The Code So Far III

In here we’re going to try to include some of the stuff we’ve presented before in our little application. We’re going to add menus to the application, submenus, and menu swapping.

Just copy and paste the following code into your project, or check out the source code at GitHub, and try it. The right mouse button should open a menu. The keys ‘s’ and ‘c’ will affect the menu options.

#include <stdlib.h>
#include <math.h>

#ifdef __APPLE__
#include <GLUT/glut.h>
#else
#include <GL/glut.h>
#endif

// angle of rotation for the camera direction
float angle = 0.0f;

// actual vector representing the camera's direction
float lx=0.0f,lz=-1.0f;

// XZ position of the camera
float x=0.0f, z=5.0f;

// the key states. These variables will be zero
//when no key is being presses
float deltaAngle = 0.0f;
float deltaMove = 0;
int xOrigin = -1;

// Constant definitions for Menus
#define RED 1
#define GREEN 2
#define BLUE 3
#define ORANGE 4

#define FILL 1
#define LINE 2

#define SHRINK 1
#define NORMAL 2

// Pop up menu identifiers
int fillMenu, shrinkMenu, mainMenu, colorMenu;

// color for the nose
float red = 1.0f, blue=0.5f, green=0.5f;

// scale of snowman
float scale = 1.0f;

// menu status
int menuFlag = 0;

void changeSize(int w, int h) {

	// Prevent a divide by zero, when window is too short
	// (you cant make a window of zero width).
	if (h == 0)
		h = 1;

	float ratio =  w * 1.0 / h;

	// Use the Projection Matrix
	glMatrixMode(GL_PROJECTION);

	// Reset Matrix
	glLoadIdentity();

	// Set the viewport to be the entire window
	glViewport(0, 0, w, h);

	// Set the correct perspective.
	gluPerspective(45.0f, ratio, 0.1f, 100.0f);

	// Get Back to the Modelview
	glMatrixMode(GL_MODELVIEW);
}

void drawSnowMan() {

	glScalef(scale, scale, scale);
	glColor3f(1.0f, 1.0f, 1.0f);

// Draw Body
	glTranslatef(0.0f ,0.75f, 0.0f);
	glutSolidSphere(0.75f,20,20);

// Draw Head
	glTranslatef(0.0f, 1.0f, 0.0f);
	glutSolidSphere(0.25f,20,20);

// Draw Eyes
	glPushMatrix();
	glColor3f(0.0f,0.0f,0.0f);
	glTranslatef(0.05f, 0.10f, 0.18f);
	glutSolidSphere(0.05f,10,10);
	glTranslatef(-0.1f, 0.0f, 0.0f);
	glutSolidSphere(0.05f,10,10);
	glPopMatrix();

// Draw Nose
	glColor3f(red, green, blue);
	glRotatef(0.0f,1.0f, 0.0f, 0.0f);
	glutSolidCone(0.08f,0.5f,10,2);

	glColor3f(1.0f, 1.0f, 1.0f);
}

void computePos(float deltaMove) {

	x += deltaMove * lx * 0.1f;
	z += deltaMove * lz * 0.1f;
}

void renderScene(void) {

	if (deltaMove)
		computePos(deltaMove);

	// Clear Color and Depth Buffers
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

	// Reset transformations
	glLoadIdentity();
	// Set the camera
	gluLookAt(	x, 1.0f, z,
			x+lx, 1.0f,  z+lz,
			0.0f, 1.0f,  0.0f);

// Draw ground

	glColor3f(0.9f, 0.9f, 0.9f);
	glBegin(GL_QUADS);
		glVertex3f(-100.0f, 0.0f, -100.0f);
		glVertex3f(-100.0f, 0.0f,  100.0f);
		glVertex3f( 100.0f, 0.0f,  100.0f);
		glVertex3f( 100.0f, 0.0f, -100.0f);
	glEnd();

// Draw 36 SnowMen

	for(int i = -3; i < 3; i++)
		for(int j=-3; j < 3; j++) {
			glPushMatrix();
			glTranslatef(i*10.0f, 0.0f, j * 10.0f);
			drawSnowMan();
			glPopMatrix();
		}
	glutSwapBuffers();
}

