Basic ball

CMakeLists.txt

@@ -35,6 +35,7 @@ else()
   else()
     add_executable(${PROJECT_NAME}
             ${PROJECT_SOURCES}
+            src/ball.h src/ball.cpp
         )
   endif()
 endif()

src/ball.cpp

@@ -0,0 +1,68 @@
+#include "ball.h"
+#include <QRect>
+#include <QWidget>
+#include <random>
+
+#define RADIUS 15
+#define TICK_SPEED 10
+#define MAX_SPEED 5.0
+#define GRAVITY 0.981
+
+double getRandomDouble(double maxValue);
+
+Ball::Ball(QWidget* parent) : m_parent{parent}, m_isSpawning{true} {
+    QRect rct = parent->rect();
+
+    m_x = rand() % rct.width(); // random x pos
+    m_y = rct.height() + 5; // start below the screen
+
+    m_kx = getRandomDouble(MAX_SPEED); // random horizontal speed
+    m_ky = -MAX_SPEED;
+
+    start(TICK_SPEED);
+}
+
+void Ball::draw(QPainter& painter) {
+    painter.drawEllipse(m_x, m_y, RADIUS * 2.0, RADIUS * 2.0);
+}
+
+void Ball::timerEvent(QTimerEvent*) {
+    if (m_ky < -MAX_SPEED)
+        m_ky = std::max(m_ky - GRAVITY, -MAX_SPEED);
+
+    // Horizontal wall collision
+    QRect rct = m_parent->rect();
+    if (m_x < RADIUS || m_x > rct.width() - RADIUS) {
+        m_kx *= -1;
+    }
+    // Ceiling collision
+    if (m_y < RADIUS) {
+        m_ky *= -1;
+    }
+    // Bottom collision (only if no longer spawning)
+    if (!m_isSpawning && m_y > rct.height() - RADIUS) {
+        // TODO: Destroy ball
+    }
+
+    m_x += m_kx;
+    m_y += m_ky;
+
+    // Once we get into the window, we're no longer "spawning"
+    if (m_isSpawning && m_y < rct.width() - RADIUS)
+        m_isSpawning = false;
+
+    // Update the window
+    m_parent->update();
+}
+
+double getRandomDouble(double maxValue) {
+    // Create a random device and a random engine
+    std::random_device rd;
+    std::mt19937 gen(rd());
+
+    // Define the range from 0 to maxValue
+    std::uniform_real_distribution<> dis(0.0, maxValue);
+
+    // Return the random value
+    return dis(gen);
+}

src/ball.h

@@ -0,0 +1,25 @@
+#ifndef BALL_H
+#define BALL_H
+
+#include <QPainter>
+#include <QTimer>
+
+class Ball : public QTimer {
+  public:
+    Ball(QWidget* parent);
+
+    void draw(QPainter& painter);
+
+  protected:
+    virtual void timerEvent(QTimerEvent*) override;
+
+  private:
+    QWidget* m_parent;
+    double m_x;
+    double m_y;
+    double m_kx;
+    double m_ky;
+    bool m_isSpawning;
+};
+
+#endif // BALL_H

src/mainwindow.cpp

@@ -1,14 +1,24 @@
 #include "mainwindow.h"
 #include "./ui_mainwindow.h"
 
-MainWindow::MainWindow(QWidget *parent)
-    : QMainWindow(parent)
-    , ui(new Ui::MainWindow)
-{
+MainWindow::MainWindow(QWidget* parent) : QMainWindow(parent), ui(new Ui::MainWindow) {
     ui->setupUi(this);
+    balls.append(std::make_shared<Ball>(this));
 }
 
-MainWindow::~MainWindow()
-{
+MainWindow::~MainWindow() {
     delete ui;
 }
+
+void MainWindow::paintEvent(QPaintEvent*) {
+    QPainter painter(this);
+
+    painter.fillRect(rect(), Qt::darkGray);
+
+    painter.setBrush(QBrush(Qt::white));
+    painter.setPen(Qt::black);
+
+    for (auto ball : balls) {
+        ball->draw(painter);
+    }
+}

src/mainwindow.h

@@ -1,23 +1,27 @@
 #ifndef MAINWINDOW_H
 #define MAINWINDOW_H
 
+#include "ball.h"
 #include <QMainWindow>
 
 QT_BEGIN_NAMESPACE
 namespace Ui {
-class MainWindow;
+    class MainWindow;
 }
 QT_END_NAMESPACE
 
-class MainWindow : public QMainWindow
-{
+class MainWindow : public QMainWindow {
     Q_OBJECT
 
-public:
-    MainWindow(QWidget *parent = nullptr);
+  public:
+    MainWindow(QWidget* parent = nullptr);
     ~MainWindow();
 
-private:
-    Ui::MainWindow *ui;
+  protected:
+    virtual void paintEvent(QPaintEvent*) override;
+
+  private:
+    Ui::MainWindow* ui;
+    QList<std::shared_ptr<Ball>> balls;
 };
 #endif // MAINWINDOW_H