kinetic-scroll-view: Use gint64 for timestamps rather than GTimeVal

GTimeVal is a pain to use, microsecond precision is not necessary for
tracking motion events (millisecond precision is fine), and the use of
glong means the potential for overflow when summing several timestamps
on 32-bit platforms is quite high. Instead, use gint64 and
g_get_real_time().

clutter-project#98

Author: Philip Withnall

mx/mx-kinetic-scroll-view.c

@@ -66,7 +66,7 @@ typedef struct {
   /* Units to store the origin of a click when scrolling */
   gfloat   x;
   gfloat   y;
-  GTimeVal time;
+  gint64   time;  /* use g_get_real_time() for this */
 } MxKineticScrollViewMotion;
 
 typedef enum {
@@ -758,12 +758,12 @@ add_motion_event (MxKineticScrollView  *scroll,
                   gfloat                y)
 {
   MxKineticScrollViewPrivate *priv = scroll->priv;
-  GTimeVal tv;
+  gint64 tv;
 
   LOG_DEBUG (scroll, "%s: x = %f, y = %f, n_motions = %u",
              G_STRFUNC, x, y, priv->n_motions);
 
-  g_get_current_time (&tv);
+  tv = g_get_real_time ();
 
   if (priv->n_motions == 0)
     {
@@ -786,8 +786,7 @@ add_motion_event (MxKineticScrollView  *scroll,
 
       priv->motion_total.x += x;
       priv->motion_total.y += y;
-      priv->motion_total.time.tv_sec += tv.tv_sec;
-      priv->motion_total.time.tv_usec += tv.tv_usec;
+      priv->motion_total.time += tv;
 
       /* Avoid overflow by only taking this branch if n_motions will not
        * overflow. Subsequent motions are ignored. */
@@ -1359,37 +1358,28 @@ release_event (MxKineticScrollView *scroll,
           gdouble value, lower, upper, step_increment, page_size,
                   d, ax, ay, y, nx, ny, n;
           gfloat frac, x_origin, y_origin;
-          GTimeVal release_time, motion_time;
+          gint64 release_time, motion_time;  /* real microseconds */
           MxAdjustment *hadjust, *vadjust;
-          glong time_diff;
+          gint64 time_diff;  /* real microseconds */
           guint duration;
 
           /* Get time delta */
-          g_get_current_time (&release_time);
+          release_time = g_get_real_time ();
 
           /* Get average position/time of last x mouse events */
           x_origin = y_origin = 0;
-          motion_time = (GTimeVal){ 0, 0 };
+          motion_time = 0;
 
           g_assert (priv->n_motions > 0);
 
           x_origin = priv->motion_total.x / priv->n_motions;
           y_origin = priv->motion_total.y / priv->n_motions;
-          motion_time.tv_sec = priv->motion_total.time.tv_sec / priv->n_motions;
-          motion_time.tv_usec = priv->motion_total.time.tv_usec / priv->n_motions;
+          motion_time = priv->motion_total.time / priv->n_motions;
 
-          /* Normalise the GTimeVal. */
-          motion_time.tv_sec += motion_time.tv_usec / G_USEC_PER_SEC;
-          motion_time.tv_usec %= G_USEC_PER_SEC;
-
-          if (motion_time.tv_sec == release_time.tv_sec)
-            time_diff = release_time.tv_usec - motion_time.tv_usec;
-          else
-            time_diff = release_time.tv_usec +
-                        (G_USEC_PER_SEC - motion_time.tv_usec);
+          time_diff = release_time - motion_time;
 
           /* Work out the fraction of 1/60th of a second that has elapsed */
-          frac = (time_diff/1000.0) / (1000.0/60.0);
+          frac = (time_diff / 1000.0) / (1000.0 / 60.0);
 
           /* See how many units to move in 1/60th of a second */
           priv->dx = (x_origin - event_x) / frac * priv->acceleration_factor;
@@ -1421,7 +1411,7 @@ release_event (MxKineticScrollView *scroll,
           LOG_DEBUG (scroll, "%s: checking duration: x_pos = %i, y_pos = %i, "
                      "event_x = %f, event_y = %f, y = %f, nx = %f, ny = %f, "
                      "n = %f, frac = %f, x_origin = %f, y_origin = %f, "
-                     "time_diff = %lu, duration = %u, "
+                     "time_diff = %" G_GINT64_FORMAT ", duration = %u, "
                      "priv->n_motions = %u, priv->dx = %f, "
                      "priv->dy = %f, priv->decel_rate = %f, "
                      "priv->overshoot = %f, priv->accumulated_delta = %f, "
@@ -1538,7 +1528,7 @@ release_event (MxKineticScrollView *scroll,
                          "upper = %f, step_increment = %f, page_size = %f, "
                          "d = %f, ax = %f, ay = %f, y = %f, nx = %f, ny = %f, "
                          "n = %f, frac = %f, x_origin = %f, y_origin = %f, "
-                         "time_diff = %lu, duration = %u, "
+                         "time_diff = %" G_GINT64_FORMAT ", duration = %u, "
                          "priv->n_motions = %u, priv->dx = %f, "
                          "priv->dy = %f, priv->decel_rate = %f, "
                          "priv->overshoot = %f, priv->accumulated_delta = %f, "