LXQt Session Settings: Add a way to Ignore Default Environment Variables Per User - or unset them

[Myrddin-Wyllt]

LXQt has a system-wide session.conf which is located in Arch at /usr/share/lxqt/session.conf. This provides some defaults for LXQt, including default environment variables. These variables should be overridden on a per-user basis (i.e., as with most other Linux programs) in ~/.config/lxqt/session.conf. The opposite seems to be occurring (i.e., system-wide session.conf overrides per-user session.conf).

Setting environment variables in LXQt Session Settings should override system-wide defaults as expected.

System-wide default environment variables override per-user session.conf if the lines are blank in the per-user session.conf.

Change the precedence/load order in Session settings in case lines are blank (i.e., add a way to ignore system default environment variables when deleted from per-user session.conf)

This issue was discovered when trying to get gtk3-mushrooms working with LXQt.
lah7/gtk3-classic#15 (comment)

[agaida]

please provide your configs and the not working environment variables.

[agaida]

just tested - works fine for me:

% grep GTK /usr/share/lxqt/session.conf 
GTK_CSD=0
GTK_OVERLAY_SCROLLING=0
---
% grep GTK $HOME/.config/lxqt/session.conf
GTK_CSD=
GTK_OVERLAY_SCROLLING=
---
% env | grep GTK                                                                                                                                                                             
GTK_CSD=
GTK_MODULES=gail:atk-bridge
GTK_OVERLAY_SCROLLING=

q.e.d.

[Myrddin-Wyllt]

Steps to reproduce behavior:

1. Open LXQt Session Settings
2. Delete GTK_CSD and GTK_OVERLAY_SCROLLING
3. Restart session (logout/in or reboot)
4. Wonder why GTK_CSD and GTK_OVERLAY_SCROLLING are still set

~ $ grep GTK /usr/share/lxqt/session.conf 
GTK_CSD=0
GTK_OVERLAY_SCROLLING=0
---
~ $ grep GTK $HOME/.config/lxqt/session.conf 
---
~ $ env | grep GTK
GTK_CSD=0
GTK_MODULES=canberra-gtk-module
GTK_OVERLAY_SCROLLING=0

The problem here is that setting these variables at all causes Client Side Decorations to be enabled in gtk3-mushrooms. I went about removing GTK_CSD and GTK_OVERLAY_SCROLLING lines in /usr/share/lxqt/session.conf as shown below:

[General]
window_manager=openbox
leave_confirmation=true

[Environment]

[Mouse]
cursor_size=18
cursor_theme=whiteglass
acc_factor=20
acc_threshold=10
left_handed=false

[Keyboard]
delay=500
interval=30
beep=false

[Font]
antialias=true
hinting=true
dpi=96

Notice the empty [Environment] section.

After this alteration, my environment looks like thus:

~ $ grep GTK /usr/share/lxqt/session.conf 
~ $ grep GTK $HOME/.config/lxqt/session.conf 
~ $ env | grep GTK
GTK_MODULES=canberra-gtk-module

Due to this, gtk3-mushrooms works now without issue; but this has revealed that the system-wide configuration is overriding per-user configuration for session.conf for environment variables when removed by user (i.e., I'd appreciate a way to ignore these somehow without editing /usr/share/lxqt/session.conf)

[agaida]

and i see no problem in the behaviour - that is exactly what xdg should do - reading configurations in different levels:

0: /usr/share/ - not used
1: /usr/share/lxqt - used (in your case the GTK config is read and valid)
2: /etc/xdg/lxqt - not used
3: /etc/lxqt - not used
4: /$HOME/.config/lxqt/ - used (in your case: you deleted the overrides, so what?)

More verbose: you deleted the GTK* lines so the valid settings from level 1 are valid. in my example i set GTK_CSD to an empty value. The only thing the application can't do right now is to unset some things - also to be expected.

[agaida]

if 0 is really needed to activate and 1 to force all the things - try to blank them '' or -1 might work

EDIT: It might be worth it for the session to implement a mechanism to unset some enviromental variables (at all levels) so i reopen the issue

[agaida]

@tsujan @palinek @luis-pereira @yan12125 - what do you think?

[agaida]

Reference is: lah7/gtk3-classic#15

and Tomasz is very clear about the need of unset GTK_CSD - so a possible solution would be in session.conf:

[Environment]
GTK_CSD=unset
GTK_OVERLAY_SCROLLING=unset

or another value instead of unset. In this case the session should unset the defined environment variable.

[tsujan]

@agaida I didn't follow the discussion but QSettings first searches in the user config file for a key-value pair and only if it isn't found, reads it from the global config file(s). KEY= means a value of false, 0, or empty string depending on whether KEY is a boolen, an integer or a string.

[tsujan]

In other words, if there is a line KEY= in the user config file, the value of KEY won't be read from the global config file but is set to false, 0 , or QString().

[agaida]

@tsujan - and we might have a problem with that. If we read something from the [Environment] section we can only set a environmental variable - but not unset it. That might be a major difference in some cases.

[tsujan]

To unset an environment variable, the code needs to support unsetting.