fix: wheel event not propagating to parent in Qt6

Qt6 QApplication::notify pre-accepts wheel events (we.setAccepted(true))
before delivery. If a widget's wheelEvent doesn't call the parent class
(which would ignore() the event), the event stays accepted and does not
propagate to parent widgets (e.g. QScrollArea). This differs from Qt5
where unhandled wheel events propagated by default.

Fix by overriding wheelEvent in DSpinBox, DDoubleSpinBox, DComboBox
following the pattern from commit fe16c8e (settings/ComboBox):
  - hasFocus(): call base class wheelEvent (stepBy + accept, default behavior)
  - no focus:  call QWidget::wheelEvent (ignore() -> event propagates)

For DSlider, which is a QWidget containing an inner QSlider with an
eventFilter on qApp, fix the eventFilter instead: when the inner slider
has no focus, call e->ignore() before returning true so the event
propagates to the parent scrollarea in Qt6.

This fixes the Qt6-specific regression where scrolling over spinbox /
combobox / slider inside a scrollarea was blocked.

Ref: DDE-72

Author: 18202781743

include/widgets/dcombobox.h

@@ -23,6 +23,8 @@ class LIBDTKWIDGETSHARED_EXPORT DComboBox : public QComboBox, public DCORE_NAMES
 protected:
     DComboBox(DComboBoxPrivate &dd, QWidget *parent);
 
+    void wheelEvent(QWheelEvent *event) override;
+
     // QComboBox interface
 public:
     virtual void showPopup() override;

include/widgets/dslider.h

@@ -1,4 +1,4 @@
-// SPDX-FileCopyrightText: 2011 - 2022 UnionTech Software Technology Co., Ltd.
+// SPDX-FileCopyrightText: 2011 - 2026 UnionTech Software Technology Co., Ltd.
 //
 // SPDX-License-Identifier: LGPL-3.0-or-later
 

include/widgets/dspinbox.h

@@ -1,4 +1,4 @@
-// SPDX-FileCopyrightText: 2015 - 2022 UnionTech Software Technology Co., Ltd.
+// SPDX-FileCopyrightText: 2015 - 2026 UnionTech Software Technology Co., Ltd.
 //
 // SPDX-License-Identifier: LGPL-3.0-or-later
 
@@ -25,6 +25,10 @@ class LIBDTKWIDGETSHARED_EXPORT DSpinBox : public QSpinBox, public DTK_CORE_NAME
 public:
     explicit DSpinBox(QWidget *parent = nullptr);
 
+protected:
+    void wheelEvent(QWheelEvent *event) override;
+
+public:
     QLineEdit *lineEdit() const;
 
     bool isAlert() const;
@@ -65,6 +69,10 @@ class LIBDTKWIDGETSHARED_EXPORT DDoubleSpinBox : public QDoubleSpinBox, public D
 public:
     explicit DDoubleSpinBox(QWidget *parent = nullptr);
 
+protected:
+    void wheelEvent(QWheelEvent *event) override;
+
+public:
     bool isAlert() const;
     void showAlertMessage(const QString &text, int duration = 3000);
     void showAlertMessage(const QString &text, QWidget *follower, int duration = 3000);

src/widgets/dcombobox.cpp

@@ -32,6 +32,7 @@
 #include <QScreen>
 #include <QStack>
 #include <QWindow>
+#include <QWheelEvent>
 
 DWIDGET_BEGIN_NAMESPACE
 
@@ -109,6 +110,7 @@ DComboBox::DComboBox(QWidget *parent)
 {
     D_D(DComboBox);
     d->init();
+    setFocusPolicy(Qt::StrongFocus);
 }
 
 DComboBox::DComboBox(DComboBoxPrivate &dd, QWidget *parent)
@@ -117,6 +119,16 @@ DComboBox::DComboBox(DComboBoxPrivate &dd, QWidget *parent)
 {
     D_D(DComboBox);
     d->init();
+    setFocusPolicy(Qt::StrongFocus);
+}
+
+void DComboBox::wheelEvent(QWheelEvent *event)
+{
+    if (hasFocus()) {
+        QComboBox::wheelEvent(event);
+    } else {
+        QWidget::wheelEvent(event);
+    }
 }
 
 /*!

src/widgets/dslider.cpp

@@ -1,4 +1,4 @@
-// SPDX-FileCopyrightText: 2011 - 2022 UnionTech Software Technology Co., Ltd.
+// SPDX-FileCopyrightText: 2011 - 2026 UnionTech Software Technology Co., Ltd.
 //
 // SPDX-License-Identifier: LGPL-3.0-or-later
 
@@ -136,7 +136,11 @@ bool DSlider::eventFilter(QObject *watched, QEvent *e)
     Q_D(DSlider);
 
     if ((watched == d->slider) && (e->type() == QEvent::Wheel)) {
-        return !d->mouseWheelEnabled;
+        if (d->mouseWheelEnabled && d->slider->hasFocus()) {
+            return false;  // let QSlider::wheelEvent handle it (stepBy + accept)
+        }
+        e->ignore();  // Qt6: un-accept so event propagates to parent (e.g. scrollarea)
+        return true;   // block delivery to the inner QSlider
     }
 
     if (e->type() == QEvent::MouseButtonRelease) {

src/widgets/dspinbox.cpp

@@ -1,4 +1,4 @@
-// SPDX-FileCopyrightText: 2015 - 2022 UnionTech Software Technology Co., Ltd.
+// SPDX-FileCopyrightText: 2015 - 2026 UnionTech Software Technology Co., Ltd.
 //
 // SPDX-License-Identifier: LGPL-3.0-or-later
 
@@ -8,6 +8,8 @@
 #include "private/dspinbox_p.h"
 #include "dlineedit.h"
 
+#include <QWheelEvent>
+
 DWIDGET_BEGIN_NAMESPACE
 
 DSpinBoxPrivate::DSpinBoxPrivate(DSpinBox *parent) :
@@ -63,6 +65,16 @@ DSpinBox::DSpinBox(QWidget *parent) :
     DObject(*new DSpinBoxPrivate(this))
 {
     d_func()->init();
+    setFocusPolicy(Qt::StrongFocus);
+}
+
+void DSpinBox::wheelEvent(QWheelEvent *event)
+{
+    if (hasFocus()) {
+        QSpinBox::wheelEvent(event);
+    } else {
+        QWidget::wheelEvent(event);
+    }
 }
 
 /*!
@@ -180,6 +192,16 @@ DDoubleSpinBox::DDoubleSpinBox(QWidget *parent) :
     DObject(*new DDoubleSpinBoxPrivate(this))
 {
     d_func()->init();
+    setFocusPolicy(Qt::StrongFocus);
+}
+
+void DDoubleSpinBox::wheelEvent(QWheelEvent *event)
+{
+    if (hasFocus()) {
+        QDoubleSpinBox::wheelEvent(event);
+    } else {
+        QWidget::wheelEvent(event);
+    }
 }
 
 bool DDoubleSpinBox::isAlert() const