Issues with window initializing using sf::ContextSettings

[42yeah]

Hi! I'm quite a newbie to sfml, and here's what I got when I am trying to initialize a sf::RenderWindow with an sf::ContextSettings:

Error. Unable to create the context. Retrying without shared context.
Warning. New context created without shared context.
 

 
Also the triangle I want is not displayed on the screen...

So here's the ContextSettings:

sf::ContextSettings settings;
settings.depthBits = 24;
settings.stencilBits = 8;
settings.antialiasingLevel = 4;
settings.majorVersion = 3;
settings.minorVersion = 3;
settings.attributeFlags = sf::ContextSettings::Core;
 

And here's the complete code, if you are interested:

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//
//  main.cpp
//  Ennoteplus
//
//  Created by Zhou hao on 2018/3/3.
//  Copyright © 2018年 whatever. All rights reserved.
//

#include <iostream>
#include <SFML/Window.hpp>
#include <SFML/Graphics.hpp>
#include <SFML/OpenGL.hpp>
#include <iostream>
#include <string>
#include <fstream>
#include <sstream>

using namespace std;

float tri[] = {
    0.0f, 0.0f, 0.0f,
    0.5f, 0.0f, 0.0f,
    0.0f, 0.5f, 0.0f
};

GLuint vao, vbo, prog;

GLuint loadProgram(string vpath, string fpath);

int main(int argc, const char * argv[]) {
    // insert code here...
   
    sf::ContextSettings settings;
    settings.depthBits = 24;
    settings.stencilBits = 8;
    settings.antialiasingLevel = 4;
    settings.majorVersion = 3;
    settings.minorVersion = 3;
    settings.attributeFlags = sf::ContextSettings::Core;
   
    sf::RenderWindow window(sf::VideoMode(800, 800), "SFML Window", sf::Style::Default, settings);
    glGenVertexArraysAPPLE(1, &vao);
    glGenBuffers(1, &vbo);
    glBindVertexArrayAPPLE(vao);
    glBindBuffer(GL_ARRAY_BUFFER, vbo);
    glBufferData(GL_ARRAY_BUFFER, sizeof(tri), tri, GL_STATIC_DRAW);
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(GLfloat) * 3, nullptr);
    glEnableVertexAttribArray(0);
   
    prog = loadProgram("Shader/vertex.glsl", "Shader/fragment.glsl");
   
    glClearColor(0.3f, 0.2f, 0.1f, 1.0f);
   
    while (window.isOpen()) {
        sf::Event event;
        while (window.pollEvent(event)) {
            if (event.type == sf::Event::Closed) {
                window.close();
            }
        }
       
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        glBindVertexArrayAPPLE(vao);
        glDrawArrays(GL_TRIANGLES, 0, 3);
       
        window.display();
    }
    return 0;
}

GLuint loadProgram(string vpath, string fpath) {
    GLuint v, f;
    stringstream ss;
    char log[512];
   
    v = glCreateShader(GL_VERTEX_SHADER);
    fstream vf(vpath);
    if (vf.good()) {
        ss << vf.rdbuf();
        string str = ss.str();
        const GLchar* g = str.c_str();
        glShaderSource(v, 1, &g, nullptr);
        glCompileShader(v);
        glGetShaderInfoLog(v, 512, nullptr, log);
        cout << "Vertex Shader: " << log << endl;
    } else {
        cout << "Bad path " << vpath.c_str() << endl;
        return static_cast<GLuint>(-1);
    }
   
    ss.str("");
    f = glCreateShader(GL_FRAGMENT_SHADER);
    fstream ff(fpath);
    if (ff.good()) {
        ss << ff.rdbuf();
        string str = ss.str();
        const GLchar* g = str.c_str();
        glShaderSource(f, 1, &g, nullptr);
        glCompileShader(f);
        glGetShaderInfoLog(f, 512, nullptr, log);
        cout << "Fragment Shader: " << log << endl;
    } else {
        cout << "Bad path " << fpath.c_str() << endl;
        return static_cast<GLuint>(-1);
    }
   
    GLuint prog;
    prog = glCreateProgram();
    glAttachShader(prog, v);
    glAttachShader(prog, f);
    glLinkProgram(prog);
    glGetProgramInfoLog(prog, 512, nullptr, log);
    cout << "Program: " << log;
    glDeleteShader(v);
    glDeleteShader(f);
    return prog;
}

 

Thanks a HUGE LOT for your help!!!
I'm using macOS High Sierra.
 

[AlexAUT]

I just skimmed over your opengl code and it looks fine so here are some guesses:

1) sf::RenderWindow does alter the state of the context after creation, so try to call window.resetGLStates() after the creation of the window.

2) Try to use a sf::Window instead of the sf::RenderWindow, since you use a 3.3 core context the graphics module of SFML won't work anyways. The sf::Window won't touch your contenxt 

3) Shader code correct?


AlexAUT

[42yeah]

I just skimmed over your opengl code and it looks fine so here are some guesses:

1) sf::RenderWindow does alter the state of the context after creation, so try to call window.resetGLStates() after the creation of the window.

2) Try to use a sf::Window instead of the sf::RenderWindow, since you use a 3.3 core context the graphics module of SFML won't work anyways. The sf::Window won't touch your contenxt 

3) Shader code correct?


AlexAUT

Hey AlexAUT! I tried all your suggestions but none of them works 
Here's my shader & program output:

Vertex Shader rc: 1
Vertex Shader:
Fragment Shader rc: 1
Fragment Shader:
Prrogram rc: 1
Program:
 

The vertex shader rc is glGetShaderiv and vertex shader is glGetShaderInfoLog. So the shaders should be working correctly.

Here's the shader code if you want:

vertex shader:

#version 330 core

layout (location = 0) in vec3 aPos;

void main() {
    gl_Position = vec4(aPos.xyz, 1.0);
}
 

fragment shader:

#version 330 core

out vec4 color;

void main() {
    color = vec4(0.1, 0.2, 0.3, 1.0);
}
 

Thanks a lot! 

[AlexAUT]

You forgot to "bind"/use the shader 

prog = ...;
glUseProgram(prog);

Some hints for the future:

Surround your opengl calls with glGetError() you could have a look at my error handling
https://github.com/AlexAUT/aw/blob/master/include/aw/graphics/core/opengl.hpp#L31
https://github.com/AlexAUT/aw/blob/master/src/aw/graphics/core/opengl.cpp#L20

basically all my opengl calls look like:

GL_CHECK(glClear(...));

and when an error occurs an exception is thrown.

And have a look at some opengl debug tools. I can highly recommend this one. It has a nice GUI where you can jump between frames and have a look at the context state (active shaders / textures / framebuffers...) at every opengl call 


AlexAUT

[42yeah]

You forgot to "bind"/use the shader 

prog = ...;
glUseProgram(prog);

Some hints for the future:

Surround your opengl calls with glGetError() you could have a look at my error handling
https://github.com/AlexAUT/aw/blob/master/include/aw/graphics/core/opengl.hpp#L31
https://github.com/AlexAUT/aw/blob/master/src/aw/graphics/core/opengl.cpp#L20

basically all my opengl calls look like:

GL_CHECK(glClear(...));

and when an error occurs an exception is thrown.

And have a look at some opengl debug tools. I can highly recommend this one. It has a nice GUI where you can jump between frames and have a look at the context state (active shaders / textures / framebuffers...) at every opengl call 


AlexAUT

AlexAUT, you're cool!
I can't mess around my mac now since i am in university again . However, i will try that as soon as I can. Thanks!!

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