[libhandy/wip/exalm/leaflet-transltions: 16/25] stackable-box: Rewrite transitions

[Alexander Mikhaylenko <alexm src gnome org>]

commit 3952cdb0348173f2c7f62f86e06bbf33e02cd674
Author: Alexander Mikhaylenko <alexm gnome org>
Date:   Wed May 27 20:37:23 2020 +0500

    stackable-box: Rewrite transitions
    
    Since the very beginning, HdyLeaflet and HdyDeck child transitions, as well
    as mode transitions when transitioning from unfolded to folded mode, only
    showed one "real" widget, matching the visible-child property value, and
    all the other widgets for mode transitions/last visible child for child
    transition as screenshots in a Cairo surface.
    
    Together with the fact visible-child changes as soon as one switches the
    page or starts a gesture it means when you start a gesture, the currently
    visible page disappears and is replaced with a screenshot, and another one
    appears instead, and if you cancel the gesture, that page disappears and
    the current one starts drawing again. This means that it's impossible to
    have animated content continue to animate while doing a gesture, unless
    you're transitioning to that content and not from it - the exact opposite
    of how, for example, WebKit back gesture works.
    
    This also causes all sorts of bugs if for any reason the currently
    visible-but-not-really widget triggers a redraw, for example,
    https://gitlab.gnome.org/GNOME/libhandy/-/issues/85, likely also
    https://gitlab.gnome.org/GNOME/libhandy/-/issues/99.
    
    Previously I tried to change it to switching visible child at the end of
    the transition, but it wasn't very successful and massively breaks the
    semantics of visible-child. For example, changing its value will first
    animate it and only then update the value.
    
    Instead, try a different approach: let all the visible children in a
    transition be actually visible, like in HdyCarousel. At most we need two
    GdkWindows for this, with one of them being used for stationary children
    and the other one for the moving ones. However, this requires constantly
    reparenting the widgets as visible-child changes and so it's a lot simpler
    to have separate window for each child, like in HdyCarousel.
    
    Since overlapping widgets block input, we must ensure they actually match
    the child allocation in unfolded mode. The easiest way to do that is to
    allocate the windows instead of the child widgets, and allocate each child
    at (0, 0).
    
    Now the transitions can be done by moving the corresponding windows. For
    over and under transitions, we also must ensure the window stacking order
    matches the transition.
    
    At this point we don't need any custom drawing for slide transition, and
    only need clipping and shadow for over and under transitions, so do just
    that.
    
    This also means there's no need for separate drawing for mode transitions
    vs child transitions, or folded vs unfolded mode.
    
    This may have performance implications for children which take a long time
    to redraw: the slowdown will happen regardless of the transition direction
    instead of only when transitioning to that child. This can be mitigated
    with a pixel cache later if it turns out to be a problem, and that would
    fix the slowdowns regardless of the transition direction.
    
    Fixes https://gitlab.gnome.org/GNOME/libhandy/-/issues/85
    Fixes https://gitlab.gnome.org/GNOME/libhandy/-/issues/260
    
    Signed-off-by: Alexander Mikhaylenko <alexm gnome org>

 src/hdy-stackable-box.c | 1097 +++++++++++++----------------------------------
 1 file changed, 309 insertions(+), 788 deletions(-)
---
diff --git a/src/hdy-stackable-box.c b/src/hdy-stackable-box.c
index b07364a8..6f37ccad 100644
--- a/src/hdy-stackable-box.c
+++ b/src/hdy-stackable-box.c
@@ -10,7 +10,6 @@
 
 #include "gtkprogresstrackerprivate.h"
 #include "hdy-animation-private.h"
-#include "hdy-cairo-private.h"
 #include "hdy-enums-private.h"
 #include "hdy-stackable-box-private.h"
 #include "hdy-shadow-helper-private.h"
@@ -89,6 +88,7 @@ typedef struct _HdyStackableBoxChildInfo HdyStackableBoxChildInfo;
 struct _HdyStackableBoxChildInfo
 {
   GtkWidget *widget;
+  GdkWindow *window;
   gchar *name;
   gboolean allow_visible;
 
@@ -116,7 +116,6 @@ struct _HdyStackableBox
   HdyStackableBoxChildInfo *visible_child;
   HdyStackableBoxChildInfo *last_visible_child;
 
-  GdkWindow* bin_window;
   GdkWindow* view_window;
 
   gboolean folded;
@@ -125,8 +124,6 @@ struct _HdyStackableBox
 
   GtkOrientation orientation;
 
-  gboolean move_bin_window_request;
-
   HdyStackableBoxTransitionType transition_type;
 
   HdySwipeTracker *tracker;
@@ -138,14 +135,7 @@ struct _HdyStackableBox
     gdouble source_pos;
     gdouble target_pos;
 
-    cairo_surface_t *start_surface;
-    GtkAllocation start_surface_allocation;
-    gdouble start_distance;
     gdouble start_progress;
-    cairo_surface_t *end_surface;
-    GtkAllocation end_surface_allocation;
-    GtkAllocation end_surface_clip;
-    gdouble end_distance;
     gdouble end_progress;
     guint tick_id;
     GtkProgressTracker tracker;
@@ -162,20 +152,14 @@ struct _HdyStackableBox
     gboolean is_gesture_active;
     gboolean is_cancelled;
 
-    cairo_surface_t *last_visible_surface;
-    GtkAllocation last_visible_surface_allocation;
     guint tick_id;
     GtkProgressTracker tracker;
     gboolean first_frame_skipped;
 
-    gint last_visible_widget_width;
-    gint last_visible_widget_height;
-
     gboolean interpolate_size;
     gboolean can_swipe_back;
     gboolean can_swipe_forward;
 
-    gboolean is_active;
     GtkPanDirection active_direction;
     gboolean is_direct_swipe;
     gint swipe_direction;
@@ -245,34 +229,6 @@ get_directed_children (HdyStackableBox *self)
          self->children_reversed : self->children;
 }
 
-/* Transitions that cause the bin window to move */
-static inline gboolean
-is_window_moving_child_transition (HdyStackableBox *self)
-{
-  GtkPanDirection direction;
-  gboolean is_rtl;
-  GtkPanDirection left_or_right, right_or_left;
-
-  if (!self->child_transition.is_active)
-    return FALSE;
-
-  direction = self->child_transition.active_direction;
-  is_rtl = gtk_widget_get_direction (GTK_WIDGET (self->container)) == GTK_TEXT_DIR_RTL;
-  left_or_right = is_rtl ? GTK_PAN_DIRECTION_RIGHT : GTK_PAN_DIRECTION_LEFT;
-  right_or_left = is_rtl ? GTK_PAN_DIRECTION_LEFT : GTK_PAN_DIRECTION_RIGHT;
-
-  switch (self->transition_type) {
-  case HDY_STACKABLE_BOX_TRANSITION_TYPE_OVER:
-    return direction == GTK_PAN_DIRECTION_UP || direction == left_or_right;
-  case HDY_STACKABLE_BOX_TRANSITION_TYPE_UNDER:
-    return direction == GTK_PAN_DIRECTION_DOWN || direction == right_or_left;
-  case HDY_STACKABLE_BOX_TRANSITION_TYPE_SLIDE:
-    return TRUE;
-  default:
-    g_assert_not_reached ();
-  }
-}
-
 static GtkPanDirection
 get_pan_direction (HdyStackableBox *self,
                    gboolean         new_child_first)
@@ -288,69 +244,85 @@ get_pan_direction (HdyStackableBox *self,
 }
 
 static gint
-get_bin_window_x (HdyStackableBox     *self,
-                  const GtkAllocation *allocation)
+get_child_window_x (HdyStackableBox          *self,
+                    HdyStackableBoxChildInfo *child_info,
+                    gint                      width)
 {
-  int x = 0;
+  gboolean is_rtl;
+  gint rtl_multiplier;
 
-  if (self->child_transition.is_gesture_active ||
-      gtk_progress_tracker_get_state (&self->child_transition.tracker) != GTK_PROGRESS_STATE_AFTER) {
-    if (self->child_transition.active_direction == GTK_PAN_DIRECTION_LEFT)
-      x = allocation->width * (1 - self->child_transition.progress);
-    if (self->child_transition.active_direction == GTK_PAN_DIRECTION_RIGHT)
-      x = -allocation->width * (1 - self->child_transition.progress);
-  }
+  if (!self->child_transition.is_gesture_active &&
+      gtk_progress_tracker_get_state (&self->child_transition.tracker) == GTK_PROGRESS_STATE_AFTER)
+    return 0;
 
