progresstracker: add GTK_SLOWDOWN environment variable

As we consolidate widgets to use progress tracker, this will allow
us to control the speed of all animations in a centralized place

1 files changed, 19 insertions, 1 deletions

diff --git a/gtk/gtkprogresstracker.c b/gtk/gtkprogresstracker.c
index 277fd9a9de..c1d3f44215 100644
--- a/gtk/gtkprogresstracker.c
+++ b/gtk/gtkprogresstracker.c
@@ -18,6 +18,7 @@
  */
 
 #include "gtkprogresstrackerprivate.h"
+#include "gtkprivate.h"
 #include "gtkcsseasevalueprivate.h"
 
 #include <math.h>
@@ -30,8 +31,25 @@
  *
  * Progress tracker will handle translating frame clock timestamps to a
  * fractional progress value for interpolating between animation targets.
+ *
+ * Progress tracker will use the GTK_SLOWDOWN environment variable to control
+ * the speed of animations. This can be useful for debugging.
  */
 
+static gdouble gtk_slowdown = 1.0;
+
+void
+_gtk_set_slowdown (gdouble factor)
+{
+  gtk_slowdown = factor;
+}
+
+gdouble
+_gtk_get_slowdown (gdouble factor)
+{
+  return gtk_slowdown;
+}
+
 /**
  * gtk_progress_tracker_init_copy:
  * @source: The source progress tracker
@@ -109,7 +127,7 @@ gtk_progress_tracker_advance_frame (GtkProgressTracker *tracker,
       return;
     }
 
-  delta = (frame_time - tracker->last_frame_time) / (gdouble) tracker->duration;
+  delta = (frame_time - tracker->last_frame_time) / gtk_slowdown / tracker->duration;
   tracker->last_frame_time = frame_time;
   tracker->iteration += delta;
 }