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Bug 2767 - SDL_JoystickInstanceID returns -1 while handling Joystick disconnect event
Summary: SDL_JoystickInstanceID returns -1 while handling Joystick disconnect event
Status: RESOLVED FIXED
Alias: None
Product: SDL
Classification: Unclassified
Component: joystick (show other bugs)
Version: 2.0.3
Hardware: All All
: P2 normal
Assignee: Sam Lantinga
QA Contact: Sam Lantinga
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2014-10-26 01:16 UTC by JKaniarz
Modified: 2017-08-15 01:20 UTC (History)
1 user (show)

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Description JKaniarz 2014-10-26 01:16:14 UTC 
When handling the SDL_JoyDeviceEvent for SDL_JOYDEVICEREMOVED there is no way to match the "which" field to a SDL_Joystick * because SDL_JostickInstanceID() return -1. This requires maintaining a map of SDL_JoystickID to SDL_Joystick* on the user side. 

At a glance, modifying SDL_JoystickInstanceID() to not call SDL_PrivateJoystickValid() would allow the ID to perpetuate after the joystick is closed. As IDs are never reused this shouldn't cause any trouble.

Here is an implementation of my proposal.

SDL_JoystickID
SDL_JoystickInstanceID(SDL_Joystick * joystick)
{
    if (!joystick) {
        return (-1);
    }

    return (joystick->instance_id);
}
Comment 1 Sam Lantinga 2017-08-14 04:45:27 UTC 
All SDL_PrivateJoystickValid() does is check to see if the joystick is NULL.

Can you provide a test case that we can use to see what you mean, and a patch that you've tested that fixes the problem?

Thanks!
Comment 2 JKaniarz 2017-08-15 00:23:29 UTC 
The commit "2015-03-24	Cleanups in the joystick code." removed these lines from SDL_PrivateJoystickValid():

    if ( joystick && joystick->closed )
    {
        valid = 0;
    }


I believe they were causing the issue I was having where the pointer was still good but I was unable to use SDL_JoystickInstanceID() during a SDL_JOYDEVICEREMOVED event. I no longer have the code that was breaking so I'm unable to test but I suspect it was inadvertently fixed.
Comment 3 Sam Lantinga 2017-08-15 01:20:02 UTC 
Oh, okay, thanks!