Make sure slider uses "x" sign before multiplicative factor.

Author: anntzer

lib/matplotlib/widgets.py

@@ -362,6 +362,7 @@ def __init__(self, ax, label, valmin, valmax, valinit=0.5, valfmt=None,
             self._fmt = ticker.ScalarFormatter()
             self._fmt.set_axis(axis)
         self._fmt.set_useOffset(False)  # No additive offset.
+        self._fmt.set_useMathText(True)  # x sign before multiplicative offset.
 
         ax.set_xticks([])
         ax.set_yticks([])