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Help => System => Topic started by: SeriousITGuy on January 29, 2015, 04:13:57 pm

Title: [Solved] Contruction sf::Vector2f from sf::FloatRect - Wrong values
Post by: SeriousITGuy on January 29, 2015, 04:13:57 pm

Hi Folks,

I have a pretty weird problem with contructing a sf::Vector2f from a sf::FloatRect, the x and y values of the vector are wrong. I create a sf::FloatRect for my game world, and want to create a sf::Vector2f for the spawn point of my character, which should spawn in the middle of the game world. I calculate the spawn position like this:

GameWorld::GameWorld( sf::RenderWindow& window)
  : _window( window )
[ ... ]
  , _worldBounds( 0.f, 0.f, 1600.f, 1200.f )
  //, _spawnPosition( 800.f, 600.f )
  , _spawnPosition( _worldBounds.width / 2.f, _worldBounds.height / 2.f )
 

The result should be 800, 600, but in reality is
_spawnPosition.x = -53687088.000000
_spawnPosition.y = -53687088.000000

Code architecture is based on the SFML Book code base.
Code Example

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GameWorld.hpp

#pragma once
#include <SFML/Graphics/RenderWindow.hpp>
#include <SFML/Graphics/Sprite.hpp>
#include <SFML/Graphics/Texture.hpp>
#include <SFML/System/Time.hpp>

class GameWorld
{
public:
  explicit GameWorld( sf::RenderWindow& window );
  void update( sf::Time dt );
  void draw();

private:
  void loadTextures();
  void buildScene();

  sf::Sprite _playerSprite;
  sf::Sprite _floorSprite;
  sf::Texture _playerTexture;
  sf::Texture _floorTexture;
  sf::RenderWindow& _window;
  sf::Vector2f _spawnPosition;
  sf::FloatRect _worldBounds;
  sf::View _worldView;
};
 

GameWorld.cpp

#include <app/GameWorld.hpp>
#include <iostream>

GameWorld::GameWorld( sf::RenderWindow& window)
  : _window( window )
  , _playerSprite()
  , _playerTexture()
  , _floorSprite()
  , _floorTexture()
  , _worldView( window.getDefaultView() )
  , _worldBounds( 0.f, 0.f, 1600.f, 1200.f )
  //, _spawnPosition( 800.f, 600.f )
  , _spawnPosition( _worldBounds.width / 2.f, _worldBounds.height / 2.f )
{
  loadTextures();
  buildScene();

  std::cout << "_worldView.x = " << std::to_string( _worldView.getSize().x ) << std::endl;
  std::cout << "_worldView.y = " << std::to_string( _worldView.getSize().y ) << std::endl;

  std::cout << "_worldView.center.x = " << std::to_string( _worldView.getCenter().x ) << std::endl;
  std::cout << "_worldView.center.y = " << std::to_string( _worldView.getCenter().y ) << std::endl;

  std::cout << "_playerSprite.x = " << std::to_string( _playerSprite.getPosition().x ) << std::endl;
  std::cout << "_playerSprite.y = " << std::to_string( _playerSprite.getPosition().y ) << std::endl;

  std::cout << "_spawnPosition.x = " << std::to_string( _spawnPosition.x ) << std::endl;
  std::cout << "_spawnPosition.y = " << std::to_string( _spawnPosition.y ) << std::endl;

  std::cout << "_worldBounds.x = " << std::to_string( _worldBounds.width ) << std::endl;
  std::cout << "_worldBounds.y = " << std::to_string( _worldBounds.height ) << std::endl;
}

void GameWorld::update( const sf::Time dt )
{
  _worldView.move( 25.f * dt.asSeconds(), 25.f * dt.asSeconds() );
}

void GameWorld::draw()
{
  _window.setView( _worldView );
  _window.draw( _floorSprite );
  _window.draw( _playerSprite );
}

void GameWorld::loadTextures()
{
  if( !_playerTexture.loadFromFile( "../media/male.png" ) ) {
    throw std::runtime_error( "Could not load image file 'male.png'" );
  }

  if( !_floorTexture.loadFromFile( "../media/grass.png" ) ) {
    throw std::runtime_error( "Could not load image file 'grass.png'" );
  }
}

void GameWorld::buildScene()
{
  _playerSprite.setTexture( _playerTexture );
  auto bounds = _playerSprite.getLocalBounds();
  _playerSprite.setOrigin( bounds.width / 2.f, bounds.height / 2.f );
  _playerSprite.setPosition( _spawnPosition );

