From a15bc47816e13ff7383c308441cbea7498ac94b0 Mon Sep 17 00:00:00 2001
From: Tim Hoffmann <2836374+timhoffm@users.noreply.github.com>
Date: Tue, 4 May 2021 22:17:56 +0200
Subject: [PATCH] Fix resetting grid visibility

Actually, there were two issues:

- 'gridOn' state should always be contained in the _tick_kw settings.
  This is needed because we support toggling via grid() and thus need
  to be able to query the state. Therefore, the _tick_kw dicts must be
  resetted instead of cleared.
- grid(some_kwarg=...) i.e. with b=None and keywords must be treated
  explicitly as b=True as the docs already propose.

Closes #20149.
---
 lib/matplotlib/axis.py            | 63 ++++++++++++++++++-------------
 lib/matplotlib/tests/test_axes.py | 13 +++++++
 2 files changed, 50 insertions(+), 26 deletions(-)

diff --git a/lib/matplotlib/axis.py b/lib/matplotlib/axis.py
index 0d18b5f5ede8..a30cae235e95 100644
--- a/lib/matplotlib/axis.py
+++ b/lib/matplotlib/axis.py
@@ -786,6 +786,18 @@ def get_children(self):
         return [self.label, self.offsetText,
                 *self.get_major_ticks(), *self.get_minor_ticks()]
 
+    def _reset_major_tick_kw(self):
+        self._major_tick_kw.clear()
+        self._major_tick_kw['gridOn'] = (
+                mpl.rcParams['axes.grid'] and
+                mpl.rcParams['axes.grid.which'] in ('both', 'major'))
+
+    def _reset_minor_tick_kw(self):
+        self._minor_tick_kw.clear()
+        self._minor_tick_kw['gridOn'] = (
+                mpl.rcParams['axes.grid'] and
+                mpl.rcParams['axes.grid.which'] in ('both', 'minor'))
+
     def clear(self):
         """
         Clear the axis.
@@ -807,14 +819,8 @@ def clear(self):
         # Clear the callback registry for this axis, or it may "leak"
         self.callbacks = cbook.CallbackRegistry()
 
-        # whether the grids are on
-        self._major_tick_kw['gridOn'] = (
-                mpl.rcParams['axes.grid'] and
-                mpl.rcParams['axes.grid.which'] in ('both', 'major'))
-        self._minor_tick_kw['gridOn'] = (
-                mpl.rcParams['axes.grid'] and
-                mpl.rcParams['axes.grid.which'] in ('both', 'minor'))
-
+        self._reset_major_tick_kw()
+        self._reset_minor_tick_kw()
         self.reset_ticks()
 
         self.converter = None
@@ -861,10 +867,10 @@ def set_tick_params(self, which='major', reset=False, **kw):
         # future new ticks will automatically get them
         if reset:
             if which in ['major', 'both']:
-                self._major_tick_kw.clear()
+                self._reset_major_tick_kw()
                 self._major_tick_kw.update(kwtrans)
             if which in ['minor', 'both']:
-                self._minor_tick_kw.clear()
+                self._reset_minor_tick_kw()
                 self._minor_tick_kw.update(kwtrans)
             self.reset_ticks()
         else:
@@ -1413,35 +1419,40 @@ def grid(self, b=None, which='major', **kwargs):
 
                 grid(color='r', linestyle='-', linewidth=2)
         """
-        if b is not None:
-            if 'visible' in kwargs and bool(b) != bool(kwargs['visible']):
+        TOGGLE = object()
+        UNSET = object()
+        visible = kwargs.pop('visible', UNSET)
+
+        if b is None:
+            if visible is UNSET:
+                if kwargs:  # grid(color='r')
+                    b = True
+                else:  # grid()
+                    b = TOGGLE
+            else:  # grid(visible=v)
+                b = visible
+        else:
+            if visible is not UNSET and bool(b) != bool(visible):
+                # grid(True, visible=False), grid(False, visible=True)
                 raise ValueError(
                     "'b' and 'visible' specify inconsistent grid visibilities")
             if kwargs and not b:  # something false-like but not None
+                # grid(0, visible=True)
                 _api.warn_external('First parameter to grid() is false, '
                                    'but line properties are supplied. The '
                                    'grid will be enabled.')
                 b = True
+
         which = which.lower()
         _api.check_in_list(['major', 'minor', 'both'], which=which)
         gridkw = {'grid_' + item[0]: item[1] for item in kwargs.items()}
-        if 'grid_visible' in gridkw:
-            forced_visibility = True
-            gridkw['gridOn'] = gridkw.pop('grid_visible')
-        else:
-            forced_visibility = False
-
         if which in ['minor', 'both']:
-            if b is None and not forced_visibility:
-                gridkw['gridOn'] = not self._minor_tick_kw['gridOn']
-            elif b is not None:
-                gridkw['gridOn'] = b
+            gridkw['gridOn'] = (not self._minor_tick_kw['gridOn']
+                                if b is TOGGLE else b)
             self.set_tick_params(which='minor', **gridkw)
         if which in ['major', 'both']:
-            if b is None and not forced_visibility:
-                gridkw['gridOn'] = not self._major_tick_kw['gridOn']
-            elif b is not None:
-                gridkw['gridOn'] = b
+            gridkw['gridOn'] = (not self._major_tick_kw['gridOn']
+                                if b is TOGGLE else b)
             self.set_tick_params(which='major', **gridkw)
         self.stale = True
 
diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
index ec9526c364eb..b793156444fb 100644
--- a/lib/matplotlib/tests/test_axes.py
+++ b/lib/matplotlib/tests/test_axes.py
@@ -4757,6 +4757,19 @@ def test_grid():
     assert not ax.xaxis.majorTicks[0].gridline.get_visible()
 
 
+def test_reset_grid():
+    fig, ax = plt.subplots()
+    ax.tick_params(reset=True, which='major', labelsize=10)
+    assert not ax.xaxis.majorTicks[0].gridline.get_visible()
+    ax.grid(color='red')  # enables grid
+    assert ax.xaxis.majorTicks[0].gridline.get_visible()
+
+    with plt.rc_context({'axes.grid': True}):
+        ax.clear()
+        ax.tick_params(reset=True, which='major', labelsize=10)
+        assert ax.xaxis.majorTicks[0].gridline.get_visible()
+
+
 def test_vline_limit():
     fig = plt.figure()
     ax = fig.gca()