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Correctly set formatters and locators on removed shared axis #14997

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Merged
merged 1 commit into from
Aug 19, 2019
+30 −11
Merged

Correctly set formatters and locators on removed shared axis #14997

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34 changes: 23 additions & 11 deletions lib/matplotlib/figure.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1596,25 +1596,37 @@ def subplots(self, nrows=1, ncols=1, sharex=False, sharey=False,
return axarr

def _remove_ax(self, ax):
def _reset_loc_form(axis):
def _reset_locators_and_formatters(axis):
# Set the formatters and locators to be associated with axis
# (where previously they may have been associated with another
# Axis isntance)
#
# Because set_major_formatter() etc. force isDefault_* to be False,
# we have to manually check if the original formatter was a
# default and manually set isDefault_* if that was the case.
majfmt = axis.get_major_formatter()
if not majfmt.axis.isDefault_majfmt:
axis.set_major_formatter(majfmt)
isDefault = majfmt.axis.isDefault_majfmt
axis.set_major_formatter(majfmt)
if isDefault:
majfmt.axis.isDefault_majfmt = True

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This doesn't make any sense to me. You get the formatter for axis and then you set the formatter for axis to that formatter, and then you set the isDefault to the value axis had before. I don't see how this code is doing anything.

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I think the confusion here stems from the mappings of formatters to axis.

  • Axis > Formatter is a one to one mapping
  • Formatter > Axis is a one to many mapping

So a single Formatter is linked to a single Axis, but many other Axis can make use of that Formatter. I agree this is a nightmare to understand, but without re-doing the internals of how this works it is how it is.

So this code is getting the formatter that axis is using, (that it might be borrowing) and then explicitly associating that formatter with axis (so it is no longer borrowing it).

majloc = axis.get_major_locator()
if not majloc.axis.isDefault_majloc:
axis.set_major_locator(majloc)
isDefault = majloc.axis.isDefault_majloc
axis.set_major_locator(majloc)
if isDefault:
majloc.axis.isDefault_majloc = True

minfmt = axis.get_minor_formatter()
if not minfmt.axis.isDefault_minfmt:
axis.set_minor_formatter(minfmt)
isDefault = majloc.axis.isDefault_minfmt
axis.set_minor_formatter(minfmt)
if isDefault:
minfmt.axis.isDefault_minfmt = True

minloc = axis.get_minor_locator()
if not minfmt.axis.isDefault_minloc:
axis.set_minor_locator(minloc)
isDefault = majloc.axis.isDefault_minloc
axis.set_minor_locator(minloc)
if isDefault:
minloc.axis.isDefault_minloc = True

def _break_share_link(ax, grouper):
siblings = grouper.get_siblings(ax)
Expand All @@ -1628,11 +1640,11 @@ def _break_share_link(ax, grouper):
self.delaxes(ax)
last_ax = _break_share_link(ax, ax._shared_y_axes)
if last_ax is not None:
_reset_loc_form(last_ax.yaxis)
_reset_locators_and_formatters(last_ax.yaxis)

last_ax = _break_share_link(ax, ax._shared_x_axes)
if last_ax is not None:
_reset_loc_form(last_ax.xaxis)
_reset_locators_and_formatters(last_ax.xaxis)

def clf(self, keep_observers=False):
"""
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7 changes: 7 additions & 0 deletions lib/matplotlib/tests/test_figure.py
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Original file line number Diff line number Diff line change
Expand Up @@ -480,3 +480,10 @@ def test_axes_removal():
axs[0].plot([datetime(2000, 1, 1), datetime(2000, 2, 1)], [0, 1])
assert isinstance(axs[0].xaxis.get_major_formatter(),
ScalarFormatter)


def test_removed_axis():
# Simple smoke test to make sure removing a shared axis works
fig, axs = plt.subplots(2, sharex=True)
axs[0].remove()
fig.canvas.draw()