Add support for horizontal CheckButtons

doc/users/next_whats_new/widget_horizontal.rst

@@ -1,23 +1,29 @@
-RadioButtons widget may now be laid out horizontally
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+CheckButtons / RadioButtons widget may now be laid out horizontally
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-The `.RadioButtons` widget's primary layout direction may now be specified with
-the *orientation* keyword argument:
+The `.CheckButtons` and `.RadioButtons` widget's primary layout direction may
+now be specified with the *orientation* keyword argument:
 
 .. plot::
     :include-source:
 
     import matplotlib.pyplot as plt
-    from matplotlib.widgets import RadioButtons
+    from matplotlib.widgets import CheckButtons, RadioButtons
 
     fig = plt.figure(figsize=(4, 2))
 
     # Default orientation is vertical:
     rbv = RadioButtons(fig.add_axes((0.05, 0.6, 0.2, 0.35)),
                        ('Radio 1', 'Radio 2', 'Radio 3'),
                        orientation='vertical')
+    cbv = CheckButtons(fig.add_axes((0.05, 0.2, 0.2, 0.35)),
+                       ('Check 1', 'Check 2', 'Check 3'),
+                       orientation='vertical')
 
     # Alternatively, a horizontal orientation may be used:
     rbh = RadioButtons(fig.add_axes((0.3, 0.6, 0.6, 0.35)),
                        ('Radio 1', 'Radio 2', 'Radio 3'),
                        orientation='horizontal')
+    cbh = CheckButtons(fig.add_axes((0.3, 0.2, 0.6, 0.35)),
+                       ('Check 1', 'Check 2', 'Check 3'),
+                       orientation='horizontal')

lib/matplotlib/tests/test_widgets.py

@@ -1041,9 +1041,11 @@ def test_lasso_set_props(ax):
     assert line.get_alpha() == 0.3
 
 
-def test_CheckButtons(ax):
+@pytest.mark.parametrize('orientation', ['vertical', 'horizontal'])
+def test_CheckButtons(ax, orientation):
     labels = ('a', 'b', 'c')
-    check = widgets.CheckButtons(ax, labels, (True, False, True))
+    check = widgets.CheckButtons(ax, labels, (True, False, True),
+                                 orientation=orientation)
     assert check.get_status() == [True, False, True]
     check.set_active(0)
     assert check.get_status() == [False, False, True]
@@ -1110,28 +1112,54 @@ def test_RadioButtons(ax, orientation):
 
 @image_comparison(['check_radio_buttons.png'], style='mpl20', remove_text=True)
 def test_check_radio_buttons_image():
-    ax = get_ax()
-    fig = ax.figure
-    fig.subplots_adjust(left=0.3)
+    fig = plt.figure()
+
+    rb1 = widgets.RadioButtons(fig.add_axes((0.05, 0.7, 0.2, 0.15)),
+                               ('Radio 1', 'Radio 2', 'Radio 3'))
 
-    rax1 = fig.add_axes((0.05, 0.7, 0.2, 0.15))
-    rb1 = widgets.RadioButtons(rax1, ('Radio 1', 'Radio 2', 'Radio 3'))
+    rb2 = widgets.RadioButtons(fig.add_axes((0.3, 0.7, 0.6, 0.15)),
+                               ('Radio 1', 'Radio 2', 'Radio 3'),
+                               orientation='horizontal')
 
-    rax2 = fig.add_axes((0.05, 0.5, 0.2, 0.15))
-    cb1 = widgets.CheckButtons(rax2, ('Check 1', 'Check 2', 'Check 3'),
+    cb1 = widgets.CheckButtons(fig.add_axes((0.05, 0.5, 0.2, 0.15)),
+                               ('Check 1', 'Check 2', 'Check 3'),
                                (False, True, True))
 
-    rax3 = fig.add_axes((0.05, 0.3, 0.2, 0.15))
+    cb2 = widgets.CheckButtons(fig.add_axes((0.3, 0.5, 0.6, 0.15)),
+                               ('Check 1', 'Check 2', 'Check 3'),
+                               (False, True, True),
+                               orientation='horizontal')
+
     rb3 = widgets.RadioButtons(
-        rax3, ('Radio 1', 'Radio 2', 'Radio 3'),
+        fig.add_axes((0.05, 0.3, 0.2, 0.15)),
+        ('Radio 1', 'Radio 2', 'Radio 3'),
+        label_props={'fontsize': [8, 12, 16],
+                     'color': ['red', 'green', 'blue']},
+        radio_props={'edgecolor': ['red', 'green', 'blue'],
+                     'facecolor': ['mistyrose', 'palegreen', 'lightblue']})
+
+    rb4 = widgets.RadioButtons(
+        fig.add_axes((0.3, 0.3, 0.6, 0.15)),
+        ('Radio 1', 'Radio 2', 'Radio 3'),
+        orientation='horizontal',
         label_props={'fontsize': [8, 12, 16],
                      'color': ['red', 'green', 'blue']},
         radio_props={'edgecolor': ['red', 'green', 'blue'],
                      'facecolor': ['mistyrose', 'palegreen', 'lightblue']})
 