-  return x;
-}
+  if (self->child_transition.active_direction != GTK_PAN_DIRECTION_LEFT &&
+      self->child_transition.active_direction != GTK_PAN_DIRECTION_RIGHT)
+    return 0;
 
-static gint
-get_bin_window_y (HdyStackableBox     *self,
-                  const GtkAllocation *allocation)
-{
-  int y = 0;
+  is_rtl = gtk_widget_get_direction (GTK_WIDGET (self->container)) == GTK_TEXT_DIR_RTL;
+  rtl_multiplier = is_rtl ? -1 : 1;
+
+  if ((self->child_transition.active_direction == GTK_PAN_DIRECTION_RIGHT) == is_rtl) {
+    if ((self->transition_type == HDY_STACKABLE_BOX_TRANSITION_TYPE_OVER ||
+         self->transition_type == HDY_STACKABLE_BOX_TRANSITION_TYPE_SLIDE) &&
+        child_info == self->visible_child)
+      return width * (1 - self->child_transition.progress) * rtl_multiplier;
+
+    if ((self->transition_type == HDY_STACKABLE_BOX_TRANSITION_TYPE_UNDER ||
+         self->transition_type == HDY_STACKABLE_BOX_TRANSITION_TYPE_SLIDE) &&
+        child_info == self->last_visible_child)
+      return -width * self->child_transition.progress * rtl_multiplier;
+  } else {
+    if ((self->transition_type == HDY_STACKABLE_BOX_TRANSITION_TYPE_UNDER ||
+         self->transition_type == HDY_STACKABLE_BOX_TRANSITION_TYPE_SLIDE) &&
+        child_info == self->visible_child)
+      return -width * (1 - self->child_transition.progress) * rtl_multiplier;
 
-  if (self->child_transition.is_gesture_active ||
-      gtk_progress_tracker_get_state (&self->child_transition.tracker) != GTK_PROGRESS_STATE_AFTER) {
-    if (self->child_transition.active_direction == GTK_PAN_DIRECTION_UP)
-      y = allocation->height * (1 - self->child_transition.progress);
-    if (self->child_transition.active_direction == GTK_PAN_DIRECTION_DOWN)
-      y = -allocation->height * (1 - self->child_transition.progress);
+    if ((self->transition_type == HDY_STACKABLE_BOX_TRANSITION_TYPE_OVER ||
+         self->transition_type == HDY_STACKABLE_BOX_TRANSITION_TYPE_SLIDE) &&
+        child_info == self->last_visible_child)
+      return width * self->child_transition.progress * rtl_multiplier;
   }
 
-  return y;
+  return 0;
 }
 
-static void
-move_resize_bin_window (HdyStackableBox *self,
-                        GtkAllocation   *allocation,
-                        gboolean         resize)
+static gint
+get_child_window_y (HdyStackableBox          *self,
+                    HdyStackableBoxChildInfo *child_info,
+                    gint                      height)
 {
-  GtkAllocation alloc;
-  gboolean move;
+  if (!self->child_transition.is_gesture_active &&
+      gtk_progress_tracker_get_state (&self->child_transition.tracker) == GTK_PROGRESS_STATE_AFTER)
+    return 0;
 
-  if (self->bin_window == NULL)
-    return;
+  if (self->child_transition.active_direction != GTK_PAN_DIRECTION_UP &&
+      self->child_transition.active_direction != GTK_PAN_DIRECTION_DOWN)
+    return 0;
 
-  if (allocation == NULL) {
-    gtk_widget_get_allocation (GTK_WIDGET (self->container), &alloc);
-    allocation = &alloc;
-  }
+  if (self->child_transition.active_direction == GTK_PAN_DIRECTION_UP) {
+    if ((self->transition_type == HDY_STACKABLE_BOX_TRANSITION_TYPE_OVER ||
+         self->transition_type == HDY_STACKABLE_BOX_TRANSITION_TYPE_SLIDE) &&
+        child_info == self->visible_child)
+      return height * (1 - self->child_transition.progress);
 
-  move = self->move_bin_window_request || is_window_moving_child_transition (self);
+    if ((self->transition_type == HDY_STACKABLE_BOX_TRANSITION_TYPE_UNDER ||
+         self->transition_type == HDY_STACKABLE_BOX_TRANSITION_TYPE_SLIDE) &&
+        child_info == self->last_visible_child)
+      return -height * self->child_transition.progress;
+  } else {
+    if ((self->transition_type == HDY_STACKABLE_BOX_TRANSITION_TYPE_UNDER ||
+         self->transition_type == HDY_STACKABLE_BOX_TRANSITION_TYPE_SLIDE) &&
+        child_info == self->visible_child)
+      return -height * (1 - self->child_transition.progress);
 
-  if (move && resize)
-    gdk_window_move_resize (self->bin_window,
-                            get_bin_window_x (self, allocation), get_bin_window_y (self, allocation),
-                            allocation->width, allocation->height);
-  else if (move)
-    gdk_window_move (self->bin_window,
-                     get_bin_window_x (self, allocation), get_bin_window_y (self, allocation));
-  else if (resize)
-    gdk_window_resize (self->bin_window,
-                       allocation->width, allocation->height);
+    if ((self->transition_type == HDY_STACKABLE_BOX_TRANSITION_TYPE_OVER ||
+         self->transition_type == HDY_STACKABLE_BOX_TRANSITION_TYPE_SLIDE) &&
+        child_info == self->last_visible_child)
+      return height * self->child_transition.progress;
+  }
 
-  self->move_bin_window_request = FALSE;
+  return 0;
 }
 
 static void
@@ -361,16 +333,11 @@ hdy_stackable_box_child_progress_updated (HdyStackableBox *self)
   if (!self->homogeneous[HDY_FOLD_FOLDED][GTK_ORIENTATION_VERTICAL] ||
       !self->homogeneous[HDY_FOLD_FOLDED][GTK_ORIENTATION_HORIZONTAL])
     gtk_widget_queue_resize (GTK_WIDGET (self->container));
-
-  move_resize_bin_window (self, NULL, FALSE);
+  else
+    gtk_widget_queue_allocate (GTK_WIDGET (self->container));
 
   if (!self->child_transition.is_gesture_active &&
       gtk_progress_tracker_get_state (&self->child_transition.tracker) == GTK_PROGRESS_STATE_AFTER) {
-    if (self->child_transition.last_visible_surface != NULL) {
-      cairo_surface_destroy (self->child_transition.last_visible_surface);
-      self->child_transition.last_visible_surface = NULL;
-    }
-
     if (self->child_transition.is_cancelled) {
       if (self->last_visible_child != NULL) {
         if (self->folded) {
@@ -462,12 +429,7 @@ static void
 hdy_stackable_box_stop_child_transition (HdyStackableBox *self)
 {
   hdy_stackable_box_unschedule_child_ticks (self);
-  self->child_transition.is_active = FALSE;
   gtk_progress_tracker_finish (&self->child_transition.tracker);
-  if (self->child_transition.last_visible_surface != NULL) {
-    cairo_surface_destroy (self->child_transition.last_visible_surface);
-    self->child_transition.last_visible_surface = NULL;
-  }
   if (self->last_visible_child != NULL) {
     gtk_widget_set_child_visible (self->last_visible_child->widget, FALSE);
     self->last_visible_child = NULL;
@@ -475,9 +437,6 @@ hdy_stackable_box_stop_child_transition (HdyStackableBox *self)
 
   self->child_transition.swipe_direction = 0;
   hdy_shadow_helper_clear_cache (self->shadow_helper);
-
-  /* Move the bin window back in place as a child transition might have moved it. */
-  self->move_bin_window_request = TRUE;
 }
 
 static void
@@ -494,7 +453,6 @@ hdy_stackable_box_start_child_transition (HdyStackableBox *self,
       self->last_visible_child != NULL &&
       /* Don't animate child transition when a mode transition is ongoing. */
       self->mode_transition.tick_id == 0) {
-    self->child_transition.is_active = TRUE;
     self->child_transition.active_direction = transition_direction;
     self->child_transition.first_frame_skipped = FALSE;
     self->child_transition.start_progress = 0;
@@ -512,7 +470,6 @@ hdy_stackable_box_start_child_transition (HdyStackableBox *self,
   }
   else {
     hdy_stackable_box_unschedule_child_ticks (self);
-    self->child_transition.is_active = FALSE;
     gtk_progress_tracker_finish (&self->child_transition.tracker);
   }
 
