matplotlib · timhoffm · Oct 6, 2020 · Sep 21, 2020 · Sep 22, 2020 · Sep 27, 2020
diff --git a/.test_pan.py.kate-swp b/.test_pan.py.kate-swp
diff --git a/doc/users/next_whats_new/panning_3d.rst b/doc/users/next_whats_new/panning_3d.rst
@@ -0,0 +1,4 @@
+Panning for mplot3d
+-------------------
+
+Click and drag with the middle mouse button to pan 3d axes.
diff --git a/lib/matplotlib/testing/widgets.py b/lib/matplotlib/testing/widgets.py
@@ -18,31 +18,35 @@ def get_ax():
     return ax
 
 
-def do_event(tool, etype, button=1, xdata=0, ydata=0, key=None, step=1):
-    """
-    Trigger an event
+def mock_event(ax, button=1, xdata=0, ydata=0, key=None, step=1):
+    r"""
+    Create a mock event that can stand in for `.Event` and its subclasses.
+
+    This event is intended to be used in tests where it can be passed into
+    event handling functions.
 
     Parameters
     ----------
-    tool : matplotlib.widgets.RectangleSelector
-    etype
-        the event to trigger
+    ax : `matplotlib.axes.Axes`
+        The axes the event will be in.
     xdata : int
-        x coord of mouse in data coords
+        x coord of mouse in data coords.
     ydata : int
-        y coord of mouse in data coords
-    button : int or str
-        button pressed None, 1, 2, 3, 'up', 'down' (up and down are used
-        for scroll events)
-    key
-        the key depressed when the mouse event triggered (see
-        :class:`KeyEvent`)
+        y coord of mouse in data coords.
+    button : None or `MouseButton` or {'up', 'down'}
+        The mouse button pressed in this event (see also `.MouseEvent`).
+    key : None or str
+        The key pressed when the mouse event triggered (see also `.KeyEvent`).
     step : int
-        number of scroll steps (positive for 'up', negative for 'down')
+        Number of scroll steps (positive for 'up', negative for 'down').
+
+    Returns
+    -------
+    event
+        A `.Event`\-like Mock instance.
     """
     event = mock.Mock()
     event.button = button
-    ax = tool.ax
     event.x, event.y = ax.transData.transform([(xdata, ydata),
                                                (xdata, ydata)])[0]
     event.xdata, event.ydata = xdata, ydata
@@ -52,6 +56,29 @@ def do_event(tool, etype, button=1, xdata=0, ydata=0, key=None, step=1):
     event.step = step
     event.guiEvent = None
     event.name = 'Custom'
+    return event
+
+
+def do_event(tool, etype, button=1, xdata=0, ydata=0, key=None, step=1):
+    """
+    Trigger an event on the given tool.
 
+    Parameters
+    ----------
+    tool : matplotlib.widgets.RectangleSelector
+    etype : str
+        The event to trigger.
+    xdata : int
+        x coord of mouse in data coords.
+    ydata : int
+        y coord of mouse in data coords.
+    button : None or `MouseButton` or {'up', 'down'}
+        The mouse button pressed in this event (see also `.MouseEvent`).
+    key : None or str
+        The key pressed when the mouse event triggered (see also `.KeyEvent`).
+    step : int
+        Number of scroll steps (positive for 'up', negative for 'down').
+    """
+    event = mock_event(tool.ax, button, xdata, ydata, key, step)
     func = getattr(tool, etype)
     func(event)
diff --git a/lib/mpl_toolkits/mplot3d/axes3d.py b/lib/mpl_toolkits/mplot3d/axes3d.py
@@ -1237,11 +1237,25 @@ def _on_move(self, event):
             self.stale = True
             self.figure.canvas.draw_idle()
 
-#        elif self.button_pressed == 2:
+        elif self.button_pressed == 2:
             # pan view
+            # get the x and y pixel coords
+            if dx == 0 and dy == 0:
+                return
+            minx, maxx, miny, maxy, minz, maxz = self.get_w_lims()
+            dx = 1-((w - dx)/w)
+            dy = 1-((h - dy)/h)
+            elev, azim = np.deg2rad(self.elev), np.deg2rad(self.azim)
             # project xv, yv, zv -> xw, yw, zw
+            dxx = (maxx-minx)*(dy*np.sin(elev)*np.cos(azim) + dx*np.sin(azim))
+            dyy = (maxy-miny)*(-dx*np.cos(azim) + dy*np.sin(elev)*np.sin(azim))
+            dzz = (maxz-minz)*(-dy*np.cos(elev))
             # pan
-#            pass
+            self.set_xlim3d(minx + dxx, maxx + dxx)
+            self.set_ylim3d(miny + dyy, maxy + dyy)
+            self.set_zlim3d(minz + dzz, maxz + dzz)
+            self.get_proj()
+            self.figure.canvas.draw_idle()
 
         # Zoom
         elif self.button_pressed in self._zoom_btn:

diff --git a/lib/mpl_toolkits/tests/test_mplot3d.py b/lib/mpl_toolkits/tests/test_mplot3d.py
@@ -5,9 +5,11 @@
 
 from mpl_toolkits.mplot3d import Axes3D, axes3d, proj3d, art3d
 import matplotlib as mpl
+from matplotlib.backend_bases import MouseButton
 from matplotlib import cm
 from matplotlib import colors as mcolors
 from matplotlib.testing.decorators import image_comparison, check_figures_equal
+from matplotlib.testing.widgets import mock_event
 from matplotlib.collections import LineCollection, PolyCollection
 from matplotlib.patches import Circle
 import matplotlib.pyplot as plt
@@ -1178,3 +1180,41 @@ def test_colorbar_pos():
     fig.canvas.draw()
     # check that actually on the bottom
     assert cbar.ax.get_position().extents[1] < 0.2
+
+
+def test_pan():
+    """Test mouse panning using the middle mouse button."""
+
+    def convert_lim(dmin, dmax):
+        """Convert min/max limits to center and range."""
+        center = (dmin + dmax) / 2
+        range_ = dmax - dmin
+        return center, range_
+
+    ax = plt.figure().add_subplot(projection='3d')
+    ax.scatter(0, 0, 0)
+    ax.figure.canvas.draw()
+
+    x_center0, x_range0 = convert_lim(*ax.get_xlim3d())
+    y_center0, y_range0 = convert_lim(*ax.get_ylim3d())
+    z_center0, z_range0 = convert_lim(*ax.get_zlim3d())
+
+    # move mouse diagonally to pan along all axis.
+    ax._button_press(
+        mock_event(ax, button=MouseButton.MIDDLE, xdata=0, ydata=0))
+    ax._on_move(
+        mock_event(ax, button=MouseButton.MIDDLE, xdata=1, ydata=1))
+
+    x_center, x_range = convert_lim(*ax.get_xlim3d())
+    y_center, y_range = convert_lim(*ax.get_ylim3d())
+    z_center, z_range = convert_lim(*ax.get_zlim3d())
+
+    # Ranges have not changed
+    assert x_range == pytest.approx(x_range0)
+    assert y_range == pytest.approx(y_range0)
+    assert z_range == pytest.approx(z_range0)
+
+    # But center positions have
+    assert x_center != pytest.approx(x_center0)
+    assert y_center != pytest.approx(y_center0)
+    assert z_center != pytest.approx(z_center0)