// Include the necessary headers and libraries #include#include // Define a custom widget class derived from QWidget class MyWidget : public QWidget { public: // Constructor and destructor definitions MyWidget(QWidget *parent = nullptr) : QWidget(parent) {} virtual ~MyWidget() {} // Override the resizeEvent method to add custom behavior virtual void resizeEvent(QResizeEvent *event) { QWidget::d_func()->resizeEvent(event); // Add more custom behavior here } };
// Include the necessary headers and libraries #includeIn this example, we define another custom widget class called MyWidget derived from QWidget. We override the paintEngine method to add custom behavior, but also return the internal paint engine object of the QWidget class using d_func(). Package library: Qt5 Gui Library Note: It is not recommended to use the QWidget d_func directly unless you have a strong understanding of the internal workings of Qt5 and have a specific use case for it. Improper use can lead to undefined behavior and other issues.#include // Define a custom widget class derived from QWidget class MyWidget : public QWidget { public: // Constructor and destructor definitions MyWidget(QWidget *parent = nullptr) : QWidget(parent) {} virtual ~MyWidget() {} // Override the paintEngine method to add custom behavior virtual QPaintEngine *paintEngine() const { return QWidget::d_func()->paintEngine(); } };