add properties groups

app/gcompose/src/ViewportPane.h

@@ -10,6 +10,7 @@ namespace uLib {
     namespace Qt { class PropertyEditor; }
 }
 
+class QSplitter;
 class QVBoxLayout;
 class QLabel;
 
@@ -39,6 +40,7 @@ private:
     QVBoxLayout* m_layout;
     QWidget* m_titleBar;
     QLabel* m_titleLabel;
+    QSplitter* m_areaSplitter;
     QWidget* m_viewport;
 
     // Display Properties Overlay