short circuit get_clearance

weasyprint/layout/float.py

@@ -118,8 +118,13 @@ def get_clearance(context, box, collapsed_margin=0):
     hypothetical_position = box.position_y + collapsed_margin
     # Hypothetical position is the position of the top border edge
     for excluded_shape in context.excluded_shapes:
+        y = excluded_shape.position_y
+        # Skip expensive attribute lookups if there's already
+        # no possibility of clearance.
+        if hypothetical_position >= y:
+            continue
+        h = excluded_shape.margin_height()
         if box.style['clear'] in (excluded_shape.style.float, 'both'):
-            y, h = excluded_shape.position_y, excluded_shape.margin_height()
             if hypothetical_position < y + h:
                 clearance = max(
                     (clearance or 0), y + h - hypothetical_position)