hello triangle

source/app/src/App.cpp

@@ -32,11 +32,17 @@ App::App():
     glfwSetErrorCallback(error_callback_s);
     glfwInit();
 
+    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
+    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 2);
+    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
+    glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
+
     mpWindow = glfwCreateWindow(640, 480, "uGLy", NULL, NULL);
     glfwSetWindowUserPointer(mpWindow, this);
     glfwSetKeyCallback(mpWindow, key_callback_s);
 
     glfwMakeContextCurrent(mpWindow);
+    glewExperimental = GL_TRUE;
     if(glewInit() != GLEW_OK) {
         error_callback_s(GLFW_NO_ERROR, "glewInit() failed");
     }
@@ -50,8 +56,71 @@ App::~App() {
 
 
 void App::game_loop() {
+    float vertices[] = {
+        .0f, .5f,
+        .5f, -.5f,
+        -.5f, -.5f
+    };
+
+    GLuint vbo;
+    glGenBuffers(1, &vbo);
+    glBindBuffer(GL_ARRAY_BUFFER, vbo);
+    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
+    
+    auto vertexSource = R"glsl(
+        #version 150 core
+        in vec2 position;
+        void main() { gl_Position = vec4(position, 0.0, 1.0); }
+    )glsl";
+
+    GLint status;
+    GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER);
+    glShaderSource(vertexShader, 1, &vertexSource, NULL);
+    glCompileShader(vertexShader);
+    glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &status);
+    if(!status) {
+        error_callback_s(GLFW_NO_ERROR, "glShaderSource() failed");
+    }
+
+    auto fragmentSource = R"glsl(
+        #version 150 core
+        uniform vec3 triangleColor;
+        out vec4 color;
+        void main() { color = vec4(triangleColor, 1.0); }
+    )glsl";
+
+    
+    GLuint fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
+    glShaderSource(fragmentShader, 1, &fragmentSource, NULL);
+    glCompileShader(fragmentShader);
+    glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &status);
+    if(!status) {
+        error_callback_s(GLFW_NO_ERROR, "glShaderSource() failed");
+    }
+
+    GLuint shaderProgram = glCreateProgram();
+    glAttachShader(shaderProgram, vertexShader);
+    glAttachShader(shaderProgram, fragmentShader);
+    glLinkProgram(shaderProgram);
+    glUseProgram(shaderProgram);
+
+    GLuint vao;
+    glGenVertexArrays(1, &vao);
+    glBindVertexArray(vao);
+    glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 0, 0);
+    glEnableVertexAttribArray(0); 
+    
+    auto start = glfwGetTime();
+
     while(!glfwWindowShouldClose(mpWindow)) {
         glfwPollEvents();
+
+        glDrawArrays(GL_TRIANGLES, 0, 3);
+
+        auto now = glfwGetTime();
+        glUniform3f(glGetUniformLocation(shaderProgram, "triangleColor"), (sin(now-start) + 1.0f) / 2.0f, 0.0f, 0.0f);
+
+        glfwSwapBuffers(mpWindow);
     }
 }