Sfml pollEvent, every new image deletes the previous one - c++

Question

My problem is that the function don't do what I want.
This "CreateWindow" function has the main loop. In the main loop I want a fixed background and, every time I press the H button, I want to draw a Card (sprite) on the background.
What's the problem here? My function draw the cards but when I press H the previous card is deleted and the next card is drawn.
This is something about the event I think, because every time an event happens (I move the mouse, I press an other key etc) the previous card is deleted...
I'm using sfml 2.0
Here is my implementation of the Graphic class
#include "Graphic.h"
#include "SFML/Graphics.hpp"
#include <iostream>
#include <string>
#include "Card.h"
#include <string>
#include <sstream>
Graphic::Graphic(int offset)
{
this->offset = offset;
}
Graphic::~Graphic()
{
//dtor
}
int Graphic::CreateWindow(sf::RenderWindow& window, Deck &deck0)
{
sf::Vector2i screenDimensions(800, 600);
//Dimensioni della window
window.create(sf::VideoMode(screenDimensions.x, screenDimensions.y), "BlackJack", sf::Style::Titlebar | sf::Style::Close);
int index = 0;
window.setKeyRepeatEnabled(false);
//settare il background
sf::Texture bTexture;
sf::Sprite bImage;
if(!bTexture.loadFromFile("Background.png"))
std::cout << "Error" << std::endl;
bImage.setTexture(bTexture);
bImage.setScale(1.0, (float)screenDimensions.y / bTexture.getSize().y);
//MAIN LOOP----------------------
while(window.isOpen())
{
sf::Event Event;
while(window.pollEvent(Event))
{
window.clear();
window.draw(bImage); // this is the function which draw the background
if (Event.type == sf::Event::Closed)
{
window.close();
}
if(Event.key.code == sf::Keyboard::H)
{
Card * y = deck0.dealFirst();
drawCard(window,y->graphNumber,y->getSeed(),offset);
offset = offset + 50;
}
window.display();
}
}
}
int Graphic::drawCard(sf::RenderWindow &window, int graphNumber, string seed, int offset)
{
std::ostringstream oss;
oss << graphNumber << seed << ".png";
std::string var = oss.str();
sf::Texture QHTexture;
sf::Sprite QHImage;
if(!QHTexture.loadFromFile(var))
std::cout<< "Error" <<std::endl;
QHImage.setTexture(QHTexture);
QHImage.setScale(0.5, 0.5);
QHImage.setPosition(offset + 100, 400);
window.draw(QHImage); //this is the function which draw the card's sprite
return 0;
}

Answer 1

Alright you shouldn't be drawing inside of your while(window.pollEvent()) loop, you should be drawing something like this:
while(window.isOpen())
{
sf::Event Event;
while(window.pollEvent(Event))
{
if (Event.type == sf::Event::Closed)
{
window.close();
}
if(Event.key.code == sf::Keyboard::H)
{
Card * y = deck0.dealFirst();
drawCard(window,y->graphNumber,y->getSeed(),offset);
offset = offset + 50;
}
}
window.clear();
window.draw(bImage); // this is the function which draw the background
window.display();
}
The way you were drawing your draw call will only happen if there is an SFML event, and will only ever clear if there is an sfml event(Which is ok if you dont want it to constantly render every frame... and aren't planning any kind of animations...).
So when you hit H an sfml event was being triggers that called your draw card function, however since your card is a local variable to the function you wrote, at the end of the function it is cleared out. You need to store your cards somewhere, such as a vector or list of sf::Sprite. So an example would be:
#include "Graphic.h"
#include "SFML/Graphics.hpp"
#include <iostream>
#include <string>
#include "Card.h"
#include <string>
#include <sstream>
Graphic::Graphic(int offset)
{
this->offset = offset;
}
Graphic::~Graphic()
{
//dtor
}
int Graphic::CreateWindow(sf::RenderWindow& window, Deck &deck0)
{
sf::Vector2i screenDimensions(800, 600);
//Dimensioni della window
window.create(sf::VideoMode(screenDimensions.x, screenDimensions.y), "BlackJack", sf::Style::Titlebar | sf::Style::Close);
int index = 0;
window.setKeyRepeatEnabled(false);
//settare il background
sf::Texture bTexture;
sf::Sprite bImage;
if(!bTexture.loadFromFile("Background.png"))
std::cout << "Error" << std::endl;
bImage.setTexture(bTexture);
bImage.setScale(1.0, (float)screenDimensions.y / bTexture.getSize().y);
//MAIN LOOP----------------------
while(window.isOpen())
{
sf::Event Event;
while(window.pollEvent(Event))
{
if (Event.type == sf::Event::Closed)
{
window.close();
}
if(Event.key.code == sf::Keyboard::H)
{
Card * y = deck0.dealFirst();
drawCard(window,y->graphNumber,y->getSeed(),offset);
offset = offset + 50;
}
}
window.clear();
window.draw(bImage); // this is the function which draw the background
for(int i = 0; i < cardList.size(); ++i)
{
window.draw(cardList[i]);
}
window.display();
}
}
int Graphic::drawCard(sf::RenderWindow &window, int graphNumber, string seed, int offset)
{
std::ostringstream oss;
oss << graphNumber << seed << ".png";
std::string var = oss.str();
sf::Texture QHTexture;
sf::Sprite QHImage;
if(!QHTexture.loadFromFile(var))
std::cout<< "Error" <<std::endl;
QHImage.setTexture(QHTexture);
QHImage.setScale(0.5, 0.5);
QHImage.setPosition(offset + 100, 400);
cardList.push_back(QHImage); //this adds the sprite to our list
return 0;
}