BUG: fix orientation of colorbar in multiplanel plot

yt/visualization/base_plot_types.py

@@ -341,7 +341,20 @@ def _set_axes(self) -> None:
         self.image.axes.set_facecolor(self.colorbar_handler.background_color)
 
         self.cax.tick_params(which="both", direction="in")
-        self.cb = self.figure.colorbar(self.image, self.cax)
+
+        # For creating a multipanel plot by ImageGrid
+        # we may need the location keyword, which was introduced since Matplotlib 3.7.0
+        cb_location = getattr(self.cax, "orientation", None)
+        if matplotlib.__version_info__ >= (3, 7):
+            cb_kwargs = {"location": cb_location}
+        else:
+            cb_kwargs = {}
+            if cb_location in ["top", "bottom"]:
+                warnings.warn(
+                    "Colorbar orientation would be wrong in the current Matplotlib version (< 3.7.0)",
+                    stacklevel=2,
+                )
+        self.cb = self.figure.colorbar(self.image, self.cax, **cb_kwargs)
 
         cb_axis: Axis
         if self.cb.orientation == "vertical":

yt/visualization/tests/test_image_comp_2D_plots.py

@@ -147,6 +147,24 @@ def test_particleprojectionplot_set_colorbar_properties():
     return p.plots[field].figure
 
 
+@pytest.mark.skipif(
+    mpl.__version_info__ < (3, 7),
+    reason="colorbar cannot currently be set horizontal in multi-panel plot with matplotlib older than 3.7.0",
+)
+@pytest.mark.parametrize("cbar_location", ["top", "bottom", "left", "right"])
+@pytest.mark.mpl_image_compare
+def test_multipanelplot_colorbar_orientation(cbar_location):
+    ds = fake_random_ds(16)
+    fields = [
+        ("gas", "density"),
+        ("gas", "velocity_x"),
+        ("gas", "velocity_y"),
+        ("gas", "velocity_magnitude"),
+    ]
+    p = SlicePlot(ds, "z", fields)
+    return p.export_to_mpl_figure((2, 2), cbar_location=cbar_location)
+
+
 class TestProfilePlot:
     @classmethod
     def setup_class(cls):