From 60d0d9caec902cf6824ce01368436e58925ceff4 Mon Sep 17 00:00:00 2001
From: Walter Bender <walter.bender@gmail.com>
Date: Tue, 10 Apr 2012 21:51:07 +0000
Subject: scroll canvas on drag

---
diff --git a/TurtleArt/tawindow.py b/TurtleArt/tawindow.py
index c1fa4a6..f6c41b4 100644
--- a/TurtleArt/tawindow.py
+++ b/TurtleArt/tawindow.py
@@ -201,6 +201,7 @@ class TurtleArtWindow():
         self.drag_group = None
         self.drag_turtle = 'move', 0, 0
         self.drag_pos = 0, 0
+        self.dragging_canvas = [False, 0, 0]
         self.turtle_movement_to_share = None
         self.paste_offset = 20  # Don't paste on top of where you copied.
 
@@ -1181,8 +1182,12 @@ class TurtleArtWindow():
 
         self.dx = 0
         self.dy = 0
+        self.dragging_canvas[1] = x
+        self.dragging_canvas[2] = y
         if spr is None:
+            self.dragging_canvas[0] = True
             return True
+        self.dragging_canvas[0] = False
         self.selected_spr = spr
 
         # From the sprite at x, y, look for a corresponding block
@@ -1685,6 +1690,16 @@ class TurtleArtWindow():
 
     def _mouse_move(self, x, y):
         """ Process mouse movements """
+
+        if self.dragging_canvas[0]:
+            dx = self.dragging_canvas[1] - x
+            dy = self.dragging_canvas[2] - y
+            self.dragging_canvas[1] = x
+            self.dragging_canvas[2] = y
+            if self.running_sugar:
+                self.activity.adjust_sw(dx, dy)
+            return True
+
         self.block_operation = 'move'
 
         # First, check to see if we are dragging or rotating a turtle.
@@ -1853,6 +1868,13 @@ class TurtleArtWindow():
         return True
 
     def button_release(self, x, y):
+        if self.dragging_canvas[0]:
+            self.dragging_canvas[0] = False
+            self.dragging_canvas[1] = x
+            self.dragging_canvas[2] = y
+            self.activity.adjust_palette()
+            return True
+
         # We may have been moving the turtle
         if self.selected_turtle is not None:
             (tx, ty) = self.selected_turtle.get_xy()
diff --git a/TurtleArtActivity.py b/TurtleArtActivity.py
index c6c00b9..8c4dcc9 100644
--- a/TurtleArtActivity.py
+++ b/TurtleArtActivity.py
@@ -112,6 +112,8 @@ class TurtleArtActivity(activity.Activity):
                 count += 1
             self.metadata['activity count'] = str(count)
 
+        self._defer_palette_move = False
+
     # Activity toolbar callbacks
 
     def do_save_as_html_cb(self, button):
@@ -380,6 +382,33 @@ class TurtleArtActivity(activity.Activity):
         self.tw.load_file(True)
         self.tw.run_button(0)
 
+    def adjust_sw(self, dx, dy):
+        ''' Adjust the scrolled window position. '''
+        hadj = self.sw.get_hadjustment()
+        hvalue = hadj.get_value() + dx
+        if hvalue < hadj.get_lower():
+            hvalue = hadj.get_lower()
+        elif hvalue > hadj.get_upper():
+            hvalue = hadj.get_upper()
+        hadj.set_value(hvalue)
+        self.sw.set_hadjustment(hadj)
+        vadj = self.sw.get_vadjustment()
+        vvalue = vadj.get_value() + dy
+        if vvalue < vadj.get_lower():
+            vvalue = vadj.get_lower()
+        elif vvalue > vadj.get_upper():
+            vvalue = vadj.get_upper()
+        vadj.set_value(vvalue)
+        self.sw.set_vadjustment(vadj)
+        self._defer_palette_move = True
+
+    def adjust_palette(self):
+        ''' Align palette to scrolled window position. '''
+        if not self.tw.hw in [XO1]:
+            self.tw.move_palettes(self.sw.get_hadjustment().get_value(),
+                                  self.sw.get_vadjustment().get_value())
+        self._defer_palette_move = False
+
     def recenter(self):
         ''' Recenter scrolled window around canvas. '''
         self.hadj_value = 0
@@ -390,8 +419,7 @@ class TurtleArtActivity(activity.Activity):
         vadj = self.sw.get_vadjustment()
         vadj.set_value(self.vadj_value)
         self.sw.set_vadjustment(vadj)
-        if not self.tw.hw in [XO1]:
-            self.tw.move_palettes(self.hadj_value, self.vadj_value)
+        self.adjust_palette()
 
     def do_fullscreen_cb(self, button):
         ''' Hide the Sugar toolbars. '''
@@ -888,7 +916,7 @@ class TurtleArtActivity(activity.Activity):
         self.hadj_value = hadj.get_value()
         vadj = self.sw.get_vadjustment()
         self.vadj_value = vadj.get_value()
-        if not self.tw.hw in [XO1]:
+        if not self.tw.hw in [XO1] and not self._defer_palette_move:
             gobject.idle_add(self.tw.move_palettes, self.hadj_value,
                              self.vadj_value)
 
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