Can Allegro update the number of joysticks at runtime? - c++

Question

Is there a way to update the number of joysticks plugged in at run-time other than constantly calling remove_joystick() then install_joystick? This proves to be extremely slow (goes from 60 FPS to around 5).
Allegro 4.2 answers only please...
void Joystick::Update() {
//If joystick input was lost, attempt to reacquire.
if(GetNumJoysticks() == 0) {
throw InputNotAvailableException("Joystick");
}
//If all joysticks were deleted remove input and do nothing.
if(_numjoysticks == 0) {
remove_joystick();
return;
}
//Update state information
if(poll_joystick() < 0) {
throw InputNotAvailableException("Joystick");
}
for(int i = 0; i < _numButtons; ++i) {
_prevButtons[i].b = _curButtons[i].b;
_prevButtons[i].name = _curButtons[i].name;
_curButtons[i].b = joy[_joyNumber].button[i].b;
_curButtons[i].name = joy[_joyNumber].button[i].name;
}
for(int i = 0; i < _numSticks; ++i) {
for(int j = 0; j < joy[_joyNumber].stick[i].num_axis; ++j) {
_prevSticks[i].axis[j].name = _curSticks[i].axis[j].name;
_prevSticks[i].axis[j].pos = _curSticks[i].axis[j].pos;
_prevSticks[i].axis[j].d1 = _curSticks[i].axis[j].d1;
_prevSticks[i].axis[j].d2 = _curSticks[i].axis[j].d2;
_curSticks[i].axis[j].name = joy[_joyNumber].stick[i].axis[j].name;
_curSticks[i].axis[j].pos = joy[_joyNumber].stick[i].axis[j].pos;
_curSticks[i].axis[j].d1 = joy[_joyNumber].stick[i].axis[j].d1;
_curSticks[i].axis[j].d2 = joy[_joyNumber].stick[i].axis[j].d2;
}
_prevSticks[i].flags = _curSticks[i].flags;
_prevSticks[i].name = _curSticks[i].name;
_curSticks[i].flags = joy[_joyNumber].stick[i].flags;
_curSticks[i].name = joy[_joyNumber].stick[i].name;
}
}
int Joystick::GetNumJoysticks() {
remove_joystick();
if(install_joystick(JOY_TYPE_DIRECTX)) {
return 0;
}
return (num_joysticks);
}

Answer 1

The 4.x series does not. The 5.x series does.
You'll have to either listen for native OS events using custom platform specific code (assuming such things exist) and only call the Allegro deinit/init functions when a change is detected, or require the user to initiate joystick refresh manually.
Under Linux, you could inotify_add_watch() /dev/input to check for changes. Looking at the 4.4 Allegro code, looks like you'd want to call the Win32 functions joyGetNumDevs() and joyGetPos(). Something like:
int WIN_MAX_JOYSTICKS = joyGetNumDevs(); // this should never change
JOYINFO ji;
int pluggedin_count = 0;
for (int i = 0; i < WIN_MAX_JOYSTICKS; ++i)
if (joyGetPos(i, &ji) == JOYERR_NOERROR) ++pluggedin_count;
if (pluggedin_count != last_pluggedin_count) /* reinit Allegro */
You'd have to do that every N seconds.
Those joy* functions are Windows functions, so read MSDN docs to learn how to use them.