Why are the rectangles/bars not swapping with each other? - c++

Question

I am writing a bubble sort visualizer. But I can't seem to figure out how to swap the rectangles/bars.
#include<iostream>
#include<SFML/Graphics.hpp>
#include<cstdlib>
#include<ctime>
#include<chrono>
#include<thread>
int main()
{
srand(time(NULL));
sf::RenderWindow window(sf::VideoMode(798, 400), "Yoo", sf::Style::Default);
sf::RectangleShape *rec=new sf::RectangleShape[133];
for (int i = 0; i < 133; i++)
{
int num = rand() % 400;
rec[i].setFillColor(sf::Color::Red);
rec[i].setSize(sf::Vector2f(4.0f, static_cast<float>(num)));
rec[i].setPosition(sf::Vector2f(static_cast<float>(i * 6), 400-num));
}
sf::Event ev;
while (window.isOpen())
{
int i = rand() % 133;
int j = rand() % 133;
while (window.pollEvent(ev))
{
if (ev.type == sf::Event::Closed())
{
window.close();
}
}
window.clear(sf::Color::White);
rec[i].setFillColor(sf::Color::Blue);
rec[j].setFillColor(sf::Color::Green);
sf::Vector2f tmp = rec[i].getPosition();
sf::Vector2f size = rec[i].getSize();
rec[i].setPosition(rec[j].getPosition());
rec[i].setSize(rec[j].getSize());
rec[j].setSize(size);
rec[j].setPosition(tmp);
for (int i = 0; i < 133; i++)
{
window.draw(rec[i]);
}
rec[i].setFillColor(sf::Color::Red);
rec[j].setFillColor(sf::Color::Red);
window.display();
std::this_thread::sleep_for(std::chrono::milliseconds(2000));
}
delete[] rec;
}
what is wrong with this code? I have tried normal swapping using std::swap to swap the rectangle array. It didn't work. So, I thought I should swap the position and size. It is not working either. But as shown in this picture, I can see the colors Blue and Green are interchanging correctly.

Answer 1

I tested your program. Your goal is to draw a green bar and a blue bar and swap them?
When you draw your rectangle, you swap them before displaying the window. So you don't see them swap. If you want, you have to draw your rectangles and display your window before swapping them.
window.clear(sf::Color::White);
rec[i].setFillColor(sf::Color::Blue);
rec[j].setFillColor(sf::Color::Green);
for (int i = 0; i < 133; i++)
{
window.draw(rec[i]);
}
window.display(); // display them before swap.
std::this_thread::sleep_for(std::chrono::milliseconds(2000));
window.clear(sf::Color::White);
sf::Vector2f tmp = rec[i].getPosition();
sf::Vector2f size = rec[i].getSize();
rec[i].setPosition(rec[j].getPosition());
rec[i].setSize(rec[j].getSize());
rec[j].setSize(size);
rec[j].setPosition(tmp);
for (int i = 0; i < 133; i++)
{
window.draw(rec[i]);
}
rec[i].setFillColor(sf::Color::Red);
rec[j].setFillColor(sf::Color::Red);
window.display(); // display them again
std::this_thread::sleep_for(std::chrono::milliseconds(2000));
something like this.