Vfrdtyky

Im trying to learn a gl in cpp and trying to create some shaders reading its documentation and following a yt tutorial.
It just had a compilation fail.
yestarday it was just printing in console Shader " + filePath + " failed to Compile
Today it printing that :

ERROR: 0:7: 'gl_position' : undeclared identifier

ERROR: 0:7: 'xy' : field selection requires structure, vector, or matrix on left
hand side
ERROR: 0:7: 'assign' : cannot convert from '2-component vector of highp float'
to 'highp float'

ERROR: 0:8: 'z' : field selection requires structure, vector, or matrix on left
hand side
ERROR: 0:9: 'w' : field selection requires structure, vector, or matrix on left
hand side

Shader shaders/colorShading.vert failed to Compile
Enter any key to quit...

this is my shader source code:

#version 130



in vec2 vertexPosition;



void main()

{

    gl_position.xy = vertexPosition * 2;

    gl_position.z = 0.0;

    gl_position.w = 1.0;

}

//////////////////////////////////////////////////////

#include "GLSLProgram.h"

#include "Error.h"



#include <fstream>

#include <vector>



GLSLProgram::GLSLProgram() :_numAttributes(0), _programID(0), _vertexShaderID(0), _fragmentShaderID(0)

{

}





GLSLProgram::~GLSLProgram()

{



}



void GLSLProgram::compileShaders(const std::string& vertexShaderFilePath, const std::string& framgmentShaderFilePath)

{

    _vertexShaderID = glCreateShader(GL_VERTEX_SHADER);

    if (_vertexShaderID == 0)

    {

        fatalError("Vertex shader failed to be created!");

    }



    _fragmentShaderID = glCreateShader(GL_FRAGMENT_SHADER);

    if (_fragmentShaderID == 0)

    {



        fatalError("Fragment shader failed to be created!");

    }







    compileShader(vertexShaderFilePath, _vertexShaderID);

    compileShader(framgmentShaderFilePath, _fragmentShaderID);

}



void GLSLProgram::linkShaders()

{



    // Attach Shaders to Program

    glAttachShader(_programID, _vertexShaderID);

    glAttachShader(_programID, _fragmentShaderID);



    // Link the Program.

    glLinkProgram(_programID);



    GLuint isLinked = 0;

    glGetProgramiv(_programID, GL_LINK_STATUS, (int *)&isLinked);

    if (GL_FALSE == isLinked) {



        GLint maxLength = 0;

        glGetProgramiv(_programID, GL_INFO_LOG_LENGTH, &maxLength);



        std::vector<char> errorLog(maxLength);

        glGetProgramInfoLog(_programID, maxLength, &maxLength, &errorLog[0]);



        glDeleteProgram(_programID);

        glDeleteShader(_vertexShaderID);

        glDeleteShader(_fragmentShaderID);



        std::printf("%sn", &(errorLog[0]));

        fatalError("Shaders failed to link!");



        return;



    }



    glDetachShader(_programID, _vertexShaderID);

    glDetachShader(_programID, _fragmentShaderID);

    glDeleteShader(_vertexShaderID);

    glDeleteShader(_fragmentShaderID);



}



void GLSLProgram::addAttribute(const std::string& attributeName)

{

    glBindAttribLocation(_programID, _numAttributes++, attributeName.c_str());

}



void GLSLProgram::use()

{

    glUseProgram(_programID);

    for (int i = 0; i < _numAttributes; i++)

    {

        glEnableVertexAttribArray(i);

    }

}



void GLSLProgram::unuse()

{

    glUseProgram(0);

    for (int i = 0; i < _numAttributes; i++)

    {

        glDisableVertexAttribArray(i);

    }

}



void GLSLProgram::compileShader(const std::string & filePath, GLuint& id)

{

    std::ifstream fileptr(filePath);

    if (fileptr.fail()) {

        // Not sold on this

        perror(filePath.c_str());

        fatalError("Failed to Open " + filePath);

    }



    std::string fileContents = "";

    std::string line;



    while (std::getline(fileptr, line))

    {

        fileContents += line + "n";

    }



    fileptr.close();



    // This is weird

    const GLchar * contentsPtr = fileContents.c_str();

    glShaderSource(id, 1, &contentsPtr, 0);



    glCompileShader(id);



    GLint success = 0;

    glGetShaderiv(id, GL_COMPILE_STATUS, &success);



    if (success == GL_FALSE) {



        GLint maxLength = 0;

        glGetShaderiv(id, GL_INFO_LOG_LENGTH, &maxLength);



        std::vector<GLchar> errorLog(maxLength);

        glGetShaderInfoLog(id, maxLength, &maxLength, &errorLog[0]);



        glDeleteShader(id);



        std::printf("%sn", &(errorLog[0]));

        fatalError("Shader " + filePath + " failed to Compile");

    }

}

The vertex shader failed to compile, because it has to be gl_Position instead of gl_position. GLSL is case sensitive. See Vertex Shader - Outputs:

void main()

{

    gl_Position.xy = vertexPosition * 2;

    gl_Position.z = 0.0;

    gl_Position.w = 1.0;

}