Handle ball collisions against platform

src/ball.cpp

@@ -12,7 +12,7 @@
 
 double getRandomDouble(double maxValue);
 
-Ball::Ball(QWidget* parent) : m_parent{parent}, m_isSpawning{true} {
+Ball::Ball(QWidget* parent, std::shared_ptr<Platform> platform) : m_parent{parent}, m_platform{platform}, m_isSpawning{true} {
     QRect rct = parent->rect();
 
     m_x = rand() % rct.width(); // random x pos
@@ -49,6 +49,11 @@ void Ball::timerEvent(QTimerEvent*) {
         return;
     }
 
+    // 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;
+    }
+
     m_x += m_kx;
     m_y += m_ky;
 

src/ball.h

@@ -1,6 +1,7 @@
 #ifndef BALL_H
 #define BALL_H
 
+#include "platform.h"
 #include <QPainter>
 #include <QTimer>
 #include <qobjectdefs.h>
@@ -9,7 +10,7 @@ class Ball : public QTimer {
     Q_OBJECT
 
   public:
-    Ball(QWidget* parent);
+    Ball(QWidget* parent, std::shared_ptr<Platform> platform);
 
     void draw(QPainter& painter);
 
@@ -21,6 +22,7 @@ class Ball : public QTimer {
 
   private:
     QWidget* m_parent;
+    std::shared_ptr<Platform> m_platform;
     double m_x;
     double m_y;
     double m_kx;

src/mainwindow.cpp

@@ -9,7 +9,7 @@ MainWindow::MainWindow(QWidget* parent) : QMainWindow(parent), ui(new Ui::MainWi
 
     platform = std::make_shared<Platform>(this);
 
-    auto ball = std::make_shared<Ball>(this);
+    auto ball = std::make_shared<Ball>(this, platform);
     connect(ball.get(), &Ball::deleted, this, &MainWindow::onDeleteBall);
     balls.append(ball);
 }

src/platform.cpp

@@ -19,8 +19,7 @@ Platform::Platform(MainWindow* parent) : m_parent{parent} {
 }
 
 void Platform::draw(QPainter& painter) {
-    QRect rct(m_x, m_y, PLATFORM_WIDTH, PLATFORM_HEIGHT);
-    painter.drawRect(rct);
+    painter.drawRect(rect());
 }
 
 void Platform::timerEvent(QTimerEvent*) {
@@ -34,3 +33,7 @@ void Platform::timerEvent(QTimerEvent*) {
 
     m_x += direction * SPEED;
 }
+
+QRect Platform::rect() const {
+    return QRect(m_x, m_y, PLATFORM_WIDTH, PLATFORM_HEIGHT);
+}

src/platform.h

@@ -18,6 +18,8 @@ class Platform : public QTimer {
 
     void draw(QPainter& painter);
 
+    QRect rect() const;
+
   protected:
     virtual void timerEvent(QTimerEvent*) override;