Added optional delta simulating a drag effect upon collision

Debug_demo/Collisions.cpp

@@ -50,7 +50,11 @@ bool applyCollision(Ball& b,
     }
 
     if (mulX == -1 || mulY == -1) {
-        b.setSpeed(QPointF(b.getSpeed().x() * mulX, b.getSpeed().y() * mulY));
+        QPointF newSpeed(b.getSpeed().x() * mulX, b.getSpeed().y() * mulY);
+        b.setSpeed(newSpeed);
+
+        b.getSpeedMotion().setDelta(QPointF(-0.1 * newSpeed.x(), -0.1 * newSpeed.y()));
+
         return true;
     }
     else {

Debug_demo/GameObject.cpp

@@ -1,26 +1,33 @@
+#include <QVector2D>
 #include "Ball.h"
 #include "GameObject.h"
 
 GameObject::GameObject(const QPointF& pos, const QPointF& speed) :
         pos_(pos), speed_(speed) {}
 
 const QPointF& GameObject::getPos() const {
-    return pos_;
+    return pos_.getValue();
 }
 
 const QPointF& GameObject::getSpeed() const {
-    return speed_;
+    return speed_.getValue();
 }
 
 //FIXME: check const
 void GameObject::calc(int msec) {
-    pos_ += speed_ * (msec / 1000.);
+    speed_.calculate(msec);
+    pos_.calculate(msec);
+    pos_.setValue(pos_.getValue() + speed_.getValue() * (msec / 1000.));
+
+    if (QVector2D(speed_.getValue()).length() < 0.03) {
+        speed_.setDelta(std::nullopt);
+    }
 }
 
 void GameObject::setPos(const QPointF& pos) {
-    pos_ = pos;
+    pos_.setValue(pos);
 }
 
 void GameObject::setSpeed(const QPointF& speed) {
-    speed_ = speed;
+    speed_.setValue(speed);
 }

Debug_demo/GameObject.h

@@ -1,10 +1,36 @@
 #pragma once
 
-
+#include <optional>
 #include <QPointF>
 #include <QRectF>
 class QPainter;
 
+struct Motion {
+    explicit Motion(const QPointF& value) : value_(value) {}
+
+    const QPointF& getValue() const {
+        return value_;
+    }
+
+    void setValue(const QPointF& value) {
+        value_ = value;
+    }
+
+    void setDelta(const std::optional<QPointF>& delta){
+        delta_ = delta;
+    }
+
+    void calculate(int msec) {
+        if (delta_) {
+            value_ += *delta_ * (msec / 1000.);
+        }
+    }
+
+private:
+    QPointF value_;
+    std::optional<QPointF> delta_;
+};
+
 struct GameObject {
 
     GameObject(const QPointF& pos, const QPointF& speed);
@@ -13,6 +39,10 @@ struct GameObject {
 
     const QPointF& getSpeed() const;
 
+    Motion& getSpeedMotion() {
+        return speed_;
+    }
+
     void setPos(const QPointF& pos);
 
     void setSpeed(const QPointF& speed);
@@ -24,7 +54,7 @@ struct GameObject {
     virtual QRectF aabb() const = 0;
 
 private:
-    QPointF pos_;
-    QPointF speed_;
+    Motion pos_;
+    Motion speed_;
 };