Hide markers when position become incoherent

src/Gui/PreviewRuler.cpp

@@ -265,6 +265,15 @@ qint64 PreviewRuler::getMarker( Marker m ) const
     return ( m == START ? m_markerStart : m_markerStop );
 }
 
+void
+PreviewRuler::hideMarker( Marker m )
+{
+    if ( m == START )
+        m_markerStart = -1;
+    else if ( m == STOP )
+        m_markerStop = -1;
+}
+
 void PreviewRuler::clear()
 {
     m_markerStart = MARKER_DEFAULT;

src/Gui/PreviewRuler.h

@@ -46,9 +46,10 @@ public:
 
     PreviewRuler( QWidget* parent = 0 );
     virtual ~PreviewRuler() { }
-    void setRenderer( GenericRenderer* renderer );
-    void setMarker( Marker m );
-    qint64 getMarker( Marker m ) const;
+    void    setRenderer( GenericRenderer* renderer );
+    void    setMarker( Marker m );
+    void    hideMarker( Marker m );
+    qint64  getMarker( Marker m ) const;
 
 public slots:
     void setFrame( qint64 frame, bool broadcastEvent = false );

src/Gui/PreviewWidget.cpp

@@ -170,11 +170,24 @@ void                        PreviewWidget::stop()
 void                        PreviewWidget::markerStartClicked()
 {
     m_ui->rulerWidget->setMarker( PreviewRuler::START );
+
+    qint64  beg = m_ui->rulerWidget->getMarker( PreviewRuler::START );
+    qint64  end = m_ui->rulerWidget->getMarker( PreviewRuler::STOP );
+    if ( beg > end )
+    {
+        m_ui->rulerWidget->hideMarker( PreviewRuler::STOP );;
+    }
 }
 
 void                        PreviewWidget::markerStopClicked()
 {
     m_ui->rulerWidget->setMarker( PreviewRuler::STOP );
+    qint64  beg = m_ui->rulerWidget->getMarker( PreviewRuler::START );
+    qint64  end = m_ui->rulerWidget->getMarker( PreviewRuler::STOP );
+    if ( beg > end )
+    {
+        m_ui->rulerWidget->hideMarker( PreviewRuler::START );;
+    }
 }
 
 void        PreviewWidget::createNewClipFromMarkers()