fixed triangle

src/main.cpp

@@ -18,13 +18,18 @@ int main(int argc, char *argv[]){
     }
     glfwMakeContextCurrent(window);
     gladLoadGL();
+    glViewport(0, 0, 640, 480);
     while(!glfwWindowShouldClose(window)){
+        glClear(GL_COLOR_BUFFER_BIT);
         float vertices[] = {
             -0.5f, -0.5f, 0.0f,
             0.5f, -0.5f, 0.0f,
             0.0f,  0.5f, 0.0f
         };  
         unsigned int VBO;
+        unsigned int VAO;
+        glGenVertexArrays(1, &VAO);
+        glBindVertexArray(VAO);
         glGenBuffers(1, &VBO);
         glBindBuffer(GL_ARRAY_BUFFER, VBO);
         glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
@@ -86,11 +91,8 @@ int main(int argc, char *argv[]){
         glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
         glEnableVertexAttribArray(0);
 
-        unsigned int VAO;
-        glGenVertexArrays(1, &VAO);
-        glBindVertexArray(VAO);
         glDrawArrays(GL_TRIANGLES, 0, 3);
-
+        
         glfwPollEvents();
         glfwSwapBuffers(window);
     }