From 446293584f10d56b91368f500c022f7a93edbe2c Mon Sep 17 00:00:00 2001
From: Mel Bourgeois <mason.bourgeois@gmail.com>
Date: Mon, 29 Apr 2024 19:37:24 -0500
Subject: [PATCH] nixgl: add module

This module enables wrapping programs which require access to libGL
with nixGL on non-NixOS systems.
---
 modules/misc/news.nix  | 12 ++++++++
 modules/misc/nixgl.nix | 64 ++++++++++++++++++++++++++++++++++++++++++
 modules/modules.nix    |  1 +
 3 files changed, 77 insertions(+)
 create mode 100644 modules/misc/nixgl.nix

diff --git a/modules/misc/news.nix b/modules/misc/news.nix
index 8f9a77cfa..801391cc2 100644
--- a/modules/misc/news.nix
+++ b/modules/misc/news.nix
@@ -1801,6 +1801,18 @@ in {
           itself.
         '';
       }
+
+      {
+        time = "2024-10-25T08:18:30+00:00";
+        condition = hostPlatform.isLinux;
+        message = ''
+          A new module is available: 'nixGL'.
+
+          NixGL solve the "OpenGL" problem with nix. The 'nixGL' module provides
+          integration of NixGL into Home Manager. See the "GPU on non-NixOS
+          systems" section in the Home Manager mantual for more.
+        '';
+      }
     ];
   };
 }
diff --git a/modules/misc/nixgl.nix b/modules/misc/nixgl.nix
new file mode 100644
index 000000000..b6cff7cc0
--- /dev/null
+++ b/modules/misc/nixgl.nix
@@ -0,0 +1,64 @@
+{ config, lib, pkgs, ... }:
+
+let cfg = config.nixGL;
+in {
+  meta.maintainers = [ lib.maintainers.smona ];
+
+  options.nixGL.prefix = lib.mkOption {
+    type = lib.types.str;
+    default = "";
+    example = lib.literalExpression
+      ''"''${inputs.nixGL.packages.x86_64-linux.nixGLIntel}/bin/nixGLIntel"'';
+    description = ''
+      The nixGL command that `lib.nixGL.wrap` should wrap packages with.
+      This can be used to provide libGL access to applications on non-NixOS systems.
+
+      Some packages are wrapped by default (e.g. kitty, firefox), but you can wrap other packages
+      as well, with `(config.lib.nixGL.wrap <package>)`. If this option is empty (the default),
+      then `lib.nixGL.wrap` is a no-op.
+    '';
+  };
+
+  config = {
+    lib.nixGL.wrap = # Wrap a single package with the configured nixGL wrapper
+      pkg:
+
+      if cfg.prefix == "" then
+        pkg
+      else
+      # Wrap the package's binaries with nixGL, while preserving the rest of
+      # the outputs and derivation attributes.
+        (pkg.overrideAttrs (old: {
+          name = "nixGL-${pkg.name}";
+
+          # Make sure this is false for the wrapper derivation, so nix doesn't expect
+          # a new debug output to be produced. We won't be producing any debug info
+          # for the original package.
+          separateDebugInfo = false;
+
+          buildCommand = ''
+            set -eo pipefail
+
+            ${
+            # Heavily inspired by https://stackoverflow.com/a/68523368/6259505
+            pkgs.lib.concatStringsSep "\n" (map (outputName: ''
+              echo "Copying output ${outputName}"
+              set -x
+              cp -rs --no-preserve=mode "${
+                pkg.${outputName}
+              }" "''$${outputName}"
+              set +x
+            '') (old.outputs or [ "out" ]))}
+
+            rm -rf $out/bin/*
+            shopt -s nullglob # Prevent loop from running if no files
+            for file in ${pkg.out}/bin/*; do
+              echo "#!${pkgs.bash}/bin/bash" > "$out/bin/$(basename $file)"
+              echo "exec -a \"\$0\" ${cfg.prefix} $file \"\$@\"" >> "$out/bin/$(basename $file)"
+              chmod +x "$out/bin/$(basename $file)"
+            done
+            shopt -u nullglob # Revert nullglob back to its normal default state
+          '';
+        }));
+  };
+}
diff --git a/modules/modules.nix b/modules/modules.nix
index ba8414721..3b4985083 100644
--- a/modules/modules.nix
+++ b/modules/modules.nix
@@ -31,6 +31,7 @@ let
     ./misc/gtk.nix
     ./misc/lib.nix
     ./misc/news.nix
+    ./misc/nixgl.nix
     ./misc/numlock.nix
     ./misc/pam.nix
     ./misc/qt.nix