simple-cpp-game-study/sfmldemo/main.cpp

#include "imgui.h"
#include "imgui-SFML.h"
#include <fmt/core.h>
#include <box2d/box2d.h>
#include <SFML/Graphics/CircleShape.hpp>
#include <SFML/Graphics/RenderWindow.hpp>
#include <SFML/System.hpp>
#include <SFML/Window/Event.hpp>

void ImGui_setup(sf::RenderWindow &window) {
  int res = ImGui::SFML::Init(window);
  if(res == 1) {
    fmt::print("ImGui returned result {}\n", res);
  } else {
    fmt::print("ImGui returned an error code={}\n", res);
  }
}

void ImGui_update(sf::RenderWindow &window, sf::Clock &deltaClock, sf::Time &tick) {
  ImGui::SFML::Update(window, deltaClock.restart());
  // ImGui::ShowDemoWindow();
  ImGui::Begin("Clock");
  sf::Vector2u size = window.getSize();
  ImGui::SetWindowPos(ImVec2(size.x - 150, 0));
  ImGui::SetWindowSize(ImVec2(150, 50));
  std::string msg = fmt::format("Time: {}\n", tick.asSeconds());
  ImGui::Button(msg.c_str());
  ImGui::End();
}

void Window_update(sf::RenderWindow &window, sf::Shape &shape) {
    window.clear();
    window.draw(shape);
    ImGui::SFML::Render(window);
    window.display();
}

struct BoxTest {
  b2Body *groundBody;
  b2Body *body;
};

struct BoxTest Box2d_setup(b2World &world) {
  b2BodyDef groundBodyDef;
  groundBodyDef.position.Set(0.0f, -10.0f);
  b2Body *groundBody = world.CreateBody(&groundBodyDef);

  b2PolygonShape groundBox;
  groundBox.SetAsBox(50.0f, 10.0f);
  groundBody->CreateFixture(&groundBox, 0.0f);

  b2BodyDef bodyDef;
  bodyDef.type = b2_dynamicBody;
  bodyDef.position.Set(3.0f, 4.0f);
  b2Body *body = world.CreateBody(&bodyDef);

  b2PolygonShape dynamicBox;
  dynamicBox.SetAsBox(1.0f, 1.0f);
  b2FixtureDef fixtureDef;
  fixtureDef.shape = &dynamicBox;

  fixtureDef.density = 1.0f;
  fixtureDef.friction = 0.3f;

  body->CreateFixture(&fixtureDef);

  BoxTest box {groundBody, body};
  return box;
}

int main() {
  fmt::print("Setting up a window for you...\n");
  sf::ContextSettings settings;
  settings.antialiasingLevel = 8;

  sf::RenderWindow window(sf::VideoMode(720, 480), "Simple Game Demo", sf::Style::Default, settings);

  // window.setFramerateLimit(60);
  window.setVerticalSyncEnabled(true);

  ImGui_setup(window);

  sf::CircleShape shape(50.f, 4);
  sf::Vector2u winSize = window.getSize();
  shape.setPosition(winSize.x / 2, winSize.y / 2);
  shape.setOrigin(50.f, 50.f);
  shape.setFillColor(sf::Color(150, 50, 250));
  shape.setOutlineThickness(10.f);
  shape.setOutlineColor(sf::Color(250, 150, 100));

  sf::Clock deltaClock;
  sf::Clock clock;
  sf::Time tick = clock.getElapsedTime();

  // very cool, c++11 lambdas doing a 1 second slept thread
  sf::Thread thread([](){
    for(int i = 0; i < 10; i++) {
      fmt::print("I'm a thread. {}\n", i);
      sf::sleep(sf::seconds(1));
    }
  });

  thread.launch();

  b2Vec2 gravity(0.0f, -10.0f);
  b2World world(gravity);
  BoxTest box = Box2d_setup(world);

  float timeStep = 1.0f / 60.0f;
  int velocityIterations = 6;
  int positionIterations = 2;

  while (window.isOpen()) {
    sf::Event event;

    // is this a main event loop
    while (window.pollEvent(event)) {
      ImGui::SFML::ProcessEvent(window, event);

      switch(event.type) {

        case sf::Event::Closed:
          fmt::print("Exiting...\n");
          window.close();
          thread.terminate();
          break;
        case sf::Event::KeyPressed:
          if(sf::Keyboard::isKeyPressed(sf::Keyboard::Left)) {
            b2Vec2 force(-200, 1000);
            box.body->ApplyForceToCenter(force, true);
          } else if(sf::Keyboard::isKeyPressed(sf::Keyboard::Right)) {
            b2Vec2 force(200, 1000);
            box.body->ApplyForceToCenter(force, true);
          }
          break;
        case sf::Event::MouseButtonPressed:
          if(sf::Mouse::isButtonPressed(sf::Mouse::Left)) {
            b2Vec2 force(-200, 1000);
            box.body->ApplyForceToCenter(force, true);
          } else if (sf::Mouse::isButtonPressed(sf::Mouse::Right)) {
            b2Vec2 force(200, 1000);
            box.body->ApplyForceToCenter(force, true);
          }
          break;
      }
    }


    // should this move up to the pollEvent loop?
    sf::Time since = clock.getElapsedTime();
    if(since - tick > sf::seconds(1)) {
      tick = since;
    }

    world.Step(timeStep, velocityIterations, positionIterations);
    b2Vec2 position = box.body->GetPosition();
    float angle = box.body->GetAngle();

    shape.setPosition(position.x * 100.0f, winSize.y - position.y * 100.0f);
    shape.setRotation(angle * 180.0f / M_PI);


    ImGui_update(window, deltaClock, tick);
    Window_update(window, shape);
  }

  ImGui::SFML::Shutdown();
}