Make script usable for the current session of Mantid

In order to make the script usable as soon as it is downloade, it is not
enough to update the pythonscripts.directories as the last commit did, but
you have also to add to the python sys path at the current running session.

Running python code is not possible inside the Framework/ScriptRepository
level. So, a notification strategy was used in order to trigger a method
of MantidUI, which can execute the python code that is necessary to add
the new paths to the python sys.

re #7097

Code/Mantid/MantidPlot/src/Mantid/MantidUI.cpp

@@ -93,6 +93,7 @@ m_finishedLoadDAEObserver(*this, &MantidUI::handleLoadDAEFinishedNotification),
   m_groupworkspacesObserver(*this,&MantidUI::handleGroupWorkspaces),
   m_ungroupworkspaceObserver(*this,&MantidUI::handleUnGroupWorkspace),
   m_workspaceGroupUpdateObserver(*this,&MantidUI::handleWorkspaceGroupUpdate),
+  m_configServiceObserver(*this,&MantidUI::handleConfigServiceUpdate),
   m_appWindow(aw), m_vatesSubWindow(NULL)
 {
 
@@ -181,6 +182,7 @@ void MantidUI::init()
   dataStore.notificationCenter.addObserver(m_groupworkspacesObserver);
   dataStore.notificationCenter.addObserver(m_ungroupworkspaceObserver);
   dataStore.notificationCenter.addObserver(m_workspaceGroupUpdateObserver);
+  Mantid::Kernel::ConfigService::Instance().addObserver(m_configServiceObserver);
 
   m_exploreAlgorithms->update();
   try
@@ -288,6 +290,7 @@ MantidUI::~MantidUI()
 {
   delete m_algMonitor;
 
+  Mantid::Kernel::ConfigService::Instance().removeObserver(m_configServiceObserver);
   Mantid::API::AnalysisDataService::Instance().notificationCenter.removeObserver(m_groupworkspacesObserver);
   Mantid::API::AnalysisDataService::Instance().notificationCenter.removeObserver(m_ungroupworkspaceObserver);
   Mantid::API::AnalysisDataService::Instance().notificationCenter.removeObserver(m_workspaceGroupUpdateObserver);
@@ -1876,6 +1879,25 @@ void MantidUI::handleWorkspaceGroupUpdate(Mantid::API::GroupUpdatedNotification_
   emit workspace_group_updated( name );
 }
 
+void MantidUI::handleConfigServiceUpdate(Mantid::Kernel::ConfigValChangeNotification_ptr pNf){
+  if (pNf->key() == "pythonscripts.directories"){
+    // this code ad the filepaths inside the pythonscripts.directories to the 
+    // python sys if they are not already there. This is to cope with the requirement
+    // at #7097 of letting python scripts usable when downloaded from Script Repository. 
+    // This code was added because changing the pythonscripts.directories update the 
+    // python path just after restarting MantidPlot.
+    QString code = QString("import sys\n\
+paths = '%1'\n\
+list_of_path = paths.split(';')\n\
+if isinstance(list_of_path,str):\n\
+  list_of_path = [list_of_path,]\n\
+for value in list_of_path:\n\
+  if value not in sys.path: sys.path.append(value)\n").arg(QString::fromStdString(pNf->curValue()));
+    // run this code silently
+    appWindow()->runPythonScript(code, false, true, true);
+  }
+}
+
 void MantidUI::manageMantidWorkspaces()
 {
 #ifdef _WIN32

Code/Mantid/MantidPlot/src/Mantid/MantidUI.h

@@ -478,6 +478,10 @@ public slots:
   void handleWorkspaceGroupUpdate(Mantid::API::GroupUpdatedNotification_ptr pNf);
   Poco::NObserver<MantidUI, Mantid::API::GroupUpdatedNotification> m_workspaceGroupUpdateObserver;
 
+  // handles notification send by ConfigService, change on pythonscripts.directories
+  void handleConfigServiceUpdate(Mantid::Kernel::ConfigValChangeNotification_ptr pNf);
+  Poco::NObserver<MantidUI, Mantid::Kernel::ConfigValChangeNotification> m_configServiceObserver;
+
   //#678
   //for savenexus algorithm
   void executeSaveNexus(QString algName,int version);