+    return true;
 }
 
 void FGMacOSXInputDevice::buildElementNameDictionary()