@@ -576,21 +533,11 @@ set_visible_child_info (HdyStackableBox               *self,
     gtk_widget_set_child_visible (self->last_visible_child->widget, !self->folded);
   self->last_visible_child = NULL;
 
-  if (self->child_transition.last_visible_surface != NULL)
-    cairo_surface_destroy (self->child_transition.last_visible_surface);
-  self->child_transition.last_visible_surface = NULL;
-
   hdy_shadow_helper_clear_cache (self->shadow_helper);
 
   if (self->visible_child && self->visible_child->widget) {
-    if (gtk_widget_is_visible (widget)) {
-      GtkAllocation allocation;
-
+    if (gtk_widget_is_visible (widget))
       self->last_visible_child = self->visible_child;
-      gtk_widget_get_allocated_size (self->last_visible_child->widget, &allocation, NULL);
-      self->child_transition.last_visible_widget_width = allocation.width;
-      self->child_transition.last_visible_widget_height = allocation.height;
-    }
     else
       gtk_widget_set_child_visible (self->visible_child->widget, !self->folded);
   }
@@ -666,19 +613,6 @@ set_visible_child_info (HdyStackableBox               *self,
   g_object_thaw_notify (G_OBJECT (self));
 }
 
-static void
-get_padding (GtkWidget *widget,
-             GtkBorder *padding)
-{
-  GtkStyleContext *context;
-  GtkStateFlags state;
-
-  context = gtk_widget_get_style_context (widget);
-  state = gtk_style_context_get_state (context);
-
-  gtk_style_context_get_padding (context, state, padding);
-}
-
 static void
 hdy_stackable_box_set_position (HdyStackableBox *self,
                                 gdouble          pos)
@@ -717,19 +651,8 @@ hdy_stackable_box_set_position (HdyStackableBox *self,
 static void
 hdy_stackable_box_mode_progress_updated (HdyStackableBox *self)
 {
-  if (gtk_progress_tracker_get_state (&self->mode_transition.tracker) == GTK_PROGRESS_STATE_AFTER) {
-    if (self->mode_transition.start_surface != NULL) {
-      cairo_surface_destroy (self->mode_transition.start_surface);
-      self->mode_transition.start_surface = NULL;
-    }
-
-    if (self->mode_transition.end_surface != NULL) {
-      cairo_surface_destroy (self->mode_transition.end_surface);
-      self->mode_transition.end_surface = NULL;
-    }
-
+  if (gtk_progress_tracker_get_state (&self->mode_transition.tracker) == GTK_PROGRESS_STATE_AFTER)
     hdy_shadow_helper_clear_cache (self->shadow_helper);
-  }
 }
 
 static gboolean
@@ -1505,6 +1428,7 @@ hdy_stackable_box_size_allocate_folded (HdyStackableBox *self,
   gint remaining_start_size, remaining_end_size, remaining_size;
   gint current_pad;
   gint max_child_size = 0;
+  gint start_position, end_position;
   gboolean box_homogeneous;
   HdyStackableBoxTransitionType mode_transition_type;
   GtkTextDirection direction;
@@ -1561,8 +1485,8 @@ hdy_stackable_box_size_allocate_folded (HdyStackableBox *self,
         continue;
       }
 
-      child_info->alloc.x = 0;
-      child_info->alloc.y = 0;
+      child_info->alloc.x = get_child_window_x (self, child_info, allocation->width);
+      child_info->alloc.y = get_child_window_y (self, child_info, allocation->height);
       child_info->alloc.width = allocation->width;
       child_info->alloc.height = allocation->height;
       child_info->visible = TRUE;
@@ -1628,48 +1552,25 @@ hdy_stackable_box_size_allocate_folded (HdyStackableBox *self,
     direction = gtk_widget_get_direction (GTK_WIDGET (self->container));
     under = (mode_transition_type == HDY_STACKABLE_BOX_TRANSITION_TYPE_OVER && direction == 
GTK_TEXT_DIR_LTR) ||
             (mode_transition_type == HDY_STACKABLE_BOX_TRANSITION_TYPE_UNDER && direction == 
GTK_TEXT_DIR_RTL);
-    self->mode_transition.start_surface_allocation.width = under ? remaining_size : start_size;
-    self->mode_transition.start_surface_allocation.height = allocation->height;
-    self->mode_transition.start_surface_allocation.x = under ? 0 : remaining_start_size - start_size;
-    self->mode_transition.start_surface_allocation.y = 0;
+    start_position = under ? 0 : remaining_start_size - start_size;
     self->mode_transition.start_progress = under ? (gdouble) remaining_size / start_size : 1;
     under = (mode_transition_type == HDY_STACKABLE_BOX_TRANSITION_TYPE_UNDER && direction == 
GTK_TEXT_DIR_LTR) ||
             (mode_transition_type == HDY_STACKABLE_BOX_TRANSITION_TYPE_OVER && direction == 
GTK_TEXT_DIR_RTL);
-    self->mode_transition.end_surface_allocation.width = end_size;
-    self->mode_transition.end_surface_allocation.height = allocation->height;
-    self->mode_transition.end_surface_allocation.x = under ? allocation->width - end_size : 
remaining_start_size + visible_size;
-    self->mode_transition.end_surface_allocation.y = 0;
-    self->mode_transition.end_surface_clip.width = end_size;
-    self->mode_transition.end_surface_clip.height = self->mode_transition.end_surface_allocation.height;
-    self->mode_transition.end_surface_clip.x = remaining_start_size + visible_size;
-    self->mode_transition.end_surface_clip.y = self->mode_transition.end_surface_allocation.y;
+    end_position = under ? allocation->width - end_size : remaining_start_size + visible_size;
     self->mode_transition.end_progress = under ? (gdouble) remaining_end_size / end_size : 1;
     break;
   case GTK_ORIENTATION_VERTICAL:
     under = mode_transition_type == HDY_STACKABLE_BOX_TRANSITION_TYPE_OVER;
-    self->mode_transition.start_surface_allocation.width = allocation->width;
-    self->mode_transition.start_surface_allocation.height = under ? remaining_size : start_size;
-    self->mode_transition.start_surface_allocation.x = 0;
-    self->mode_transition.start_surface_allocation.y = under ? 0 : remaining_start_size - start_size;
+    start_position = under ? 0 : remaining_start_size - start_size;
     self->mode_transition.start_progress = under ? (gdouble) remaining_size / start_size : 1;
     under = mode_transition_type == HDY_STACKABLE_BOX_TRANSITION_TYPE_UNDER;
-    self->mode_transition.end_surface_allocation.width = allocation->width;
-    self->mode_transition.end_surface_allocation.height = end_size;
-    self->mode_transition.end_surface_allocation.x = 0;
-    self->mode_transition.end_surface_allocation.y = remaining_start_size + visible_size;
-    self->mode_transition.end_surface_clip.width = self->mode_transition.end_surface_allocation.width;
-    self->mode_transition.end_surface_clip.height = end_size;
-    self->mode_transition.end_surface_clip.x = self->mode_transition.end_surface_allocation.x;
-    self->mode_transition.end_surface_clip.y = remaining_start_size + visible_size;
+    end_position = remaining_start_size + visible_size;
     self->mode_transition.end_progress = under ? (gdouble) remaining_end_size / end_size : 1;
     break;
   default:
     g_assert_not_reached ();
   }
 
-  self->mode_transition.start_distance = start_size;
-  self->mode_transition.end_distance = end_size;
-
   /* Allocate visible child. */
   if (orientation == GTK_ORIENTATION_HORIZONTAL) {
     visible_child->alloc.width = visible_size;
@@ -1687,10 +1588,7 @@ hdy_stackable_box_size_allocate_folded (HdyStackableBox *self,
   }
 
