fix: make volume/progress sliders draggable

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/widget/clickableslider.hpp

@@ -16,17 +16,34 @@ protected:
     void mousePressEvent(QMouseEvent *event) override
     {
         if (event->button() == Qt::LeftButton) {
-            int val;
-            if (orientation() == Qt::Horizontal) {
-                val = minimum() + (maximum() - minimum()) * event->pos().x() / width();
-            } else {
-                val = minimum() + (maximum() - minimum()) * (height() - event->pos().y()) / height();
-            }
-            setValue(val);
+            // Jump the handle to the clicked position first so Qt's own
+            // press handler sees the click "on" the handle and starts drag.
+            const int val = posToValue(event->pos());
+            setSliderPosition(val);
             emit sliderMoved(val);
-            event->accept();
-        } else {
-            QSlider::mousePressEvent(event);
         }
+        // Always forward so the slider enters drag mode normally.
+        QSlider::mousePressEvent(event);
+    }
+
+    void mouseMoveEvent(QMouseEvent *event) override
+    {
+        // During a drag, keep snapping to cursor position.
+        if (event->buttons() & Qt::LeftButton) {
+            const int val = posToValue(event->pos());
+            setSliderPosition(val);
+            emit sliderMoved(val);
+        }
+        QSlider::mouseMoveEvent(event);
+    }
+
+private:
+    int posToValue(const QPoint &pos) const
+    {
+        const int span  = orientation() == Qt::Horizontal ? width() : height();
+        const int pixel = orientation() == Qt::Horizontal ? pos.x() : (height() - pos.y());
+        if (span <= 0) return minimum();
+        const int val = minimum() + (maximum() - minimum()) * pixel / span;
+        return qBound(minimum(), val, maximum());
     }
 };