Re #8637. Add capability to specify multiple runs.

Each run is treated as a single point in the scan (in the order they're
given), a scan_index entry is inserted and the runs are merged together.
They can then be treated as other scan runs. This allows scans from
non-ADARA-enabled instruments to use the functionality of this interface.

The loading algorithm had to be changed from LoadEventNexus to Load for
this. This then required changes around that code to catch if the user
tries to load the wrong kind of file.

Code/Mantid/MantidQt/CustomInterfaces/inc/MantidQtCustomInterfaces/StepScan.h

@@ -53,6 +53,7 @@ private slots:
 private:
   void initLayout();
   void startLiveListener();
+  bool mergeRuns();
   void setupOptionControls();
   void clearNormalizationCombobox();
   Mantid::API::IAlgorithm_sptr setupStepScanAlg();

Code/Mantid/MantidQt/CustomInterfaces/inc/MantidQtCustomInterfaces/StepScan.ui

@@ -21,6 +21,9 @@
        <property name="label" stdset="0">
         <string>Data source</string>
        </property>
+       <property name="multipleFiles" stdset="0">
+        <bool>true</bool>
+       </property>
        <property name="optional" stdset="0">
         <bool>true</bool>
        </property>

Code/Mantid/MantidQt/CustomInterfaces/src/StepScan.cpp

@@ -166,21 +166,35 @@ void StepScan::startLiveListenerComplete(bool error)
 
 void StepScan::loadFile(bool async)
 {
-  const QString filename = m_uiForm.mWRunFiles->getFirstFilename();
+  const QString filename = m_uiForm.mWRunFiles->getUserInput().asString();
   // This handles the fact that mwRunFiles emits the filesFound signal more than
   // we want (on some platforms). TODO: Consider dealing with this up in mwRunFiles.
-  if ( filename != m_inputFilename )
+  if ( filename != m_inputFilename && m_uiForm.mWRunFiles->isValid() )
   {
     m_inputFilename = filename;
 
     // Remove any previously-loaded workspaces
     cleanupWorkspaces();
 
-    IAlgorithm_sptr alg = AlgorithmManager::Instance().create("LoadEventNexus");
-    alg->setPropertyValue("Filename", filename.toStdString());
-    m_inputWSName = "__" + QFileInfo(filename).baseName().toStdString();
-    alg->setPropertyValue("OutputWorkspace", m_inputWSName);
-    alg->setProperty("LoadMonitors", true);
+    IAlgorithm_sptr alg = AlgorithmManager::Instance().create("Load");
+    try {
+      alg->setPropertyValue("Filename", filename.toStdString());
+      if ( m_uiForm.mWRunFiles->getFilenames().size() == 1 )
+      {
+        m_inputWSName = "__" + QFileInfo(filename).baseName().toStdString();
+      }
+      else
+      {
+        m_inputWSName = "__multifiles";
+      }
+      alg->setPropertyValue("OutputWorkspace", m_inputWSName);
+      alg->setProperty("LoadMonitors", true);
+    }
+    catch (std::exception&) // Have to catch at this level as different exception types can happen
+    {
+      QMessageBox::warning(this,"File loading failed","Is this an event nexus file?");
+      return;
+    }
 
     if ( async )
     {
@@ -198,6 +212,9 @@ void StepScan::loadFile(bool async)
 void StepScan::loadFileComplete(bool error)
 {
   disconnect(m_algRunner, SIGNAL(algorithmComplete(bool)), this, SLOT(loadFileComplete(bool)));
+
+  if ( m_inputWSName == "__multifiles" && !error ) error = mergeRuns();
+
   if ( ! error )
   {
     setupOptionControls();
@@ -208,6 +225,35 @@ void StepScan::loadFileComplete(bool error)
   }
 }
 
+bool StepScan::mergeRuns()
+{
+  // Get hold of the group workspace and go through the entries adding an incrementing scan_index variable
+  WorkspaceGroup_const_sptr wsGroup = AnalysisDataService::Instance().retrieveWS<WorkspaceGroup>(m_inputWSName);
+  if ( !wsGroup ) return true; // Shouldn't be possible, but be defensive
+
+  for ( size_t i = 0; i < wsGroup->size(); ++i )
+  {
+    // Add a scan_index variable to each workspace, counting from 1
+    MatrixWorkspace_sptr ws = boost::static_pointer_cast<MatrixWorkspace>(wsGroup->getItem(i));
+    if ( !ws ) return true; // Again, shouldn't be possible (unless there's a group within a group?)
+    IAlgorithm_sptr addScanIndex = AlgorithmManager::Instance().create("AddSampleLog");
+    addScanIndex->setPropertyValue("Workspace",ws->name());
+    addScanIndex->setProperty("LogName","scan_index");
+    addScanIndex->setProperty("LogType","Number Series");
+    addScanIndex->setProperty("LogText",Strings::toString(i+1));
+    if ( ! addScanIndex->execute() ) return true;
+  }
+
+  IAlgorithm_sptr merge = AlgorithmManager::Instance().create("MergeRuns");
+  merge->setPropertyValue("InputWorkspaces",m_inputWSName);
+  const std::string summedWSName = "__summed_multifiles";
+  merge->setPropertyValue("OutputWorkspace",summedWSName);
+  if ( ! merge->execute() ) return true;
+  m_inputWSName = summedWSName;
+
+  return false;
+}
+
 void StepScan::setupOptionControls()
 {
   MatrixWorkspace_const_sptr outWS = AnalysisDataService::Instance().retrieveWS<MatrixWorkspace>(m_inputWSName);