From 23b2b49321c1b757ba8a9cd77ad121ce789bd8ea Mon Sep 17 00:00:00 2001
From: Matthias Clasen <mclasen@redhat.com>
Date: Mon, 7 Dec 2015 18:28:06 -0500
Subject: [PATCH] x11: Implement drag cancel animation

Showing the drag cancel animation can be done in the X11
drag context implementation now that we hold the drag
window there, and have the start coordinates.

Since we can't control if and when the application destroys
the drag widget, we take a snapshot of the window contents
and display that during the animation. This should be good
enough for all practical purposes.
---
 gdk/x11/gdkdnd-x11.c | 94 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 94 insertions(+)

diff --git a/gdk/x11/gdkdnd-x11.c b/gdk/x11/gdkdnd-x11.c
index 79244769a4..d634cf6a37 100644
--- a/gdk/x11/gdkdnd-x11.c
+++ b/gdk/x11/gdkdnd-x11.c
@@ -193,6 +193,8 @@ static GdkWindow * gdk_x11_drag_context_get_drag_window (GdkDragContext *context
 static void        gdk_x11_drag_context_set_hotspot (GdkDragContext  *context,
                                                      gint             hot_x,
                                                      gint             hot_y);
+static void        gdk_x11_drag_context_drop_done     (GdkDragContext  *context,
+                                                       gboolean         success);
 
 static void
 gdk_x11_drag_context_class_init (GdkX11DragContextClass *klass)
@@ -213,6 +215,7 @@ gdk_x11_drag_context_class_init (GdkX11DragContextClass *klass)
   context_class->get_selection = gdk_x11_drag_context_get_selection;
   context_class->get_drag_window = gdk_x11_drag_context_get_drag_window;
   context_class->set_hotspot = gdk_x11_drag_context_set_hotspot;
+  context_class->drop_done = gdk_x11_drag_context_drop_done;
 }
 
 static void
@@ -2486,3 +2489,94 @@ gdk_x11_drag_context_set_hotspot (GdkDragContext *context,
   x11_context->hot_x = hot_x;
   x11_context->hot_y = hot_y;
 }
+
+static double
+ease_out_cubic (double t)
+{
+  double p = t - 1;
+  return p * p * p + 1;
+}
+
+
+#define ANIM_TIME 500000 /* half a second */
+
+typedef struct _GdkDragAnim GdkDragAnim;
+struct _GdkDragAnim {
+  GdkX11DragContext *context;
+  GdkFrameClock *frame_clock;
+  gint64 start_time;
+};
+
+static void
+gdk_drag_anim_destroy (GdkDragAnim *anim)
+{
+  g_object_unref (anim->context);
+  g_slice_free (GdkDragAnim, anim);
+}
+
+static gboolean
+gdk_drag_anim_timeout (gpointer data)
+{
+  GdkDragAnim *anim = data;
+  GdkX11DragContext *context = anim->context;
+  GdkFrameClock *frame_clock = anim->frame_clock;
+  gint64 current_time;
+  double f;
+  double t;
+
+  if (!frame_clock)
+    return G_SOURCE_REMOVE;
+
+  current_time = gdk_frame_clock_get_frame_time (frame_clock);
+
+  f = (current_time - anim->start_time) / (double) ANIM_TIME;
+
+  if (f >= 1.0)
+    return G_SOURCE_REMOVE;
+
+  t = ease_out_cubic (f);
+
+  gdk_window_show (context->drag_window);
+  gdk_window_move (context->drag_window,
+                   context->last_x + (context->start_x - context->last_x) * t,
+                   context->last_y + (context->start_y - context->last_y) * t);
+  gdk_window_set_opacity (context->drag_window, 1.0 - f);
+
+  return G_SOURCE_CONTINUE;
+}
+
+static void
+gdk_x11_drag_context_drop_done (GdkDragContext *context,
+                                gboolean        success)
+{
+  GdkX11DragContext *x11_context = GDK_X11_DRAG_CONTEXT (context);
+  GdkDragAnim *anim;
+  GdkPixbuf *pixbuf;
+  cairo_surface_t *surface;
+  cairo_pattern_t *pattern;
+
+  if (success)
+    return;
+
+  pixbuf = gdk_pixbuf_get_from_window (x11_context->drag_window,
+                                       0, 0,
+                                       gdk_window_get_width (x11_context->drag_window),
+                                       gdk_window_get_height (x11_context->drag_window));
+  surface = gdk_cairo_surface_create_from_pixbuf (pixbuf, 0, x11_context->drag_window);
+  pattern = cairo_pattern_create_for_surface (surface);
+
+  gdk_window_set_background_pattern (x11_context->drag_window, pattern);
+
+  cairo_pattern_destroy (pattern);
+  cairo_surface_destroy (surface);
+  g_object_unref (pixbuf);
+
+  anim = g_slice_new0 (GdkDragAnim);
+  anim->context = g_object_ref (x11_context);
+  anim->frame_clock = gdk_window_get_frame_clock (x11_context->drag_window);
+  anim->start_time = gdk_frame_clock_get_frame_time (anim->frame_clock);
+
+  gdk_threads_add_timeout_full (G_PRIORITY_DEFAULT, 17,
+                                gdk_drag_anim_timeout, anim,
+                                (GDestroyNotify) gdk_drag_anim_destroy);
+}