Add waveform preference for inverting scroll wheel zoom

As the scroll direction has been "inverted" from some time already
added a preference toggle to invert it, so that users can keep the behaviour if they prefer

src/preferences/dialog/dlgprefwaveform.cpp

@@ -95,6 +95,10 @@ DlgPrefWaveform::DlgPrefWaveform(QWidget* pParent, MixxxMainWindow* pMixxx,
             &QCheckBox::clicked,
             this,
             &DlgPrefWaveform::slotSetZoomSynchronization);
+    connect(invertScrollWheelZoom,
+            &QCheckBox::clicked,
+            this,
+            &DlgPrefWaveform::slotSetInvertScrollWheelZoom);
     connect(allVisualGain,
             QOverload<double>::of(&QDoubleSpinBox::valueChanged),
             this,
@@ -156,6 +160,7 @@ void DlgPrefWaveform::slotUpdate() {
     endOfTrackWarningTimeSpinBox->setValue(factory->getEndOfTrackWarningTime());
     endOfTrackWarningTimeSlider->setValue(factory->getEndOfTrackWarningTime());
     synchronizeZoomCheckBox->setChecked(factory->isZoomSync());
+    invertScrollWheelZoom->setChecked(factory->isScrollWheelZoomInverted());
     allVisualGain->setValue(factory->getVisualGain(WaveformWidgetFactory::All));
     lowVisualGain->setValue(factory->getVisualGain(WaveformWidgetFactory::Low));
     midVisualGain->setValue(factory->getVisualGain(WaveformWidgetFactory::Mid));
@@ -213,6 +218,8 @@ void DlgPrefWaveform::slotResetToDefaults() {
 
     synchronizeZoomCheckBox->setChecked(true);
 
+    invertScrollWheelZoom->setChecked(false);
+
     // RGB overview.
     waveformOverviewComboBox->setCurrentIndex(2);
 
@@ -265,6 +272,10 @@ void DlgPrefWaveform::slotSetZoomSynchronization(bool checked) {
     WaveformWidgetFactory::instance()->setZoomSync(checked);
 }
 
+void DlgPrefWaveform::slotSetInvertScrollWheelZoom(bool checked) {
+    WaveformWidgetFactory::instance()->setInvertScrollWheelZoom(checked);
+}
+
 void DlgPrefWaveform::slotSetVisualGainAll(double gain) {
     WaveformWidgetFactory::instance()->setVisualGain(WaveformWidgetFactory::All,gain);
 }

src/preferences/dialog/dlgprefwaveform.h

@@ -28,6 +28,7 @@ class DlgPrefWaveform : public DlgPreferencePage, public Ui::DlgPrefWaveformDlg
     void slotSetWaveformOverviewType(int index);
     void slotSetDefaultZoom(int index);
     void slotSetZoomSynchronization(bool checked);
+    void slotSetInvertScrollWheelZoom(bool checked);
     void slotSetVisualGainAll(double gain);
     void slotSetVisualGainLow(double gain);
     void slotSetVisualGainMid(double gain);

src/preferences/dialog/dlgprefwaveformdlg.ui

@@ -416,6 +416,16 @@ Select from different types of displays for the waveform, which differ primarily
        </property>
       </widget>
      </item>
+      <item row="8" column="1" colspan="3">
+        <widget class="QCheckBox" name="invertScrollWheelZoom">
+          <property name="toolTip">
+            <string>Inverts the zoom direction when using the scroll wheel. When checked, it will act in reverse of your operational system default behaviour.</string>
+          </property>
+          <property name="text">
+            <string>Invert zoom direction when using the scroll wheel</string>
+          </property>
+        </widget>
+      </item>
      <item row="11" column="0">
       <widget class="QLabel" name="cachedWaveforms">
        <property name="text">

src/waveform/waveformwidgetfactory.cpp

@@ -107,6 +107,7 @@ WaveformWidgetFactory::WaveformWidgetFactory()
           m_endOfTrackWarningTime(30),
           m_defaultZoom(WaveformWidgetRenderer::s_waveformDefaultZoom),
           m_zoomSync(true),
+          m_invertScrollWheelZoom(false),
           m_overviewNormalized(false),
           m_openGlAvailable(false),
           m_openGlesAvailable(false),
@@ -307,6 +308,9 @@ bool WaveformWidgetFactory::setConfig(UserSettingsPointer config) {
     bool zoomSync = m_config->getValue(ConfigKey("[Waveform]", "ZoomSynchronization"), m_zoomSync);
     setZoomSync(zoomSync);
 
+    bool invertScrollWheelZoom = m_config->getValue(ConfigKey("[Waveform]", "InvertScrollWheelZoom"), m_invertScrollWheelZoom);
+    setInvertScrollWheelZoom(invertScrollWheelZoom);
+
     int beatGridAlpha = m_config->getValue(ConfigKey("[Waveform]", "beatGridAlpha"), m_beatGridAlpha);
     setDisplayBeatGridAlpha(beatGridAlpha);
 
@@ -569,6 +573,13 @@ void WaveformWidgetFactory::setZoomSync(bool sync) {
     }
 }
 
+void WaveformWidgetFactory::setInvertScrollWheelZoom(bool invert) {
+    m_invertScrollWheelZoom = invert;
+    if (m_config) {
+        m_config->set(ConfigKey("[Waveform]", "InvertScrollWheelZoom"), ConfigValue(m_invertScrollWheelZoom));
+    }
+}
+
 void WaveformWidgetFactory::setDisplayBeatGridAlpha(int alpha) {
     m_beatGridAlpha = alpha;
     if (m_waveformWidgetHolders.size() == 0) {

src/waveform/waveformwidgetfactory.h

@@ -109,6 +109,9 @@ class WaveformWidgetFactory : public QObject, public Singleton<WaveformWidgetFac
     void setZoomSync(bool sync);
     int isZoomSync() const { return m_zoomSync;}
 
+    void setInvertScrollWheelZoom(bool invert);
+    bool isScrollWheelZoomInverted() const { return m_invertScrollWheelZoom; }
+
     void setDisplayBeatGridAlpha(int alpha);
     int getBeatGridAlpha() const { return m_beatGridAlpha; }
 
@@ -178,6 +181,7 @@ class WaveformWidgetFactory : public QObject, public Singleton<WaveformWidgetFac
     int m_endOfTrackWarningTime;
     double m_defaultZoom;
     bool m_zoomSync;
+    bool m_invertScrollWheelZoom;
     double m_visualGain[FilterCount];
     bool m_overviewNormalized;
 

src/widget/wwaveformviewer.cpp

@@ -177,7 +177,12 @@ void WWaveformViewer::mouseReleaseEvent(QMouseEvent* /*event*/) {
 
 void WWaveformViewer::wheelEvent(QWheelEvent* event) {
     if (m_waveformWidget) {
-        if (event->angleDelta().y() > 0) {
+        int y = event->angleDelta().y();
+        if (WaveformWidgetFactory::instance()->isScrollWheelZoomInverted()) {
+            y *= -1;
+        }
+
+        if (y > 0) {
             onZoomChange(m_waveformWidget->getZoomFactor() / 1.05);
         } else {
             onZoomChange(m_waveformWidget->getZoomFactor() * 1.05);