   /* Allocate starting children. */
-  if (orientation == GTK_ORIENTATION_HORIZONTAL)
-    current_pad = -self->mode_transition.start_surface_allocation.x;
-  else
-    current_pad = -self->mode_transition.start_surface_allocation.y;
+  current_pad = -start_position;
 
   for (children = directed_children; children; children = children->next) {
     child_info = children->data;
@@ -1723,10 +1621,7 @@ hdy_stackable_box_size_allocate_folded (HdyStackableBox *self,
   }
 
   /* Allocate ending children. */
-  if (orientation == GTK_ORIENTATION_HORIZONTAL)
-    current_pad = self->mode_transition.end_surface_allocation.x;
-  else
-    current_pad = self->mode_transition.end_surface_allocation.y;
+  current_pad = end_position;
 
   for (children = g_list_last (directed_children); children; children = children->prev) {
     child_info = children->data;
@@ -1910,16 +1805,10 @@ hdy_stackable_box_size_allocate_unfolded (HdyStackableBox *self,
   if (orientation == GTK_ORIENTATION_HORIZONTAL) {
     start_pad = (gint) ((visible_child->alloc.x) * (1.0 - self->mode_transition.current_pos));
     end_pad = (gint) ((allocation->width - (visible_child->alloc.x + visible_child->alloc.width)) * (1.0 - 
self->mode_transition.current_pos));
-
-    self->mode_transition.start_distance = visible_child->alloc.x;
-    self->mode_transition.end_distance = allocation->width - (visible_child->alloc.x + 
visible_child->alloc.width);
   }
   else {
     start_pad = (gint) ((visible_child->alloc.y) * (1.0 - self->mode_transition.current_pos));
     end_pad = (gint) ((allocation->height - (visible_child->alloc.y + visible_child->alloc.height)) * (1.0 - 
self->mode_transition.current_pos));
-
-    self->mode_transition.start_distance = visible_child->alloc.y;
-    self->mode_transition.end_distance = allocation->height - (visible_child->alloc.y + 
visible_child->alloc.height);
   }
 
   mode_transition_type = self->transition_type;
@@ -1985,6 +1874,74 @@ hdy_stackable_box_size_allocate_unfolded (HdyStackableBox *self,
   }
 }
 
+static HdyStackableBoxChildInfo *
+get_top_overlap_child (HdyStackableBox *self)
+{
+  gboolean is_rtl, start;
+
+  is_rtl = gtk_widget_get_direction (GTK_WIDGET (self->container)) == GTK_TEXT_DIR_RTL;
+
+  start = (self->child_transition.active_direction == GTK_PAN_DIRECTION_LEFT && !is_rtl) ||
+          (self->child_transition.active_direction == GTK_PAN_DIRECTION_RIGHT && is_rtl) ||
+           self->child_transition.active_direction == GTK_PAN_DIRECTION_UP;
+
+  if (!self->last_visible_child)
+    return self->visible_child;
+
+  switch (self->transition_type) {
+  case HDY_STACKABLE_BOX_TRANSITION_TYPE_SLIDE:
+    // Nothing overlaps in this case
+    return NULL;
+  case HDY_STACKABLE_BOX_TRANSITION_TYPE_OVER:
+    return start ? self->visible_child : self->last_visible_child;
+  case HDY_STACKABLE_BOX_TRANSITION_TYPE_UNDER:
+    return start ? self->last_visible_child : self->visible_child;
+  default:
+    g_assert_not_reached ();
+  }
+}
+
+static void
+restack_windows (HdyStackableBox *self)
+{
+  HdyStackableBoxChildInfo *child_info, *overlap_child;
+  GList *l;
+
+  overlap_child = get_top_overlap_child (self);
+
+  switch (self->transition_type) {
+  case HDY_STACKABLE_BOX_TRANSITION_TYPE_SLIDE:
+    // Nothing overlaps in this case
+    return;
+  case HDY_STACKABLE_BOX_TRANSITION_TYPE_OVER:
+    for (l = g_list_last (self->children); l; l = l->prev) {
+      child_info = l->data;
+
+      if (child_info->window)
+        gdk_window_raise (child_info->window);
+
+      if (child_info == overlap_child)
+        break;
+    }
+
+    break;
+  case HDY_STACKABLE_BOX_TRANSITION_TYPE_UNDER:
+    for (l = self->children; l; l = l->next) {
+      child_info = l->data;
+
+      if (child_info->window)
+        gdk_window_raise (child_info->window);
+
+      if (child_info == overlap_child)
+        break;
+    }
+
+    break;
+  default:
+    g_assert_not_reached ();
+  }
+}
+
 void
 hdy_stackable_box_size_allocate (HdyStackableBox *self,
                                  GtkAllocation   *allocation)
@@ -2003,7 +1960,6 @@ hdy_stackable_box_size_allocate (HdyStackableBox *self,
     gdk_window_move_resize (self->view_window,
                             allocation->x, allocation->y,
                             allocation->width, allocation->height);
-    move_resize_bin_window (self, allocation, TRUE);
   }
 
   /* Prepare children information. */
@@ -2072,612 +2028,158 @@ hdy_stackable_box_size_allocate (HdyStackableBox *self,
 
   /* Apply visibility and allocation. */
   for (children = directed_children; children; children = children->next) {
+    GtkAllocation alloc;
+
     child_info = children->data;
 
     gtk_widget_set_child_visible (child_info->widget, child_info->visible);
-    if (!child_info->visible)
-      continue;
-
-    gtk_widget_size_allocate (child_info->widget, &child_info->alloc);
-    if (gtk_widget_get_realized (widget))
-      gtk_widget_show (child_info->widget);
-  }
-}
 
-static void
-hdy_stackable_box_draw_under (HdyStackableBox *self,
-                              cairo_t         *cr)
-{
-  GtkWidget *widget = GTK_WIDGET (self->container);
-  GtkAllocation allocation;
-  int x, y;
-
-  gtk_widget_get_allocation (widget, &allocation);
-
-  x = get_bin_window_x (self, &allocation);
-  y = get_bin_window_y (self, &allocation);
-
-  if (gtk_cairo_should_draw_window (cr, self->bin_window)) {
-    gint clip_x, clip_y, clip_w, clip_h;
-    gdouble progress;
-
-    clip_x = 0;
-    clip_y = 0;
-    clip_w = allocation.width;
-    clip_h = allocation.height;
-
-    switch (self->child_transition.active_direction) {
-    case GTK_PAN_DIRECTION_LEFT:
-      clip_x = x;
-      clip_w -= x;
-      break;
-    case GTK_PAN_DIRECTION_RIGHT:
-      clip_w += x;
-      break;
-    case GTK_PAN_DIRECTION_UP:
-      clip_y = y;
-      clip_h -= y;
-      break;
-    case GTK_PAN_DIRECTION_DOWN:
-      clip_h += y;
-      break;
-    default:
-      g_assert_not_reached ();
-      break;
+    if (child_info->window &&
+        child_info->visible != gdk_window_is_visible (child_info->window)) {
+      if (child_info->visible)
+        gdk_window_show (child_info->window);
+      else
+        gdk_window_hide (child_info->window);
     }
 
-    progress = self->child_transition.progress;
-
-    cairo_save (cr);
-    cairo_rectangle (cr, clip_x, clip_y, clip_w, clip_h);
-    cairo_clip (cr);
-    gtk_container_propagate_draw (self->container,
-                                  self->visible_child->widget,
-                                  cr);
-    cairo_translate (cr, x, y);
-    hdy_shadow_helper_draw_shadow (self->shadow_helper, cr, allocation.width,
-                                   allocation.height, progress,
-                                   self->child_transition.active_direction);
-    cairo_restore (cr);
-  }
-
-  if (self->child_transition.last_visible_surface &&
-      gtk_cairo_should_draw_window (cr, self->view_window)) {
-    switch (self->child_transition.active_direction) {
-    case GTK_PAN_DIRECTION_LEFT:
-      x -= allocation.width;
-      break;
-    case GTK_PAN_DIRECTION_RIGHT:
-      x += allocation.width;
-      break;
-    case GTK_PAN_DIRECTION_UP:
-      y -= allocation.height;
-      break;
-    case GTK_PAN_DIRECTION_DOWN:
-      y += allocation.height;
-      break;
-    default:
-      g_assert_not_reached ();
-      break;
-    }
+    if (!child_info->visible)
+      continue;
 
