Refactor window size, update selection cursor on new screen

src/Dodge/Base/Window.hs

@@ -45,8 +45,8 @@ screenPolygonBord xbord ybord cfig w = [tr, tl, bl, br]
     bl = theTransform (V2 (- hw) (- hh))
 
 halfWidth, halfHeight :: Configuration -> Float
-halfWidth w = _windowX w / 2
-halfHeight w = _windowY w / 2
+halfWidth = (0.5 *) .  windowXFloat
+halfHeight = (0.5 *) .  windowYFloat
 
 -- | A box of the size of the screen in screen centered coordinates
 screenBox :: Configuration -> [Point2]