Question

I am trying to build a simple openGL and SDL program that just refuses to work.

I am using the latest nvidia driver (285.something if i remember) and i use mingw to compile. The machine i use runs Windows7.
My knowledge of mingw is somewhat limited so this might be a very simple linking error.

The version of SDL im using is 1.2 (should i upgrade to 1.3?)

At first, everything worked fine, but i was merely opening an opengl window through SDL.
here’s the code for the original makefile

all:
g++ -o sdlGL.exe esg.cpp tiletest.cpp -lmingw32 -lSDLmain -lSDL -lopengl32 -lglu32

and these are the 2 functions that were called

    void init_sdl(int width, int height) {
        //Start SDL
        if(SDL_Init(SDL_INIT_EVERYTHING) != 0) {
            fDebug << "Failed to init SDL" << std::endl;
            quit(1);
        }

        //Set SDL attrib.
        SDL_GL_SetAttribute( SDL_GL_RED_SIZE, 8 );
        SDL_GL_SetAttribute( SDL_GL_GREEN_SIZE, 8 );
        SDL_GL_SetAttribute( SDL_GL_BLUE_SIZE, 8 );
        SDL_GL_SetAttribute( SDL_GL_ALPHA_SIZE, 8 );
        SDL_GL_SetAttribute( SDL_GL_DEPTH_SIZE, 16 );
        SDL_GL_SetAttribute( SDL_GL_DOUBLEBUFFER, 1 );

        //Set SDL video mode
        if( SDL_SetVideoMode(width, height, 0, SDL_OPENGL) == 0 ) {
            fDebug << "Failed to set SDL video mode" << std::endl;
            quit(1);
        }
    }

    //Initializes OpenGL
    void init_opengl(int width, int height, bool alpha) {
        // Set the OpenGL state after creating the context with SDL_SetVideoMode
        glClearColor( 0, 0, 0, 0 );
        glClear(GL_COLOR_BUFFER_BIT);
        glEnable( GL_TEXTURE_2D ); // Need this to display a texture

        if(alpha) {
            glEnable (GL_BLEND);
            glBlendFunc (GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
        }

        glViewport( 0, 0, width, height );
        glMatrixMode( GL_PROJECTION );
        glLoadIdentity();
        glOrtho( 0, width, height, 0, -1, 1 );
        glMatrixMode( GL_MODELVIEW );
        glLoadIdentity();
    }

Now for the inclusions:

#include "SDL/SDL.h"
#include "SDL/SDL_image.h"
#include "SDL/SDL_opengl.h"
#include <iostream>
#include <fstream>
#include <vector>
#include <algorithm>

With that code, everything worked fine.
Then i added some functions to take care of shaders and shader programs

    void CreateShader(GLenum eShaderType, const std::string &strShaderFile, std::vector<GLuint> &shaderList) {
        GLuint shader = glCreateShader(eShaderType);
        const char *strFileData = strShaderFile.c_str();
        glShaderSource(shader, 1, &strFileData, NULL);

        glCompileShader(shader);

        GLint status;
        glGetShaderiv(shader, GL_COMPILE_STATUS, &status);


        shaderList.push_back(shader);
    }

    void ClearShader(std::vector<GLuint> &shaderList) {
        std::for_each(shaderList.begin(), shaderList.end(), glDeleteShader);
    }

    GLuint CreateProgram(const std::vector<GLuint> &shaderList) {
        GLuint program = glCreateProgram();

        for(size_t iLoop = 0; iLoop < shaderList.size(); iLoop++)
            glAttachShader(program, shaderList[iLoop]);

        glLinkProgram(program);

        GLint status;
        glGetProgramiv (program, GL_LINK_STATUS, &status);

        for(size_t iLoop = 0; iLoop < shaderList.size(); iLoop++)
            glDetachShader(program, shaderList[iLoop]);

        return program;
    }

Now, the compiler complains that glCreateShader, glShaderSource, glCompileShader, glGetShaderiv, glDeleteShader, glCreateProgram, glAttachShader, glLinkProgram, glGetProgramiv and glDetachShader were not declared in this scope.

i figured i needed to include glee or glew (right?) so i went with glew.
I then added -glew32 to my makefile and added glew.h to my inclusions

#include "GL/glew.h"

Now, the compiler lists a ton of errors for glew.h like —- does not name a type and —- was not declared in this scope.

I have no idea what to do to fix this.
I should add that i have not much experience with openGL.

Answer 1

GLEW handles the platform-specific #includes for the GL header(s), so you no longer need SDL_opengl.h. It also #includes the appropriate GLU header so you don’t need that either.

As Xavier pointed out #include <GL/glew.h> before anything else. If I recall correctly it tends to conflict with windows.h.