From f98abcc2bff53188311a417a08d53350185c266f Mon Sep 17 00:00:00 2001
From: Sascha Silbe <silbe@activitycentral.com>
Date: Mon, 21 Mar 2011 14:15:40 +0000
Subject: accelerated scrolling WIP

---
diff --git a/src/sugar/graphics/window.py b/src/sugar/graphics/window.py
index 506c046..f5bd8d3 100644
--- a/src/sugar/graphics/window.py
+++ b/src/sugar/graphics/window.py
@@ -308,8 +308,8 @@ class MultiModeWindow(gtk.Window):
     A transition effect may be provided when switching between modes.
     """
 
-    _SCROLL_INTERVAL_MS = 40
-    _SCROLL_TIME_MS = 500
+    _SCROLL_INTERVAL_MS = 300
+    _SCROLL_TIME_MS = 2100
     _SCROLL_STEPS = _SCROLL_TIME_MS // _SCROLL_INTERVAL_MS
 
     def __init__(self, modes, **args):
@@ -339,6 +339,8 @@ class MultiModeWindow(gtk.Window):
         self.__scroll_step = 0
         self.__scroll_direction = 1
         self.__scroll_start_time = None
+        self.__scroll_old_snaphot = None
+        self.__scroll_new_snaphot = None
 
         for mode in modes:
             self.__vboxes[mode] = gtk.VBox()
@@ -394,11 +396,33 @@ class MultiModeWindow(gtk.Window):
         else:
             self.__scroll_direction = -1
 
+        old_pixmap = self.__vboxes[self._current_mode].get_snapshot()
+        self.__scroll_old_snapshot = gtk.image_new_from_pixmap(old_pixmap,
+                                                               None)
+
+        # gtk.OffscreenWindow is only available in PyGtk 2.22+, so we need to
+        # resort to a hack for now
         self.__vboxes[mode].hide()
+        self.__vboxes[mode].connect('expose-event', self._switch_to_mode_cb)
         self.__layout.put(self.__vboxes[mode],
                           self.__width * self.__scroll_direction, 0)
         self.__vboxes[mode].resize_children()
         self.__vboxes[mode].show()
+#        gobject.idle_add(self._switch_to_mode_cb)
+
+    @trace()
+    def _switch_to_mode_cb(self, *args):
+        new_pixmap = self.__vboxes[self._next_mode].get_snapshot()
+        self.__layout.remove(self.__vboxes[self._next_mode])
+        self.__scroll_new_snapshot = gtk.image_new_from_pixmap(new_pixmap,
+                                                               None)
+
+        self.__layout.remove(self.__vboxes[self._current_mode])
+        self.__layout.add(self.__scroll_old_snapshot)
+        self.__layout.put(self.__scroll_new_snapshot,
+                          self.__width * self.__scroll_direction, 0)
+        self.__layout.show_all()
+
         gobject.timeout_add(MultiModeWindow._SCROLL_INTERVAL_MS,
                             self.__scroll_cb)
 
@@ -436,8 +460,8 @@ class MultiModeWindow(gtk.Window):
                 self._unfullscreen_button_timeout_id = None
 
             self._unfullscreen_button_timeout_id = \
-                gobject.timeout_add_seconds( \
-                    _UNFULLSCREEN_BUTTON_VISIBILITY_TIMEOUT, \
+                gobject.timeout_add_seconds(
+                    _UNFULLSCREEN_BUTTON_VISIBILITY_TIMEOUT,
                     self.__unfullscreen_button_timeout_cb)
 
     def unfullscreen(self):
@@ -573,8 +597,8 @@ class MultiModeWindow(gtk.Window):
                     self._unfullscreen_button_timeout_id = None
 
                 self._unfullscreen_button_timeout_id = \
-                    gobject.timeout_add_seconds( \
-                        _UNFULLSCREEN_BUTTON_VISIBILITY_TIMEOUT, \
+                    gobject.timeout_add_seconds(
+                        _UNFULLSCREEN_BUTTON_VISIBILITY_TIMEOUT,
                         self.__unfullscreen_button_timeout_cb)
         return False
 
@@ -625,22 +649,34 @@ class MultiModeWindow(gtk.Window):
 
         pixel_per_step = self.__width // MultiModeWindow._SCROLL_STEPS
         scroll_pixels = self.__scroll_step * pixel_per_step
+        #~ if self.__scroll_direction == 1:
+            #~ self.__layout.move(self.__vboxes[self._current_mode],
+                               #~ -scroll_pixels, 0)
+            #~ self.__layout.move(self.__vboxes[self._next_mode],
+                               #~ self.__width - scroll_pixels, 0)
+        #~ else:
+            #~ self.__layout.move(self.__vboxes[self._current_mode],
+                               #~ scroll_pixels, 0)
+            #~ self.__layout.move(self.__vboxes[self._next_mode],
+                               #~ scroll_pixels - self.__width, 0)
         if self.__scroll_direction == 1:
-            self.__layout.move(self.__vboxes[self._current_mode],
+            self.__layout.move(self.__scroll_old_snapshot,
                                -scroll_pixels, 0)
-            self.__layout.move(self.__vboxes[self._next_mode],
+            self.__layout.move(self.__scroll_new_snapshot,
                                self.__width - scroll_pixels, 0)
         else:
-            self.__layout.move(self.__vboxes[self._current_mode],
+            self.__layout.move(self.__scroll_old_snapshot,
                                scroll_pixels, 0)
-            self.__layout.move(self.__vboxes[self._next_mode],
+            self.__layout.move(self.__scroll_new_snapshot,
                                scroll_pixels - self.__width, 0)
         return True
 
     @trace()
     def _switch_mode_now(self):
-        self.__layout.remove(self.__vboxes[self._current_mode])
-        self.__layout.move(self.__vboxes[self._next_mode], 0, 0)
+#        self.__layout.remove(self.__vboxes[self._current_mode])
+        self.__layout.add(self.__vboxes[self._next_mode])
+        self.__layout.remove(self.__scroll_old_snapshot)
+        self.__layout.remove(self.__scroll_new_snapshot)
         self._current_mode = self._next_mode
         self._next_mode = None
 
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