Bug report

Bug summary

When setting the linewidth to a value close to zero (like 1e-15) and having a dashed linestyle in a pyplot, the application freezes.

Code for reproduction

frommatplotlibimportpyplotaspltx= [0,1]y= [0,1]p=plt.plot(x,y,ls="--",lw=0.1,ms=0.1,marker="o",alpha=1.0)# ok# plt.setp(p, lw = 1e-3)# freezeplt.setp(p,lw=1e-15)plt.show()

Actual outcome

The window opens but no plot (not even axis) is shown, instead the window is not responding.

Expected outcome

Primary Expectation: The application should not freeze.
Secondary Expectation: Show either no line at all or as thin as displayable.

Matplotlib version

• Operating system: Windows 7
• Matplotlib version: 2.2.4 (same with 3.1.0)
• Matplotlib backend (print(matplotlib.get_backend())): TkAgg (same with Qt5Agg/PySide2)
• Python version: 3.6.5 32bit

installed with pip