Fix waveform zooming

Fixes mixxxdj#11626

src/waveform/widgets/allshader/waveformwidget.cpp

@@ -1,5 +1,7 @@
 #include "waveform/widgets/allshader/waveformwidget.h"
 
+#include <QApplication>
+
 #include "waveform/renderers/allshader/waveformrendererabstract.h"
 
 using namespace allshader;
@@ -51,3 +53,8 @@ void WaveformWidget::resizeGL(int w, int h) {
         renderer->allshaderWaveformRenderer()->resizeGL(w, h);
     }
 }
+
+void WaveformWidget::wheelEvent(QWheelEvent* event) {
+    QApplication::sendEvent(parentWidget(), event);
+    event->accept();
+}

src/waveform/widgets/allshader/waveformwidget.h

@@ -26,4 +26,5 @@ class allshader::WaveformWidget : public ::WGLWidget,
     }
 
   private:
+    void wheelEvent(QWheelEvent* event) override;
 };

src/waveform/widgets/glwaveformwidgetabstract.cpp

@@ -1,6 +1,13 @@
 #include "waveform/widgets/glwaveformwidgetabstract.h"
 
+#include <QApplication>
+
 GLWaveformWidgetAbstract::GLWaveformWidgetAbstract(const QString& group, QWidget* parent)
         : WaveformWidgetAbstract(group),
           WGLWidget(parent) {
 }
+
+void GLWaveformWidgetAbstract::wheelEvent(QWheelEvent* event) {
+    QApplication::sendEvent(parentWidget(), event);
+    event->accept();
+}

src/waveform/widgets/glwaveformwidgetabstract.h

@@ -41,4 +41,7 @@ class GLWaveformWidgetAbstract : public WaveformWidgetAbstract, public WGLWidget
     }
 
 #endif // !defined(QT_NO_OPENGL) && !defined(QT_OPENGL_ES_2)
+
+  private:
+    void wheelEvent(QWheelEvent* event) override;
 };

src/widget/wwaveformviewer.cpp

@@ -187,7 +187,7 @@ void WWaveformViewer::wheelEvent(QWheelEvent* event) {
     if (m_waveformWidget) {
         if (event->angleDelta().y() > 0) {
             onZoomChange(m_waveformWidget->getZoomFactor() / 1.05);
-        } else {
+        } else if (event->angleDelta().y() < 0) {
             onZoomChange(m_waveformWidget->getZoomFactor() * 1.05);
         }
     }