Spawn balls on a timer

src/ball.cpp

@@ -43,7 +43,7 @@ void Ball::timerEvent(QTimerEvent*) {
     }
     // Bottom collision (only if no longer spawning)
     if (!m_isSpawning && m_y > rct.height() - RADIUS) {
-        emit deleted(this);
+        emit fellThrough(this);
         stop();
         m_parent->update();
         return;
@@ -51,7 +51,10 @@ void Ball::timerEvent(QTimerEvent*) {
 
     // Platform collision (only if no longer spawning)
     if (!m_isSpawning && m_platform->rect().intersects(QRect(m_x, m_y, RADIUS * 2.0, RADIUS * 2.0))) {
-        m_ky *= -1;
+        emit caught(this);
+        stop();
+        m_parent->update();
+        return;
     }
 
     m_x += m_kx;

src/ball.h

@@ -15,7 +15,8 @@ class Ball : public QTimer {
     void draw(QPainter& painter);
 
   signals:
-    void deleted(Ball* ball);
+    void fellThrough(Ball* ball);
+    void caught(Ball* ball);
 
   protected:
     virtual void timerEvent(QTimerEvent*) override;

src/mainwindow.cpp

@@ -4,14 +4,18 @@
 #include <memory>
 #include <qnamespace.h>
 
-MainWindow::MainWindow(QWidget* parent) : QMainWindow(parent), ui(new Ui::MainWindow), leftArrowPressed{false}, rightArrowPressed{false} {
+#define INIT_SPAWN_SPEED 1500.0
+#define SPAWN_SPEED_INCREASE 100.0
+#define MIN_SPAWN_SPEED 100.0
+
+MainWindow::MainWindow(QWidget* parent) : QMainWindow(parent), ui(new Ui::MainWindow), leftArrowPressed{false}, rightArrowPressed{false}, m_spawnInterval{INIT_SPAWN_SPEED} {
     ui->setupUi(this);
 
-    platform = std::make_shared<Platform>(this);
+    connect(&m_spawnTimer, &QTimer::timeout, this, &MainWindow::onBallSpawn);
+    m_spawnTimer.start(m_spawnInterval);
 
-    auto ball = std::make_shared<Ball>(this, platform);
-    connect(ball.get(), &Ball::deleted, this, &MainWindow::onDeleteBall);
-    balls.append(ball);
+    platform = std::make_shared<Platform>(this);
+    spawnBall();
 }
 
 MainWindow::~MainWindow() {
@@ -33,7 +37,7 @@ void MainWindow::paintEvent(QPaintEvent*) {
     platform->draw(painter);
 }
 
-void MainWindow::onDeleteBall(Ball* ball) {
+void MainWindow::deleteBall(Ball* ball) {
     // Remove the ball from the list by checking the raw pointer
     // This will also free it (smart ptrs).
     for (auto it = balls.begin(); it != balls.end(); ++it) {
@@ -45,6 +49,30 @@ void MainWindow::onDeleteBall(Ball* ball) {
     }
 }
 
+void MainWindow::spawnBall() {
+    auto ball = std::make_shared<Ball>(this, platform);
+    connect(ball.get(), &Ball::fellThrough, this, &MainWindow::ballFell);
+    connect(ball.get(), &Ball::caught, this, &MainWindow::ballCaught);
+    balls.append(ball);
+}
+
+void MainWindow::ballFell(Ball* ball) {
+    deleteBall(ball);
+    // TODO: Game over
+}
+
+void MainWindow::ballCaught(Ball* ball) {
+    m_spawnInterval -= SPAWN_SPEED_INCREASE;
+    if (m_spawnInterval < MIN_SPAWN_SPEED)
+        m_spawnInterval = MIN_SPAWN_SPEED;
+    deleteBall(ball);
+}
+
+void MainWindow::onBallSpawn() {
+    spawnBall();
+    m_spawnTimer.start(m_spawnInterval);
+}
+
 void MainWindow::keyPressEvent(QKeyEvent* event) {
     switch (event->key()) {
         case Qt::Key_Left: leftArrowPressed = true; break;

src/mainwindow.h

@@ -25,15 +25,22 @@ class MainWindow : public QMainWindow {
     bool rightArrowPressed;
 
   private slots:
-    void onDeleteBall(Ball* ball); // Slot to handle the ball deletion
+    void ballFell(Ball* ball);
+    void ballCaught(Ball* ball);
+    void onBallSpawn();
 
   protected:
     virtual void paintEvent(QPaintEvent*) override;
 
+    void deleteBall(Ball* ball);
+    void spawnBall();
+
     void keyPressEvent(QKeyEvent* event) override;
     void keyReleaseEvent(QKeyEvent* event) override;
 
   private:
+    float m_spawnInterval;
+    QTimer m_spawnTimer;
     Ui::MainWindow* ui;
     QList<std::shared_ptr<Ball>> balls;
     std::shared_ptr<Platform> platform;