PR Summary

Fixes #6284. The problem was that autoscaling was ignoring all axis limits when any of them were infinite. However we should handle this on a case by case basis: If only the x-limits are infinite, we can still use the y-limits, and vice versa. This makes autoscaling work properly with vspans (which only have infinite y-limits).

In order to reproduce the issue (and verify it is fixed), try this:

import matplotlib.pyplot as plt

fig, ax = plt.subplots()
ax.axvspan(1,2)

bx = ax.twinx()
bx.plot([0,.5], [1,2])
plt.show()

If fixed, you should see that the vspan does not disappear.

PR Checklist

• Has Pytest style unit tests
• Code is PEP 8 compliant
• n/a New features are documented, with examples if plot related
• n/a Documentation is sphinx and numpydoc compliant
• n/a Added an entry to doc/users/whats_new.rst if major new feature
• n/a Documented in doc/api/api_changes.rst if API changed in a backward-incompatible way