Better datetime axis compatibility

src/plopp/backends/common.py

@@ -36,6 +36,7 @@ def union(self, other: BoundingBox) -> BoundingBox:
         """
         Return the union of this bounding box with another one.
         """
+
         return BoundingBox(
             xmin=_none_min(self.xmin, other.xmin),
             xmax=_none_max(self.xmax, other.xmax),

src/plopp/backends/matplotlib/canvas.py

@@ -6,6 +6,7 @@
 import matplotlib.pyplot as plt
 import numpy as np
 import scipp as sc
+from matplotlib import dates as mdates
 from matplotlib.collections import QuadMesh
 from mpl_toolkits.axes_grid1 import make_axes_locatable
 
@@ -14,6 +15,10 @@
 from .utils import fig_to_bytes, is_sphinx_build, make_figure
 
 
+def _to_floats(x):
+    return mdates.date2num(x) if np.issubdtype(x.dtype, np.datetime64) else x
+
+
 def _none_if_not_finite(x: Union[float, int, None]) -> Union[float, int, None]:
     if x is None:
         return None
@@ -149,9 +154,11 @@ def autoscale(self):
         lines = [line for line in self.ax.lines if hasattr(line, '_plopp_mask')]
         for line in lines:
             line_mask = sc.array(dims=['x'], values=line._plopp_mask)
-            line_x = sc.DataArray(data=sc.array(dims=['x'], values=line.get_xdata()))
+            line_x = sc.DataArray(
+                data=sc.array(dims=['x'], values=_to_floats(line.get_xdata()))
+            )
             line_y = sc.DataArray(
-                data=sc.array(dims=['x'], values=line.get_ydata()),
+                data=sc.array(dims=['x'], values=_to_floats(line.get_ydata())),
                 masks={'mask': line_mask},
             )
             line_bbox = BoundingBox(

tests/backends/matplotlib/mpl_figure_test.py

@@ -1,9 +1,12 @@
 # SPDX-License-Identifier: BSD-3-Clause
 # Copyright (c) 2023 Scipp contributors (https://github.com/scipp)
+import numpy as np
+import scipp as sc
 
 from plopp.backends.matplotlib import MatplotlibBackend
 from plopp.backends.matplotlib.interactive import InteractiveFig
 from plopp.backends.matplotlib.static import StaticFig
+from plopp.core import Node
 from plopp.graphics.imageview import ImageView
 from plopp.graphics.lineview import LineView
 
@@ -30,3 +33,27 @@ def test_create_interactive_fig2d(use_ipympl):
     b = MatplotlibBackend()
     fig = b.figure2d(View=ImageView)
     assert isinstance(fig, InteractiveFig)
+
+
+def test_datetime_compatibility_between_1d_and_2d_figures():
+    b = MatplotlibBackend()
+    # 2d data
+    t = np.arange(
+        np.datetime64('2017-03-16T20:58:17'), np.datetime64('2017-03-16T21:15:17'), 20
+    )
+    time = sc.array(dims=['time'], values=t)
+    z = sc.arange('z', 50.0, unit='m')
+    v = 10 * np.random.random(z.shape + time.shape)
+    da2d = sc.DataArray(
+        data=sc.array(dims=['z', 'time'], values=v), coords={'time': time, 'z': z}
+    )
+    fig = b.figure2d(ImageView, Node(da2d))
+    assert len(fig.ax.lines) == 0
+    assert len(fig.ax.collections) == 1
+
+    # 1d data
+    v = np.random.rand(time.sizes['time'])
+    da1d = sc.DataArray(data=sc.array(dims=['time'], values=v), coords={'time': time})
+    b.figure1d(LineView, Node(da1d), ax=fig.ax)
+    assert len(fig.ax.lines) > 0
+    assert len(fig.ax.collections) == 1

tests/backends/matplotlib/mpl_lineview_test.py

@@ -44,7 +44,7 @@ def test_grid():
 
 
 def test_ax():
-    fig, ax = plt.subplots()
+    _, ax = plt.subplots()
     assert len(ax.lines) == 0
     da = data_array(ndim=1)
     _ = LineView(Node(da), ax=ax)