Now using inotify on Linux to avoid constantly polling joystick connections (#96)

src/SFML/Window/JoystickManager.cpp

@@ -93,6 +93,7 @@ void JoystickManager::update()
 ////////////////////////////////////////////////////////////
 JoystickManager::JoystickManager()
 {
+    JoystickImpl::initialize();
 }
 
 
@@ -104,6 +105,8 @@ JoystickManager::~JoystickManager()
         if (m_joysticks[i].state.connected)
             m_joysticks[i].joystick.close();
     }
+
+    JoystickImpl::cleanup();
 }
 
 } // namespace priv

src/SFML/Window/Linux/JoystickImpl.cpp

@@ -26,39 +26,121 @@
 // Headers
 ////////////////////////////////////////////////////////////
 #include <SFML/Window/JoystickImpl.hpp>
+#include <SFML/System/Err.hpp>
+#include <sys/inotify.h>
 #include <sys/stat.h>
 #include <unistd.h>
 #include <errno.h>
 #include <cstdio>
 
 
+namespace
+{
+    int notifyFd = -1;
+    int inputFd = -1;
+    bool plugged[sf::Joystick::Count];
+
+    void updatePluggedList()
+    {
+        for (unsigned int i = 0; i < sf::Joystick::Count; ++i)
+        {
+            char name[32];
+            std::snprintf(name, sizeof(name), "/dev/input/js%u", i);
+            struct stat info;
+            plugged[i] = (stat(name, &info) == 0);
+        }
+    }
+
+    bool canRead(int descriptor)
+    {
+	    fd_set set;
+	    FD_ZERO(&set);
+	    FD_SET(descriptor, &set);
+        timeval timeout = {0, 0};
+        return select(descriptor + 1, &set, NULL, NULL, &timeout) > 0 &&
+               FD_ISSET(notifyFd, &set);
+    }
+}
+
+
 namespace sf
 {
 namespace priv
 {
+////////////////////////////////////////////////////////////
+void JoystickImpl::initialize()
+{
+    // Reset the array of plugged joysticks
+    std::fill(plugged, plugged + Joystick::Count, false);
+
+    // Create the inotify instance
+    notifyFd = inotify_init();
+    if (notifyFd < 0)
+    {
+        err() << "Failed to initialize inotify, joystick connections and disconnections won't be notified" << std::endl;
+        return;
+    }
+
+    // Watch nodes created and deleted in the /dev/input directory
+    inputFd = inotify_add_watch(notifyFd, "/dev/input", IN_CREATE | IN_DELETE);
+    if (inputFd < 0)
+    {
+        err() << "Failed to initialize inotify, joystick connections and disconnections won't be notified" << std::endl;
+        return;
+    }
+
+    // Do an initial scan
+    updatePluggedList();
+}
+
+
+////////////////////////////////////////////////////////////
+void JoystickImpl::cleanup()
+{
+    // Stop watching the /dev/input directory
+    if (inputFd >= 0)
+        inotify_rm_watch(notifyFd, inputFd);
+
+    // Close the inotify file descriptor
+    if (inputFd >= 0)
+        ::close(notifyFd);
+}
+
+
 ////////////////////////////////////////////////////////////
 bool JoystickImpl::isConnected(unsigned int index)
 {
-    char name[32];
+    // First check if new joysticks were added/removed since last update
-    std::sprintf(name, "/dev/input/js%u", index);
+    if (canRead(notifyFd))
+    {
+        // Don't bother decomposing and interpreting the filename, just do a full scan
+        updatePluggedList();
 
-    struct stat info; 
+        // Flush all the pending events
-    return stat(name, &info) == 0; 
+        while (canRead(notifyFd))
+        {
+            char buffer[128];
+            read(notifyFd, buffer, sizeof(buffer));
+        }
+	}
+
+    // Then check if the joystick is connected
+    return plugged[index];
 }
 
 
 ////////////////////////////////////////////////////////////
 bool JoystickImpl::open(unsigned int index)
 {
-    char name[32];
+    if (plugged[index])
-    std::sprintf(name, "/dev/input/js%u", index);
-
-    m_file = ::open(name, O_RDONLY);
-    if (m_file > 0)
     {
-        // Use non-blocking mode
+        char name[32];
-        fcntl(m_file, F_SETFL, O_NONBLOCK);
+        std::snprintf(name, sizeof(name), "/dev/input/js%u", index);
 
+        // Open the joystick's file descriptor (read-only and non-blocking)
+        m_file = ::open(name, O_RDONLY | O_NONBLOCK);
+        if (m_file >= 0)
+        {
             // Retrieve the axes mapping
             ioctl(m_file, JSIOCGAXMAP, m_mapping);
 
@@ -72,6 +154,11 @@ bool JoystickImpl::open(unsigned int index)
             return false;
         }
     }
+    else
+    {
+        return false;
+    }
+}
 
 
 ////////////////////////////////////////////////////////////

src/SFML/Window/Linux/JoystickImpl.hpp

@@ -49,6 +49,18 @@ class JoystickImpl
 {
 public :
 
