0003865: game stops responding to keyboard control input

MantisBT - Zandronum
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ID	Project	Category	View Status	Date Submitted	Last Update
0003865	Zandronum	[All Projects] Bug	public	2020-10-14 00:35	2022-03-30 13:09

Reporter	phineas
Assigned To
Priority	normal	Severity	minor	Reproducibility	always
Status	new	Resolution	open
Platform	PC architecture x86-64	OS	Linux Mint 20 Ulyana	OS Version	Linux 5.4.0-47-g
Product Version	3.1-beta
Target Version		Fixed in Version

Summary	0003865: game stops responding to keyboard control input
Description	I selected 3.1 beta though I've not downloaded such yet. This problem exists in both 3.01 and 3.1alpha. I've uploaded a complete description of this bug on my website including a WAD file I used to test. See: 'http://chapsoftware.com/linuxKeyboard.htm [^]' for better description and 'http://chapsoftware.com/Files/forwardTest.wad [^]' for my test wad file.
Steps To Reproduce	Load wad file into game, move forward with up arrow key, turn left or right slightly with left or right arrow key, keep up arrow key down the whole time and watch as you crawl to a stop. Go to end of hall and pick up repeating fire weapons and hold left ctrl key down to fire, see ammo inventory when you stop firing. For me, it's every 14 shots, so stops would be 386, 372, etc.
Additional Information	I may be reached at prfunky-AT-altslashgo.com for questions.
Tags	No tags attached.
Relationships
Attached Files	forwardTest.wad (125,541) 2020-10-14 00:35 /tracker/file_download.php?file_id=2634&type=bug

Issue History
Date Modified	Username	Field	Change
2020-10-14 00:35	phineas	New Issue
2020-10-14 00:35	phineas	File Added: forwardTest.wad
2021-10-07 10:31	phineas	Note Added: 0021781
2022-03-28 19:25	Zardoz	Note Added: 0022171
2022-03-30 13:09	Zardoz	Note Added: 0022175

Notes

It isn't fixed on 3.1 .
Tested on Ubuntu 21.10, using the DEB pagackage from DRDTeams repository.
Looks that it's a bug of SDL 1.2 on Linux :'https://www.bay12games.com/dwarves/mantisbt/view.php?id=7778 [^]'

> With the help of an X protocol tracer (http://www.chiark.greenend.org.uk/~sgtatham/xtruss/ [^]), the X Input Method protocol specification (http://www.x.org/releases/X11R7.7/doc/libX11/XIM/xim.html [^]), and several mugs of tea, I think I've found the cause.

When there's an X Input Method server (IMS) present, as there usually is on Ubuntu, Dwarf Fortress (DF) sends all its keyboard events to the IMS using the XIM protocol. In normal operation, when DF receives a KeyPress event from the X server, it passes it to the IMS in an XIM_FORWARD_EVENT message. The IMS (assuming it's not interested in this event) passes it back in another XIM_FORWARD_EVENT message, this time with the "synchronous" flag set. The "synchronous" flag tells DF that it now needs to send an XIM_SYNC_REPLY message, which it duly does.

When things go wrong, DF sends the XIM_FORWARD_EVENT message as usual, but fails to read the reply message and hence never sends the XIM_SYNC_REPLY message. Instead, it just carries on sending XIM_FORWARD_EVENT messages. It looks like the IMS refuses to deal with these, presumably because it's still waiting for XIM_SYNC_REPLY. This means that the keypresses never get forwarded back to DF, and it sits there unresponsive.

I've found that I can reproduce the bug simply by pressing F11 a few times in rapid succession (about five times in a second is usually enough).

I doubt that DF deliberately interfaces with input methods itself, so presumably this bug is somewhere in the depths of SDL or whatever library is implementing the XIM protocol.

For the record, on my Ubuntu 14.04 LTS system, the version of the SDL packages is "1.2.15-8ubuntu1.1".

With GZDoom looks that this not happens, as uses SDL 2 (and have better support of multiscreen setups as side effect).
As workaround, looks that killing the XIM related daemon should stop the problem (I couldn't totaly verified this, as tthis bug it's pretty random, and sometime only strikes when I'm playing a few hours. )