first commit

CMakeLists.txt

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+cmake_minimum_required(VERSION 3.24)
+project(glapp2)
+
+set(CMAKE_CXX_STANDARD  17)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+set(CMAKE_CXX_STANDARD 17)
+
+add_executable(glapp2 main.cpp)
+
+find_package(OpenGL)
+if(${OPENGL_FOUND})
+    target_link_libraries(glapp2 ${OPENGL_LIBRARIES})
+    message(${OPENGL_LIBRARIES})
+    target_link_libraries(glapp2 OpenGL::GL)
+endif()
+
+find_package(GLEW)
+if(${GLEW_FOUND})
+    message(${GLEW_LIBRARIES})
+    message(${GLEW_INCLUDE_DIRS})
+    target_link_libraries(glapp2 ${GLEW_LIBRARIES})
+endif()
+#include_directories(glapp2 /usr/include/GLFW)
+#target_link_libraries(glapp2 glfw3)
+find_package(glfw3)
+if(${GLFW3_FOUND})
+    target_link_libraries(glapp2 glfw)
+endif()

fragment.glsl

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+#version 430
+out vec4 color;
+void main() {
+color = vec4(0.3,0.7,0.5,1.0);
+}

main.cpp

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+#include <iostream>
+#include <GL/glew.h>
+#include <GLFW/glfw3.h>
+
+#include <string>
+#include <iostream>
+#include <fstream>
+#include <sstream>
+
+using namespace std;
+#define vaoNum 1
+GLuint  rederingProgram;
+GLuint vao[vaoNum];
+
+void printShaderLog(GLuint shader){
+    int len = 0;
+    int chWrittn = 0;
+    char* log;
+    glGetShaderiv(shader,GL_INFO_LOG_LENGTH,&len);
+    if(len>0){
+        log = (char*)malloc(len);
+        glGetShaderInfoLog(shader,len,&chWrittn,log);
+        cout<<"Shader Info Log:"<<log<<endl;
+        free(log);
+    }
+}
+
+bool checkOpenGLError(){
+    bool foundError = false;
+    int glErr = glGetError();
+    while (glErr !=GL_NO_ERROR){
+        cout<<"glError: "<<glErr<<endl;
+        foundError = true;
+        glErr = glGetError();
+    }
+    return foundError;
+}
+
+string readfile(char *filename) {
+    fstream fs(filename);
+    stringstream buffer;
+    buffer << fs.rdbuf();
+    return buffer.str();
+}
+
+GLuint prepareShader(int shaderTYPE, char* filename){
+    GLint shaderCompliled;
+    string shaderStr = readfile(filename);
+    const char* shaderSrc = shaderStr.c_str();
+    GLuint shaderRef = glCreateShader(shaderTYPE);
+    glShaderSource(shaderRef,1,&shaderSrc,NULL);
+    glCompileShader(shaderRef);
+    checkOpenGLError();
+    glGetShaderiv(shaderRef,GL_COMPILE_STATUS,&shaderCompliled);
+    if(shaderCompliled !=1){
+        cout<<"shader compilation error."<<endl;
+        printShaderLog(shaderRef);
+    }
+    return shaderRef;
+}
+
+void printProgramLog(int prog){
+    int len = 0;
+    int chWrittn = 0;
+    char* log;
+    glGetProgramiv(prog, GL_INFO_LOG_LENGTH,&len);
+    if(len>0){
+        log = (char*)malloc(len);
+        glGetProgramInfoLog(prog,len,&chWrittn,log);
+        cout<<"Prog Info Log: "<<log<<endl;
+        free(log);
+    }
+}
+
+int finalizeShaderProgram(GLuint sprogram){
+    GLint linked;
+    glLinkProgram(sprogram);
+    checkOpenGLError();
+    glGetProgramiv(sprogram,GL_LINK_STATUS,&linked);
+    if(linked !=1){
+        cout<<"linking failed"<<endl;
+        printProgramLog(sprogram);
+    }
+    return sprogram;
+}
+
+GLuint createShaderProgram(char* vertex,char* fragment){
+    GLuint vShader = prepareShader(GL_VERTEX_SHADER,vertex);
+    GLuint fShader = prepareShader(GL_FRAGMENT_SHADER,fragment);
+    GLuint vfprogram = glCreateProgram();
+    glAttachShader(vfprogram,vShader);
+    glAttachShader(vfprogram,fShader);
+    finalizeShaderProgram(vfprogram);
+    return  vfprogram;
+}
+
+void window_size_callback(GLFWwindow* win, int newWidth,int newHeight){
+    glViewport(0,0,newWidth,newHeight);
+}
+
+void display(GLFWwindow* window){
+    glClear(GL_DEPTH_BUFFER_BIT);
+    glClearColor(0.1,0.2,0.3,0.4);
+    glClear(GL_COLOR_BUFFER_BIT);
+
+    glUseProgram(rederingProgram);
+    glDrawArrays(GL_TRIANGLES,0,3);
+}
+
+void init(GLFWwindow* window){
+    rederingProgram = createShaderProgram("../vertex.glsl","../fragment.glsl");
+    int width,height;
+    glfwGetFramebufferSize(window,&width,&height);
+    double aspect = (float)width/(float)height;
+    glGenVertexArrays(1,vao);
+    glBindVertexArray(vao[0]);
+}
+
+int main() {
+
+    if(!glfwInit()){exit(EXIT_FAILURE);}
+    std::cout<<__LINE__<<std::endl;
+    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR,4);
+    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR,3);
+    GLFWwindow *window  = glfwCreateWindow(600,400,"triangle", nullptr, nullptr);
+    std::cout<<__LINE__<<std::endl;
+    glfwMakeContextCurrent(window);
+    std::cout<<__LINE__<<std::endl;
+    if(glewInit() != GLEW_OK){exit(EXIT_FAILURE);}
+    std::cout<<__LINE__<<std::endl;
+    init(window);
+    std::cout<<__LINE__<<std::endl;
+    glfwSetWindowSizeCallback(window,window_size_callback);
+    std::cout<<__LINE__<<std::endl;
+    while(!glfwWindowShouldClose(window)){
+        std::cout<<__LINE__<<std::endl;
+        display(window);
+        glfwSwapBuffers(window);
+        glfwPollEvents();
+    }
+    std::cout<<__LINE__<<std::endl;
+    glfwDestroyWindow(window);
+    glfwTerminate();
+
+
+//    cout << readfile("../vertex.glsl") << endl;
+    std::cout << "Hello, World!" << std::endl;
+    exit(EXIT_SUCCESS);
+    return 0;
+}

vertex.glsl

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+#version 430
+
+void main() {
+	if(gl_VertexID==0)
+	gl_Position = vec4(0.25,0.25,0.0,1.0);
+	else if(gl_VertexID==1)
+	gl_Position = vec4(0.5,0.5,0.0,1.0);
+	else if(gl_VertexID==2)
+	gl_Position = vec4(0.25,0.5,0.0,1.0);
+}