Snap 3D rotation to 5 degree increments with Ctrl

Chirag3841 · Chirag3841 · commit 7325c4a540e2 · 2026-02-12T14:57:49.000+05:30
diff --git a/lib/mpl_toolkits/mplot3d/axes3d.py b/lib/mpl_toolkits/mplot3d/axes3d.py
@@ -174,12 +174,17 @@ def __init__(
 
         self.mouse_init()
         fig = self.get_figure(root=True)
+        self._snap_rotation = False
         fig.canvas.callbacks._connect_picklable(
             'motion_notify_event', self._on_move)
         fig.canvas.callbacks._connect_picklable(
             'button_press_event', self._button_press)
         fig.canvas.callbacks._connect_picklable(
             'button_release_event', self._button_release)
+        fig.canvas.callbacks._connect_picklable(
+           'key_press_event', self._key_press)
+        fig.canvas.callbacks._connect_picklable(
+            'key_release_event', self._key_release)
         self.set_top_view()
 
         self.patch.set_linewidth(0)
@@ -1355,6 +1360,16 @@ def clear(self):
 
         self.grid(mpl.rcParams['axes3d.grid'])
 
+    def _key_press(self, event):
+        if event.key in ("control", "ctrl"):
+            self._snap_rotation = True
+
+
+    def _key_release(self, event):
+        if event.key in ("control", "ctrl"):
+            self._snap_rotation = False
+
+
     def _button_press(self, event):
         if event.inaxes == self:
             self.button_pressed = event.button
@@ -1597,6 +1612,11 @@ def _on_move(self, event):
 
                 q = dq * q
                 elev, azim, roll = np.rad2deg(q.as_cardan_angles())
+            if getattr(self, "_snap_rotation", False):
+                step = 5
+                elev = float(step * round(elev / step))
+                azim = float(step * round(azim / step))
+                roll = float(step * round(roll / step))
 
             # update view
             vertical_axis = self._axis_names[self._vertical_axis]
diff --git a/lib/mpl_toolkits/mplot3d/tests/test_axes3d.py b/lib/mpl_toolkits/mplot3d/tests/test_axes3d.py
@@ -2785,3 +2785,53 @@ def test_axis_get_tightbbox_includes_offset_text():
             f"bbox.x1 ({bbox.x1}) should be >= offset_bbox.x1 ({offset_bbox.x1})"
         assert bbox.y1 >= offset_bbox.y1 - 1e-6, \
             f"bbox.y1 ({bbox.y1}) should be >= offset_bbox.y1 ({offset_bbox.y1})"
+
+
+class DummyEvent:
+    def __init__(self, xdata=None, ydata=None, inaxes=None):
+        self.xdata = xdata
+        self.ydata = ydata
+        self.inaxes = inaxes
+        self.x = 0
+        self.y = 0
+        self.button = 1
+
+
+def _is_multiple_of_step(val, step):
+    return np.isclose(val, step * round(val / step), atol=5e-2)
+
+
+def test_ctrl_rotation_snaps_to_5deg(monkeypatch):
+    fig = plt.figure()
+    ax = fig.add_subplot(projection="3d")
+
+    ax.M = np.eye(4)
+    ax._pseudo_w = 1
+    ax._pseudo_h = 1
+
+    ax.button_pressed = 1
+    ax._rotate_btn = [1]
+    ax._sx, ax._sy = 0.0, 0.0
+
+    ax.elev = 12.3
+    ax.azim = 33.7
+    ax.roll = 2.2
+
+    ax._snap_rotation = True
+
+    monkeypatch.setitem(plt.rcParams, "axes3d.mouserotationstyle", "azel")
+
+    captured = {}
+
+    def fake_view_init(elev=None, azim=None, roll=None, **kwargs):
+        captured["elev"] = elev
+        captured["azim"] = azim
+        captured["roll"] = roll
+
+    monkeypatch.setattr(ax, "view_init", fake_view_init)
+
+    event = DummyEvent(xdata=0.1, ydata=0.1, inaxes=ax)
+    ax._on_move(event)
+
+    assert _is_multiple_of_step(captured["elev"], 5)
+    assert _is_multiple_of_step(captured["azim"], 5)
