/* 
 * @skyLibrary
 * Title : star drawing in 3D program
 * Date : 2013/7/7 ~ 2013/7/7
 * How to use : 
 *		1. use up, down, left, right key in your key board to move star in that way.
 *		2. click mouse right button and you can change the star shape statements by click each menu item.
 * Purpose :
 *		just practice OpenGL.
 */

#include <GL/glut.h>

#define SOLID_MODE 1
#define LINE_MODE 2
#define POINT_MODE 3

int iMode = SOLID_MODE;
GLboolean bEdgeFlag = true;

static GLfloat xRot = 0.0f;
static GLfloat yRot = 0.0f;

void RenderScene()
{
	glClear(GL_COLOR_BUFFER_BIT);

	if(iMode == LINE_MODE)
		glPolygonMode(GL_FRONT_AND_BACK,GL_LINE);

	if(iMode == POINT_MODE)
		glPolygonMode(GL_FRONT_AND_BACK,GL_POINT);

	if(iMode == SOLID_MODE)
		glPolygonMode(GL_FRONT_AND_BACK,GL_FILL);

	glPushMatrix();
	glRotatef(xRot, 1.0f, 0.0f, 0.0f);
	glRotatef(yRot, 0.0f, 1.0f, 0.0f);

	//start drawing triangle
	glBegin(GL_TRIANGLES);
	
		//setup kind of line which is outter line or not.
		glEdgeFlag(bEdgeFlag);
		glVertex2f(-20.0f, 0.0f);
		glEdgeFlag(TRUE);
		glVertex2f(20.0f, 0.0f);
		glVertex2f(0.0f, 40.0f);

		glVertex2f(-20.0f,0.0f);
		glVertex2f(-60.0f,-20.0f);
		glEdgeFlag(bEdgeFlag);
		glVertex2f(-20.0f,-40.0f);
		glEdgeFlag(TRUE);

		glVertex2f(-20.0f,-40.0f);
		glVertex2f(0.0f, -80.0f);
		glEdgeFlag(bEdgeFlag);
		glVertex2f(20.0f, -40.0f);		
		glEdgeFlag(TRUE);

		glVertex2f(20.0f, -40.0f);		
		glVertex2f(60.0f, -20.0f);
		glEdgeFlag(bEdgeFlag);
		glVertex2f(20.0f, 0.0f);
		glEdgeFlag(TRUE);

		// Center square as two triangles
		glEdgeFlag(bEdgeFlag);
		glVertex2f(-20.0f, 0.0f);
		glVertex2f(-20.0f,-40.0f);
		glVertex2f(20.0f, 0.0f);
		
		glVertex2f(-20.0f,-40.0f);
		glVertex2f(20.0f, -40.0f);
		glVertex2f(20.0f, 0.0f);
		glEdgeFlag(TRUE);

	glEnd();

	glPopMatrix();

	glutSwapBuffers();
}

//menu event function
void ClickMenu(int value)
{
	switch(value)
	{
	case 1: iMode = SOLID_MODE; break;
	case 2: iMode = LINE_MODE; break;
	case 3: iMode = POINT_MODE; break;
	case 4: bEdgeFlag = true; break;
	case 5: 
	default: bEdgeFlag = false; break;
	}

	//repaint by calling callback function
	glutPostRedisplay();
}

//key event function
void SpecialKeys(int key, int x, int y)
{
	if(key == GLUT_KEY_DOWN)
	{
		xRot += 5.0f;
	}
	else if(key == GLUT_KEY_UP)
	{
		xRot -= 5.0f;
	}
	else if(key == GLUT_KEY_LEFT)
	{
		yRot += 5.0f;
	}
	else if(key == GLUT_KEY_RIGHT)
	{
		yRot -= 5.0f;
	}

	if(key > 365.0f)
		xRot = 0.0f;

	if(key < -1.0f)
		xRot = 355.0f;

	if(key > 356.0f)
		yRot = 0.0f;

	if(key < -1.0f)
		yRot = 355.0f;

	//repaint by calling callback function
	glutPostRedisplay();
}

//register backgroung color & base drawing color
void SetupRC()
{
	glClearColor( 0.0f, 0.0f, 0.0f, 1.0f);
	
	glColor3f(0.0f, 1.0f, 0.0f);
	
	//glShadeModel(GL_FLAT);

	//glFrontFace(GL_CCW);
}

void ChangeSize(int w, int h)
{
	GLfloat nRange = 100.0f;

	// Prevent a divide by zero
	if(h == 0)
		h = 1;

	// Set Viewport to window dimensions
    glViewport(0, 0, w, h);

	// Reset projection matrix stack
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();

	// Establish clipping volume (left, right, bottom, top, near, far)
    if (w <= h) 
		glOrtho (-nRange, nRange, -nRange*h/w, nRange*h/w, -nRange, nRange);
    else 
		glOrtho (-nRange*w/h, nRange*w/h, -nRange, nRange, -nRange, nRange);

	// Reset Model view matrix stack
	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();
}

void main()
{
	int nModeMenu;
	int nEdgeMenu;
	int nMainMenu;

	//register glut mode & create window
	glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
	glutCreateWindow("star");
	
	//make Mode sub menu 
	nModeMenu = glutCreateMenu(ClickMenu);
	glutAddMenuEntry("Solid", 1);
	glutAddMenuEntry("Outline", 2);
	glutAddMenuEntry("Points", 3);

	//make Edge boolean sub menu
	nEdgeMenu = glutCreateMenu(ClickMenu);
	glutAddMenuEntry("On", 4);
	glutAddMenuEntry("Off", 5);

	//make main menu that add Mode menu and Edge Menu
	nMainMenu = glutCreateMenu(ClickMenu);
	glutAddSubMenu("Mode", nModeMenu);
	glutAddSubMenu("Edge", nEdgeMenu);
	glutAttachMenu(GLUT_RIGHT_BUTTON);

	//register callback function & event function
	glutReshapeFunc(ChangeSize);
	glutSpecialFunc(SpecialKeys);
	glutDisplayFunc(RenderScene);
	SetupRC();
	
	glutMainLoop();
}