From 4b0051164962dca99176c3d167f6f062b5339aed Mon Sep 17 00:00:00 2001
From: Philipp Rudiger <P.Rudiger@ed.ac.uk>
Date: Wed, 14 Nov 2018 20:43:26 +0000
Subject: [PATCH] Improved Param and HoloViews pane cleanup

---
 panel/holoviews.py | 32 +++++++++++++++++++++++---------
 panel/pane.py      |  1 -
 panel/param.py     |  2 +-
 3 files changed, 24 insertions(+), 11 deletions(-)

diff --git a/panel/holoviews.py b/panel/holoviews.py
index bb835a50ef..0711e98147 100644
--- a/panel/holoviews.py
+++ b/panel/holoviews.py
@@ -51,6 +51,15 @@ def _update_widgets(self):
             widgets, values = self.widgets_from_dimensions(self.object, self.widgets,
                                                            self.widget_type)
         self._values = values
+
+        # Clean up anything models listening to the previous widgets
+        for _, cbs in self._callbacks.items():
+            for cb in list(cbs):
+                if cb.inst in self.widget_box.objects:
+                    print(cb)
+                    cb.inst.param.unwatch(cb)
+                    cbs.remove(cb)
+
         self.widget_box.objects = widgets
         if widgets and not self.widget_box in self.layout.objects:
             self.layout.append(self.widget_box)
@@ -89,6 +98,11 @@ def _render(self, doc, comm, root):
         if comm:
             kwargs['comm'] = comm
         plot = renderer.get_plot(self.object, **kwargs)
+        ref = root.ref['id']
+        if ref in self._plots:
+            old_plot = self._plots[ref]
+            old_plot.comm = None
+            old_plot.cleanup()
         self._plots[root.ref['id']] = plot
         return plot
 
@@ -96,20 +110,21 @@ def _get_model(self, doc, root=None, parent=None, comm=None):
         """
         Should return the Bokeh model to be rendered.
         """
+        ref = root.ref['id']
         plot = self._render(doc, comm, root)
         child_pane = Pane(plot.state, _temporary=True)
         model = child_pane._get_model(doc, root, parent, comm)
+        self._models[ref] = model
+        self._link_object(doc, root, parent, comm)
         if self.widget_box.objects:
             self._link_widgets(child_pane, root, comm)
-        self._models[root.ref['id']] = model
-        self._link_object(doc, root, parent, comm)
         return model
 
     def _link_widgets(self, pane, root, comm):
-        from holoviews.core.util import cross_index
-
         def update_plot(change):
+            from holoviews.core.util import cross_index
             from holoviews.plotting.bokeh.plot import BokehPlot
+
             widgets = self.widget_box.objects
             if self.widget_type == 'scrubber':
                 key = cross_index([v for v in self._values.values()], widgets[0].value)
@@ -130,10 +145,9 @@ def update_plot():
                 pane.object = plot.state
 
         ref = root.ref['id']
-        if ref not in self._callbacks:
-            for w in self.widget_box.objects:
-                watcher = w.param.watch(update_plot, 'value')
-                self._callbacks[ref].append(watcher)
+        for w in self.widget_box.objects:
+            watcher = w.param.watch(update_plot, 'value')
+            self._callbacks[ref].append(watcher)
 
     @classmethod
     def widgets_from_dimensions(cls, object, widget_types={}, widgets_type='individual'):
@@ -200,7 +214,7 @@ def is_bokeh_element_plot(plot):
     Checks whether plotting instance is a HoloViews ElementPlot rendered
     with the bokeh backend.
     """
-    from holoviews.plotting.plot import GenericElementPlot, GenericOverlayPlot 
+    from holoviews.plotting.plot import GenericElementPlot, GenericOverlayPlot
     return (plot.renderer.backend == 'bokeh' and isinstance(plot, GenericElementPlot)
             and not isinstance(plot, GenericOverlayPlot))
 
diff --git a/panel/pane.py b/panel/pane.py
index 24f593c4f5..6eb90d134c 100644
--- a/panel/pane.py
+++ b/panel/pane.py
@@ -185,7 +185,6 @@ def update_models():
                                      (type(self).__name__, old_model, new_model))
                     else:
                         parent.children[index] = new_model
-                        self._models[root.ref['id']] = new_model
 
             if comm:
                 update_models()
diff --git a/panel/param.py b/panel/param.py
index c0ddf2e59f..76367dfd53 100644
--- a/panel/param.py
+++ b/panel/param.py
@@ -445,7 +445,7 @@ def update_pane(*events):
     def _get_model(self, doc, root=None, parent=None, comm=None):
         ref = root.ref['id']
         if ref in self._callbacks:
-            self._cleanup(ref)
+            self._cleanup(root)
         model = self._inner_layout._get_model(doc, root, parent, comm)
         self._link_object_params(doc, root, parent, comm)
         self._models[ref] = model