Functional draft for backlight scrollwheel feature

plugin-backlight/backlight.cpp

@@ -25,7 +25,7 @@
  * END_COMMON_COPYRIGHT_HEADER */
 
 #include "backlight.h"
-#include <QEvent>
+#include <QWheelEvent>
 
 LXQtBacklight::LXQtBacklight(const ILXQtPanelPluginStartupInfo &startupInfo):
         QObject(),
@@ -35,6 +35,10 @@ LXQtBacklight::LXQtBacklight(const ILXQtPanelPluginStartupInfo &startupInfo):
     // use our own icon
     m_backlightButton->setIcon(QIcon::fromTheme(QStringLiteral("brightnesssettings")));
 
+    // NOTE: Redirect (mouse) events to LXQtBacklight event filter
+    m_backlightButton->setMouseTracking(true);
+    m_backlightButton->installEventFilter(this);
+
     connect(m_backlightButton, &QToolButton::clicked, this, &LXQtBacklight::showSlider);
 
     m_backlightSlider = nullptr;
@@ -61,6 +65,25 @@ void LXQtBacklight::deleteSlider()
     //printf("Deleted\n");
 }
 
+bool LXQtBacklight::eventFilter(QObject *obj, QEvent *event)
+{
+    if (obj == m_backlightButton) {
+        if (event->type() == QEvent::Wheel) {
+            if(! m_backlightSlider) {
+                // NOTE: Workaround to prevent crash
+                // TODO: The event can probably be handled directly in the plugin
+                m_backlightSlider = new SliderDialog(m_backlightButton);
+                connect(m_backlightSlider, &SliderDialog::dialogClosed, this, &LXQtBacklight::deleteSlider);
+            }
+            auto ev = static_cast<QWheelEvent*>(event);
+            m_backlightSlider->handleWheelEvent(ev);
+            return true;
+        }
+    }
+
+    return QObject::eventFilter(obj, event);
+}
+
 void LXQtBacklight::showSlider(bool)
 {
     if(! m_backlightSlider) {

plugin-backlight/backlight.h

@@ -57,6 +57,9 @@ protected Q_SLOTS:
     void showSlider(bool);
     void deleteSlider();
 
+protected:
+    bool eventFilter(QObject* obj, QEvent* event) override;
+
 private:
     QToolButton *m_backlightButton;
     SliderDialog *m_backlightSlider;

plugin-backlight/sliderdialog.cpp

@@ -26,7 +26,7 @@
 
 #include <QVBoxLayout>
 #include <QFrame>
-#include <QEvent>
+#include <QWheelEvent>
 #include <QDebug>
 #include "sliderdialog.h"
 
@@ -106,6 +106,18 @@ void SliderDialog::updateBacklight()
         m_slider->setValue( (m_backlight->getBacklight() * 100) / maxBacklight);
 }
 
+void SliderDialog::handleWheelEvent(QWheelEvent *event) {
+    auto cur_pos = m_slider->sliderPosition();
+    // auto cur_pos = m_backlight->getBacklight();
+    auto delta = event->angleDelta().y() / QWheelEvent::DefaultDeltasPerStep;
+    auto step = delta * m_slider->singleStep();
+    auto value = cur_pos + step;
+    qInfo().nospace() << "Handling backlight wheel event (set value: " << value << ")";
+    // m_slider->setSliderPosition(m_slider->sliderPosition()
+    //                   + (event->angleDelta().y() / QWheelEvent::DefaultDeltasPerStep * m_slider->singleStep()));
+    m_slider->setValue(value);
+}
+
 void SliderDialog::downButtonClicked(bool)
 {
     m_slider->setValue(m_slider->value() - 1);

plugin-backlight/sliderdialog.h

@@ -41,13 +41,14 @@ class SliderDialog: public QDialog
 public:
     SliderDialog(QWidget *parent);
     void updateBacklight();
+    void handleWheelEvent(QWheelEvent* event);
 
 Q_SIGNALS:
     void dialogClosed();
 
 protected:
     bool event(QEvent *event) override;
-    
+
 private:
     QSlider *m_slider;
     QToolButton *m_upButton, *m_downButton;