White square SFML - c++

Question

I've faced with The white square problem at SFML C++ while I'm trying to display a textured button. I've got an ImageButton.h which inherits from Button.h. The texture is loaded successfully (checked in debugger). But in the end, I see a white square. How to solve it?
Button.h
#ifndef BUTTON_H
#define BUTTON_H
#include<SFML/Graphics.hpp>
class Button
{
public:
Button();
Button(sf::Vector2f size, sf::Vector2f pos,sf::Color outlineColor, float sizeOutline);
void virtual draw(sf::RenderWindow* w) = 0;
protected:
sf::RectangleShape frame;
};
#endif // !BUTTON_H
Button.cpp
#include "Button.h"
Button::Button()
{
}
Button::Button(sf::Vector2f size, sf::Vector2f pos,sf::Color outlineColor, float sizeOutline)
{
frame.setPosition(pos);
frame.setSize(size);
frame.setOutlineColor(outlineColor);
frame.setOutlineThickness(sizeOutline);
}
ImageButton.h
#ifndef IMAGE_BUTTON_H
#define IMAGE_BUTTON_H
#include"Button.h"
class ImageButton : public Button
{
public:
ImageButton();
ImageButton(sf::Vector2f size, sf::Vector2f pos, sf::Color outlineColor, float sizeOutline, std::string path);
void draw(sf::RenderWindow* w);
private:
sf::Texture backTexture;
sf::Sprite background;
};
#endif // !IMAGE_BUTTON_H
ImageButton.cpp
#include "ImageButton.h"
ImageButton::ImageButton()
{
}
ImageButton::ImageButton(sf::Vector2f size, sf::Vector2f pos, sf::Color outlineColor, float sizeOutline, std::string path)
: Button(size,pos,outlineColor,sizeOutline)
{
backTexture.loadFromFile(path, sf::IntRect(sf::Vector2i(pos.x,pos.y),sf::Vector2i(size.x,size.y)));
backTexture.setSmooth(true);
background.setTexture(backTexture);
background.setPosition(pos);
}
void ImageButton::draw(sf::RenderWindow* w)
{
w->draw(this->background);
w->draw(this->frame);
}
programm.h
#ifndef PROGRAMM_H
#define PROGRAMM_H
#include<SFML/Graphics.hpp>
#include"ImageButton.h"
class programm
{
public:
programm();
void run();
private:
ImageButton b;
sf::RenderWindow* window;
sf::Event e;
void render();
void update();
};
#endif // !PROGRAMM_H
programm.cpp
#include "programm.h"
programm::programm()
{
this->window = new sf::RenderWindow(sf::VideoMode(600, 600), "Novel Editor", sf::Style::Close);
this->window->setPosition(sf::Vector2i(0, 0));
this->window->setFramerateLimit(60);
this->b = ImageButton(sf::Vector2f(50.f, 50.f), sf::Vector2f(50.f, 50.f), sf::Color::Yellow, 5.f, "images\\putin.png");
}
void programm::run()
{
while (this->window->isOpen())
{
while (this->window->pollEvent(e))
{
update();
}
}
}
void programm::render()
{
this->window->clear();
b.draw(this->window);
this->window->display();
}
void programm::update()
{
switch (e.type)
{
case sf::Event::Closed:
{
this->window->close();
break;
}
default:
break;
}
render();
}
Screenshot

Answer 1

programm::programm()
{
...
this->b = ImageButton(...); //< this line cause the bug
}
You are initializing your image button this->b by assigning from a local ImageButton. Now the sprite will have the texture reference of the local instance's texture, and when the local instance will "die" the texture will be freed. You need to maintain the lifetime of the texture
Solution 1: override the assignment operator and set texture there like this
ImageButton& operator=(const ImageButton& ref) {
backTexture = ref.backTexture;
background = ref.background;
background.setTexture(backTexture);
return *this;
}
Solution 2: Create a TextureManager and make it as your texture API for all your program, maintain your texture lifetime through it.
Solution 3: initialize the image button at programm constructor
programm::programm()
:b (sf::Vector2f(50.f, 50.f), sf::Vector2f(50.f, 50.f), sf::Color::Yellow, 5.f, "img.jpg")
{
...
}
Another bug
void ImageButton::draw(sf::RenderWindow* w)
{
w->draw(this->background);
w->draw(this->frame);
}
you're drawing your frame after the background, and your frame's fill color by default is white
Solution 1: draw frame first and draw background next
Solution 2: set your frame fill color alpha to 0
Button::Button(sf::Vector2f size, sf::Vector2f pos, sf::Color outlineColor, float sizeOutline)
{
frame.setPosition(pos);
frame.setSize(size);
frame.setOutlineColor(outlineColor);
frame.setFillColor(sf::Color(0, 0, 0, 0)); // <----
frame.setOutlineThickness(sizeOutline);
}

Answer 2

The problem you and others (on reddit,
on SO,
and elsewhere)
are facing is caused by the way the constructor and assignment operator of
sf::Sprite are (not) implemented: Since the developers decided to not
implement specialized functions and didn't make them private, the compiler
provides defaults that are not aware of the semantics of the m_texture
pointer and therefore doing a binary copy. This may be not the best approach but
it's documented.
So if you are using a sf::Sprite member in your class without taking
special measures for copying, the compiler will assume default assignment
semantics and therefore invoke the (invalid) assignment semantics of the
sf::Sprite class. The local ImageButton object you create in the
program invokes this default assignment of ImageButton
programm::programm()
{
this->window = new sf::RenderWindow(sf::VideoMode(600, 600), "Novel Editor", sf::Style::Close);
this->window->setPosition(sf::Vector2i(0, 0));
this->window->setFramerateLimit(60);
this->b = ImageButton(sf::Vector2f(50.f, 50.f), sf::Vector2f(50.f, 50.f), sf::Color::Yellow, 5.f, "images\\putin.png");
}
the Sprite in member b takes over the pointer texture from the
Sprite within the local ImageButton whose lifetime is limited to the
scope of the programm constructor. Beyond that, the sprite in your
member b holds a reference to a destroyed texture object which causes
is undefined behaviour (see also sf::Sprite Class Reference (SFML / Learn / 2.4.1 Documentation)):
If the source texture is destroyed and the sprite tries to use it,
the behavior is undefined.
By the way, I'd suggest directly using sf::RenderWindow window in the
program class not via pointer, so you could change your code to something
like this (note that I used button instead of b and shortened inlined
the implementation for the sake of brevity).
class programm
{
public:
programm():
window(sf::VideoMode(600, 600), "Novel Editor", sf::Style::Close);
button(sf::Vector2f(50.f, 50.f), sf::Vector2f(50.f, 50.f),
sf::Color::Yellow, 5.f, "images\\putin.png")
{
window->setPosition(sf::Vector2i(0, 0));
window->setFramerateLimit(60);
}
// ...
private:
// ...
sf::RenderWindow window;
ImageButton button;
};
Another option would be to provide a specialized assignment operator
(thakee nathees shows how)
or copy constructor for your ImageButton class that takes care of the
deep copy of the texture object.
Alternatively, you could think about implementing a wrapper class for
sf::Sprite to fix this issue and use this instead for you application(s).