Update doc.

src/content/docs/en/i-i/04.troubleshooting.md

@@ -5,13 +5,46 @@ lastUpdated: 2024-02-24
 ---
 
 :::tip[Tip]
-Press `Ctrl`+`F` to search or see the right sidebar to find your problem
+On this page, press `Ctrl`+`F` to search or see the right sidebar to find your problem
 :::
 
+# Prerequisite for environment variable
+:::note
+We've already given you related notice in `install.sh` but some users ignored it when submitting issues.
+:::
+
+The environment variable `$ILLOGICAL_IMPULSE_VIRTUAL_ENV` must be set properly, else the AGS config will not work.
+
+We've made a default config in `~/.config/hypr/hyprland/env.conf` but you need to make sure the file is included and the config is applied properly. A restart for Hyprland is often required.
+
+You may run `./diagnose` to recheck its value. The output should contain something like this:
+```
+[===diagnose===] declare -p ILLOGICAL_IMPULSE_VIRTUAL_ENV
+declare -x ILLOGICAL_IMPULSE_VIRTUAL_ENV="/home/myself/.local/state/ags/.venv"
+[---SUCCESS---]
+```
+Where `myself` represents the actual username. It should not be something like below:
+```
+[===diagnose===] declare -p ILLOGICAL_IMPULSE_VIRTUAL_ENV
+./diagnose: line 30: declare: ILLOGICAL_IMPULSE_VIRTUAL_ENV: not found
+[---EXIT 1---]
+```
+or
+```
+[===diagnose===] declare -p ILLOGICAL_IMPULSE_VIRTUAL_ENV
+declare -x ILLOGICAL_IMPULSE_VIRTUAL_ENV="\$XDG_STATE_HOME/ags/.venv"
+[---SUCCESS---]
+```
+For the case above, the `$XDG_STATE_HOME` is not expanded, which seems really weird (maybe a Hyprland bug?). In such case you may directly specify its value in `~/.config/hypr/custom/env.conf` as:
+```conf
+env = ILLOGICAL_IMPULSE_VIRTUAL_ENV, /home/myself/.local/state/ags/.venv
+```
+And remember to replace `myself` with actual username.
+
 # Hints
 
 - If there's a problem with something, the first thing to do is to fire up a terminal (`Super`+`T`) and run it. Look for errors/warnings that could be problematic.
-- The bar, sidebars, cheatsheet, etc. are powered by AGS. Open a terminal and run `pkill ags; ags`
+- The bar, sidebars, cheatsheet, etc. are powered by AGS. Open a terminal and run `pkill agsv1; agsv1`.
 
 > Use some common sense. If you can't figure out, [open a discussion](https://github.com/end-4/dots-hyprland/discussions) for help.