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Bug 5097 - Emscripten: connecting and disconnecting real-joysticks can close virtual joysticks
Summary: Emscripten: connecting and disconnecting real-joysticks can close virtual joy...
Status: NEW
Alias: None
Product: SDL
Classification: Unclassified
Component: joystick (show other bugs)
Version: HG 2.0
Hardware: Other Other
: P2 normal
Assignee: Sam Lantinga
QA Contact: Sam Lantinga
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2020-04-18 15:52 UTC by David Ludwig
Modified: 2020-04-18 16:13 UTC (History)
1 user (show)

See Also:

Attachments
Fix #1: use SDL_GetNextJoystickInstanceID() for alloc'ing joystick-ids in Emscripten joystick backend (2.55 KB, patch)
2020-04-18 16:13 UTC, David Ludwig 		Details | Diff
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Description David Ludwig 2020-04-18 15:52:40 UTC 
SDL2's Emscripten joystick backend appears to be allocating SDL_JoystickIDs using its own, private, integer counter, rather than through SDL_GetNextJoystickInstanceID().  This can have harmful effects if and when a virtual joystick is attached (using functionality new to SDL 2.0.13+).  For example, when connecting and disconnecting real game-controller hardware, Emscripten's joystick backend can assign an SDL_Joystick a SDL_JoystickID that is being used by an active virtual-joystick (which uses a different, joystick-subsystem backend).
Comment 1 David Ludwig 2020-04-18 16:13:38 UTC 
Created attachment 4310 [details]
Fix #1: use SDL_GetNextJoystickInstanceID() for alloc'ing joystick-ids in Emscripten joystick backend

Here is an attempt at a fix.  It seems to work fine for me, however it could, perhaps, use more testing, and maybe review by someone more familiar with SDL2's Emscripten joystick backend.