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Vim/Gtk3 crashes with BadMatch after Alt-Tabbing to a different desktop #18

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jmacloue opened this issue Jan 8, 2020 · 5 comments
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Vim/Gtk3 crashes with BadMatch after Alt-Tabbing to a different desktop #18

jmacloue opened this issue Jan 8, 2020 · 5 comments
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@ThomasAdam
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help wanted Development help required (see `difficulty:*`) type:bug Something's broken!

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@jmacloue
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jmacloue commented Jan 8, 2020

Possibly related to fvwmorg/fvwm#59

I'm using Slackware64-current, FVWM 2.6.9 and Vim 8.2.0050 - both sufficiently recent though not the bleeding edge. FVWM configured with 4 desktops with 2x2 screens.

gVim is built with Gtk3 GUI and works as expected most of the time - until I try to Alt-Tab to another desktop and WindowList is drawn over gVim window. The xscope output is as follows:

96.50: Client 1 -->   12 bytes
	 ............REQUEST: SetInputFocus
	           revert-to: Parent
	               focus: WIN 04400008
	                time: TIM 00a9b8a0
96.51: 					  32 bytes <-- X11 Server 1
					 ..............ERROR: Match
					        minor opcode: 0000
					        major opcode: 2a
96.51: 					  32 bytes <-- X11 Server 1
					 ..............EVENT: ClientMessage
					              source: SendEvent
					              format: 20
					              window: WIN 04400007
					                type: <WM_PROTOCOLS>

As far as I understand, it happens as follows. WindowList steals the input focus and informs gVim of it by sending a PartiallyObscured NotifyEvent, and as gVim tries to get it back from it - it is no longer visible as another desktop is already shown, which is in line with X11 Proto spec .

According to gVim bug #1392, Gtk3 is already handling this scenario by guarding XSetInputFocus() invocation but somehow it is not enough for FVWM.

Alt-Tabbing over the same desktop works as expected, so I believe it is related to how FVWM implements multiple desktops. Though I don't see such problems with other Gtk3 applications - it looks quite generic so it may surface elsewhere as well, and a fix or a good workaround would certainly be nice: maybe guarding XSetInputFocus() in fvwm/focus.c same as Gtk3 does?

PS Previous gVim version built against Gtk2 does not have this problem - most likely building current gVim against Gtk2 will also "fix" - or, rather, obscure it, but eventually Gtk2 will become obsolete.
@ThomasAdam
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Can you provide me with a backtrace, please? I've tried to reproduce this, but cannot.

@jmacloue
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Can you provide me with a backtrace, please? I've tried to reproduce this, but cannot.

Hm-m, that's strange - I have the same issue consistently on three workstations (all Slackware64-current). Among other things it means that my configuration (almost identical) may be to blame for this, so I need to review it first.

And, of all the possible stack traces, which one would be the most useful?

To my understanding, it could be that gVim receives a BadMatch event actually intended to something /under/ its window: like, root window trying to get focus back and not expecting this to fail. Sorry if it is utter heresy, I'm not a programmer. But if I am correct - the answer may lie in stack traces issued by gVim (and all underlying Gtk3 multi-threaded orchestra), main FVWM process, or FvwmPager. Posting all three would certainly be an overkill.

@ThomasAdam
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And, of all the possible stack traces, which one would be the most useful?

If it's vim which is crashing, that'll definitely help me. Any/all strack traces which are coredumping will help, especially if it's FVWM.

@jmacloue
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Sorry, did too much reading on the matter to post a proper bug report. Let's start from the way to reproduce.

OS details:

  • Platform: Slackware64 14.2 and current
  • FVWM fvwm 2.6.9-2-g749ed65c compiled with: ./configure --prefix=/opt/jmcl --enable-mandoc "CFLAGS=-g -O2 -fPIC" --libdir=/opt/jmcl/lib64 --enable-debug-msgs --disable-perllib
  • Vim 8.2.0110 compiled with: ./configure --prefix=/opt/jmcl/ --enable-multibyte --with-features=huge --with-x --enable-gui=gtk3 "CFLAGS=-g -O2 -fPIC" STRIP=/bin/true
  • Gtk3 3.18.9 (also reproduces with 3.24.13) - from stock Slackware
  • Xorg 1.18.3 (also reproduces with 1.20.6) - from stock Slackware

Steps to reproduce:

  1. Start FVWM with default config: /opt/jmcl/bin/fvm -f /opt/jmcl/share/fvwm/default-config/config
  2. Switch to Desktop 2 and start an xterm
  3. Switch to Desktop 0 and invoke gVim: /opt/jmcl/bin/vim -f -g
  4. With focus in gVim window use Alt-Tab to switch to xterm at Desktop 2
  5. gVim exits with an error:

BadMatch (invalid parameter attributes)
Vim: Got X error
Vim: Finished.