-    x += self->child_transition.last_visible_surface_allocation.x;
-    y += self->child_transition.last_visible_surface_allocation.y;
+    if (child_info->window)
+      gdk_window_move_resize (child_info->window,
+                              child_info->alloc.x,
+                              child_info->alloc.y,
+                              child_info->alloc.width,
+                              child_info->alloc.height);
 
-    if (gtk_widget_get_valign (self->last_visible_child->widget) == GTK_ALIGN_END &&
-        self->child_transition.last_visible_widget_height > allocation.height)
-      y -= self->child_transition.last_visible_widget_height - allocation.height;
-    else if (gtk_widget_get_valign (self->last_visible_child->widget) == GTK_ALIGN_CENTER)
-      y -= (self->child_transition.last_visible_widget_height - allocation.height) / 2;
+    alloc.x = 0;
+    alloc.y = 0;
+    alloc.width = child_info->alloc.width;
+    alloc.height = child_info->alloc.height;
+    gtk_widget_size_allocate (child_info->widget, &alloc);
 
-    cairo_save (cr);
-    cairo_set_source_surface (cr, self->child_transition.last_visible_surface, x, y);
-    cairo_paint (cr);
-    cairo_restore (cr);
+    if (gtk_widget_get_realized (widget))
+      gtk_widget_show (child_info->widget);
   }
+
+  restack_windows (self);
 }
 
-static void
-hdy_stackable_box_draw_over (HdyStackableBox *self,
-                             cairo_t         *cr)
+gboolean
+hdy_stackable_box_draw (HdyStackableBox *self,
+                        cairo_t         *cr)
 {
   GtkWidget *widget = GTK_WIDGET (self->container);
+  GList *stacked_children, *l;
+  HdyStackableBoxChildInfo *child_info, *overlap_child;
+  gboolean is_transition;
+  gboolean is_vertical;
+  gboolean is_rtl;
+  gboolean is_over;
+  GtkAllocation shadow_rect;
+  gdouble shadow_progress, mode_progress;
+  GtkPanDirection shadow_direction;
 
-  if (self->child_transition.last_visible_surface &&
-      gtk_cairo_should_draw_window (cr, self->view_window)) {
-    GtkAllocation allocation;
-    gint x, y, clip_x, clip_y, clip_w, clip_h, shadow_x, shadow_y;
-    gdouble progress;
-    GtkPanDirection direction;
+  overlap_child = get_top_overlap_child (self);
 
-    gtk_widget_get_allocation (widget, &allocation);
+  is_transition = self->child_transition.is_gesture_active ||
+                  gtk_progress_tracker_get_state (&self->child_transition.tracker) != 
GTK_PROGRESS_STATE_AFTER ||
+                  gtk_progress_tracker_get_state (&self->mode_transition.tracker) != 
GTK_PROGRESS_STATE_AFTER;
 
-    x = get_bin_window_x (self, &allocation);
-    y = get_bin_window_y (self, &allocation);
+  if (!is_transition ||
+      self->transition_type == HDY_STACKABLE_BOX_TRANSITION_TYPE_SLIDE ||
+      !overlap_child) {
+    for (l = self->children; l; l = l->next) {
+      child_info = l->data;
 
-    clip_x = 0;
-    clip_y = 0;
-    clip_w = allocation.width;
-    clip_h = allocation.height;
-    shadow_x = 0;
-    shadow_y = 0;
+      if (!gtk_cairo_should_draw_window (cr, child_info->window))
+        continue;
 
-    switch (self->child_transition.active_direction) {
-    case GTK_PAN_DIRECTION_LEFT:
-      shadow_x = x - allocation.width;
-      clip_w = x;
-      x = 0;
-      direction = GTK_PAN_DIRECTION_RIGHT;
-      break;
-    case GTK_PAN_DIRECTION_RIGHT:
-      clip_x = shadow_x = x + allocation.width;
-      clip_w = -x;
-      x = 0;
-      direction = GTK_PAN_DIRECTION_LEFT;
-      break;
-    case GTK_PAN_DIRECTION_UP:
-      shadow_y = y - allocation.height;
-      clip_h = y;
-      y = 0;
-      direction = GTK_PAN_DIRECTION_DOWN;
-      break;
-    case GTK_PAN_DIRECTION_DOWN:
-      clip_y = shadow_y = y + allocation.height;
-      clip_h = -y;
-      y = 0;
-      direction = GTK_PAN_DIRECTION_UP;
-      break;
-    default:
-      g_assert_not_reached ();
-      break;
+      gtk_container_propagate_draw (self->container,
+                                    child_info->widget,
+                                    cr);
     }
 
-    x += self->child_transition.last_visible_surface_allocation.x;
-    y += self->child_transition.last_visible_surface_allocation.y;
-
-    if (gtk_widget_get_valign (self->last_visible_child->widget) == GTK_ALIGN_END &&
-        self->child_transition.last_visible_widget_height > allocation.height)
-      y -= self->child_transition.last_visible_widget_height - allocation.height;
-    else if (gtk_widget_get_valign (self->last_visible_child->widget) == GTK_ALIGN_CENTER)
-      y -= (self->child_transition.last_visible_widget_height - allocation.height) / 2;
-
-    progress = 1 - self->child_transition.progress;
-
-    cairo_save (cr);
-    cairo_rectangle (cr, clip_x, clip_y, clip_w, clip_h);
-    cairo_clip (cr);
-    cairo_set_source_surface (cr, self->child_transition.last_visible_surface, x, y);
-    cairo_paint (cr);
-    cairo_translate (cr, shadow_x, shadow_y);
-    hdy_shadow_helper_draw_shadow (self->shadow_helper, cr, allocation.width,
-                                   allocation.height, progress, direction);
-    cairo_restore (cr);
+    return GDK_EVENT_PROPAGATE;
   }
 
-  if (gtk_cairo_should_draw_window (cr, self->bin_window))
-    gtk_container_propagate_draw (self->container,
-                                  self->visible_child->widget,
-                                  cr);
-}
-
-static void
-hdy_stackable_box_draw_slide (HdyStackableBox *self,
-                              cairo_t         *cr)
-{
-  GtkWidget *widget = GTK_WIDGET (self->container);
+  stacked_children = self->transition_type == HDY_STACKABLE_BOX_TRANSITION_TYPE_UNDER ?
+                     self->children_reversed : self->children;
 
-  if (self->child_transition.last_visible_surface &&
-      gtk_cairo_should_draw_window (cr, self->view_window)) {
-    GtkAllocation allocation;
-    int x, y;
+  is_vertical = gtk_orientable_get_orientation (GTK_ORIENTABLE (widget)) == GTK_ORIENTATION_VERTICAL;
+  is_rtl = gtk_widget_get_direction (widget) == GTK_TEXT_DIR_RTL;
+  is_over = self->transition_type == HDY_STACKABLE_BOX_TRANSITION_TYPE_OVER;
 
-    gtk_widget_get_allocation (widget, &allocation);
-
-    x = get_bin_window_x (self, &allocation);
-    y = get_bin_window_y (self, &allocation);
+  cairo_save (cr);
 
-    switch (self->child_transition.active_direction) {
-    case GTK_PAN_DIRECTION_LEFT:
-      x -= allocation.width;
-      break;
-    case GTK_PAN_DIRECTION_RIGHT:
-      x += allocation.width;
-      break;
-    case GTK_PAN_DIRECTION_UP:
-      y -= allocation.height;
-      break;
-    case GTK_PAN_DIRECTION_DOWN:
-      y += allocation.height;
-      break;
-    default:
-      g_assert_not_reached ();
-      break;
+  shadow_rect.x = 0;
+  shadow_rect.y = 0;
+  shadow_rect.width = gtk_widget_get_allocated_width (widget);
+  shadow_rect.height = gtk_widget_get_allocated_height (widget);
+
+  if (is_vertical)
+    if (!is_over) {
+      shadow_rect.y = overlap_child->alloc.y + overlap_child->alloc.height;
+      shadow_rect.height -= shadow_rect.y;
+      shadow_direction = GTK_PAN_DIRECTION_UP;
+      mode_progress = self->mode_transition.end_progress;
+    } else {
+      shadow_rect.height = overlap_child->alloc.y;
+      shadow_direction = GTK_PAN_DIRECTION_DOWN;
+      mode_progress = self->mode_transition.start_progress;
+    }
+  else
+    if (is_over == is_rtl) {
+      shadow_rect.x = overlap_child->alloc.x + overlap_child->alloc.width;
+      shadow_rect.width -= shadow_rect.x;
+      shadow_direction = GTK_PAN_DIRECTION_LEFT;
+      mode_progress = self->mode_transition.end_progress;
+    } else {
+      shadow_rect.width = overlap_child->alloc.x;
+      shadow_direction = GTK_PAN_DIRECTION_RIGHT;
+      mode_progress = self->mode_transition.start_progress;
     }
 
