Now PreviewWidget slider can be used to set the preview starting frame.

src/GUI/PreviewWidget.cpp

@@ -96,11 +96,6 @@ void    PreviewWidget::seekSliderPressed()
 
 void    PreviewWidget::seekSliderMoved( int )
 {
-    if ( m_renderer->isRendering() == false )
-    {
-        m_ui->seekSlider->setValue( 0 );
-        return ;
-    }
     if ( m_ui->seekSlider->value() == m_ui->seekSlider->maximum() )
     {
         m_endReached = true;

src/Workflow/MainWorkflow.cpp

@@ -187,13 +187,13 @@ void        MainWorkflow::previousFrame()
 
 void        MainWorkflow::setPosition( float pos )
 {
-    if ( m_renderStarted == false )
-        return ;
-    //Since any track can be reactivated, we reactivate all of them, and let them
-    //unable themself if required.
-    for ( unsigned int i = 0; i < m_trackCount; ++i)
-        activateTrack( i );
-
+    if ( m_renderStarted == true )
+    {
+        //Since any track can be reactivated, we reactivate all of them, and let them
+        //unable themself if required.
+        for ( unsigned int i = 0; i < m_trackCount; ++i)
+            activateTrack( i );
+    }
     qint64  frame = static_cast<qint64>( (float)m_length * pos );
     m_currentFrame = frame;
     emit frameChanged( frame );