fix: the widget's theme is not updated after changing parent

Change-Id: I744c4e15b0663c2d8eafdf74ce7d2ff0630bde28

src/widgets/dapplication.cpp

@@ -695,6 +695,10 @@ bool DApplication::notify(QObject *obj, QEvent *event)
                     menu->setStyle(style);
                 }
         }
+    } else if (event->type() == QEvent::ParentChange) {
+        if (QWidget *widget = qobject_cast<QWidget*>(obj)) {
+            DThemeManager::instance()->updateThemeOnParentChanged(widget);
+        }
     }
 
     return QApplication::notify(obj, event);

src/widgets/dthememanager.cpp

@@ -327,5 +327,35 @@ DThemeManager::DThemeManager()
     setTheme("light");
 }
 
+static void updateWidgetTheme(DThemeManager *manager, QWidget *widget, QWidget *baseWidget, const QString &theme)
+{
+    inseritStyle(widget, baseWidget);
+
+    Q_EMIT manager->widgetThemeChanged(widget, theme);
+
+    for (QObject *child : widget->children()) {
+        if (QWidget *cw = qobject_cast<QWidget*>(child)) {
+            if (widget->property("_d_dtk_theme").isValid())
+                return;
+
+            updateWidgetTheme(manager, cw, baseWidget, theme);
+        }
+    }
+}
+
+void DThemeManager::updateThemeOnParentChanged(QWidget *widget)
+{
+    if (widget->property("_d_dtk_theme").isValid())
+        return;
+
+    QWidget *base_widget = nullptr;
+    const QString &theme = this->theme(widget, &base_widget);
+
+    if (!base_widget)
+        return;
+
+    updateWidgetTheme(this, widget, base_widget, theme);
+}
+
 
 DWIDGET_END_NAMESPACE

src/widgets/dthememanager.h

@@ -54,7 +54,12 @@ public Q_SLOTS:
 protected:
     DThemeManager();
 
+    void updateThemeOnParentChanged(QWidget *widget);
+
     QString m_theme;
+
+private:
+    friend class DApplication;
 };
 
 DWIDGET_END_NAMESPACE