[libchamplain] Use view height for computing y delta in the keyboard mapping demo

[Jiří Techet <jiritechet src gnome org>]

commit b470dc9d12f6fe301d21f4d9504d27ca1301b246
Author: Jiří Techet <techet gmail com>
Date:   Sun Oct 19 21:41:16 2014 +0200

    Use view height for computing y delta in the keyboard mapping demo

 demos/keyboard-mapping.py |   11 ++++++-----
 1 files changed, 6 insertions(+), 5 deletions(-)
---
diff --git a/demos/keyboard-mapping.py b/demos/keyboard-mapping.py
index 85444c1..7b7663d 100755
--- a/demos/keyboard-mapping.py
+++ b/demos/keyboard-mapping.py
@@ -25,15 +25,16 @@ class KeyboardMapping:
         window.show_all()
 
     def on_key_press(self, widget, ev):
-        delta = self.widget.get_allocation().width / 4
+        deltax = self.widget.get_allocation().width / 4
+        deltay = self.widget.get_allocation().height / 4
         if ev.keyval == Gdk.KEY_Left: 
-            self.scroll(-delta, 0)
+            self.scroll(-deltax, 0)
         elif ev.keyval == Gdk.KEY_Right: 
-            self.scroll(delta, 0)
+            self.scroll(deltax, 0)
         elif ev.keyval == Gdk.KEY_Up: 
-            self.scroll(0, -delta)
+            self.scroll(0, -deltay)
         elif ev.keyval == Gdk.KEY_Down: 
-            self.scroll(0, delta)
+            self.scroll(0, deltay)
         elif ev.keyval == Gdk.KEY_plus or ev.keyval == Gdk.KEY_KP_Add:
             self.view.zoom_in()
         elif ev.keyval == Gdk.KEY_minus or ev.keyval == Gdk.KEY_KP_Subtract: