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FIX: use requested style for empty bar charts. #31973

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FIX: use requested style for empty bar charts. #31973

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18 changes: 18 additions & 0 deletions lib/matplotlib/axes/_axes.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2453,6 +2453,15 @@ def bar(self, x, height, width=0.8, bottom=None, *, align="center",
linewidth = kwargs.pop('linewidth', None)
hatch = kwargs.pop('hatch', None)

# store style for an empty data scenario that would otherwise be lost.
legend_fallback_kwargs = {
'facecolor': facecolor[0] if len(facecolor) else 'none',
'edgecolor': edgecolor,
'linewidth': linewidth,
'label': '_nolegend_',
'hatch': hatch,
}

# Because xerr and yerr will be passed to errorbar, most dimension
# checking and processing will be left to the errorbar method.
xerr = kwargs.pop('xerr', None)
Expand Down Expand Up @@ -2618,6 +2627,14 @@ def bar(self, x, height, width=0.8, bottom=None, *, align="center",
self.add_patch(r)
patches.append(r)

if not patches:
legend_fallback = mpatches.Rectangle(
xy=(0, 0), width=0, height=0,
**legend_fallback_kwargs)
legend_fallback._internal_update(kwargs)
else:
legend_fallback = None

if xerr is not None or yerr is not None:
if orientation == 'vertical':
# using list comps rather than arrays to preserve unit info
Expand Down Expand Up @@ -2646,6 +2663,7 @@ def bar(self, x, height, width=0.8, bottom=None, *, align="center",
bar_container = BarContainer(patches, errorbar, datavalues=datavalues,
orientation=orientation,
label=bar_container_label)
bar_container._legend_fallback = legend_fallback
self.add_container(bar_container)

if tick_labels is not None:
Expand Down
2 changes: 2 additions & 0 deletions lib/matplotlib/legend_handler.py
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Original file line number Diff line number Diff line change
Expand Up @@ -39,6 +39,8 @@ def legend_artist(self, legend, orig_handle, fontsize, handlebox)

def update_from_first_child(tgt, src):
first_child = next(iter(src.get_children()), None)
if first_child is None:
first_child = getattr(src, '_legend_fallback', None)
if first_child is not None:
tgt.update_from(first_child)

Expand Down
33 changes: 33 additions & 0 deletions lib/matplotlib/tests/test_legend.py
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Expand Up @@ -663,6 +663,39 @@ def test_empty_bar_chart_with_legend():
plt.legend()


def test_empty_bar_chart_legend_style():
# issue #21506
Comment on lines +666 to +667

@QuLogic QuLogic Aug 11, 2026

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Suggested change
def test_empty_bar_chart_legend_style():
# issue #21506
def test_empty_bar_chart_legend_style():

_, ax = plt.subplots()
ax.bar([], [], color='red', alpha=0.3, label='empty')
assert mpl.colors.same_color(
ax.legend().legend_handles[0].get_facecolor(),
mpl.colors.to_rgba('red', 0.3),

@QuLogic QuLogic Aug 11, 2026

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You can pass this directly instead of eager resolving it.

Suggested change
mpl.colors.to_rgba('red', 0.3),
('red', 0.3),

)

_, ax = plt.subplots()
ax.bar([], [], label='a')
ax.bar([], [], label='b')
handles = ax.legend().legend_handles
assert mpl.colors.same_color(handles[0].get_facecolor(), 'C0')
assert mpl.colors.same_color(handles[1].get_facecolor(), 'C1')

_, ax = plt.subplots()
ax.bar([], [],
facecolor='red', edgecolor='black', linewidth=3,
label='styled', hatch='//')
handle = ax.legend().legend_handles[0]
assert mpl.colors.same_color(handle.get_edgecolor(), 'black')

@QuLogic QuLogic Aug 11, 2026

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Should you not be checking facecolor as well?

assert handle.get_linewidth() == 3
assert handle.get_hatch() == '//'

_, ax = plt.subplots()
ax.barh([], [], color='green', label='h')
assert mpl.colors.same_color(
ax.legend().legend_handles[0].get_facecolor(),
'green',
)


@image_comparison(['shadow_argument_types.png'], remove_text=True, style='mpl20',
tol=0 if platform.machine() == 'x86_64' else 0.028)
def test_shadow_argument_types():
Expand Down
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