Modifier key repeats by itself after pressing/releasing another key

sd427 · 2022-05-10 18:15:08

I've used various window managers over the years, and in the past with other window managers, Alt-F3 was the default keypress to lower a window. I am currently running xfce 4.12 and 4.16 on two different hosts, one Fedora 28 (xfce 4.12) and one CentOS 8 (xfce 4.16). For both instances of xfce, I have changed the keyboard shortcut for Lower Window to be Alt-F3. I like to quickly switch between xfce-terminal windows, by holding down Alt, then pressing F3 over and over, to cycle through the windows. Sometimes I press F3 very quickly, a split second in between distinct key presses, and sometimes not so quickly, but never holding F3 down.

This has always worked fine, until my new setup with xfce 4.16. I can press and hold Alt, then press F3, but I have to quickly release both keys, in order for exactly one window to lower. I can release F3, but if I keep holding Alt down, the Lower Window action then repeats very quickly, cycling through all of the windows under the cursor.

Is there a configuration I am missing, or is this a new behavior, or ???

Last edited by sd427 (2022-05-10 19:53:41)

ToZ · 2022-05-10 22:16:38

Replicating this setup on my my system, I can't replicate the issue. Going to throw the obvious out here - can it be an issue with the keyboard itself? Sticky F3 key? Does the same happen if you change the shortcut to another F key?

Do you have any accessibility features enabled? Settings Manager > Accessibility > Keyboard.

sd427 · 2022-05-10 22:45:27

It might be an issue with Citrix Viewer, not sure. For a few months, I was accessing a different CentOS box, but with Gnome instead of Xfce, via Citrix Viewer, and it did not have the issue. I am accessing the Fedora w/Xfce 4.12 box via xrdp and Xvnc.

I just heard that our shop will be moving away from CentOS, to Ubuntu, due to lack of official support from Citrix for CentOS and/or Xfce. sad

Nothing enabled in Accessibility. And the same behavior occurs with the default shortcut of Shift-Alt-Page Down.

Last edited by sd427 (2022-05-10 22:49:08)

sd427 · 2022-05-12 19:54:20

Specifically for Lower Window, I cleared the existing Ctrl-F3 shortcut, and assigned Ctrl-F3 to the Lower Window function, and that behaves as I expect, I can leave the Ctrl key pressed, and then press/release F3 to cycle through windows by lowering the top most window. But I just saw that a mouse middle-click in the title bar will lower the window, so that is a good workaround.

The Alt key still repeats for all the other Alt-* shortcuts, but I would rarely need to repeat a given operation over and over while holding down Alt.

Still very odd that the Alt key does not repeat by itself (after one press of another key) in any other environment, including Xfce that I access via xrdp/xvnc.

sd427 · 2022-05-12 22:49:01

Ok, I was able to switch to Gnome on the box with the issue. When I configure Gnome with Alt-F3 as the shortcut for lower window, it works as I expect, I can hold down Alt, and hit F3 repeatedly to toggle/rotate between open windows. This requires turning on window focus as "Sloppy", IE, window focus follows the mouse. With Xfce, the weird repeat behavior occurs with either setting, click to focus, or focus follows mouse.

My issue seems to be something that was introduced between Xfce 4.12 and 4.16.

Last edited by sd427 (2022-05-12 22:51:54)

sd427 · 2022-05-12 23:00:24

More details on the versions that are installed:

libxfce4ui.x86_64                   4.16.0-2.el8
libxfce4util.x86_64                 4.16.0-4.el8
xfce-polkit.x86_64                  0.3-3.el8
xfce4-appfinder.x86_64              4.16.1-3.el8
xfce4-panel.x86_64                  4.16.3-1.el8
xfce4-power-manager.x86_64          4.16.0-1.el8
xfce4-pulseaudio-plugin.x86_64      0.4.3-3.el8
xfce4-screensaver.x86_64            4.16.0-3.el8
xfce4-session.x86_64                4.16.0-3.el8
xfce4-settings.x86_64               4.16.2-1.el8
xfce4-terminal.x86_64               0.8.10-2.el8

ToZ · 2022-05-13 00:04:21

I think it would probably be best to create a bug report. I would start with xfwm4. If it doesn't belong there, the developer will move it.

sd427 · 2022-05-13 20:06:58

More findings. In Settings/Keyboard, I disabled Key Repeat. In the test area, holding keys still repeat, I assume because I am accessing a Linux VDI remotely, my local OS is repeating keystrokes. That is a better workaround that restores the behavior I expect.

But, using xev, there is still a curious difference between the Alt key and other modifiers, like Shift and Ctrl. If I press and hold Shift, Ctrl, or Alt by themselves, xev shows me a single KeyPress event, with no KeyRelease event, that is to be expected. If I then press and release any other key, while holding Shift or Ctrl, xev shows both the KeyPress and KeyRelease events for that other key, again, I think that is to be expected. However, for Alt, after the initial press and hold for the Alt key, if I then press and release any other key, xev only shows the KeyPress event for that other key. While still holding Alt, if I again press and release another key, I then see the KeyRelease event for the previous key, immediately followed by the KeyPress event for the new key. That cycle can be repeated any number of times, until I finally release Alt.

Holding the Alt key delays when the KeyRelease event occurs for that other key, that is why xfce then goes into repeat mode.

Last edited by sd427 (2022-05-13 20:09:34)

sd427 · 2022-05-13 20:11:04

Unfortunately, I don't have xev available on my Linux host running Xfce 4.12 to see how it behaves. But on that host with 4.12, xfce does have Key Repeat enabled in the Keyboard settings.