  _floorTexture.setRepeated( true );
  _floorSprite.setTexture( _floorTexture );
  _floorSprite.setTextureRect( sf::IntRect( _worldBounds ) );
  _floorSprite.setPosition( _worldBounds.left, _worldBounds.top );

  _worldView.setCenter( _spawnPosition );
}

 

Application.cpp

#include <app/Application.hpp>
#include <SFML/Window/Event.hpp>

Application::Application()
  : _window( { 800, 600 }, "Game Demo", sf::Style::Close )
  , _timeStep( sf::seconds( 1.f / 60.f ) )
  , _gameWorld( _window )
{
}

void Application::run()
{
  sf::Clock appClock;
  sf::Time timeSinceLastFrame{ sf::Time::Zero };

  while( _window.isOpen() ) {
    sf::Time dt = appClock.restart();
    timeSinceLastFrame += dt;

    while( timeSinceLastFrame > _timeStep ) {
      timeSinceLastFrame -= _timeStep;

      handleEvents();
      update( _timeStep );      
    }

    render();
  }
}

void Application::handleEvents()
{
  sf::Event evt;

  while( _window.pollEvent( evt ) ) {
    if( evt.type == sf::Event::Closed ) {
      _window.close();
    }
  }
}

void Application::update( const sf::Time dt)
{
  _gameWorld.update( dt );
}

void Application::render()
{
  _window.clear();

  _gameWorld.draw();

  _window.display();
}
 

Visual Studio 2013.4 with SFML 2.2 stable

I can't track down the source of the problem. Any thoughts?
Every suggestion welcome, I go crazy about this.

Cheers!

Title: Re: Contruction sf::Vector2f from sf::FloatRect - Wrong values
Post by: Hapax on January 29, 2015, 04:31:24 pm

_spawnposition is created before _worldbounds so its initialisation is first.

This works:

#include <SFML/Graphics.hpp>
#include <iostream>

struct Test
{
        sf::FloatRect m_worldBounds;
        sf::Vector2f m_spawnPosition;
        Test():
                m_worldBounds(0.f, 0.f, 1600.f, 1200.f),
                m_spawnPosition(m_worldBounds.width / 2.f, m_worldBounds.height / 2.f)
        {
        }
};

int main()
{
        Test test;
        std::cout << test.m_worldBounds.width << "x" << test.m_worldBounds.height << std::endl;
        std::cout << "(" << test.m_spawnPosition.x << ", " << test.m_spawnPosition.y << ")" << std::endl;

        return EXIT_SUCCESS;
}

but this does not:

#include <SFML/Graphics.hpp>
#include <iostream>

struct Test
{
        sf::Vector2f m_spawnPosition; // wrong way around
        sf::FloatRect m_worldBounds; // wrong way around
        Test():
                m_worldBounds(0.f, 0.f, 1600.f, 1200.f),
                m_spawnPosition(m_worldBounds.width / 2.f, m_worldBounds.height / 2.f)
        {
        }
};

int main()
{
        Test test;
        std::cout << test.m_worldBounds.width << "x" << test.m_worldBounds.height << std::endl;
        std::cout << "(" << test.m_spawnPosition.x << ", " << test.m_spawnPosition.y << ")" << std::endl;
       
        return EXIT_SUCCESS;
}

Title: Re: Contruction sf::Vector2f from sf::FloatRect - Wrong values
Post by: SeriousITGuy on January 30, 2015, 08:21:09 am

Doh, going over the code hundreds of times and I didn't notice the wrong order in the class declaration. Just one of those days I guess. Thanks, it works now!  ;)

Title: Re: [Solved] Contruction sf::Vector2f from sf::FloatRect - Wrong values
Post by: Hapax on January 31, 2015, 04:07:25 pm

No worries. I didn't even know this happened until I saw your problem ;D

Title: Re: [Solved] Contruction sf::Vector2f from sf::FloatRect - Wrong values
Post by: Jesper Juhl on January 31, 2015, 04:15:16 pm

The C++ standard is fairly explicit in mentioning that member initialization happens in declared order (regardless of the order you mention them in initialization lists).
The standard can be a bitch to read though, so if you want a more human readable explanation of the details, then read the "Initialization order" section of this page: http://en.cppreference.com/w/cpp/language/initializer_list