-    x += self->child_transition.last_visible_surface_allocation.x;
-    y += self->child_transition.last_visible_surface_allocation.y;
-
-    if (gtk_widget_get_valign (self->last_visible_child->widget) == GTK_ALIGN_END &&
-        self->child_transition.last_visible_widget_height > allocation.height)
-      y -= self->child_transition.last_visible_widget_height - allocation.height;
-    else if (gtk_widget_get_valign (self->last_visible_child->widget) == GTK_ALIGN_CENTER)
-      y -= (self->child_transition.last_visible_widget_height - allocation.height) / 2;
-
-    cairo_save (cr);
-    cairo_set_source_surface (cr, self->child_transition.last_visible_surface, x, y);
-    cairo_paint (cr);
-    cairo_restore (cr);
-  }
-
-  if (gtk_cairo_should_draw_window (cr, self->bin_window))
-    gtk_container_propagate_draw (self->container,
-                                  self->visible_child->widget,
-                                  cr);
-}
-
-static void
-hdy_stackable_box_draw_over_or_under (HdyStackableBox *self,
-                                      cairo_t         *cr)
-{
-  gboolean is_rtl;
-  GtkPanDirection direction, left_or_right, right_or_left;
-
-  direction = self->child_transition.active_direction;
-
-  is_rtl = gtk_widget_get_direction (GTK_WIDGET (self->container)) == GTK_TEXT_DIR_RTL;
-  left_or_right = is_rtl ? GTK_PAN_DIRECTION_RIGHT : GTK_PAN_DIRECTION_LEFT;
-  right_or_left = is_rtl ? GTK_PAN_DIRECTION_LEFT : GTK_PAN_DIRECTION_RIGHT;
+  if (gtk_progress_tracker_get_state (&self->mode_transition.tracker) != GTK_PROGRESS_STATE_AFTER) {
+    shadow_progress = mode_progress;
+  } else {
+    GtkPanDirection direction = self->child_transition.active_direction;
+    GtkPanDirection left_or_right = is_rtl ? GTK_PAN_DIRECTION_RIGHT : GTK_PAN_DIRECTION_LEFT;
 
-  switch (self->transition_type) {
-  case HDY_STACKABLE_BOX_TRANSITION_TYPE_OVER:
-    if (direction == GTK_PAN_DIRECTION_UP || direction == left_or_right)
-      hdy_stackable_box_draw_over (self, cr);
-    else if (direction == GTK_PAN_DIRECTION_DOWN || direction == right_or_left)
-      hdy_stackable_box_draw_under (self, cr);
-    else
-      g_assert_not_reached ();
-    break;
-  case HDY_STACKABLE_BOX_TRANSITION_TYPE_UNDER:
     if (direction == GTK_PAN_DIRECTION_UP || direction == left_or_right)
-      hdy_stackable_box_draw_under (self, cr);
-    else if (direction == GTK_PAN_DIRECTION_DOWN || direction == right_or_left)
-      hdy_stackable_box_draw_over (self, cr);
+      shadow_progress = self->child_transition.progress;
     else
-      g_assert_not_reached ();
-    break;
-  case HDY_STACKABLE_BOX_TRANSITION_TYPE_SLIDE:
-  default:
-    g_assert_not_reached ();
-  }
-}
-
-static gboolean
-hdy_stackable_box_draw_unfolded (HdyStackableBox *self,
-                                 cairo_t         *cr)
-{
-  GtkWidget *widget = GTK_WIDGET (self->container);
-  gboolean is_horizontal = gtk_orientable_get_orientation (GTK_ORIENTABLE (widget)) == 
GTK_ORIENTATION_HORIZONTAL;
-  GList *directed_children, *children;
-  HdyStackableBoxChildInfo *child_info;
-  GtkAllocation allocation, child_allocation;
+      shadow_progress = 1 - self->child_transition.progress;
 
-  directed_children = get_directed_children (self);
-
-  gtk_widget_get_allocation (widget, &allocation);
-
-  gtk_widget_get_allocation (self->visible_child->widget, &child_allocation);
-  cairo_save (cr);
-  cairo_rectangle (cr,
-                   0,
-                   0,
-                   is_horizontal ? child_allocation.x : allocation.width,
-                   is_horizontal ? allocation.height : child_allocation.y);
-  cairo_clip (cr);
-  for (children = directed_children; children; children = children->next) {
-    child_info = children->data;
-
-    if (child_info == self->visible_child)
-      break;
-
-    gtk_container_propagate_draw (self->container,
-                                  child_info->widget,
-                                  cr);
+    if (is_over)
+      shadow_progress = 1 - shadow_progress;
   }
 
-  if (self->mode_transition.start_progress < 1) {
-    gint w, h;
-    w = is_horizontal ? child_allocation.x : allocation.width;
-    h = is_horizontal ? allocation.height : child_allocation.y;
-    if (is_horizontal)
-      w = self->mode_transition.start_distance;
-    else
-      h = self->mode_transition.start_distance;
-
-    cairo_translate (cr,
-                     is_horizontal ? child_allocation.x - w : 0,
-                     is_horizontal ? 0 : child_allocation.y - h);
-    hdy_shadow_helper_draw_shadow (self->shadow_helper, cr, w, h,
-                                   self->mode_transition.start_progress,
-                                   is_horizontal ? GTK_PAN_DIRECTION_RIGHT : GTK_PAN_DIRECTION_DOWN);
-  }
-
-  cairo_restore (cr);
+  cairo_rectangle (cr, shadow_rect.x, shadow_rect.y, shadow_rect.width, shadow_rect.height);
+  cairo_clip (cr);
 
-  gtk_container_propagate_draw (self->container,
-                                self->visible_child->widget,
-                                cr);
+  for (l = stacked_children; l; l = l->next) {
+    child_info = l->data;
 
-  gtk_widget_get_allocation (self->visible_child->widget, &child_allocation);
-  cairo_save (cr);
-  cairo_rectangle (cr,
-                   is_horizontal ? child_allocation.x + child_allocation.width : 0,
-                   is_horizontal ? 0 : child_allocation.y + child_allocation.height,
-                   is_horizontal ? allocation.width - child_allocation.x - child_allocation.width : 
allocation.width,
-                   is_horizontal ? allocation.height : allocation.height - child_allocation.y - 
child_allocation.height);
-  cairo_clip (cr);
-  for (children = g_list_last (directed_children); children; children = children->prev) {
-    child_info = children->data;
+    if (!gtk_cairo_should_draw_window (cr, child_info->window))
+      continue;
 
-    if (child_info == self->visible_child)
-      break;
+    if (child_info == overlap_child)
+      cairo_restore (cr);
 
     gtk_container_propagate_draw (self->container,
                                   child_info->widget,
                                   cr);
   }
 