Last edited by sd427 (2022-05-13 20:12:03)

ToZ · 2022-05-14 11:14:19

sd427 wrote:

Holding the Alt key delays when the KeyRelease event occurs for that other key, that is why xfce then goes into repeat mode.

I'm not seeing the same.

Command:

xev | awk -F'[ )]+' '/^KeyPress/ { a[NR+2] } NR in a { printf "%-3s %s\n", $5, $8 }'

Test #1 - Pres/release modifier keys (Alt, Shift, Control)
Result:

64  Alt_L
37  Control_L
50  Shift_L

Test #2 - Press modifier key (Alt, Shift, Control) then 'b', then release
Result:

64  Alt_L
56  b
50  Shift_L
56  B
37  Control_L
56  b

Test #3 - Press modifier key (Alt, Shift, Control), then 'b' 'n' 'm', then release
Result:

64  Alt_L
56  b
57  n
58  m
50  Shift_L
56  B
57  N
58  M
37  Control_L
56  b
57  n
58  m

Key repeat enabled (delay = 500, speed = 20)

ToZ · 2022-05-14 11:35:31

Test #4 - Clear the Alt+F3 shortcut. Press and hold Alt then press and hold F3
Result:

sd427 · 2022-05-17 21:26:40

I am not saying your setup has the same issue, but you won't see what I am talking about regarding xev, since you are not showing both KeyPress and KeyRelease events.

However, I am suspicious that my issue is being caused by something external to xfce, but if so, why does it not cause a similar issue when I access my other Linux host, the one with Xfce 4.12?

sd427 · 2022-05-17 22:29:10

Btw, to run xev and only see keyboard events, instead of using awk, use "xev -event keyboard".

sd427 · 2022-05-17 22:56:48

For test #4, clear any Alt+F3 shortcut. Launch xev. Press and hold Alt, then quickly press and release F3, but keep Alt held down. If you are viewing both KeyPress and KeyRelease events from xev, do you see the KeyRelease event for the F3 key? For me, I do not see the KeyRelease event for F3. While still holding down Alt, press and release F3 one more time. Do you now see a KeyRelease event first, followed by the second F3 KeyPress event? If so, that is what I am seeing. The KeyRelease for the first press of F3 does not appear until you later press and release F3 a second time. When I finally let go of Alt, then I see both the KeyRelease for F3, and the KeyRelease for Alt.

ToZ · 2022-05-17 23:19:05

sd427 wrote:

I am not saying your setup has the same issue, but you won't see what I am talking about regarding xev, since you are not showing both KeyPress and KeyRelease events.
However, I am suspicious that my issue is being caused by something external to xfce, but if so, why does it not cause a similar issue when I access my other Linux host, the one with Xfce 4.12?

This is whats interesting. Plus I'm not connecting via Citrix. I guess what I was trying to demonstrate was that basic Xfce, for me at least, doesn't exhibit this issue. Maybe the issue is a result of both a change in Xfce and the Citrix client. I think you're best step forward is to create a bug report and see what the developer says. He may have some more ideas.

Last edited by ToZ (2022-05-17 23:20:23)

sd427 · 2022-06-06 18:52:14

On our internal company website, I found this info about how Citrix Workspace influences keyboard repeat behavior with modifier keys:

Repeat Ctrl down/up events sent to software on Linux VDA from Citrix Workspace App for Windows when holding down Ctrl key

A: The Linux VDA has been using a new registry to control the function of special keys’ auto-repeat since version 1811. Run this on your CentOS VDA to disable only for modifier keys(KEY_LCtrl, KEY_RCtrl, KEY_Alt, KEY_AltLang, KEY_ShiftL, KEY_ShiftR):

/opt/Citrix/VDA/bin/ctxreg create -k "HKLM\System\CurrentControlSet\Control\Citrix\Xorg" -t "REG_DWORD" -v "SynthesizedKeyUps" -d "0x00000001" --force

Also this info from Citrix:

https://support.citrix.com/article/CTX219689

Last edited by sd427 (2022-06-06 18:54:53)

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#1 2022-05-10 18:15:08

Modifier key repeats by itself after pressing/releasing another key

#2 2022-05-10 22:16:38

Re: Modifier key repeats by itself after pressing/releasing another key

#3 2022-05-10 22:45:27

Re: Modifier key repeats by itself after pressing/releasing another key

#4 2022-05-12 19:54:20

Re: Modifier key repeats by itself after pressing/releasing another key

#5 2022-05-12 22:49:01

Re: Modifier key repeats by itself after pressing/releasing another key

#6 2022-05-12 23:00:24

Re: Modifier key repeats by itself after pressing/releasing another key

#7 2022-05-13 00:04:21

Re: Modifier key repeats by itself after pressing/releasing another key

#8 2022-05-13 20:06:58

Re: Modifier key repeats by itself after pressing/releasing another key

#9 2022-05-13 20:11:04

Re: Modifier key repeats by itself after pressing/releasing another key

#10 2022-05-14 11:14:19

Re: Modifier key repeats by itself after pressing/releasing another key

#11 2022-05-14 11:35:31

Re: Modifier key repeats by itself after pressing/releasing another key

#12 2022-05-17 21:26:40

Re: Modifier key repeats by itself after pressing/releasing another key

#13 2022-05-17 22:29:10

Re: Modifier key repeats by itself after pressing/releasing another key

#14 2022-05-17 22:56:48

Re: Modifier key repeats by itself after pressing/releasing another key

#15 2022-05-17 23:19:05

Re: Modifier key repeats by itself after pressing/releasing another key

#16 2022-06-06 18:52:14

Re: Modifier key repeats by itself after pressing/releasing another key

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