GLUT timer function - c++

Question

I am trying to get my tokens on a board game to fall slowly. Right now, they fall, but they fall so fast. How could I implement the timer function in my code? Right now I do a loop, that updates the y coordinate of glTranslate. But it is still too fast! the top y is the y coordinate where I press on the screen, and the bottomy is the coordinates of the lowest open spot for a token.
col =0;
double bottomy = 0;
int row = 0;
circlex = (double)x / width ;
circley = (double)y / height ;
row = board.getRow(col) + 1;
bottomy = 500 - (25*row);
for( double topy = y ; topy <= bottomy; topy += 2 ){
glTranslatef(circlex, circley, 0.0f);
circley += .0000000000000000001;
display();
}
r = board.makeMove(col);

Answer 1

You can use glutTimerFunc to execute a function at a regular time period. This has the signature
void glutTimerFunc(unsigned int msecs,
void (*func)(int value),
value);
For example if your drawing function was
void UpdateTokens(int time);
Then you could call an update every 0.5 seconds with the following call (where current_time was the current simulation time)
glutTimerFunc(500, UpdateTokens, current_time);
For more precise timing, I would recommend using <chrono> instead, and performing your timing using things like std::chrono::duration with a std::chrono::steady_clock.

Answer 2

The actual problem here is how glut works. Basically, the user only gets a image presented at the end of the main loop. As long as you do not return from the mouse function, nothing is presented on screen. You can solve the problem by transferring the work to the display function and distribute the translation across multiple frames:
global variables:
double circlex = 0, circley = 0, bottomy = 0;
bool isfalling = false;
int topy = 0;
mouse_func:
if (isfalling == false) //Prevents the user from clicking during an animation
{
circlex = (double)x / width ;
circley = (double)y / height ;
int row = board.getRow(col) + 1;
bottomy = 500 - (25*row);
topy = y;
isfalling = true;
}
display_func:
if (isfalling)
{
circley += .0000000000000000001;
topy += 2;
if (topy >= bottomy)
isfalling = false;
}
glTranslatef(circlex, circley, 0.0f);
display();