-  if (self->mode_transition.start_progress < 1) {
-    gint w, h;
-    w = is_horizontal ? child_allocation.x : allocation.width;
-    h = is_horizontal ? allocation.height : child_allocation.y;
-    if (is_horizontal)
-      w = self->mode_transition.start_distance;
-    else
-      h = self->mode_transition.start_distance;
-
-    cairo_translate (cr,
-                     is_horizontal ? child_allocation.x - w : 0,
-                     is_horizontal ? 0 : child_allocation.y - h);
-    hdy_shadow_helper_draw_shadow (self->shadow_helper, cr, w, h,
-                                   self->mode_transition.start_progress,
-                                   is_horizontal ? GTK_PAN_DIRECTION_RIGHT : GTK_PAN_DIRECTION_DOWN);
-  }
-
-  if (self->mode_transition.end_progress < 1) {
-    gint w, h;
-    w = allocation.width - (is_horizontal ? (child_allocation.x + child_allocation.width) : 0);
-    h = allocation.height - (is_horizontal ? 0 : (child_allocation.y + child_allocation.height));
-    if (is_horizontal)
-      w = self->mode_transition.end_distance;
-    else
-      h = self->mode_transition.end_distance;
-
-    cairo_translate (cr,
-                     is_horizontal ? child_allocation.x + child_allocation.width : 0,
-                     is_horizontal ? 0 : child_allocation.y + child_allocation.height);
-    hdy_shadow_helper_draw_shadow (self->shadow_helper, cr, w, h,
-                                   self->mode_transition.end_progress,
-                                   is_horizontal ? GTK_PAN_DIRECTION_LEFT : GTK_PAN_DIRECTION_UP);
-  }
-
+  cairo_save (cr);
+  cairo_translate (cr, shadow_rect.x, shadow_rect.y);
+  hdy_shadow_helper_draw_shadow (self->shadow_helper, cr,
+                                 shadow_rect.width, shadow_rect.height,
+                                 shadow_progress, shadow_direction);
   cairo_restore (cr);
 
-  return FALSE;
-}
-
-gboolean
-hdy_stackable_box_draw (HdyStackableBox *self,
-                        cairo_t         *cr)
-{
-  GtkWidget *widget = GTK_WIDGET (self->container);
-  GList *directed_children, *children;
-  HdyStackableBoxChildInfo *child_info;
-  GtkAllocation allocation;
-
-  if (!self->folded)
-    return hdy_stackable_box_draw_unfolded (self, cr);
-
-  directed_children = get_directed_children (self);
-
-  if (gtk_cairo_should_draw_window (cr, self->view_window)) {
-    GtkStyleContext *context;
-
-    context = gtk_widget_get_style_context (widget);
-    gtk_render_background (context,
-                           cr,
-                           0, 0,
-                           gtk_widget_get_allocated_width (widget),
-                           gtk_widget_get_allocated_height (widget));
-  }
-
-  if (self->visible_child) {
-    if (gtk_progress_tracker_get_state (&self->mode_transition.tracker) != GTK_PROGRESS_STATE_AFTER &&
-        self->folded) {
-      gboolean is_horizontal = gtk_orientable_get_orientation (GTK_ORIENTABLE (widget)) == 
GTK_ORIENTATION_HORIZONTAL;
-
-      if (self->mode_transition.start_surface == NULL &&
-          self->mode_transition.start_surface_allocation.width != 0 &&
-          self->mode_transition.start_surface_allocation.height != 0) {
-        self->mode_transition.start_surface =
-          gdk_window_create_similar_surface (gtk_widget_get_window (widget),
-                                             CAIRO_CONTENT_COLOR_ALPHA,
-                                             self->mode_transition.start_surface_allocation.width,
-                                             self->mode_transition.start_surface_allocation.height);
-
-        for (children = directed_children; children; children = children->next) {
-          g_autoptr (cairo_t) pattern_cr = NULL;
-          g_autoptr (cairo_surface_t) subsurface = NULL;
-
-          child_info = children->data;
-
-          if (child_info == self->visible_child)
-            break;
-
-          if (!gtk_widget_get_child_visible (child_info->widget))
-            continue;
-
-          gtk_widget_get_allocation (child_info->widget, &allocation);
-          subsurface = cairo_surface_create_for_rectangle (self->mode_transition.start_surface,
-                                                           allocation.x - 
self->mode_transition.start_surface_allocation.x,
-                                                           allocation.y - 
self->mode_transition.start_surface_allocation.y,
-                                                           allocation.width,
-                                                           allocation.height);
-          pattern_cr = cairo_create (subsurface);
-          gtk_widget_draw (child_info->widget, pattern_cr);
-        }
-      }
-
-      if (self->mode_transition.end_surface == NULL &&
-          self->mode_transition.end_surface_allocation.width != 0 &&
-          self->mode_transition.end_surface_allocation.height != 0) {
-        self->mode_transition.end_surface =
-          gdk_window_create_similar_surface (gtk_widget_get_window (widget),
-                                             CAIRO_CONTENT_COLOR_ALPHA,
-                                             self->mode_transition.end_surface_allocation.width,
-                                             self->mode_transition.end_surface_allocation.height);
-
-        for (children = g_list_last (directed_children); children; children = children->prev) {
-          g_autoptr (cairo_t) pattern_cr = NULL;
-          g_autoptr (cairo_surface_t) subsurface = NULL;
-
-          child_info = children->data;
-
-          if (child_info == self->visible_child)
-            break;
-
-          if (!gtk_widget_get_child_visible (child_info->widget))
-            continue;
-
-          gtk_widget_get_allocation (child_info->widget, &allocation);
-          subsurface = cairo_surface_create_for_rectangle (self->mode_transition.end_surface,
-                                                           allocation.x - 
self->mode_transition.end_surface_allocation.x,
-                                                           allocation.y - 
self->mode_transition.end_surface_allocation.y,
-                                                           allocation.width,
-                                                           allocation.height);
-          pattern_cr = cairo_create (subsurface);
-          gtk_widget_draw (child_info->widget, pattern_cr);
-        }
-      }
-
-      cairo_rectangle (cr,
-                       0, 0,
-                       gtk_widget_get_allocated_width (widget),
-                       gtk_widget_get_allocated_height (widget));
-      cairo_clip (cr);
-
-      cairo_save (cr);
-      if (self->mode_transition.start_surface != NULL) {
-        cairo_rectangle (cr,
-                         self->mode_transition.start_surface_allocation.x,
-                         self->mode_transition.start_surface_allocation.y,
-                         self->mode_transition.start_surface_allocation.width,
-                         self->mode_transition.start_surface_allocation.height);
-        cairo_clip (cr);
-        cairo_set_source_surface (cr, self->mode_transition.start_surface,
-                                  self->mode_transition.start_surface_allocation.x,
-                                  self->mode_transition.start_surface_allocation.y);
-        cairo_paint (cr);
-
-        if (self->mode_transition.start_progress < 1) {
-          gint w, h;
-          w = self->mode_transition.start_surface_allocation.width;
-          h = self->mode_transition.start_surface_allocation.height;
-          if (is_horizontal)
-            w = self->mode_transition.start_distance;
-          else
-            h = self->mode_transition.start_distance;
-
-          cairo_translate (cr,
-                           self->mode_transition.start_surface_allocation.width - w,
-                           self->mode_transition.start_surface_allocation.height - h);
-          hdy_shadow_helper_draw_shadow (self->shadow_helper, cr, w, h,
-                                         self->mode_transition.start_progress,
-                                         is_horizontal ? GTK_PAN_DIRECTION_RIGHT : GTK_PAN_DIRECTION_DOWN);
-        }
-      }
-      cairo_restore (cr);
-
-      cairo_save (cr);
-      if (self->mode_transition.end_surface != NULL) {
-        cairo_rectangle (cr,
-                         self->mode_transition.end_surface_clip.x,
-                         self->mode_transition.end_surface_clip.y,
-                         self->mode_transition.end_surface_clip.width,
-                         self->mode_transition.end_surface_clip.height);
-        cairo_clip (cr);
-        cairo_set_source_surface (cr, self->mode_transition.end_surface,
-                                  self->mode_transition.end_surface_allocation.x,
-                                  self->mode_transition.end_surface_allocation.y);
-        cairo_paint (cr);
-
-        if (self->mode_transition.end_progress < 1) {
-          gint w, h;
-          w = self->mode_transition.end_surface_allocation.width;
-          h = self->mode_transition.end_surface_allocation.height;
-          if (is_horizontal)
-            w = self->mode_transition.end_distance;
-          else
-            h = self->mode_transition.end_distance;
-
-          cairo_translate (cr, self->mode_transition.end_surface_clip.x,
-                           self->mode_transition.end_surface_clip.y);
-          hdy_shadow_helper_draw_shadow (self->shadow_helper, cr, w, h,
-                                         self->mode_transition.end_progress,
-                                         is_horizontal ? GTK_PAN_DIRECTION_LEFT : GTK_PAN_DIRECTION_UP);
-        }
-      }
-      cairo_restore (cr);
-
-      if (gtk_cairo_should_draw_window (cr, self->bin_window))
-        gtk_container_propagate_draw (self->container,
-                                      self->visible_child->widget,
-                                      cr);
-    }
-    else if (self->child_transition.is_gesture_active ||
-             gtk_progress_tracker_get_state (&self->child_transition.tracker) != GTK_PROGRESS_STATE_AFTER) {
-      if (self->child_transition.last_visible_surface == NULL &&
-          self->last_visible_child != NULL) {
-        g_autoptr (cairo_t) pattern_cr = NULL;
-
-        gtk_widget_get_allocation (self->last_visible_child->widget,
-                                   &self->child_transition.last_visible_surface_allocation);
-        self->child_transition.last_visible_surface =
-          gdk_window_create_similar_surface (gtk_widget_get_window (widget),
-                                             CAIRO_CONTENT_COLOR_ALPHA,
-                                             self->child_transition.last_visible_surface_allocation.width,
-                                             self->child_transition.last_visible_surface_allocation.height);
-        pattern_cr = cairo_create (self->child_transition.last_visible_surface);
-        /* We don't use propagate_draw here, because we don't want to apply
-         * the bin_window offset
-         */
-        gtk_widget_draw (self->last_visible_child->widget, pattern_cr);
-      }
-
-      cairo_rectangle (cr,
-                       0, 0,
-                       gtk_widget_get_allocated_width (widget),
-                       gtk_widget_get_allocated_height (widget));
-      cairo_clip (cr);
-
-      switch (self->transition_type) {
-      case HDY_STACKABLE_BOX_TRANSITION_TYPE_OVER:
-      case HDY_STACKABLE_BOX_TRANSITION_TYPE_UNDER:
-        hdy_stackable_box_draw_over_or_under (self, cr);
-        break;
-      case HDY_STACKABLE_BOX_TRANSITION_TYPE_SLIDE:
-        hdy_stackable_box_draw_slide (self, cr);
-        break;
-      default:
-        g_assert_not_reached ();
-      }
-    }
-    else if (gtk_cairo_should_draw_window (cr, self->bin_window))
-      gtk_container_propagate_draw (self->container,
-                                    self->visible_child->widget,
-                                    cr);
-  }
-
-  return FALSE;
+  return GDK_EVENT_PROPAGATE;
 }
 
