Add tests for roll, and for rotation using mouse

Add tests for roll (test_axes3d_roll), for rotation using the mouse (test_rotate), and for rotation using the mouse when roll is nonzero (test_rotate_roll). The latter fails if the roll angle is passed with wrong units (issue matplotlib#28256).

lib/mpl_toolkits/mplot3d/tests/test_axes3d.py

@@ -1095,6 +1095,14 @@ def test_axes3d_rotated():
     ax.view_init(90, 45, 0)  # look down, rotated. Should be square
 
 
+@mpl3d_image_comparison(['axes3d_roll.png'],
+                        remove_text=False, style='mpl20')
+def test_axes3d_roll():
+    fig = plt.figure()
+    ax = fig.add_subplot(1, 1, 1, projection='3d')
+    ax.view_init(0, 0, 45)
+
+
 def test_plotsurface_1d_raises():
     x = np.linspace(0.5, 10, num=100)
     y = np.linspace(0.5, 10, num=100)
@@ -1766,6 +1774,51 @@ def test_shared_axes_retick():
     assert ax2.get_zlim() == (-0.5, 2.5)
 
 
+def test_rotate():
+    """Test rotating using the left mouse button."""
+    fig = plt.figure()
+    ax = fig.add_subplot(1, 1, 1, projection='3d')
+    ax.view_init(0, 0, 0)
+    ax.figure.canvas.draw()
+
+    # drag mouse horizontally to change azimuth
+    dx = 0.1
+    dy = 0.2
+    ax._button_press(
+        mock_event(ax, button=MouseButton.LEFT, xdata=0, ydata=0))
+    ax._on_move(
+        mock_event(ax, button=MouseButton.LEFT,
+                       xdata=dx*ax._pseudo_w, ydata=dy*ax._pseudo_h))
+    ax.figure.canvas.draw()
+    print(ax._pseudo_w)
+    print(ax.elev)
+    assert ax.azim == -dx*180
+    assert ax.elev == -dy*180
+    assert ax.roll == 0
+
+
+def test_rotate_roll():
+    """Test rotating using the left mouse button, when roll is nonzero."""
+    fig = plt.figure()
+    ax = fig.add_subplot(1, 1, 1, projection='3d')
+    ax.view_init(0, 0, 30)
+    ax.figure.canvas.draw()
+
+    # drag mouse horizontally to change azimuth
+    dx = 0.1
+    dy = 0.2
+    ax._button_press(
+        mock_event(ax, button=MouseButton.LEFT, xdata=0, ydata=0))
+    ax._on_move(
+        mock_event(ax, button=MouseButton.LEFT,
+                       xdata=dx*ax._pseudo_w, ydata=dy*ax._pseudo_h))
+    ax.figure.canvas.draw()
+    roll = np.deg2rad(ax.roll)
+    assert ax.elev == (-dy*180*np.cos(roll)+dx*180*np.sin(roll))
+    assert ax.azim == (-dy*180*np.sin(roll)-dx*180*np.cos(roll))
+    assert ax.roll == 30
+
+
 def test_pan():
     """Test mouse panning using the middle mouse button."""