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Bug 3356

Summary: SDL_GetError returns "Unknown touch device" on first touch on OS X
Product: SDL Reporter: Elisée Maurer <eliseegw+libsdl>
Component: videoAssignee: Sam Lantinga <slouken>
Status: RESOLVED INVALID QA Contact: Sam Lantinga <slouken>
Severity: normal    
Priority: P2    
Version: 2.0.4   
Hardware: x86_64   
OS: Mac OS X 10.11   

Description Elisée Maurer 2016-06-09 14:23:48 UTC 
This is a followup to https://bugzilla.libsdl.org/show_bug.cgi?id=2054

It looks like the patch in https://hg.libsdl.org/SDL/rev/7fc4a8be47a8 missed a fix in SDL_cocoawindow's touchesBeganWithEvent event handler.

That event handler calls SDL_GetNumTouchFingers (as seen here: https://hg.libsdl.org/SDL/file/b82c0f22d22a/src/video/cocoa/SDL_cocoawindow.m#l1000), which in turn calls SDL_GetTouch, triggering SDL_SetError("Unknown touch device");
Comment 1 Elisée Maurer 2016-06-14 05:00:28 UTC 
After reading on other bugs, this comment in particular: https://bugzilla.libsdl.org/show_bug.cgi?id=3321#c3, I'm not 100% sure anymore if SDL error being set spuriously is viewed as a bug or not by the dev team, considering SDL_GetError() does indicate it should not be called unless an SDL function has returned an error value.

So feel free to close if appropriate.
Comment 2 Sam Lantinga 2017-08-12 02:17:25 UTC 
Yes, the SDL error message is only valid if an API function returns an error.

Thanks!