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Partial fix for grid alpha #22234

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Merged
merged 1 commit into from
Feb 11, 2022
Merged

Partial fix for grid alpha #22234

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10 changes: 8 additions & 2 deletions lib/matplotlib/axis.py
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Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,7 @@
from matplotlib import _api
import matplotlib.artist as martist
import matplotlib.cbook as cbook
import matplotlib.colors as mcolors
import matplotlib.lines as mlines
import matplotlib.scale as mscale
import matplotlib.text as mtext
Expand Down Expand Up @@ -143,7 +144,12 @@ def __init__(
grid_linestyle = mpl.rcParams["grid.linestyle"]
if grid_linewidth is None:
grid_linewidth = mpl.rcParams["grid.linewidth"]
if grid_alpha is None:
if grid_alpha is None and not mcolors._has_alpha_channel(grid_color):
# alpha precedence: kwarg > color alpha > rcParams['grid.alpha']
# Note: only resolve to rcParams if the color does not have alpha
# otherwise `grid(color=(1, 1, 1, 0.5))` would work like
# grid(color=(1, 1, 1, 0.5), alpha=rcParams['grid.alpha'])
# so the that the rcParams default would override color alpha.
grid_alpha = mpl.rcParams["grid.alpha"]
grid_kw = {k[5:]: v for k, v in kwargs.items()}

Expand Down Expand Up @@ -1413,7 +1419,7 @@ def grid(self, visible=None, which='major', **kwargs):
visible = True
which = which.lower()
_api.check_in_list(['major', 'minor', 'both'], which=which)
gridkw = {'grid_' + item[0]: item[1] for item in kwargs.items()}
gridkw = {f'grid_{name}': value for name, value in kwargs.items()}
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No functional change, only better formatting for readability.

if which in ['minor', 'both']:
gridkw['gridOn'] = (not self._minor_tick_kw['gridOn']
if visible is None else visible)
Expand Down
6 changes: 6 additions & 0 deletions lib/matplotlib/colors.py
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Original file line number Diff line number Diff line change
Expand Up @@ -121,6 +121,12 @@ def is_color_like(c):
return True


def _has_alpha_channel(c):
"""Return whether *c* is a color with an alpha channel."""
# 4-element sequences are interpreted as r, g, b, a
return not isinstance(c, str) and len(c) == 4


def _check_color_like(**kwargs):
"""
For each *key, value* pair in *kwargs*, check that *value* is color-like.
Expand Down
9 changes: 9 additions & 0 deletions lib/matplotlib/tests/test_colors.py
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Expand Up @@ -1166,6 +1166,15 @@ def test_colormap_reversing(name):
assert_array_almost_equal(cmap(np.nan), cmap_r(np.nan))


def test_has_alpha_channel():
assert mcolors._has_alpha_channel((0, 0, 0, 0))
assert mcolors._has_alpha_channel([1, 1, 1, 1])
assert not mcolors._has_alpha_channel('blue') # 4-char string!
assert not mcolors._has_alpha_channel('0.25')
assert not mcolors._has_alpha_channel('r')
assert not mcolors._has_alpha_channel((1, 0, 0))


def test_cn():
matplotlib.rcParams['axes.prop_cycle'] = cycler('color',
['blue', 'r'])
Expand Down