Update sdist/nix/README.md

sdist/nix/README.md

@@ -3,8 +3,9 @@
 - See also [Install scripts | illogical-impulse](https://ii.clsty.link/en/dev/inst-script/)
 - See also [#1061](https://github.com/end-4/dots-hyprland/issues/1061)
 
-NOTE: The sdist/nix is not for NixOS but every distro, using Nix and home-manager.
+**NOTE: The sdist/nix is not for NixOS but every distro, using Nix and home-manager.**
 
+## plan
 TODO:
 Write a proper `flake.nix` and optionally `home.nix` and other files under `./sdist/nix/iiqs-hm/` to install all dependencies that `./sdist/arch/install-deps.sh` does. (**excluding** the screenlock)
 
@@ -23,3 +24,74 @@ Note that this script must be idempotent.
 
 TODO:
 Write guide for people already use nix, so they can manually grab things from this repo to their own Nix/home-manager configurations to install the dependencies.
+
+## Attentions
+### PAM
+On non-NixOS distros, programs using PAM (typically screen locker) will not work if installed via Nix, so user has to use their own distro's package for the screen lock.
+
+- One problem is that Debian(-based) distros use modified version of PAM which supports `@include` directive in `/etc/pam.d` config files but the PAM from Nix does not support it, see [this comment](https://github.com/NixOS/nixpkgs/issues/128523#issuecomment-1086106614).
+- Another problem is the location of a suid helper binary that is necessary, see [this comment](https://github.com/end-4/dots-hyprland/issues/1061#issuecomment-3403195230).
+
+The problem could be solved by using the system-provided libpam instead.
+
+See also https://github.com/caelestia-dots/shell/issues/668
+
+### NixGL
+On non-NixOS distros, packages installed via home-manager have problem accessing GPU, especially Hyprland because it requires GPU acceleration to launch. `nixGL` should be used to address the problem. Example code in `home.nix`:
+```
+{ config, lib, pkgs, nixgl, ... }:
+{
+  nixGL.packages = nixgl.packages;
+  nixGL.defaultWrapper = "mesa";
+  
+  # other lines not showed here ...
+
+  home = {
+    packages = with pkgs; [
+      cowsay           # normal packages that does not need nixGL
+      lolcat
+      # other lines not showed here ...
+    ]
+    ++ [
+    (config.lib.nixGL.wrap pkgs.firefox-bin)
+    (config.lib.nixGL.wrap pkgs.hyprland)
+    # other lines not showed here ...
+    ];
+    # other lines not showed here ...
+  };
+}
+```
+
+And in `flake.nix`:
+```nix
+{
+  inputs = {
+    nixpkgs.url = "nixpkgs/nixos-25.05";
+    home-manager = {
+      url = "github:nix-community/home-manager/release-25.05";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+    hyprland = {
+      url = "github:hyprwm/Hyprland";
+    };
+    nixgl.url = "github:nix-community/nixGL";
+  };
+  outputs = { nixpkgs, home-manager, nixgl, ... }:
+    let
+      lib = nixpkgs.lib;
+      system = "x86_64-linux";
+      pkgs = import nixpkgs {
+        inherit system;
+        overlays = [ nixgl.overlay ];
+      };
+    in {
+      homeConfigurations = {
+        mydot = home-manager.lib.homeManagerConfiguration {
+          inherit pkgs;
+          extraSpecialArgs = { inherit nixgl; };
+          modules = [ ./home.nix ];
+          };
+        };
+      };
+}
+```