evdev: switch to libevdev for fetching the events

libevdev is a library that wraps the evdev subsystem, with
the ability to synchronize the state after a SYN_DROPPED event
from the kernel.

https://bugzilla.gnome.org/show_bug.cgi?id=706494

README.in

@@ -38,6 +38,11 @@ When building the CEx100 backend, Clutter also depends on:
 
   • libgdl
 
+When building the evdev input backend, Clutter also depends on:
+
+  • xkbcommon
+  • libevdev
+
 If you are building the API reference you will also need:
 
   • GTK-Doc ≥ @GTK_DOC_REQ_VERSION@

clutter/evdev/clutter-device-manager-evdev.c

@@ -35,6 +35,7 @@
 
 #include <glib.h>
 #include <gudev/gudev.h>
+#include <libevdev/libevdev.h>
 
 #include "clutter-backend.h"
 #include "clutter-debug.h"
@@ -124,6 +125,7 @@ struct _ClutterEventSource
 
   ClutterInputDeviceEvdev *device;    /* back pointer to the slave evdev device */
   GPollFD event_poll_fd;              /* file descriptor of the /dev node */
+  struct libevdev *dev;
 };
 
 static gboolean
@@ -411,73 +413,23 @@ notify_button (ClutterEventSource *source,
   queue_event (event);
 }
 
-static gboolean
+static void
-clutter_event_dispatch (GSource     *g_source,
+dispatch_one_event (ClutterEventSource *source,
-                        GSourceFunc  callback,
+		    struct input_event *e,
-                        gpointer     user_data)
+		    int                *dx,
+		    int                *dy)
 {
-  ClutterEventSource *source = (ClutterEventSource *) g_source;
+  guint32 _time;
-  ClutterInputDevice *input_device = (ClutterInputDevice *) source->device;
-  struct input_event ev[8];
-  ClutterEvent *event;
-  gint len, i, dx = 0, dy = 0;
-  uint32_t _time;
-  ClutterStage *stage;
-
-  _clutter_threads_acquire_lock ();
-
-  stage = _clutter_input_device_get_stage (input_device);
-
-  /* Don't queue more events if we haven't finished handling the previous batch
-   */
-  if (!clutter_events_pending ())
-    {
-       len = read (source->event_poll_fd.fd, &ev, sizeof (ev));
-       if (len < 0 || len % sizeof (ev[0]) != 0)
-       {
-         if (errno != EAGAIN)
-           {
-             ClutterDeviceManager *manager;
-             ClutterInputDevice *device;
-             const gchar *device_path;
-
-             device = CLUTTER_INPUT_DEVICE (source->device);
-
-             if (CLUTTER_HAS_DEBUG (EVENT))
-               {
-                 device_path =
-                   _clutter_input_device_evdev_get_device_path (source->device);
-
-                 CLUTTER_NOTE (EVENT, "Could not read device (%s), removing.",
-                               device_path);
-               }
-
-             /* remove the faulty device */
-             manager = clutter_device_manager_get_default ();
-             _clutter_device_manager_remove_device (manager, device);
-
-           }
-         goto out;
-       }
-
-       /* Drop events if we don't have any stage to forward them to */
-       if (!stage)
-         goto out;
-
-       for (i = 0; i < len / sizeof (ev[0]); i++)
-         {
-           struct input_event *e = &ev[i];
 
   _time = e->time.tv_sec * 1000 + e->time.tv_usec / 1000;
 
   switch (e->type)
     {
     case EV_KEY:
-
       /* don't repeat mouse buttons */
       if (e->code >= BTN_MOUSE && e->code < KEY_OK)
 	if (e->value == AUTOREPEAT_VALUE)
-                   continue;
+	  return;
 
       switch (e->code)
 	{
@@ -510,11 +462,11 @@ clutter_event_dispatch (GSource     *g_source,
       break;
 
     case EV_SYN:
-               /* Nothing to do here? */
+      /* Nothing to do here */
       break;
 
     case EV_MSC:
-               /* Nothing to do here? */
+      /* Nothing to do here */
       break;
 
     case EV_REL:
@@ -522,10 +474,10 @@ clutter_event_dispatch (GSource     *g_source,
       switch (e->code)
 	{
 	case REL_X:
-                   dx += e->value;
+	  *dx += e->value;
 	  break;
 	case REL_Y:
-                   dy += e->value;
+	  *dy += e->value;
 	  break;
 
