Polling Joystick Events

SDL Development
1

Hi Guys, i have a question concerning joysticks.

I was wonder what the best(fastest) way to get(or poll) joysticks event without having a loop.
I am write a simple GUI program to test joysticks and the image below is what i have so far(started a few hours ago).

But my issue is if i used SDL_PollEvent(SDL_Event* event) i will need a loop, and if i use SDL_WaitEvent my program will stop.
So how can i go around this ? I was thinking of using SDL_AddEventWatch or even run the joystick events on a different thread Any Ideas ? Thank you

Joysticks
Joysticks502Ă—530 9.09 KB

2

What’s wrong with a loop?

3

Because i want the program to carry on and not stay in the loop for the time i am using the joystick. and all the approaches, i tried so far will eventually get the program stopped.

4

I don’t think that’s a problem.

If you frequently call something like

SDL_Event ev;
while(SDL_PollEvent(&ev))
{
    // handle events
}

Your program can run normally - because that while-loop frequently runs out of current events and exits, so afterwards your normal program can run on.

This is what games do every frame - and event handling only takes a tiny amount of time per frame, even at 120Hz, so you shouldn’t have to worry that your application becomes unresponsive.

1 Like
5

I understand what you are saying. Now i am having troubling implementing it.

Should i make another function and call it x amount of time i need the joystick inputs ?
PS. Since this is not a game there’s not main loop.
for example:

void Joystick::JoystickInputs(int index)
{
     //make sure the joystick is opened and ready
    if((myJoystick = SDL_JoystickOpen(index)))
    {  
    //Enable the joystick event state
    SDL_JoystickEventState(SDL_ENABLE);
    SDL_Event event;
    
    while(SDL_PollEvent(&event))
    {
        switch(event.type)
        {
        case SDL_KEYDOWN:
   
        case SDL_JOYAXISMOTION:
    
            if(event.jaxis.value < -3200 || event.jaxis.value > 3200)
            {
                if (event.jaxis.axis == 0) //left to right
                {
                    qDebug() << event.jaxis.value;
    
                }
                if(event.jaxis.axis == 1) //up and down
                {
    
                }
            }
          }
    
      }
            
    //close the current opened joystick
    SDL_JoystickClose(myJoystick);
    }
}