Function PollJoysticks

source/application.cpp:1646–1688

void PollJoysticks()
// It's best to call this function only directly from MsgSleep() or when there is an instance of
// MsgSleep() closer on the call stack than the nearest dialog's message pump (e.g. MsgBox).
// This is because events posted to the thread indirectly by us here would be discarded or mishandled
// by a non-standard (dialog) message pump.
//
// Polling the joysticks this way rather than using joySetCapture() is preferable for several reasons:
// 1) I believe joySetCapture() internally polls the joystick anyway, via a system timer, so it probably
//    doesn't perform much better (if at all) than polling "manually".
// 2) joySetCapture() only supports 4 buttons;
// 3) joySetCapture() will fail if another app is already capturing the joystick;
// 4) Even if the joySetCapture() succeeds, other programs (e.g. older games), would be prevented from
//    capturing the joystick while the script in question is running.
{
	// Even if joystick hotkeys aren't currently allowed to fire, poll it anyway so that hotkey
	// messages can be buffered for later.
	static DWORD sButtonsPrev[MAX_JOYSTICKS] = {0}; // Set initial state to "all buttons up for all joysticks".
	JOYINFOEX jie;
	DWORD buttons_newly_down;

	for (int i = 0; i < MAX_JOYSTICKS; ++i)
	{
		if (!Hotkey::sJoystickHasHotkeys[i])
			continue;
		// Reset these every time in case joyGetPosEx() ever changes them. Also, most systems have only one joystick,
		// so this code will hardly ever be executed more than once (and sometimes zero times):
		jie.dwSize = sizeof(JOYINFOEX);
		jie.dwFlags = JOY_RETURNBUTTONS; // vs. JOY_RETURNALL
		if (joyGetPosEx(i, &jie) != JOYERR_NOERROR) // Skip this joystick and try the others.
			continue;
		// The exclusive-or operator determines which buttons have changed state.  After that,
		// the bitwise-and operator determines which of those have gone from up to down (the
		// down-to-up events are currently not significant).
		buttons_newly_down = (jie.dwButtons ^ sButtonsPrev[i]) & jie.dwButtons;
		sButtonsPrev[i] = jie.dwButtons;
		if (!buttons_newly_down)
			continue;
		// See if any of the joystick hotkeys match this joystick ID and one of the buttons that
		// has just been pressed on it.  If so, queue up (buffer) the hotkey events so that they will
		// be processed when messages are next checked:
		Hotkey::TriggerJoyHotkeys(i, buttons_newly_down);
	}
}