feat: velocity tracking w/ rendering lines

src/Ball.cpp

@@ -5,7 +5,10 @@
 #include "Constants.hpp"
 
 Ball::Ball(float radius, const sf::Vector2f& pos, const sf::Vector2f& vel)
-    : m_radius(radius), m_velocity(vel) {
+    : m_radius(radius),
+      m_velocity(vel),
+      m_lastPosition(pos),
+      m_pixelVelocity(vel) {
     m_shape.setRadius(radius);
     m_shape.setOrigin(sf::Vector2f(radius, radius));
     m_shape.setPosition(pos);
@@ -13,17 +16,30 @@ Ball::Ball(float radius, const sf::Vector2f& pos, const sf::Vector2f& vel)
 }
 
 void Ball::update(float dt) {
+    if (m_atRest) return;
     m_velocity.y += Constants::GRAVITY * dt;
     m_shape.move(m_velocity * dt);
+
+    sf::Vector2f currentPosition = m_shape.getPosition();
+    m_pixelVelocity = (currentPosition - m_lastPosition) / dt;
+    m_lastPosition = currentPosition;
+
     handleWallCollision();
 }
 
 void Ball::draw(sf::RenderWindow& window) { window.draw(m_shape); }
 
-void Ball::applyImpulse(const sf::Vector2f& impulse) { m_velocity += impulse; }
+void Ball::applyImpulse(const sf::Vector2f& impulse) {
+    m_velocity += impulse;
+    m_atRest = false;
+}
 
 sf::Vector2f Ball::getPosition() const { return m_shape.getPosition(); }
 
+sf::Vector2f Ball::getVelocity() const { return m_velocity; }
+
+bool Ball::isAtRest() const { return m_atRest; }
+
 void Ball::handleWallCollision() {
     sf::Vector2f pos = m_shape.getPosition();
 
@@ -51,6 +67,13 @@ void Ball::handleWallCollision() {
     if (pos.y + m_radius >= Constants::HEIGHT - 1.0f) {
         m_velocity.x *= Constants::FRICTION;
         if (std::abs(m_velocity.x) < 5.f) m_velocity.x = 0.f;
+        if (std::abs(m_pixelVelocity.x) < Constants::REST_PIXEL_VELOCITY &&
+            std::abs(m_pixelVelocity.y) < Constants::REST_PIXEL_VELOCITY) {
+            m_velocity = {0.f, 0.f};
+            m_atRest = true;
+        }
+    } else {
+        m_atRest = false;
     }
 
     m_shape.setPosition(pos);