PR Summary

Closes #13530

Before, if we inverted the colorbar the tick trimming logic was incorrect and we trimmed all the ticks! This fixes that.

import matplotlib.pyplot as plt
import numpy as np
import matplotlib.colors as mcolors

fig, axs = plt.subplots(2, 1)
axs = axs.flat
ax = axs[0]
pc = ax.pcolormesh(10**np.arange(1,5).reshape(2, 2), norm=mcolors.LogNorm())
cbar = fig.colorbar(pc, ax=ax, extend='both')
ticks = cbar.get_ticks()
cbar.ax.invert_yaxis()

ax = axs[1]
pc = ax.pcolormesh(np.arange(1,5).reshape(2, 2))
cbar = fig.colorbar(pc, ax=ax, extend='both')
ticks = cbar.get_ticks()
cbar.ax.invert_yaxis()
cbar.minorticks_on()
plt.show()

Before:

Note this also gives an error and the figure can't be saved:

  File "/Users/jklymak/matplotlib/lib/matplotlib/axis.py", line 1312, in get_minorticklocs
    minor_locs = self.minor.locator()
  File "/Users/jklymak/matplotlib/lib/matplotlib/colorbar.py", line 272, in __call__
    return ticks[(ticks >= vmin - rtol) & (ticks <= vmax + rtol)]
TypeError: only integer scalar arrays can be converted to a scalar index

After:

and no error....

PR Checklist

• Has Pytest style unit tests
• Code is Flake 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