Notes

#include<GL/glut.h>
#include <stdio.h>

bool isTriangle = true;

void drawFigure(){
glBegin(GL_LINE_LOOP);

if (isTriangle) {
glVertex2f(0, 0);
glVertex2f(0.9, 0.9);
glVertex2f(0, 0.9);
} else {
glVertex2f(0, 0);
glVertex2f(0.9, 0);
glVertex2f(0.9, 0.9);
glVertex2f(0, 0.9);
}

glEnd();
}

void myDisplay(){
glClearColor(0.0, 0.0, 0.0, 1.0);
glClear(GL_COLOR_BUFFER_BIT);

//your drawing code will here
drawFigure();

glutSwapBuffers();
}

void myMouse(int button, int status, int x, int y){

/*isTriangle = button == GLUT_LEFT_BUTTON;
printf("x: %d; y: %d n", x, y);*/

switch(button) {
case GLUT_LEFT_BUTTON:
//your code here
printf("x: %d; y: %d n", x, y);
if (status == GLUT_UP) { }
if (status == GLUT_DOWN) { }
break;
default: break;
}

glutPostRedisplay();
}

void myKeyboard(unsigned char c, int x, int y){

//isTriangle = c=='t';

switch(c) {
case 't': isTriangle = true;
//your code here
break;
default: isTriangle = false;
break;
}

glutPostRedisplay();
}

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

switch(key) {

case GLUT_KEY_UP:
//your code here
break;
case GLUT_KEY_DOWN:
//your code here
break;
case GLUT_KEY_LEFT:
//your code here
break;
case GLUT_KEY_RIGHT:
//your code here
break;
case GLUT_KEY_F2:
//your code here
break;

default: break;
}

glutPostRedisplay();
}

void myInit(){
//#pragma comment(linker, "/SUBSYSTEM:windows /ENTRY:mainCRTStartup")
}

int main(int* argc, char** argv){
myInit();
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
glutInitWindowSize(600, 600);
glutInitWindowPosition(0,0);
glutCreateWindow(argv[0]);

glutDisplayFunc(myDisplay);

glutKeyboardFunc(myKeyboard);
glutSpecialFunc(mySpecial);
glutMouseFunc(myMouse);

glutMainLoop();
return 0;
}