Re #2633. Match anywhere in algorithm name when typing in combobox.

Once 2 characters have been entered in the AlgorithmDock combobox's
lineedit, all algorithms that match the entered string anywhere in
their name should pop up.

There seem to be problems on RHEL6 though so this may not stick.

Code/Mantid/MantidQt/MantidWidgets/src/AlgorithmSelectorWidget.cpp

@@ -5,6 +5,64 @@
 using namespace Mantid::Kernel;
 using namespace Mantid::API;
 
+namespace {
+  // Customised QCompleter to match anywhere in an algorithm name, not just from the start
+  // Adapted from python code in http://stackoverflow.com/questions/5129211/qcompleter-custom-completion-rules
+  class InlineCompleter : public QCompleter
+  {
+  public:
+    InlineCompleter(QWidget * parent = NULL)
+     : QCompleter(parent), m_local_completion_prefix(), m_source_model(NULL)
+    {
+    }
+
+    void setModel ( QAbstractItemModel * model )
+    {
+      m_source_model = model;
+      QCompleter::setModel(m_source_model);
+    }
+
+    QStringList splitPath ( const QString & path ) const
+    {
+      m_local_completion_prefix = path;
+      updateModel();
+      QStringList sl;
+      sl << "";
+      return sl;
+    }
+
+  private:
+    void updateModel() const
+    {
+      class InnerProxyModel : public QSortFilterProxyModel
+      {
+      public:
+        // This method is called for each algorithm and returns true if the text
+        // entered so far matches anywhere in the algorithm name
+        bool filterAcceptsRow(int source_row, const QModelIndex &source_parent) const
+        {
+          // Only start matching once the 2nd character has been typed
+          if ( local_completion_prefix.size() < 2 ) return false;
+
+          QModelIndex index0 = sourceModel()->index(source_row,0,source_parent);
+          return sourceModel()->data(index0).toString().lower().contains(local_completion_prefix.lower());
+        }
+        QString local_completion_prefix;
+      };
+
+      InnerProxyModel * proxy_model = new InnerProxyModel;
+      proxy_model->local_completion_prefix = m_local_completion_prefix;
+      proxy_model->setSourceModel(m_source_model);
+      // Yes I know this is evil, but it's necessary to call the current method
+      // from the overridden splitPath above.
+      const_cast<InlineCompleter *>(this)->QCompleter::setModel(proxy_model);
+    }
+
+    mutable QString m_local_completion_prefix;
+    QAbstractItemModel * m_source_model;
+  };
+}
+
 namespace MantidQt
 {
 namespace MantidWidgets
@@ -30,11 +88,21 @@ namespace MantidWidgets
 
     m_findAlg = new FindAlgComboBox;
     m_findAlg->setEditable(true);
-    m_findAlg->completer()->setCompletionMode(QCompleter::PopupCompletion);
+    m_findAlg->setInsertPolicy(QComboBox::NoInsert);
+
+    // Must use full InlineCompleter type for pointer as overridden
+    // setModel method called below is NOT virtual.
+    InlineCompleter * completer = new InlineCompleter(m_findAlg);
+    completer->setCompletionMode(QCompleter::PopupCompletion);
+    completer->setModel(m_findAlg->model());
+    m_findAlg->setCompleter(completer);
+
     connect(m_findAlg,SIGNAL(enterPressed()),
         this,SLOT(executeSelected()));
     connect(m_findAlg,SIGNAL(editTextChanged(const QString&)),
         this,SLOT(findAlgTextChanged(const QString&)));
+    connect(completer,SIGNAL(highlighted(const QString&)),
+        m_findAlg,SLOT(setEditText(const QString&)));
 
     m_execButton = new QPushButton("Execute");
     connect(m_execButton,SIGNAL(clicked()),