// -----------------------------------
//             KEYBOARD
// -----------------------------------

void processNormalKeys(unsigned char key, int xx, int yy) {

	glutSetMenu(mainMenu);
	switch (key) {
		case 27:
			glutDestroyMenu(mainMenu);
			glutDestroyMenu(fillMenu);
			glutDestroyMenu(colorMenu);
			glutDestroyMenu(shrinkMenu);
			exit(0);
			break;

		case 's':
			if (!menuFlag)
			  glutChangeToSubMenu(2,"Shrink",shrinkMenu);
			break;
		case 'c':
			if (!menuFlag)
				glutChangeToSubMenu(2,"Color",colorMenu);
			break;
	}
	if (key == 27)
		exit(0);
}

void pressKey(int key, int xx, int yy) {

	switch (key) {
		case GLUT_KEY_UP : deltaMove = 0.5f; break;
		case GLUT_KEY_DOWN : deltaMove = -0.5f; break;
	}
}

void releaseKey(int key, int x, int y) {

	switch (key) {
		case GLUT_KEY_UP :
		case GLUT_KEY_DOWN : deltaMove = 0;break;
	}
}

// -----------------------------------
//             MOUSE
// -----------------------------------

void mouseMove(int x, int y) {

	// this will only be true when the left button is down
	if (xOrigin >= 0) {

		// update deltaAngle
		deltaAngle = (x - xOrigin) * 0.001f;

		// update camera's direction
		lx = sin(angle + deltaAngle);
		lz = -cos(angle + deltaAngle);
	}
}

void mouseButton(int button, int state, int x, int y) {

	// only start motion if the left button is pressed
	if (button == GLUT_LEFT_BUTTON) {

		// when the button is released
		if (state == GLUT_UP) {
			angle += deltaAngle;
			xOrigin = -1;
		}
		else  {// state = GLUT_DOWN
			xOrigin = x;
		}
	}
}

// -----------------------------------
//             MENUS
// -----------------------------------

void processMenuStatus(int status, int x, int y) {

	if (status == GLUT_MENU_IN_USE)
		menuFlag = 1;
	else
		menuFlag = 0;
}

void processMainMenu(int option) {

	// nothing to do in here
	// all actions are for submenus
}

void processFillMenu(int option) {

	switch (option) {

		case FILL: glPolygonMode(GL_FRONT, GL_FILL); break;
		case LINE: glPolygonMode(GL_FRONT, GL_LINE); break;
	}
}

void processShrinkMenu(int option) {

	switch (option) {

		case SHRINK: scale = 0.5f; break;
		case NORMAL: scale = 1.0f; break;
	}
}

void processColorMenu(int option) {

	switch (option) {
		case RED :
			red = 1.0f;
			green = 0.0f;
			blue = 0.0f; break;
		case GREEN :
			red = 0.0f;
			green = 1.0f;
			blue = 0.0f; break;
		case BLUE :
			red = 0.0f;
			green = 0.0f;
			blue = 1.0f; break;
		case ORANGE :
			red = 1.0f;
			green = 0.5f;
			blue = 0.5f; break;
	}
}

void createPopupMenus() {

	shrinkMenu = glutCreateMenu(processShrinkMenu);

	glutAddMenuEntry("Shrink",SHRINK);
	glutAddMenuEntry("NORMAL",NORMAL);

	fillMenu = glutCreateMenu(processFillMenu);

	glutAddMenuEntry("Fill",FILL);
	glutAddMenuEntry("Line",LINE);

	colorMenu = glutCreateMenu(processColorMenu);
	glutAddMenuEntry("Red",RED);
	glutAddMenuEntry("Blue",BLUE);
	glutAddMenuEntry("Green",GREEN);
	glutAddMenuEntry("Orange",ORANGE);

	mainMenu = glutCreateMenu(processMainMenu);

	glutAddSubMenu("Polygon Mode", fillMenu);
	glutAddSubMenu("Color", colorMenu);
	// attach the menu to the right button
	glutAttachMenu(GLUT_RIGHT_BUTTON);

	// this will allow us to know if the menu is active
	glutMenuStatusFunc(processMenuStatus);
}

// -----------------------------------
//             MAIN
// -----------------------------------

int main(int argc, char **argv) {

	// init GLUT and create window
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA);
	glutInitWindowPosition(100,100);
	glutInitWindowSize(320,320);
	glutCreateWindow("Lighthouse3D - GLUT Tutorial");

	// register callbacks
	glutDisplayFunc(renderScene);
	glutReshapeFunc(changeSize);
	glutIdleFunc(renderScene);

	glutIgnoreKeyRepeat(1);
	glutKeyboardFunc(processNormalKeys);
	glutSpecialFunc(pressKey);
	glutSpecialUpFunc(releaseKey);

	// here are the two new functions
	glutMouseFunc(mouseButton);
	glutMotionFunc(mouseMove);

	// OpenGL init
	glEnable(GL_DEPTH_TEST);
	glEnable(GL_CULL_FACE);

	// init Menus
	createPopupMenus();

	// enter GLUT event processing cycle
	glutMainLoop();

	return 1;
}