Nuke the grid centering code

It was causing problems when there was exactly a screenful of items to
be displayed as the layout would bounce betwen having a scrollbar and
not having a scrollbar.

src/calibre/gui2/library/alternate_views.py

@@ -558,33 +558,6 @@ class GridView(QListView):
         self.setPalette(pal)
         self.delegate.highlight_color = pal.color(pal.Text)
 
-    def center_grid(self):
-        if self.gui.library_view.alternate_views.current_view is not self:
-            return
-        layout_width = self.viewport().width() + self.padding_left
-        try:
-            sz = self.spacing()*2 + self.delegate.item_size.width()
-            num = layout_width // sz
-        except (AttributeError, ZeroDivisionError):
-            return
-        extra = max(0, int((layout_width - (num * sz)) / 2))
-        if extra != self.padding_left:
-            self.padding_left = extra
-            self.setViewportMargins(self.padding_left, 0, 0, 0)
-
-    def resizeEvent(self, e):
-        self.center_grid()
-        return QListView.resizeEvent(self, e)
-
-    def event(self, e):
-        if e.type() == e.Paint:
-            p = QPainter(self)
-            # Without this the viewport margin is rendered in QPalette::Window
-            # instead of QPalette::Base
-            p.fillRect(0, 0, self.padding_left+2, self.height(), self.palette().color(QPalette.Base))
-            p.end()
-        return QListView.event(self, e)
-
     def refresh_settings(self):
         size_changed = (
             gprefs['cover_grid_width'] != self.delegate.original_width or
@@ -612,7 +585,6 @@ class GridView(QListView):
             self.render_thread = Thread(target=self.render_covers)
             self.render_thread.daemon = True
             self.render_thread.start()
-        self.center_grid()
 
     def render_covers(self):
         q = self.delegate.render_queue