refs #401 Implementation of IJoystick for Linux

Basically, the implementation uses the API described in the kernel
documentation. It listens for new events that come from the device.
It also supports joystick hotplugging.

* https://www.kernel.org/doc/Documentation/input/joystick-api.txt

src/blackinput/linux/joystick_linux.cpp

@@ -7,29 +7,135 @@
  * contained in the LICENSE file.
  */
 
+#include "blackmisc/logmessage.h"
 #include "joystick_linux.h"
+#include <QFile>
+#include <QFileSystemWatcher>
+#include <QSocketNotifier>
+#include <QSignalMapper>
+#include <linux/joystick.h>
+#include <unistd.h>
+#include <fcntl.h>
 
+using namespace BlackMisc;
 using namespace BlackMisc::Hardware;
 
+namespace
+{
+    inline QString inputDevicesDir()
+    {
+        return QStringLiteral("/dev/input/");
+    }
+}
+
 namespace BlackInput
 {
     CJoystickLinux::CJoystickLinux(QObject *parent) :
-        IJoystick(parent)
+        IJoystick(parent),
+        m_mapper(new QSignalMapper(this)),
+        m_inputWatcher(new QFileSystemWatcher(this))
     {
-    }
+        connect(m_mapper, static_cast<void (QSignalMapper::*)(QObject *)>(&QSignalMapper::mapped), this, &CJoystickLinux::ps_readInput);
 
-    CJoystickLinux::~CJoystickLinux()
-    {
+        m_inputWatcher->addPath(inputDevicesDir());
+        connect(m_inputWatcher, &QFileSystemWatcher::directoryChanged, this, &CJoystickLinux::ps_directoryChanged);
+        ps_directoryChanged(inputDevicesDir());
     }
 
     void CJoystickLinux::startCapture()
     {
+
     }
 
     void CJoystickLinux::triggerButton(const CJoystickButton button, bool isPressed)
     {
-        if(!isPressed) emit buttonUp(button);
+        if (!isPressed) emit buttonUp(button);
         else emit buttonDown(button);
     }
 
+    void CJoystickLinux::cleanupJoysticks()
+    {
+        for (auto it = m_joysticks.begin(); it != m_joysticks.end();)
+        {
+            if (!it.value()->exists())
+            {
+                it.value()->deleteLater();
+                it = m_joysticks.erase(it);
+            }
+            else
+            {
+                ++it;
+            }
+        }
+    }
+
+    void CJoystickLinux::addJoystickDevice(const QString &path)
+    {
+        Q_ASSERT(!m_joysticks.contains(path));
+
+        QFile *joystick = new QFile(path, this);
+        if (joystick->open(QIODevice::ReadOnly))
+        {
+            char name[256];
+            if (ioctl(joystick->handle(), JSIOCGNAME(sizeof(name)), name) < 0)
+            {
+                strncpy(name, "Unknown", sizeof(name));
+            }
+
+            CLogMessage(this).info("Found joystick: %1") << name;
+
+            fcntl(joystick->handle(), F_SETFL, O_NONBLOCK);
+
+            /* Forward */
+            struct js_event event;
+            while (joystick->read(reinterpret_cast<char *>(&event), sizeof(event)) == sizeof(event)) {}
+
+            QSocketNotifier *notifier = new QSocketNotifier(joystick->handle(), QSocketNotifier::Read, joystick);
+            m_mapper->setMapping(notifier, joystick);
+            connect(notifier, &QSocketNotifier::activated, m_mapper, static_cast<void (QSignalMapper::*)()>(&QSignalMapper::map));
+            notifier->setEnabled(true);
+
+            m_joysticks.insert(path, joystick);
+        }
+        else
+        {
+            joystick->deleteLater();
+        }
+    }
+
+    void CJoystickLinux::ps_directoryChanged(QString path)
+    {
+        cleanupJoysticks();
+
+        QDir dir(path, QLatin1String("js*"), 0, QDir::System);
+        for (const auto &entry : dir.entryInfoList())
+        {
+            QString f = entry.absoluteFilePath();
+            if (!m_joysticks.contains(f))
+            {
+                addJoystickDevice(f);
+            }
+        }
+    }
+
+    void CJoystickLinux::ps_readInput(QObject *object)
+    {
+        QFile *joystick = qobject_cast<QFile *>(object);
+        Q_ASSERT(joystick);
+
+        struct js_event event;
+        while (joystick->read(reinterpret_cast<char *>(&event), sizeof(event)) == sizeof(event))
+        {
+            switch (event.type & ~JS_EVENT_INIT)
+            {
+            case JS_EVENT_BUTTON:
+                if (event.value)
+                    emit buttonDown(CJoystickButton(event.number));
+                else
+                    emit buttonUp(CJoystickButton(event.number));
+
+                break;
+            }
+        }
+    }
 } // namespace BlackInput