PR Summary

Closes#10874. See also#11004, and#10881. This is a more general backstop than the ticking fixes being proposed in#10874.

If a text obejct is created, but never drawn, its renderer never gets set (self._renderer). Subsequnet calls toself.get_window_extent() that do not specify the renderer fail withRuntimeError('Cannot get window extent w/o renderer').

Here I propose that we fall back on the cached renderer for the figure.

Test code:

import matplotlibmatplotlib.use('Agg')import matplotlib.pyplot as pltfig = plt.figure()ax = fig.add_subplot(111, frameon=True)ax.plot()plt.get_current_fig_manager().canvas.draw()for xtick in ax.get_xticklabels():    bb = xtick.get_window_extent()

PR Checklist

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