The Qt5Agg backend is extremely slow when panning a plot. When continuously moving the mouse the refresh rates go down further. At some point it takes multiple seconds for the plot to redraw, leaving the user interface completely unresponsive. On the same machine the Qt4Agg backend works fine in comparison.

import matplotlib
matplotlib.use("Qt5Agg")
import matplotlib.pyplot as plt
plt.plot(np.range(5))
plt.show()