Fix issue with Mixer key events and Track Label Button focus (#7870)

A follow up to #7762 to fix various issues involving key events and focus grabbing problems.

src/gui/MixerChannelView.cpp

@@ -235,6 +235,10 @@ void MixerChannelView::keyPressEvent(QKeyEvent* ke)
 	{
 		m_fader->adjustByDialog();
 	}
+	else
+	{
+		ke->ignore();
+	}
 }
 
 void MixerChannelView::setChannelIndex(int index)

src/gui/SampleTrackWindow.cpp

@@ -267,7 +267,7 @@ void SampleTrackWindow::closeEvent(QCloseEvent* ce)
 		hide();
 	}
 
-	m_stv->m_tlb->setFocus();
+	m_stv->setFocus();
 	m_stv->m_tlb->setChecked(false);
 }
 

src/gui/instrument/InstrumentTrackWindow.cpp

@@ -539,8 +539,8 @@ void InstrumentTrackWindow::closeEvent( QCloseEvent* event )
 		hide();
 	}
 
-	m_itv->m_tlb->setFocus();
-	m_itv->m_tlb->setChecked( false );
+	m_itv->setFocus();
+	m_itv->m_tlb->setChecked(false);
 }
 
 

src/gui/tracks/TrackLabelButton.cpp

@@ -47,6 +47,7 @@ TrackLabelButton::TrackLabelButton( TrackView * _tv, QWidget * _parent ) :
 	m_iconName()
 {
 	setAcceptDrops( true );
+	setFocusPolicy(Qt::NoFocus);
 	setCursor( QCursor( embed::getIconPixmap( "hand" ), 3, 3 ) );
 	setToolButtonStyle( Qt::ToolButtonTextBesideIcon );