**Course Title:** Qt 6 Application Development with C++ **Section Title:** Graphics and Animations in Qt **Topic:** Creating an interactive graphical application with custom graphics and animations. ### Overview In this lab topic, we'll dive into creating interactive graphical applications using Qt's powerful graphics and animation framework. We'll explore how to create custom graphics, animations, and interactive elements, making your applications more engaging and user-friendly. ### Step 1: Setting up the Graphics Scene To begin, we need to set up a `QGraphicsScene` to serve as the container for our graphics items. Create a new Qt project or open an existing one and add the necessary includes: ```cpp #include <QGraphicsScene> #include <QGraphicsView> ``` Next, create a `QGraphicsScene` instance and set it up in your application's constructor: ```cpp MyApplication::MyApplication(QWidget *parent) : QMainWindow(parent) { // Create a new graphics scene scene_ = new QGraphicsScene(this); // Set the scene's size scene_->setSceneRect(0, 0, 400, 400); // Create a graphics view to display the scene view_ = new QGraphicsView(scene_, this); // Set the central widget to the graphics view setCentralWidget(view_); } ``` ### Step 2: Creating Custom Graphics Items Create a new class that inherits from `QGraphicsItem` to create custom graphics items. In this example, let's create a `MyRectItem` class: ```cpp class MyRectItem : public QGraphicsItem { public: MyRectItem(QGraphicsItem *parent = nullptr); QRectF boundingRect() const override; QPainterPath shape() const override; void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget = nullptr) override; private: QRectF rect_; }; ``` Implement the `paint` method to draw the rectangle: ```cpp void MyRectItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget) { painter->setBrush(Qt::blue); painter->drawRect(rect_); } ``` ### Step 3: Animating Graphics Items To animate graphics items, we'll use `QPropertyAnimation` to animate the item's position. Create a new instance of `QPropertyAnimation` and animate the `MyRectItem` instance: ```cpp QPropertyAnimation *animation = new QPropertyAnimation(myRectItem, "pos"); animation->setDuration(1000); animation->setStartValue(QPointF(0, 0)); animation->setEndValue(QPointF(300, 300)); animation->start(); ``` ### Step 4: Adding Interactivity To make the application interactive, we'll add mouse event handling to the `MyRectItem` class: ```cpp void MyRectItem::mousePressEvent(QGraphicsSceneMouseEvent *event) { // Handle mouse press event } void MyRectItem::mouseMoveEvent(QGraphicsSceneMouseEvent *event) { // Handle mouse move event } ``` ### Step 5: Putting it all Together Create a new instance of `MyRectItem` and add it to the graphics scene: ```cpp MyRectItem *myRectItem = new MyRectItem(); scene_->addItem(myRectItem); ``` Run the application to see the interactive graphical application with custom graphics and animations. ### Conclusion In this lab topic, we've covered the basics of creating an interactive graphical application with custom graphics and animations using Qt's graphics and animation framework. You've learned how to: * Set up a `QGraphicsScene` and create custom graphics items * Animate graphics items using `QPropertyAnimation` * Add interactivity to graphics items using mouse event handling For more information on Qt's graphics and animation framework, please refer to the [Qt Documentation](https://doc.qt.io/qt-6/graphicsview.html). ### Practical Takeaways * Create custom graphics items by inheriting from `QGraphicsItem` * Use `QPropertyAnimation` to animate graphics items * Add interactivity to graphics items using mouse event handling ### What's Next? In the next topic, we'll cover packaging Qt applications for distribution using the Qt Installer Framework and CMake. Please leave a comment below if you have any questions or need further clarification on any of the topics covered in this lab.