1 files changed, 130 insertions, 0 deletions
diff --git a/src/animation/egg-frame-source.c b/src/animation/egg-frame-source.c
new file mode 100644
index 0000000..5672a05
--- /dev/null
+++ b/src/animation/egg-frame-source.c
@@ -0,0 +1,130 @@
+/* egg-frame-source.c
+ *
+ * Copyright (C) 2010-2016 Christian Hergert <christian@hergert.me>
+ *
+ * This file is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU Lesser General Public License as published by the Free
+ * Software Foundation; either version 2.1 of the License, or (at your option)
+ * any later version.
+ *
+ * This file is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
+ * License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "animation/egg-frame-source.h"
+
+typedef struct
+{
+   GSource parent;
+   guint   fps;
+   guint   frame_count;
+   gint64  start_time;
+} EggFrameSource;
+
+static gboolean
+egg_frame_source_prepare (GSource *source,
+                          gint    *timeout_)
+{
+   EggFrameSource *fsource = (EggFrameSource *)(gpointer)source;
+   gint64 current_time;
+   guint elapsed_time;
+   guint new_frame_num;
+   guint frame_time;
+
+   current_time = g_source_get_time(source) / 1000;
+   elapsed_time = current_time - fsource->start_time;
+   new_frame_num = elapsed_time * fsource->fps / 1000;
+
+   /* If time has gone backwards or the time since the last frame is
+    * greater than the two frames worth then reset the time and do a
+    * frame now */
+   if (new_frame_num < fsource->frame_count ||
+       new_frame_num - fsource->frame_count > 2) {
+      /* Get the frame time rounded up to the nearest ms */
+      frame_time = (1000 + fsource->fps - 1) / fsource->fps;
+
+      /* Reset the start time */
+      fsource->start_time = current_time;
+
+      /* Move the start time as if one whole frame has elapsed */
+      fsource->start_time -= frame_time;
+      fsource->frame_count = 0;
+      *timeout_ = 0;
+      return TRUE;
+   } else if (new_frame_num > fsource->frame_count) {
+      *timeout_ = 0;
+      return TRUE;
+   } else {
+      *timeout_ = (fsource->frame_count + 1) * 1000 / fsource->fps - elapsed_time;
+      return FALSE;
+   }
+}
+
+static gboolean
+egg_frame_source_check (GSource *source)
+{
+   gint timeout_;
+   return egg_frame_source_prepare(source, &timeout_);
+}
+
+static gboolean
+egg_frame_source_dispatch (GSource     *source,
+                           GSourceFunc  source_func,
+                           gpointer     user_data)
+{
+   EggFrameSource *fsource = (EggFrameSource *)(gpointer)source;
+   gboolean ret;
+
+   if ((ret = source_func(user_data)))
+      fsource->frame_count++;
+   return ret;
+}
+
+static GSourceFuncs source_funcs = {
+   egg_frame_source_prepare,
+   egg_frame_source_check,
+   egg_frame_source_dispatch,
+};
+
+/**
+ * egg_frame_source_add:
+ * @frames_per_sec: (in): Target frames per second.
+ * @callback: (in) (scope notified): A #GSourceFunc to execute.
+ * @user_data: (in): User data for @callback.
+ *
+ * Creates a new frame source that will execute when the timeout interval
+ * for the source has elapsed. The timing will try to synchronize based
+ * on the end time of the animation.
+ *
+ * Returns: A source id that can be removed with g_source_remove().
+ */
+guint
+egg_frame_source_add (guint       frames_per_sec,
+                      GSourceFunc callback,
+                      gpointer    user_data)
+{
+   EggFrameSource *fsource;
+   GSource *source;
+   guint ret;
+
+   g_return_val_if_fail (frames_per_sec > 0, 0);
+   g_return_val_if_fail (frames_per_sec <= 120, 0);
+
+   source = g_source_new(&source_funcs, sizeof(EggFrameSource));
+   fsource = (EggFrameSource *)(gpointer)source;
+   fsource->fps = frames_per_sec;
+   fsource->frame_count = 0;
+   fsource->start_time = g_get_monotonic_time() / 1000;
+   g_source_set_callback(source, callback, user_data, NULL);
+   g_source_set_name(source, "EggFrameSource");
+
+   ret = g_source_attach(source, NULL);
+   g_source_unref(source);
+
+   return ret;
+}