+    ////////////////////////////////////////////////////////////
+    /// \brief Perform the global initialization of the joystick module
+    ///
+    ////////////////////////////////////////////////////////////
+    static void initialize();
+
+    ////////////////////////////////////////////////////////////
+    /// \brief Perform the global cleanup of the joystick module
+    ///
+    ////////////////////////////////////////////////////////////
+    static void cleanup();
+
     ////////////////////////////////////////////////////////////
     /// \brief Check if a joystick is currently connected
     ///

src/SFML/Window/OSX/JoystickImpl.cpp

@@ -30,15 +30,16 @@
 #include <SFML/Window/OSX/HIDInputManager.hpp>
 #include <SFML/Window/OSX/HIDJoystickManager.hpp>
 
-// Translation unit namespace
+
-namespace {
+namespace
-    ////////////////////////////////////////////////////////////
+{
     bool JoystickButtonSortPredicate(IOHIDElementRef b1, IOHIDElementRef b2)
     {
         return IOHIDElementGetUsage(b1) < IOHIDElementGetUsage(b2);
     }
 }
 
+
 namespace sf
 {
 namespace priv
@@ -47,6 +48,20 @@ namespace priv
 JoystickImpl::Location JoystickImpl::m_locationIDs[sf::Joystick::Count] = { 0 };
 
 
+////////////////////////////////////////////////////////////
+void JoystickImpl::initialize()
+{
+    // Nothing to do
+}
+
+
+////////////////////////////////////////////////////////////
+void JoystickImpl::cleanup()
+{
+    // Nothing to do
+}
+
+
 ////////////////////////////////////////////////////////////
 bool JoystickImpl::isConnected(unsigned int index)
 {

src/SFML/Window/OSX/JoystickImpl.hpp

@@ -46,6 +46,18 @@ class JoystickImpl
 {
 public :
 
+    ////////////////////////////////////////////////////////////
+    /// \brief Perform the global initialization of the joystick module
+    ///
+    ////////////////////////////////////////////////////////////
+    static void initialize();
+
+    ////////////////////////////////////////////////////////////
+    /// \brief Perform the global cleanup of the joystick module
+    ///
+    ////////////////////////////////////////////////////////////
+    static void cleanup();
+
     ////////////////////////////////////////////////////////////
     /// \brief Check if a joystick is currently connected
     ///

src/SFML/Window/Win32/JoystickImpl.cpp

@@ -35,10 +35,9 @@ namespace
 {
     struct ConnectionCache
     {
-        ConnectionCache() : connected(false), firstTime(true) {}
+        ConnectionCache() : connected(false) {}
         bool connected;
         sf::Clock timer;
-        bool firstTime;
     };
 
     const sf::Time connectionRefreshDelay = sf::milliseconds(500);
@@ -49,6 +48,33 @@ namespace sf
 {
 namespace priv
 {
+////////////////////////////////////////////////////////////
+void JoystickImpl::initialize()
+{
+    // Perform the initial scan and populate the connection cache
+    for (unsigned int i = 0; i < Joystick::Count; ++i)
+    {
+        ConnectionCache& cache = connectionCache[i];
+
+        // Check if the joystick is connected
+        JOYINFOEX joyInfo;
+        joyInfo.dwSize = sizeof(joyInfo);
+        joyInfo.dwFlags = 0;
+        cache.connected = joyGetPosEx(JOYSTICKID1 + i, &joyInfo) == JOYERR_NOERROR;
+
+        // start the timeout
+        cache.timer.restart();
+    }
+}
+
+
+////////////////////////////////////////////////////////////
+void JoystickImpl::cleanup()
+{
+    // Nothing to do
+}
+
+
 ////////////////////////////////////////////////////////////
 bool JoystickImpl::isConnected(unsigned int index)
 {
@@ -56,10 +82,9 @@ bool JoystickImpl::isConnected(unsigned int index)
     // because of a strange (buggy?) behaviour of joyGetPosEx when joysticks
     // are just plugged/unplugged -- it takes really long and kills the app performances
     ConnectionCache& cache = connectionCache[index];
-    if (cache.firstTime || (cache.timer.getElapsedTime() > connectionRefreshDelay))
+    if (cache.timer.getElapsedTime() > connectionRefreshDelay)
     {
         cache.timer.restart();
-        cache.firstTime = false;
 
         JOYINFOEX joyInfo;
         joyInfo.dwSize = sizeof(joyInfo);

src/SFML/Window/Win32/JoystickImpl.hpp

@@ -54,6 +54,18 @@ class JoystickImpl
 {
 public :
 
+    ////////////////////////////////////////////////////////////
+    /// \brief Perform the global initialization of the joystick module
+    ///
+    ////////////////////////////////////////////////////////////
+    static void initialize();
+
+    ////////////////////////////////////////////////////////////
+    /// \brief Perform the global cleanup of the joystick module
+    ///
+    ////////////////////////////////////////////////////////////
+    static void cleanup();
+
     ////////////////////////////////////////////////////////////
     /// \brief Check if a joystick is currently connected
     ///