[gnome-builder/wip/plugins] animation: update animation values during GdkFrameClock::after-paint

[Christian Hergert <chergert src gnome org>]

commit 7019f1e06231874348244d2a03c3af40a0b92f7f
Author: Christian Hergert <christian hergert me>
Date:   Wed Jun 10 17:01:10 2015 -0700

    animation: update animation values during GdkFrameClock::after-paint
    
    This gives us the most amount of time to be able to draw the next frame
    during animated sequences. Upon the "update" signal, if we get the same
    offset as what we projected, we can avoid the secondary update.

 libide/theatrics/ide-animation.c |   96 ++++++++++++++++++++++++++++---------
 1 files changed, 72 insertions(+), 24 deletions(-)
---
diff --git a/libide/theatrics/ide-animation.c b/libide/theatrics/ide-animation.c
index fd76bad..3e44557 100644
--- a/libide/theatrics/ide-animation.c
+++ b/libide/theatrics/ide-animation.c
@@ -18,6 +18,7 @@
 
 #include <glib/gi18n.h>
 #include <gobject/gvaluecollector.h>
+#include <gdk/gdk.h>
 #include <gtk/gtk.h>
 #include <string.h>
 
@@ -45,13 +46,15 @@ struct _IdeAnimation
 {
   GInitiallyUnowned  parent_instance;
 
-  gpointer           target;         /* Target object to animate */
-  guint64            begin_msec;     /* Time in which animation started */
-  guint              duration_msec;  /* Duration of animation */
-  guint              mode;           /* Tween mode */
-  guint              tween_handler;  /* GSource performing tweens */
-  GArray            *tweens;         /* Array of tweens to perform */
-  GdkFrameClock     *frame_clock;     /* An optional frame-clock for sync. */
+  gpointer           target;              /* Target object to animate */
+  guint64            begin_msec;          /* Time in which animation started */
+  guint              duration_msec;       /* Duration of animation */
+  guint              mode;                /* Tween mode */
+  gulong             tween_handler;       /* GSource or signal handler */
+  gulong             after_paint_handler; /* signal handler */
+  gdouble            last_offset;         /* Track our last offset */
+  GArray            *tweens;              /* Array of tweens to perform */
+  GdkFrameClock     *frame_clock;         /* An optional frame-clock for sync. */
 };
 
 G_DEFINE_TYPE (IdeAnimation, ide_animation, G_TYPE_INITIALLY_UNOWNED)
@@ -279,29 +282,33 @@ ide_animation_unload_begin_values (IdeAnimation *animation)
 
 /**
  * ide_animation_get_offset:
- * @animation: (in): A #IdeAnimation.
+ * @animation: A #IdeAnimation.
+ * @frame_time: the time to present the frame, or 0 for current timing.
  *
  * Retrieves the position within the animation from 0.0 to 1.0. This
  * value is calculated using the msec of the beginning of the animation
  * and the current time.
  *
  * Returns: The offset of the animation from 0.0 to 1.0.
- * Side effects: None.
  */
 static gdouble
-ide_animation_get_offset (IdeAnimation *animation)
+ide_animation_get_offset (IdeAnimation *animation,
+                          gint64        frame_time)
 {
-  GdkFrameClock *frame_clock;
   gdouble offset;
   gint64 frame_msec;
 
   g_return_val_if_fail (IDE_IS_ANIMATION (animation), 0.0);
 
-  if (GTK_IS_WIDGET (animation->target) &&
-      (frame_clock = gtk_widget_get_frame_clock (animation->target)))
-    frame_msec = gdk_frame_clock_get_frame_time (frame_clock) / 1000UL;
-  else
-    frame_msec = g_get_monotonic_time () / 1000UL;
+  if (frame_time == 0)
+    {
+      if (animation->frame_clock != NULL)
+        frame_time = gdk_frame_clock_get_frame_time (animation->frame_clock);
+      else
+        frame_time = g_get_monotonic_time ();
+    }
+
+  frame_msec = frame_time / 1000L;
 
   offset = (gdouble) (frame_msec - animation->begin_msec) /
            (gdouble) animation->duration_msec;
@@ -447,9 +454,9 @@ ide_animation_set_target (IdeAnimation *animation,
  * Side effects: None.
  */
 static gboolean
-ide_animation_tick (IdeAnimation *animation)
+ide_animation_tick (IdeAnimation *animation,
+                    gdouble       offset)
 {
-  gdouble offset;
   gdouble alpha;
   GValue value = { 0 };
   Tween *tween;
@@ -457,7 +464,9 @@ ide_animation_tick (IdeAnimation *animation)
 
   g_return_val_if_fail (IDE_IS_ANIMATION (animation), FALSE);
 