Details

gdb's threads apply all bt after Vim exited is not particularly interesting:

Thread 3 (Thread 0x7fffe962e700 (LWP 3738)):
#0  0x00007ffff47692fd in poll () at /lib64/libc.so.6
fvwmorg/fvwm#1  0x00007ffff5fbf964 in  () at /usr/lib64/libglib-2.0.so.0
fvwmorg/fvwm#2  0x00007ffff5fbfce2 in g_main_loop_run () at /usr/lib64/libglib-2.0.so.0
fvwmorg/fvwm#3  0x00007ffff65db986 in  () at /usr/lib64/libgio-2.0.so.0
fvwmorg/fvwm#4  0x00007ffff5fe5275 in  () at /usr/lib64/libglib-2.0.so.0
fvwmorg/fvwm#5  0x00007fffed7fc684 in start_thread () at /lib64/libpthread.so.0
fvwmorg/fvwm#6  0x00007ffff4774eed in clone () at /lib64/libc.so.6

Thread 2 (Thread 0x7fffe9e2f700 (LWP 3737)):
#0  0x00007ffff47692fd in poll () at /lib64/libc.so.6
fvwmorg/fvwm#1  0x00007ffff5fbf964 in  () at /usr/lib64/libglib-2.0.so.0
fvwmorg/fvwm#2  0x00007ffff5fbfa6c in g_main_context_iteration ()
    at /usr/lib64/libglib-2.0.so.0
fvwmorg/fvwm#3  0x00007ffff5fbfaa9 in  () at /usr/lib64/libglib-2.0.so.0
fvwmorg/fvwm#4  0x00007ffff5fe5275 in  () at /usr/lib64/libglib-2.0.so.0
fvwmorg/fvwm#5  0x00007fffed7fc684 in start_thread () at /lib64/libpthread.so.0
fvwmorg/fvwm#6  0x00007ffff4774eed in clone () at /lib64/libc.so.6

Thread 1 (Thread 0x7ffff7f81900 (LWP 3733)):
#0  0x00007ffff46a7ff0 in exit () at /lib64/libc.so.6
fvwmorg/fvwm#1  0x0000000000518fc8 in mch_exit (r=r@entry=1) at os_unix.c:3360
fvwmorg/fvwm#2  0x0000000000612b59 in getout (exitval=exitval@entry=1) at main.c:1708
fvwmorg/fvwm#3  0x00000000004dfce1 in preserve_exit () at misc1.c:2151
fvwmorg/fvwm#4  0x00000000005160dc in x_error_handler (dpy=<optimized out>, error_event=<optimized out>) at os_unix.c:1550
fvwmorg/fvwm#5  0x00007ffff55f74b5 in _XError () at /usr/lib64/libX11.so.6
fvwmorg/fvwm#6  0x00007ffff55f4537 in  () at /usr/lib64/libX11.so.6
fvwmorg/fvwm#7  0x00007ffff55f45e5 in  () at /usr/lib64/libX11.so.6
fvwmorg/fvwm#8  0x00007ffff55f4e85 in _XEventsQueued () at /usr/lib64/libX11.so.6
fvwmorg/fvwm#9  0x00007ffff55e70e7 in XPending () at /usr/lib64/libX11.so.6
fvwmorg/fvwm#10 0x00007ffff726c7c1 in  () at /usr/lib64/libgdk-3.so.0
fvwmorg/fvwm#11 0x00007ffff5fbf3e1 in g_main_context_check ()
    at /usr/lib64/libglib-2.0.so.0
fvwmorg/fvwm#12 0x00007ffff5fbf908 in  () at /usr/lib64/libglib-2.0.so.0
fvwmorg/fvwm#13 0x00007ffff5fbfa6c in g_main_context_iteration ()
    at /usr/lib64/libglib-2.0.so.0
fvwmorg/fvwm#14 0x00000000005ed144 in gui_mch_wait_for_chars (wtime=4000)
    at gui_gtk_x11.c:6293
fvwmorg/fvwm#15 0x00000000005b7181 in ui_wait_for_chars_or_timer (wtime=4000, wait_func=
    0x5dcb40 <gui_wait_for_chars_3>, interrupted=0x7fffffffd4cc, ignore_input=0) at ui.c:487
fvwmorg/fvwm#16 0x00000000005b8f0c in inchar_loop (buf=buf@entry=0x8c50bc <typebuf_init+60> "", maxlen=maxlen@entry=68, wtime=wtime@entry=-1, tb_change_cnt=tb_change_cnt@entry=9, wait_func=wait_func@entry=
    0x5dcb20 <gui_wait_for_chars_or_timer>, resize_func=resize_func@entry=0x0)
    at ui.c:383
fvwmorg/fvwm#17 0x00000000005dd285 in gui_wait_for_chars_buf (buf=0x8c50bc <typebuf_init+60> "", maxlen=68, wtime=-1, tb_change_cnt=9) at gui.c:2964
fvwmorg/fvwm#18 0x00000000005b8956 in ui_inchar (buf=buf@entry=0x8c50bc <typebuf_init+60> "", maxlen=maxlen@entry=68, wtime=wtime@entry=-1, tb_change_cnt=tb_change_cnt@entry=9) at ui.c:225
fvwmorg/fvwm#19 0x00000000004a8bb1 in inchar (buf=0x8c50bc <typebuf_init+60> "", maxlen=204, wait_time=-1) at getchar.c:3364
fvwmorg/fvwm#20 0x00000000004a9867 in vgetorpeek (advance=advance@entry=1)
    at getchar.c:3143
fvwmorg/fvwm#21 0x00000000004aa92d in vgetc () at getchar.c:1616
fvwmorg/fvwm#22 0x00000000004aadb9 in safe_vgetc () at getchar.c:1850
fvwmorg/fvwm#23 0x00000000004f9589 in normal_cmd (oap=oap@entry=0x7fffffffd900, toplevel=toplevel@entry=1) at normal.c:569
fvwmorg/fvwm#24 0x0000000000613ada in main_loop (cmdwin=cmdwin@entry=0, noexmode=noexmode@entry=0) at main.c:1511
fvwmorg/fvwm#25 0x0000000000615142 in vim_main2 () at main.c:901
fvwmorg/fvwm#26 0x000000000041400e in main (argc=<optimized out>, argv=<optimized out>)
    at main.c:444

