From 3620c908014d7395a30cc908ae2e43f90a004053 Mon Sep 17 00:00:00 2001
From: Philipp Rudiger <P.Rudiger@ed.ac.uk>
Date: Fri, 14 Oct 2016 17:56:40 +0100
Subject: [PATCH 1/2] Added stream activate and deactivate methods

---
 holoviews/streams.py | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/holoviews/streams.py b/holoviews/streams.py
index 5a6f0c9cce..3394efdce5 100644
--- a/holoviews/streams.py
+++ b/holoviews/streams.py
@@ -106,6 +106,9 @@ def trigger(cls, streams):
         for subscriber in subscribers:
             subscriber(**dict(union))
 
+        for stream in streams:
+            stream.deactivate()
+
 
     def __init__(self, preprocessors=[], source=None, subscribers=[], **params):
         """
@@ -125,6 +128,15 @@ def __init__(self, preprocessors=[], source=None, subscribers=[], **params):
         if source:
             self.registry[id(source)].append(self)
 
+
+    def deactivate(self):
+        """
+        Allows defining an action after the stream has been triggered,
+        e.g. resetting parameters on streams with transient events.
+        """
+        pass
+
+
     @property
     def source(self):
         return self._source
@@ -153,6 +165,7 @@ def update(self, trigger=True, **kwargs):
         If trigger is enabled, the trigger classmethod is invoked on
         this particular Stream instance.
         """
+        self.activate()
         params = self.params().values()
         constants = [p.constant for p in params]
         for param in params:
@@ -161,9 +174,6 @@ def update(self, trigger=True, **kwargs):
         for (param, const) in zip(params, constants):
             param.constant = const
 
-        if trigger:
-            self.trigger([self])
-
 
     def __repr__(self):
         cls_name = self.__class__.__name__

From 48b8643b3ba3a08500cd535402c95b499273696e Mon Sep 17 00:00:00 2001
From: Philipp Rudiger <P.Rudiger@ed.ac.uk>
Date: Fri, 14 Oct 2016 19:43:50 +0100
Subject: [PATCH 2/2] Added pyqt4 to travis.yml

---
 .travis.yml          | 2 +-
 holoviews/streams.py | 4 +++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/.travis.yml b/.travis.yml
index 94b98eefec..9bb6a43524 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -24,7 +24,7 @@ install:
   - conda update -q conda
   # Useful for debugging any issues with conda
   - conda info -a
-  - conda create -q -n test-environment python=$TRAVIS_PYTHON_VERSION scipy numpy freetype nose bokeh pandas jupyter ipython=4.2.0 param matplotlib=1.5.1 xarray datashader
+  - conda create -q -n test-environment python=$TRAVIS_PYTHON_VERSION scipy numpy freetype nose bokeh pandas jupyter ipython=4.2.0 param pyqt=4 matplotlib=1.5.1 xarray datashader
   - source activate test-environment
   - conda install -c conda-forge  -c scitools iris sip=4.18 plotly
   - if [[ "$TRAVIS_PYTHON_VERSION" == "3.4" ]]; then
diff --git a/holoviews/streams.py b/holoviews/streams.py
index 3394efdce5..fe8399efd2 100644
--- a/holoviews/streams.py
+++ b/holoviews/streams.py
@@ -165,7 +165,6 @@ def update(self, trigger=True, **kwargs):
         If trigger is enabled, the trigger classmethod is invoked on
         this particular Stream instance.
         """
-        self.activate()
         params = self.params().values()
         constants = [p.constant for p in params]
         for param in params:
@@ -174,6 +173,9 @@ def update(self, trigger=True, **kwargs):
         for (param, const) in zip(params, constants):
             param.constant = const
 
+        if trigger:
+            self.trigger([self])
+
 
     def __repr__(self):
         cls_name = self.__class__.__name__