// Lab 1-1.
 // This is the same as the first simple example in the course book,
 // but with a few error checks.
 // Remember to copy your file to a new on appropriate places during the lab so you keep old results.
 // Note that the files "lab1-1.frag", "lab1-1.vert" are required.
 
 #include "GL_utilities.h"
 #include "MicroGlut.h"
 // uses framework OpenGL
 // uses framework Cocoa
 
 // Globals
 // Data would normally be read from files
 GLfloat vertices[] =
 {
 	-0.5f,-0.5f,0.0f,
 	-0.5f,0.5f,0.0f,
 	0.5f,-0.5f,0.0f
 };
 
 // vertex array object
 unsigned int vertexArrayObjID;
 
 void init(void)
 {
 	// vertex buffer object, used for uploading the geometry
 	unsigned int vertexBufferObjID;
 	// Reference to shader program
 	GLuint program;
 
 	dumpInfo();
 
 	// GL inits
 	glClearColor(0.2,0.2,0.5,0);
 	glDisable(GL_DEPTH_TEST);
 	printError("GL inits");
 
 	// Load and compile shader
 	program = loadShaders("lab1-1.vert", "lab1-1.frag");
 	printError("init shader");
 	
 	// Upload geometry to the GPU:
 	
 	// Allocate and activate Vertex Array Object
 	glGenVertexArrays(1, &vertexArrayObjID);
 	glBindVertexArray(vertexArrayObjID);
 	// Allocate Vertex Buffer Objects
 	glGenBuffers(1, &vertexBufferObjID);
 	
 	// VBO for vertex data
 	glBindBuffer(GL_ARRAY_BUFFER, vertexBufferObjID);
 	glBufferData(GL_ARRAY_BUFFER, 9*sizeof(GLfloat), vertices, GL_STATIC_DRAW);
 	glVertexAttribPointer(glGetAttribLocation(program, "in_Position"), 3, GL_FLOAT, GL_FALSE, 0, 0); 
 	glEnableVertexAttribArray(glGetAttribLocation(program, "in_Position"));
 	
 	// End of upload of geometry
 	
 	printError("init arrays");
 }
 
 
 void display(void)
 {
 	printError("pre display");
 
 	// clear the screen
 	glClear(GL_COLOR_BUFFER_BIT);
 
 	glBindVertexArray(vertexArrayObjID);	// Select VAO
 	glDrawArrays(GL_TRIANGLES, 0, 3);	// draw object
 	
 	printError("display");
 	
 	glutSwapBuffers();
 }
 
 int main(int argc, char *argv[])
 {
 	glutInit(&argc, argv);
 	glutInitContextVersion(3, 2);
 	glutInitWindowSize(600, 600);
 	glutCreateWindow ("GL3 white triangle example");
 	glutDisplayFunc(display); 
 	init ();
 	glutMainLoop();
 	return 0;
 }