SF::Text memory access bug on draw()

[jjfortherear]

I've got a strange problem with drawing text, I made a video describing it and walking through the debugger:



The code can be found here:

https://github.com/odkken/Doors

Call stack:

    ntdll.dll!775915de()   Unknown
    [Frames below may be incorrect and/or missing, no symbols loaded for ntdll.dll]   
    ntdll.dll!775915de()   Unknown
    ntdll.dll!7758014e()   Unknown
>   sfml-graphics-d-2.dll!sf::priv::glCheckError(const char * file, unsigned int line) Line 107   C++
    sfml-graphics-d-2.dll!sf::RenderTarget::draw(const sf::Drawable & drawable, const sf::RenderStates & states) Line 146   C++
    RPG.exe!ShowingDoors::Draw(Game * game) Line 96   C++
    RPG.exe!Game::Draw() Line 30   C++
    RPG.exe!Game::Loop() Line 41   C++
    RPG.exe!main() Line 13   C++
    RPG.exe!__tmainCRTStartup() Line 536   C
    RPG.exe!mainCRTStartup() Line 377   C
    kernel32.dll!769833aa()   Unknown
    ntdll.dll!775a9ef2()   Unknown
    ntdll.dll!775a9ec5()   Unknown


EDIT:

I got it working by making my vector of doors a vector of pointers to doors.  Don't know why that was necessary, but there you go.

[eXpl0it3r]

First step in debugging things you don't understand is to create a minimal example from scratch, just to see if there's a problem directly with SFML, or if it's just within your code, e.g.:

#include <SFML/Graphics.hpp>

int main()
{
    sf::RenderWindow window(sf::VideoMode(1024, 768), "Hello World");
    sf::Font font;
    font.loadFromFile("fonts/arial.ttf");
    sf::Text text;
    text.setFont(font);

    while(window.isOpen())
    {
         sf::Event event;
         while(window.pollEvent(event))
         {
             if(event.type == sf::Event::Closed)
                  window.close();
         }

         window.clear();
         window.draw(text);
         window.display();
    }
}

If that does work without problems, then it's something within your structure.

Also if you actually try to draw a text on top of the door rectangle, then you can't draw the text first and then the rectangle, otherwise the rectangle will cover up the text.

Edit: Not sure if this could be part of the problem, but since you have the sf::Font as member of the Doors class, you load the font for every door instance, thus you end up with x copies of the same font. It's not really good to do this, but I'm not sure if it could cause such a problem.

[jjfortherear]

Also if you actually try to draw a text on top of the door rectangle, then you can't draw the text first and then the rectangle, otherwise the rectangle will cover up the text.

I realize that: the doors are supposed to cover the text.

I'll post a minimal example tomorrow, gotta hit the sack for now.

[eXpl0it3r]

I'll post a minimal example tomorrow, gotta hit the sack for now.

Okay, also it could be useful if you would provide the project file, so we could directly run your code.

Btw whenever you start with a SFML project, you nearly always want to start with an empty project instead of a Win32 application.

[Laurent]

Compiler? OS? Version of SFML?

[eXpl0it3r]

Compiler? OS? Version of SFML?

YouTube video?
He uses VS 2012 and well then obviously Windows.

But the version is a good question, did you recompile SFML on your own? Because the RC version doesn't properly work with VS 2012.

[jjfortherear]

I built SFML with cmake, I think it's a couple weeks old (not sure where to find the exact build#).

I fixed (circumnavigated) the issue by making it a vector of pointers to the objects, rather than a vector of objects.  I still don't know why this would cause an issue - as you saw, the sprites drew just fine.

[eXpl0it3r]

I fixed (circumnavigated) the issue by making it a vector of pointers to the objects, rather than a vector of objects. I still don't know why this would cause an issue - as you saw, the sprites drew just fine.

Well then its because you didn't implement a copy constructor and when you push_back things into a vector the elements get copied around and if the space within the vector is to small, everything will get moved. I further guess that the problem lies with the local defined sf::Font. Fonts, textures, sounds etc are (heavy) resource objects and one should always manage them separatly and only pass reference (or smart pointers) around.