project: implement searching

I can't believe this has been unimplemented this whole time...

app/panel/project/project.cpp

@@ -58,6 +58,7 @@ ProjectPanel::ProjectPanel(QWidget *parent) :
   layout->addWidget(explorer_);
   connect(explorer_, &ProjectExplorer::DoubleClickedItem, this, &ProjectPanel::ItemDoubleClickSlot);
   connect(explorer_, &ProjectExplorer::SelectionChanged, this, &ProjectPanel::SelectionChanged);
+  connect(toolbar, &ProjectToolbar::SearchChanged, explorer_, &ProjectExplorer::SetSearchFilter);
 
   // Set toolbar's view to the explorer's view
   toolbar->SetView(explorer_->view_type());

app/widget/projectexplorer/projectexplorer.cpp

@@ -67,6 +67,7 @@ ProjectExplorer::ProjectExplorer(QWidget *parent) :
 
   // Set up sort filter proxy model
   sort_model_.setSourceModel(&model_);
+  sort_model_.setFilterCaseSensitivity(Qt::CaseInsensitive);
   sort_model_.setSortRole(ProjectViewModel::kInnerTextRole);
 
   // Add tree view to stacked widget
@@ -301,6 +302,11 @@ void ProjectExplorer::RenameSelectedItem()
   }
 }
 
+void ProjectExplorer::SetSearchFilter(const QString &s)
+{
+  sort_model_.setFilterFixedString(s);
+}
+
 void ProjectExplorer::ShowContextMenu()
 {
   Menu menu;

app/widget/projectexplorer/projectexplorer.h

@@ -94,6 +94,8 @@ public slots:
 
   void RenameSelectedItem();
 
+  void SetSearchFilter(const QString &s);
+
 signals:
   /**
    * @brief Emitted when an Item is double clicked