 	  /* Note: we assume that REL_WHEEL is for *vertical* scroll wheels.
@@ -543,11 +495,108 @@ clutter_event_dispatch (GSource     *g_source,
       g_warning ("Unhandled event of type %d", e->type);
       break;
     }
+}
+
+static void
+sync_source (ClutterEventSource *source)
+{
+  struct input_event ev;
+  int err;
+  int dx = 0, dy = 0;
+  const gchar *device_path;
+
+  /* We read a SYN_DROPPED, ignore it and sync the device */
+  err = libevdev_next_event (source->dev, LIBEVDEV_READ_SYNC, &ev);
+  while (err == 1)
+    {
+      dispatch_one_event (source, &ev, &dx, &dy);
+      err = libevdev_next_event (source->dev, LIBEVDEV_READ_SYNC, &ev);
+    }
+
+  if (err != -EAGAIN && CLUTTER_HAS_DEBUG (EVENT))
+    {
+      device_path = _clutter_input_device_evdev_get_device_path (source->device);
+
+      CLUTTER_NOTE (EVENT, "Could not sync device (%s).", device_path);
     }
 
   if (dx != 0 || dy != 0)
+    {
+      guint32 _time = ev.time.tv_sec * 1000 + ev.time.tv_usec / 1000;
       notify_relative_motion (source, _time, dx, dy);
     }
+}
+
+static void
+fail_source (ClutterEventSource *source,
+	     int                 error)
+{
+  ClutterDeviceManager *manager;
+  ClutterInputDevice *device;
+  const gchar *device_path;
+
+  device = CLUTTER_INPUT_DEVICE (source->device);
+
+  if (CLUTTER_HAS_DEBUG (EVENT))
+    {
+      device_path = _clutter_input_device_evdev_get_device_path (source->device);
+
+      CLUTTER_NOTE (EVENT, "Could not read device (%s): %s. Removing.",
+		    device_path, strerror (error));
+    }
+
+  /* remove the faulty device */
+  manager = clutter_device_manager_get_default ();
+  _clutter_device_manager_remove_device (manager, device);
+}
+
+static gboolean
+clutter_event_dispatch (GSource     *g_source,
+                        GSourceFunc  callback,
+                        gpointer     user_data)
+{
+  ClutterEventSource *source = (ClutterEventSource *) g_source;
+  ClutterInputDevice *input_device = (ClutterInputDevice *) source->device;
+  struct input_event ev;
+  ClutterEvent *event;
+  ClutterStage *stage;
+  int err, dx = 0, dy = 0;
+
+  _clutter_threads_acquire_lock ();
+
+  stage = _clutter_input_device_get_stage (input_device);
+
+  /* Don't queue more events if we haven't finished handling the previous batch
+   */
+  if (clutter_events_pending ())
+    goto queue_event;
+
+  err = libevdev_next_event (source->dev, LIBEVDEV_READ_NORMAL, &ev);
+  while (err != -EAGAIN)
+    {
+      if (err == 1)
+	sync_source (source);
+      else if (err == 0)
+	dispatch_one_event (source, &ev, &dx, &dy);
+      else
+	{
+	  fail_source (source, -err);
+	  goto out;
+	}
+
+      err = libevdev_next_event (source->dev, LIBEVDEV_READ_NORMAL, &ev);
+    }
+
+  if (dx != 0 || dy != 0)
+    {
+      guint32 _time = ev.time.tv_sec * 1000 + ev.time.tv_usec / 1000;
+      notify_relative_motion (source, _time, dx, dy);
+    }
+
+ queue_event:
+  /* Drop events if we don't have any stage to forward them to */
+  if (stage == NULL)
+    goto out;
 
   /* Pop an event off the queue if any */
   event = clutter_event_get ();
@@ -619,14 +668,15 @@ clutter_event_source_new (ClutterInputDeviceEvdev *input_device)
 	}
     }
 
+  /* Tell evdev to use the monotonic clock for its timestamps */
+  clkid = CLOCK_MONOTONIC;
+  ioctl (fd, EVIOCSCLOCKID, &clkid);
+
   /* setup the source */
   event_source->device = input_device;
   event_source->event_poll_fd.fd = fd;
   event_source->event_poll_fd.events = G_IO_IN;
-
+  libevdev_new_from_fd (fd, &event_source->dev);
-  /* Tell evdev to use the monotonic clock for its timestamps */
-  clkid = CLOCK_MONOTONIC;
-  ioctl (fd, EVIOCSCLOCKID, &clkid);
 
   /* and finally configure and attach the GSource */
   g_source_set_priority (source, CLUTTER_PRIORITY_EVENTS);
@@ -650,6 +700,7 @@ clutter_event_source_free (ClutterEventSource *source)
   /* ignore the return value of close, it's not like we can do something
    * about it */
   close (source->event_poll_fd.fd);
+  libevdev_free (source->dev);
 
   g_source_destroy (g_source);
   g_source_unref (g_source);

configure.ac

@@ -480,7 +480,7 @@ AS_IF([test "x$enable_evdev" = "xyes"],
         AS_IF([test "x$have_evdev" = "xyes"],
               [
                 CLUTTER_INPUT_BACKENDS="$CLUTTER_INPUT_BACKENDS evdev"
-                BACKEND_PC_FILES="$BACKEND_PC_FILES gudev-1.0 xkbcommon"
+                BACKEND_PC_FILES="$BACKEND_PC_FILES gudev-1.0 libevdev xkbcommon"
                 experimental_input_backend="yes"
                 AC_DEFINE([HAVE_EVDEV], [1], [Have evdev support for input handling])
                 SUPPORT_EVDEV=1