loading texture in SFML with std::future - c++

Question

Visual Studio Express 2012, CTP1 c++ compiler
The following code works. It loads an image and displays it on the window until you close it.
#include <memory>
#include <SFML/Graphics.hpp>
int main()
{
sf::RenderWindow window(sf::VideoMode(800,600), "hello");
auto Load = []() -> std::unique_ptr<sf::Texture> {
std::unique_ptr<sf::Texture> tex_ptr(new sf::Texture);
tex_ptr->loadFromFile("hello.png");
return tex_ptr;
};
auto tex_ptr = Load();
sf::Sprite spr(*tex_ptr);
while (window.isOpen())
{
sf::Event ev;
while (window.pollEvent(ev))
{
if (ev.type == sf::Event::Closed)
window.close();
}
window.clear();
window.draw(spr);
window.display();
}
}
In the following code, I'm trying to load the image asyncronously using std::async. It prints "load success", which indicates that the load succeeded in the lambda. Then, outside, after I've retrieved the texture from the future, I check other properties of the texture. The size prints out correctly. However, no image shows up. I just get a black window, which closes on command.
#include <future>
#include <memory>
#include <iostream>
#include <SFML/Graphics.hpp>
int main()
{
sf::RenderWindow window(sf::VideoMode(800,600), "hello");
auto Load = []() -> std::unique_ptr<sf::Texture> {
std::unique_ptr<sf::Texture> tex_ptr(new sf::Texture);
if (tex_ptr->loadFromFile("hello.png"))
std::cout << "load success\n";
else
std::cout << "load failure\n";
return tex_ptr;
};
auto tex_ptr_future = std::async(std::launch::async, Load);
auto tex_ptr = tex_ptr_future.get();
sf::Sprite spr(*tex_ptr);
// Oddly, this prints out exactly what I expect
auto size = tex_ptr->getSize();
std::cout << size.x << 'x' << size.y << '\n';
while (window.isOpen())
{
sf::Event ev;
while (window.pollEvent(ev))
{
if (ev.type == sf::Event::Closed)
window.close();
}
window.clear();
window.draw(spr); // nothin'
window.display();
}
}
Does anybody see anything I'm doing wrong?