 static void
@@ -2723,6 +2225,49 @@ hdy_stackable_box_child_visibility_notify_cb (GObject    *obj,
   }
 }
 
+static void
+register_window (HdyStackableBox          *self,
+                 HdyStackableBoxChildInfo *child)
+{
+  GtkWidget *widget = GTK_WIDGET (self->container);
+  GdkWindowAttr attributes = { 0 };
+  GdkWindowAttributesType attributes_mask;
+
+  attributes.x = child->alloc.x;
+  attributes.y = child->alloc.y;
+  attributes.width = child->alloc.width;
+  attributes.height = child->alloc.height;
+  attributes.window_type = GDK_WINDOW_CHILD;
+  attributes.wclass = GDK_INPUT_OUTPUT;
+  attributes.visual = gtk_widget_get_visual (widget);
+  attributes.event_mask = gtk_widget_get_events (widget);
+  attributes_mask = (GDK_WA_X | GDK_WA_Y) | GDK_WA_VISUAL;
+
+  attributes.event_mask = gtk_widget_get_events (widget) |
+                          gtk_widget_get_events (child->widget);
+
+  child->window = gdk_window_new (self->view_window, &attributes, attributes_mask);
+  gtk_widget_register_window (widget, child->window);
+
+  gtk_widget_set_parent_window (child->widget, child->window);
+
+  gdk_window_show (child->window);
+}
+
+static void
+unregister_window (HdyStackableBox          *self,
+                   HdyStackableBoxChildInfo *child)
+{
+  GtkWidget *widget = GTK_WIDGET (self->container);
+
+  if (!child->window)
+    return;
+
+  gtk_widget_unregister_window (widget, child->window);
+  gdk_window_destroy (child->window);
+  child->window = NULL;
+}
+
 void
 hdy_stackable_box_add (HdyStackableBox *self,
                        GtkWidget       *widget)
@@ -2731,10 +2276,6 @@ hdy_stackable_box_add (HdyStackableBox *self,
 
   g_return_if_fail (gtk_widget_get_parent (widget) == NULL);
 
-  gtk_widget_set_child_visible (widget, FALSE);
-  gtk_widget_set_parent_window (widget, self->bin_window);
-  gtk_widget_set_parent (widget, GTK_WIDGET (self->container));
-
   child_info = g_new0 (HdyStackableBoxChildInfo, 1);
   child_info->widget = widget;
   child_info->allow_visible = TRUE;
@@ -2742,10 +2283,11 @@ hdy_stackable_box_add (HdyStackableBox *self,
   self->children = g_list_append (self->children, child_info);
   self->children_reversed = g_list_prepend (self->children_reversed, child_info);
 
-  if (self->bin_window)
-    gdk_window_set_events (self->bin_window,
-                           gdk_window_get_events (self->bin_window) |
-                           gtk_widget_get_events (widget));
+  if (gtk_widget_get_realized (GTK_WIDGET (self->container)))
+    register_window (self, child_info);
+
+  gtk_widget_set_child_visible (widget, FALSE);
+  gtk_widget_set_parent (widget, GTK_WIDGET (self->container));
 
   g_signal_connect (widget, "notify::visible",
                     G_CALLBACK (hdy_stackable_box_child_visibility_notify_cb), self);
@@ -2787,6 +2329,8 @@ hdy_stackable_box_remove (HdyStackableBox *self,
   if (gtk_widget_get_visible (widget))
     gtk_widget_queue_resize (GTK_WIDGET (self->container));
 
+  unregister_window (self, child_info);
+
   gtk_widget_unparent (widget);
 }
 
@@ -2939,9 +2483,6 @@ hdy_stackable_box_finalize (GObject *object)
 
   hdy_stackable_box_unschedule_child_ticks (self);
 
-  if (self->child_transition.last_visible_surface != NULL)
-    cairo_surface_destroy (self->child_transition.last_visible_surface);
-
   G_OBJECT_CLASS (hdy_stackable_box_parent_class)->finalize (object);
 }
 
@@ -2953,8 +2494,6 @@ hdy_stackable_box_realize (HdyStackableBox *self)
   GdkWindowAttr attributes = { 0 };
   GdkWindowAttributesType attributes_mask;
   GList *children;
-  HdyStackableBoxChildInfo *child_info;
-  GtkBorder padding;
 
   gtk_widget_set_realized (widget, TRUE);
   gtk_widget_set_window (widget, g_object_ref (gtk_widget_get_parent_window (widget)));
@@ -2975,37 +2514,19 @@ hdy_stackable_box_realize (HdyStackableBox *self)
                                       &attributes, attributes_mask);
   gtk_widget_register_window (widget, self->view_window);
 
-  get_padding (widget, &padding);
-  attributes.x = padding.left;
-  attributes.y = padding.top;
-  attributes.width = allocation.width;
-  attributes.height = allocation.height;
-
-  for (children = self->children; children != NULL; children = children->next) {
-    child_info = children->data;
-    attributes.event_mask |= gtk_widget_get_events (child_info->widget);
-  }
-
-  self->bin_window = gdk_window_new (self->view_window, &attributes, attributes_mask);
-  gtk_widget_register_window (widget, self->bin_window);
-
-  for (children = self->children; children != NULL; children = children->next) {
-    child_info = children->data;
-
-    gtk_widget_set_parent_window (child_info->widget, self->bin_window);
-  }
-
-  gdk_window_show (self->bin_window);
+  for (children = self->children; children != NULL; children = children->next)
+    register_window (self, children->data);
 }
 
 void
 hdy_stackable_box_unrealize (HdyStackableBox *self)
 {
   GtkWidget *widget = GTK_WIDGET (self->container);
+  GList *children;
+
+  for (children = self->children; children != NULL; children = children->next)
+    unregister_window (self, children->data);
 
-  gtk_widget_unregister_window (widget, self->bin_window);
-  gdk_window_destroy (self->bin_window);
-  self->bin_window = NULL;
   gtk_widget_unregister_window (widget, self->view_window);
   gdk_window_destroy (self->view_window);
   self->view_window = NULL;