Improve performance when moving channels in the Mixer

include/MixerChannelView.h

@@ -64,6 +64,7 @@ class MixerChannelView : public QWidget
 	void keyPressEvent(QKeyEvent* ke) override;
 
 	void reset();
+
 	int channelIndex() const { return m_channelIndex; }
 	void setChannelIndex(int index);
 

include/MixerView.h

@@ -83,7 +83,6 @@ class LMMS_EXPORT MixerView : public QWidget, public ModelView,
 
 	// move the channel to the left or right
 	void moveChannelLeft(int index);
-	void moveChannelLeft(int index, int focusIndex);
 	void moveChannelRight(int index);
 
 	void renameChannel(int index);

src/core/Mixer.cpp

@@ -644,12 +644,13 @@ FloatModel * Mixer::channelSendModel( mix_ch_t fromChannel, mix_ch_t toChannel )
 
 void Mixer::mixToChannel( const SampleFrame* _buf, mix_ch_t _ch )
 {
-	if( m_mixerChannels[_ch]->m_muteModel.value() == false )
+	const auto channel = m_mixerChannels[_ch];
+	if (!channel->m_muteModel.value())
 	{
-		m_mixerChannels[_ch]->m_lock.lock();
-		MixHelpers::add( m_mixerChannels[_ch]->m_buffer, _buf, Engine::audioEngine()->framesPerPeriod() );
-		m_mixerChannels[_ch]->m_hasInput = true;
-		m_mixerChannels[_ch]->m_lock.unlock();
+		channel->m_lock.lock();
+		MixHelpers::add(channel->m_buffer, _buf, Engine::audioEngine()->framesPerPeriod());
+		channel->m_hasInput = true;
+		channel->m_lock.unlock();
 	}
 }
 

src/gui/MixerChannelView.cpp

@@ -248,13 +248,7 @@ void MixerChannelView::keyPressEvent(QKeyEvent* ke)
 
 void MixerChannelView::setChannelIndex(int index)
 {
-	MixerChannel* mixerChannel = Engine::mixer()->mixerChannel(index);
-	m_fader->setModel(&mixerChannel->m_volumeModel);
-	m_muteButton->setModel(&mixerChannel->m_muteModel);
-	m_soloButton->setModel(&mixerChannel->m_soloModel);
-	m_effectRackView->setModel(&mixerChannel->m_fxChain);
 	m_channelNumberLcd->setValue(index);
-	m_renameLineEdit->setText(elideName(mixerChannel->m_name));
 	m_channelIndex = index;
 }
 

src/gui/MixerView.cpp

@@ -433,38 +433,29 @@ void MixerView::deleteUnusedChannels()
 	}
 }
 
-
-
-void MixerView::moveChannelLeft(int index, int focusIndex)
+void MixerView::moveChannelLeft(int index)
 {
 	// can't move master or first channel left or last channel right
-	if (index <= 1 || index >= m_mixerChannelViews.size()) return;
-
-	Mixer *m = getMixer();
-
-	// Move instruments channels
-	m->moveChannelLeft(index);
+	if (index <= 1 || index >= m_mixerChannelViews.size()) { return; }
 
-	// Update widgets models
-	m_mixerChannelViews[index]->setChannelIndex(index);
-	m_mixerChannelViews[index - 1]->setChannelIndex(index - 1);
-
-	// Focus on new position
-	setCurrentMixerChannel(focusIndex);
-}
+	m_mixer->moveChannelLeft(index);
 
+	const auto layoutIndex = chLayout->indexOf(m_mixerChannelViews[index]);
+	assert(layoutIndex >= 1);
 
+	chLayout->removeWidget(m_mixerChannelViews[index]);
+	chLayout->insertWidget(layoutIndex - 1, m_mixerChannelViews[index]);
 
-void MixerView::moveChannelLeft(int index)
-{
-	moveChannelLeft(index, index - 1);
+	m_mixerChannelViews[index]->setChannelIndex(index - 1);
+	m_mixerChannelViews[index - 1]->setChannelIndex(index);
+	std::swap(m_mixerChannelViews[index - 1], m_mixerChannelViews[index]);
 }
 
 
 
 void MixerView::moveChannelRight(int index)
 {
-	moveChannelLeft(index + 1, index + 1);
+	moveChannelLeft(index + 1);
 }