allow setting None to lim

tests/test_canvas.py

@@ -56,6 +56,14 @@ def test_namespaces(backend: str):
     canvas.y.label.family = "Arial"
     assert canvas.y.label.family == "Arial"
 
+    # test lim
+    canvas.x.lim = (-1, 1)
+    assert canvas.x.lim == pytest.approx((-1, 1))
+    canvas.x.lim = (-0.4, None)
+    assert canvas.x.lim == pytest.approx((-0.4, 1))
+    canvas.x.lim = (None, 0.6)
+    assert canvas.x.lim == pytest.approx((-0.4, 0.6))
+
     # test errors
     with pytest.raises(ValueError):
         canvas.x.lim = (1, 0)

whitecanvas/backend/matplotlib/_labels.py

@@ -202,9 +202,9 @@ def _plt_get_limits(self) -> tuple[float, float]:
         axes = self._canvas()._axes
         x0, x1 = getattr(axes, f"get_{self._axis_name}lim")()
         if getattr(axes, f"{self._axis_name}axis_inverted")():
-            return x1, x0
+            return float(x1), float(x0)
         else:
-            return x0, x1
+            return float(x0), float(x1)
 
     def _plt_set_limits(self, limits: tuple[float, float]):
         axes = self._canvas()._axes

whitecanvas/canvas/_namespaces.py

@@ -312,7 +312,11 @@ def lim(self) -> tuple[float, float]:
     @lim.setter
     def lim(self, lim: tuple[float, float]):
         low, high = lim
-        if low >= high:
+        if low is None or high is None:
+            _low, _high = self._get_object()._plt_get_limits()
+            low = low if low is not None else _low
+            high = high if high is not None else _high
+        elif low >= high:
             a = type(self).__name__[0].lower()
             raise ValueError(
                 f"low must be less than high, but got {lim!r}. If you "
@@ -322,8 +326,9 @@ def lim(self, lim: tuple[float, float]):
         # implemented in JS (such as bokeh) and the python callback is not
         # enabled. Otherwise axis linking fails.
         with self.events.blocked():
-            self._get_object()._plt_set_limits(lim)
-        self.events.lim.emit(lim)
+            self._get_object()._plt_set_limits((low, high))
+        self.events.lim.emit((low, high))
+        self._draw_canvas()
         return None
 
     @property