Use scaled display size in wallpaper constraint.

    private Point getDefaultDisplaySize() {

        Point p = new Point();

        try {

            mIWindowManager.getInitialDisplaySize(Display.DEFAULT_DISPLAY, p);

        } catch (RemoteException e) {

            // not remote

        }

        WindowManager wm = (WindowManager)mContext.getSystemService(Context.WINDOW_SERVICE);

        Display d = wm.getDefaultDisplay();

        d.getRealSize(p);

        return p;

    }