Compare and Swap Holoviews Extension (#733)

* initial fix for comparing and swaping hv enviroment

* add docstring and check for supported backends

* pre-commit

* refactor

* update docstring

* update comments and docstring

* add to internal API

---------

Co-authored-by: Orhan Eroglu <32553057+erogluorhan@users.noreply.github.com>

docs/internal_api/index.rst

@@ -303,6 +303,7 @@ Visualization
    plot.dataarray_plot._plot_data_as_points
    plot.dataarray_plot._polygon_raster
    plot.dataarray_plot._point_raster
+   plot.utils.HoloviewsBackend
 
 Slicing
 -------

uxarray/plot/dataarray_plot.py

@@ -20,6 +20,8 @@
 
 import warnings
 
+import uxarray.plot.utils
+
 
 def plot(uxda, **kwargs):
     """Default Plotting Method for UxDataArray."""
@@ -229,8 +231,7 @@ def _point_raster(
         # apply projection to coordinates
         lon, lat, _ = projection.transform_points(ccrs.PlateCarree(), lon, lat).T
 
-    # this will be fixed in #733
-    hv.extension("bokeh")
+    uxarray.plot.utils.backend.assign(backend=backend)
 
     # construct a dask dataframe from coordinates and data
     point_dict = {"lon": lon, "lat": lat, "var": uxda.data}
@@ -241,7 +242,6 @@ def _point_raster(
 
     if backend == "matplotlib":
         # use holoviews matplotlib backend
-        hv.extension("matplotlib")
         raster = hds_rasterize(
             points,
             pixel_ratio=pixel_ratio,
@@ -258,7 +258,6 @@ def _point_raster(
         )
     elif backend == "bokeh":
         # use holoviews bokeh backend
-        hv.extension("bokeh")
         raster = hds_rasterize(
             points,
             pixel_ratio=pixel_ratio,
@@ -315,9 +314,10 @@ def _polygon_raster(
 
     hv_polygons = hv.Polygons(gdf, vdims=[uxda.name])
 
+    uxarray.plot.utils.backend.assign(backend=backend)
+
     if backend == "matplotlib":
         # use holoviews matplotlib backend
-        hv.extension("matplotlib")
         raster = hds_rasterize(
             hv_polygons,
             pixel_ratio=pixel_ratio,
@@ -334,7 +334,6 @@ def _polygon_raster(
         )
     elif backend == "bokeh":
         # use holoviews bokeh backend
-        hv.extension("bokeh")
         raster = hds_rasterize(
             hv_polygons,
             pixel_ratio=pixel_ratio,
@@ -404,15 +403,14 @@ def polygons(
 
     hv_polygons = hv.Polygons(gdf, vdims=[uxda.name])
 
+    uxarray.plot.utils.backend.assign(backend=backend)
     if backend == "matplotlib":
         # use holoviews matplotlib backend
-        hv.extension("matplotlib")
 
         return hv_polygons.opts(colorbar=colorbar, cmap=cmap, **kwargs)
 
     elif backend == "bokeh":
         # use holoviews bokeh backend
-        hv.extension("bokeh")
         return hv_polygons.opts(
             width=width,
             height=height,
@@ -521,9 +519,10 @@ def _plot_data_as_points(
     verts = np.column_stack([lon, lat, uxda.values])
     hv_points = Points(verts, vdims=["z"])
 
+    uxarray.plot.utils.backend.assign(backend=backend)
+
     if backend == "matplotlib":
         # use holoviews matplotlib backend
-        hv.extension("matplotlib")
         return hv_points.opts(
             color="z",
             colorbar=colorbar,
@@ -535,7 +534,6 @@ def _plot_data_as_points(
 
     elif backend == "bokeh":
         # use holoviews bokeh backend
-        hv.extension("bokeh")
         return hv_points.opts(
             color="z",
             width=width,

uxarray/plot/grid_plot.py

@@ -8,6 +8,8 @@
 import numpy as np
 import holoviews as hv
 
+import uxarray.plot.utils
+
 
 def plot(grid: Grid, **kwargs):
     """Default Plotting Method for Grid."""
@@ -42,15 +44,14 @@ def mesh(
 
     hv_paths = hv.Path(gdf)
 
+    uxarray.plot.utils.backend.assign(backend=backend)
+
     if backend == "matplotlib":
         # use holoviews matplotlib backend
-        hv.extension("matplotlib")
-
         return hv_paths.opts(**kwargs)
 
     elif backend == "bokeh":
         # use holoviews bokeh backend
-        hv.extension("bokeh")
         return hv_paths.opts(
             width=width, height=height, xlabel=xlabel, ylabel=ylabel, **kwargs
         )
@@ -174,14 +175,14 @@ def _plot_coords_as_points(
     else:
         raise ValueError("Invalid element selected.")
 
+    uxarray.plot.utils.backend.assign(backend=backend)
+
     if backend == "matplotlib":
         # use holoviews matplotlib backend
-        hv.extension("matplotlib")
         return hv_points.opts(**kwargs)
 
     elif backend == "bokeh":
         # use holoviews bokeh backend
-        hv.extension("bokeh")
         return hv_points.opts(
             width=width, height=height, xlabel=xlabel, ylabel=ylabel, **kwargs
         )

uxarray/plot/utils.py

@@ -0,0 +1,32 @@
+import holoviews as hv
+
+
+class HoloviewsBackend:
+    """Utility class to compare and set a HoloViews plotting backend for
+    visualization."""
+
+    def __init__(self):
+        self.backend = None
+
+    def assign(self, backend: str):
+        """Assigns a backend for use with HoloViews visualization.
+
+        Parameters
+        ----------
+        backend : str
+            Plotting backend to use, one of 'matplotlib', 'bokeh'
+        """
+
+        if backend not in ["bokeh", "matplotlib"]:
+            raise ValueError(
+                f"Unsupported backend. Expected one of ['bokeh', 'matplotlib'], but received {backend}"
+            )
+
+        if backend != self.backend:
+            # only call hv.extension if it needs to be changed
+            hv.extension(backend)
+            self.backend = backend
+
+
+# global reference to holoviews backend utility class
+backend = HoloviewsBackend()