-  offset = ide_animation_get_offset (animation);
+  if (offset == animation->last_offset)
+    return offset < 1.0;
+
   alpha = gAlphaFuncs[animation->mode](offset);
 
   /*
@@ -503,6 +512,8 @@ ide_animation_tick (IdeAnimation *animation)
     }
 #endif
 
+  animation->last_offset = offset;
+
   return offset < 1.0;
 }
 
@@ -521,8 +532,11 @@ ide_animation_timeout_cb (gpointer user_data)
 {
   IdeAnimation *animation = user_data;
   gboolean ret;
+  gdouble offset;
+
+  offset = ide_animation_get_offset (animation, 0);
 
-  if (!(ret = ide_animation_tick (animation)))
+  if (!(ret = ide_animation_tick (animation, offset)))
     ide_animation_stop (animation);
 
   return ret;
@@ -539,13 +553,40 @@ ide_animation_widget_tick_cb (GdkFrameClock *frame_clock,
   g_assert (IDE_IS_ANIMATION (animation));
 
   if (animation->tween_handler)
-    if (!(ret = ide_animation_tick (animation)))
-      ide_animation_stop (animation);
+    {
+      gdouble offset;
+
+      offset = ide_animation_get_offset (animation, 0);
+
+      if (!(ret = ide_animation_tick (animation, offset)))
+        ide_animation_stop (animation);
+    }
 
   return ret;
 }
 
 
+static void
+ide_animation_widget_after_paint_cb (GdkFrameClock *frame_clock,
+                                     IdeAnimation  *animation)
+{
+  gint64 base_time;
+  gint64 interval;
+  gint64 next_frame_time;
+  gdouble offset;
+
+  g_assert (GDK_IS_FRAME_CLOCK (frame_clock));
+  g_assert (IDE_IS_ANIMATION (animation));
+
+  base_time = gdk_frame_clock_get_frame_time (frame_clock);
+  gdk_frame_clock_get_refresh_info (frame_clock, base_time, &interval, &next_frame_time);
+
+  offset = ide_animation_get_offset (animation, next_frame_time);
+
+  ide_animation_tick (animation, offset);
+}
+
+
 /**
  * ide_animation_start:
  * @animation: (in): A #IdeAnimation.
@@ -573,14 +614,19 @@ ide_animation_start (IdeAnimation *animation)
                           "update",
                           G_CALLBACK (ide_animation_widget_tick_cb),
                           animation);
+      animation->after_paint_handler =
+        g_signal_connect (animation->frame_clock,
+                          "after-paint",
+                          G_CALLBACK (ide_animation_widget_after_paint_cb),
+                          animation);
       gdk_frame_clock_begin_updating (animation->frame_clock);
     }
   else
     {
       animation->begin_msec = g_get_monotonic_time () / 1000UL;
       animation->tween_handler = ide_frame_source_add (FALLBACK_FRAME_RATE,
-                                                 ide_animation_timeout_cb,
-                                                 animation);
+                                                       ide_animation_timeout_cb,
+                                                       animation);
     }
 }
 
@@ -606,6 +652,7 @@ ide_animation_stop (IdeAnimation *animation)
         {
           gdk_frame_clock_end_updating (animation->frame_clock);
           g_signal_handler_disconnect (animation->frame_clock, animation->tween_handler);
+          g_signal_handler_disconnect (animation->frame_clock, animation->after_paint_handler);
           animation->tween_handler = 0;
         }
       else
@@ -892,6 +939,7 @@ ide_animation_init (IdeAnimation *animation)
   animation->duration_msec = 250;
   animation->mode = IDE_ANIMATION_EASE_IN_OUT_QUAD;
   animation->tweens = g_array_new (FALSE, FALSE, sizeof (Tween));
+  animation->last_offset = -G_MINDOUBLE;
 }