(just indicates Vim received an X error which triggered an unclean exit, no indication on what was the request that caused the error)

I have tried using xscope to get the X11 exchange that led to the error - here's the event dump:

xscope-vim.txt.gz

(note an exchange at the end of file - SetInputFocus to parent and subsequent BadMatch - supposedly as the target is not visible)

Must be some kind of race condition as with GDK_SYNCHRONIZE=1 the error doesn't happen, and sometimes (very rare - 5% of time) it takes more than one Alt-Tab to crash Vim. Here's xscope output taken with GDK_SYNCHRONIZE=1 in the same scenario:

xscope-sync.txt.gz

Also when the WindowList menu pops outside of gVim window - Alt-Tab doesn't crash gVim.

Using mouse binding to show WindowList works the same as Alt-Tab: almost always a crash when it paints over gVim, works without a crash if outside gVim.

To re-iterate, nothing I have seen so far indicates that the issue is isolated to Vim, looks more a general Gtk3 problem with FVWM.

PS I have used Xephyr in a window to run the tests: Xephyr -screen 1024x768 :2, with xscope in front of it: xscope -i1 -o2, and set DISPLAY to ":1".

PPS And, no, GDK_SYNCHRONIZE=1 is not a proper fix and not too good a workaround.

@ThomasAdam
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Perfect. Thank you -- I'll try and get round to looking at this soon.

I'm moving this to the fvwm3 repository so I don't lose it -- any fixes I have, I will backport to fvwm2, as it's a common bug in the core.

@ThomasAdam ThomasAdam transferred this issue from fvwmorg/fvwm Jan 13, 2020
@ThomasAdam ThomasAdam added the type:bug Something's broken! label Jan 13, 2020
@ThomasAdam ThomasAdam added this to the post-1.0 milestone May 3, 2020
@ThomasAdam ThomasAdam self-assigned this May 3, 2020
@NsCDE NsCDE mentioned this issue Dec 9, 2020
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@ThomasAdam ThomasAdam removed this from the post-1.0 milestone Dec 20, 2020
@ThomasAdam ThomasAdam added the help wanted Development help required (see `difficulty:*`) label Dec 20, 2020
@NsCDE NsCDE mentioned this issue Mar 17, 2021
Closed
@ThomasAdam ThomasAdam moved this to To do in FVWM3 Sep 18, 2022
@ThomasAdam ThomasAdam added this to FVWM3 Sep 18, 2022
@github-project-automation github-project-automation bot moved this from To do to Done in FVWM3 Oct 28, 2024
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