-    rax4 = fig.add_axes((0.05, 0.1, 0.2, 0.15))
+    cb3 = widgets.CheckButtons(
+        fig.add_axes((0.05, 0.1, 0.2, 0.15)),
+        ('Check 1', 'Check 2', 'Check 3'), (False, True, True),
+        label_props={'fontsize': [8, 12, 16],
+                     'color': ['red', 'green', 'blue']},
+        frame_props={'edgecolor': ['red', 'green', 'blue'],
+                     'facecolor': ['mistyrose', 'palegreen', 'lightblue']},
+        check_props={'color': ['red', 'green', 'blue']})
+
     cb4 = widgets.CheckButtons(
-        rax4, ('Check 1', 'Check 2', 'Check 3'), (False, True, True),
+        fig.add_axes((0.3, 0.1, 0.6, 0.15)),
+        ('Check 1', 'Check 2', 'Check 3'), (False, True, True),
+        orientation='horizontal',
         label_props={'fontsize': [8, 12, 16],
                      'color': ['red', 'green', 'blue']},
         frame_props={'edgecolor': ['red', 'green', 'blue'],

lib/matplotlib/widgets.py

@@ -1012,7 +1012,8 @@ class CheckButtons(AxesWidget):
     """
 
     def __init__(self, ax, labels, actives=None, *, useblit=True,
-                 label_props=None, frame_props=None, check_props=None):
+                 label_props=None, frame_props=None, check_props=None,
+                 orientation='vertical'):
         """
         Add check buttons to `~.axes.Axes` instance *ax*.
 
@@ -1047,9 +1048,15 @@ def __init__(self, ax, labels, actives=None, *, useblit=True,
             black color, and 1.0 linewidth.
 
             .. versionadded:: 3.7
+        orientation : {'vertical', 'horizontal'}
+            The orientation of the buttons: 'vertical' places buttons from top
+            to bottom, 'horizontal' places buttons from left to right.
+
+            .. versionadded:: 3.9
         """
         super().__init__(ax)
 
+        _api.check_in_list(['vertical', 'horizontal'], orientation=orientation)
         _api.check_isinstance((dict, None), label_props=label_props,
                               frame_props=frame_props, check_props=check_props)
 
@@ -1063,14 +1070,29 @@ def __init__(self, ax, labels, actives=None, *, useblit=True,
         self._useblit = useblit and self.canvas.supports_blit
         self._background = None
 
-        ys = np.linspace(1, 0, len(labels)+2)[1:-1]
+        if orientation == 'vertical':
+            # Place buttons from top to bottom with buttons at (0.15, y) and labels
+            # at (0.25, y), where y is evenly spaced within the Axes.
+            button_ys = label_ys = np.linspace(1, 0, len(labels) + 2)[1:-1]
+            button_xs = np.full_like(button_ys, 0.15)
+            label_xs = np.full_like(label_ys, 0.25)
+            label_ha = 'left'
+            label_va = 'center'
+        else:
+            # Place buttons from left to right with buttons at (x, 0.15) and labels
+            # at (x, 0.25), where x is evenly spaced within the Axes.
+            button_xs = label_xs = np.linspace(0, 1, len(labels) + 2)[1:-1]
+            button_ys = np.full_like(button_xs, 0.15)
+            label_ys = np.full_like(label_xs, 0.25)
+            label_ha = 'center'
+            label_va = 'bottom'
 
         label_props = _expand_text_props(label_props)
         self.labels = [
-            ax.text(0.25, y, label, transform=ax.transAxes,
-                    horizontalalignment="left", verticalalignment="center",
+            ax.text(x, y, label, transform=ax.transAxes,
+                    horizontalalignment=label_ha, verticalalignment=label_va,
                     **props)
-            for y, label, props in zip(ys, labels, label_props)]
+            for x, y, label, props in zip(label_xs, label_ys, labels, label_props)]
         text_size = np.array([text.get_fontsize() for text in self.labels]) / 2
 
         frame_props = {
@@ -1082,7 +1104,7 @@ def __init__(self, ax, labels, actives=None, *, useblit=True,
         }
         frame_props.setdefault('facecolor', frame_props.get('color', 'none'))
         frame_props.setdefault('edgecolor', frame_props.pop('color', 'black'))
-        self._frames = ax.scatter([0.15] * len(ys), ys, **frame_props)
+        self._frames = ax.scatter(button_xs, button_ys, **frame_props)
         check_props = {
             'linewidth': 1,
             's': text_size**2,
@@ -1092,7 +1114,7 @@ def __init__(self, ax, labels, actives=None, *, useblit=True,
             'animated': self._useblit,
         }
         check_props.setdefault('facecolor', check_props.pop('color', 'black'))
-        self._checks = ax.scatter([0.15] * len(ys), ys, **check_props)
+        self._checks = ax.scatter(button_xs, button_ys, **check_props)
         # The user may have passed custom colours in check_props, so we need to
         # create the checks (above), and modify the visibility after getting
         # whatever the user set.