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Bug 3287

Summary: In 2.0.4 Fullscreen/ShowWindow started causing repeat SDL_KEYDOWN on X11
Product: SDL Reporter: Kevin Locke <kevin>
Component: videoAssignee: Sam Lantinga <slouken>
Status: ASSIGNED --- QA Contact: Sam Lantinga <slouken>
Severity: blocker    
Priority: P2 CC: akari, asmith, crobinso, icculus
Version: HG 2.0   
Hardware: x86_64   
OS: Linux   
Attachments: Example program which causes the issue by pressing f
Example program output for changeset 6ab4d6f34afb
Example program output for changeset 1021c9bd0f64

Description Kevin Locke 2016-03-10 21:35:05 UTC 
Created attachment 2391 [details]
Example program which causes the issue by pressing f

Starting in the 2.0.4 release, toggling fullscreen in response to an SDL_KEYDOWN event can cause a repeat SDL_KEYDOWN event to be fired immediately on X11 when the mouse cursor is not inside the (non-fullscreen) window.

I bisected the issue down to changeset 1021c9bd0f64 <http://hg.libsdl.org/SDL/rev/1021c9bd0f64> which introduced handling of the X11 KeymapNotify event.  I presume a KeymapNotify is sent as part of the fullscreen+enter events which causes keydown to be emitted again immediately, but I am not familiar enough with the details to know for sure. 

The attachment sdl-repeat-keydown-fullscreen.c demonstrates the issue on my system.  On 2.0.4, when the window has focus and the user presses 'f' to toggle fullscreen, the window becomes fullscreen then a repeat SDL_KEYDOWN event is emitted, then the window becomes non-fullscreen again.  On 2.0.3 and earlier pressing 'f' toggles fullscreen and no repeat SDL_KEYDOWN event is emitted leaving the window in fullscreen.

The attachment output-1021c9bd0f64.txt has the event output produced for changeset 1021c9bd0f64 and output-6ab4d6f34afb.txt for 6ab4d6f34afb (its parent).

An obvious workaround is to prevent repeat keypresses from toggling fullscreen, and I am making that change to my affected programs, but I assumed the behavior was unintentional and may be worth fixing to save other SDL developers the effort of tracking down this issue.

Thanks,
Kevin
Comment 1 Kevin Locke 2016-03-10 21:35:46 UTC 
Created attachment 2392 [details]
Example program output for changeset 6ab4d6f34afb
Comment 2 Kevin Locke 2016-03-10 21:36:06 UTC 
Created attachment 2393 [details]
Example program output for changeset 1021c9bd0f64
Comment 3 Cole Robinson 2016-05-06 15:18:21 UTC 
qemu is suffering from the same problem, and I can confirm that changeset 1021c9bd0f64 is the culprit for SDL_SetWindowFullscreen

qemu has another similar issue with repeat KEYDOWN events on ShowWindow. I bisected to just a few commits earlier:

  https://hg.libsdl.org/SDL/rev/e55dad50b3ae
  Author: Sam Lantinga <slouken@libsdl.org>
  Date:   Thu May 28 09:52:48 2015 -0700

      Fixed X11 build, added code to print initial modifiers to checkkeys

  https://hg.libsdl.org/SDL/rev/7099e2df7b29
  Author: Sam Lantinga <slouken@libsdl.org>
  Date:   Thu May 28 09:33:47 2015 -0700

      Fixed bug 2736 - X11 doesn't set KMOD_NUM and KMOD_CAPS to system state


Since the commits overlap I assume it's the same root issue.

CCing Ryan C. Gordon who was commenting in the referenced bug #2736
Comment 4 Alex Smith 2016-09-21 10:57:24 UTC 
Also seeing this bug here on 2.0.4 and latest HG. Worked around by ignoring repeat keypresses for fullscreen toggling.
Comment 5 Sam Lantinga 2016-10-01 19:50:39 UTC 
Hey Ryan, can you fix this for 2.0.5? This is a pretty critical regression.
Comment 6 Cole Robinson 2017-10-20 12:48:50 UTC 
The fullscreen issue seems fixed with 2.0.6, at least the SDL2-2.0.6-2 version in Fedora 27. The similar ShowWindow issues I mentioned in Comment #3 are still present though and are the more crippling problem for qemu's SDL usage...
Comment 7 Andrey Alexeyev 2017-11-11 18:20:24 UTC 
This is still not fixed as of SDL 2.0.7 / 2.0.8dev.
Comment 8 Andrey Alexeyev 2017-11-11 18:40:15 UTC 
Seems like user events, at least those generated when handling a legit SDL_KEYDOWN, are affected by this as well. I'll see if I can construct a test case later.