OpenGL reverse movement - c++

Question

I'm trying to decrease the values of 'left_eye_b' and 'left_eye_b'and then increase the values again to simulate wink on a human I made on OpenGL.
Here I created the eye:
left_eye_b=10.0;
left_eye_s=10.0;
glColor3f(1.0f, 1.0f, 0.0f);
glBegin(GL_POLYGON);
for (float i = 0; i <= (2 * p); i += 0.001) { // Left Eye Inside
x = 10.0 * cos(i) - 24.56;
y = left_eye_s * sin(i) + 56.45;
glVertex2f(x, y);
}
glEnd();
glColor3f(0.0f, 0.0f, 0.0f);
glPointSize(2);
glBegin(GL_POINTS);
for (float i = 0; i <= (2 * p); i += 0.001) { // Left Eye Border
x = 10.0 * cos(i) - 24.56;
y = left_eye_b * sin(i) + 56.45;
glVertex2f(x, y);
}
glEnd();
Here is where I tried to make the eye wink:
void timer(int a) {
/// Simulating Wink
if (left_eye_b >= 1.12)
left_eye_b -= 0.1; // Eye Close
if (left_eye_s >= 1.12)
left_eye_s -= 0.1;
glutTimerFunc(10, timer, 1);
if (left_eye_b <= 10.0)
left_eye_b += 0.1; // Eye Open
if (left_eye_s <= 10.0)
left_eye_s += 0.1;
glutPostRedisplay();
glutTimerFunc(10, timer, 1);
}
Problem statement:
If I remove the 'eye open' part, I works perfectly and the eye closes.
However, I want to use the 'Eye Open' part to make increase the values back and
open the eye again after a few seconds.
Any suggestion about how that can be achieved?

Answer 1

Add a variable that indicates whether the eye will be opened or closed. The value of the variable is 1.0 to open and -1.0 to close:
double eye_change = -1.0;
Change the sign of the variable when the exe has opened or closed:
void timer(int a) {
left_eye_b += 0.1 * eye_change;
left_eye_s += 0.1 * eye_change;
if (left_eye_b <= 1.12)
eye_change = 1.0;
if (left_eye_b >= 10.0)
eye_change = -1.0;
glutPostRedisplay();
glutTimerFunc(10, timer, 1);
}