Can not input parenthesis in VM when using `virt-manager`

[ChipZhang]

Host OS is Ubuntu 20.04 desktop. x11vnc and virt-manager are installed in the host OS.

When connecting from another PC using remmina VNC plugin, I can not type parenthesis shift+9/0 into VM, other keys are OK, including 9, 0 themselves. But it works fine for a text editor app in the host. It also works fine if using physical keyboard to input parenthesis in VM.

My x11vnc is started with arguments: /usr/bin/x11vnc -nevershared -forever -auth /var/run/lightdm/root/:0 -display WAIT:0 -rfbport 5900 -rfbauth /etc/x11vnc-passwd -repeat -nomodtweak -clear_mods -clear_keys

I've also tries many other arguments combinations -modtweak, -nomodtweak, -xkb, -noxkb, -capslock, ... None is woking!

version: x11vnc: 0.9.16 lastmod: 2019-01-05

Debug log:

08/05/2024 16:46:50 # keyboard(down, 0xffe1 "Shift_L") uip=0  177615.1816
08/05/2024 16:46:50 keyboard(): KeySym 0xffe1 "Shift_L" -> KeyCode 0x32
08/05/2024 16:46:50 XTestFakeKeyEvent(dpy, keycode=0x32 "Shift_L", down)
08/05/2024 16:46:50 calling XTestFakeKeyEvent(50, 1)  177615.1818
08/05/2024 16:46:50 # keyboard(down, 0x28 "parenleft") uip=0  177615.3275
08/05/2024 16:46:50 keyboard(): KeySym 0x28 "parenleft" -> KeyCode 0xbb
08/05/2024 16:46:50 XTestFakeKeyEvent(dpy, keycode=0xbb "parenleft", down)
08/05/2024 16:46:50 calling XTestFakeKeyEvent(187, 1)  177615.3280
08/05/2024 16:46:50 # keyboard(up, 0x28 "parenleft") uip=0  177615.4892
08/05/2024 16:46:50 keyboard(): KeySym 0x28 "parenleft" -> KeyCode 0xbb
08/05/2024 16:46:50 XTestFakeKeyEvent(dpy, keycode=0xbb "parenleft", up)
08/05/2024 16:46:50 calling XTestFakeKeyEvent(187, 0)  177615.4894
08/05/2024 16:46:50 # keyboard(up, 0xffe1 "Shift_L") uip=0  177615.6319
08/05/2024 16:46:50 keyboard(): KeySym 0xffe1 "Shift_L" -> KeyCode 0x32
08/05/2024 16:46:50 XTestFakeKeyEvent(dpy, keycode=0x32 "Shift_L", up)
08/05/2024 16:46:50 calling XTestFakeKeyEvent(50, 0)  177615.6322

[hsiang0100]

Issue Cause

The KeySym "parenleft" is mapped to two keycodes (18 and 187). You can verify this using "xmodmap -pk". Currently, x11vnc prioritizes the mapping with no modifiers, which results in an unexpected keycode (187) being returned.

Solutions

1. Filter Specific Keycodes in x11vnc: Start x11vnc with the -skip_keycodes option to filter out specific keycodes: x11vnc -skip_keycodes 187,188

2. Modify xmodmap: Update the keycode mappings using xmodmap.

3. Adjust x11vnc Source Code: Modify the x11vnc source code to handle KeySym-to-keycode conversion.

You can choose the solution that best fits your needs.

[ChipZhang]

@hsiang0100

Thanks for your reply!

But adding parameters -skip_keycodes 187,188 still does not solve my problem.

I should point out that, it is very weird, the parenthesis is OK for all apps, except for virt-manager.

Output for command xmodmap -pk|grep -E '\b(18|187)\b':

     18    	0x0039 (9)	0x0028 (parenleft)	0x0039 (9)	0x0028 (parenleft)	
    187    	0x0028 (parenleft)	0x0000 (NoSymbol)	0x0028 (parenleft)	

I am newbie in terms of x11vnc and X11 keyboard mechanisms under the hood. Does this output mean The KeySym "parenleft" is mapped to two keycodes (18 and 187)., as you mentioned?

[ChipZhang]

@hsiang0100

I finally got it working. I must use -skip_keycodes 187,188 combined with -modtweak, to make parenthesis working in VM, both params are required. But -modtweak introduces other problems. It's painful.

Thank you!

[hsiang0100]

What problems you encounter~?