nixos/extra-layouts: avoid all rebuilds

Just setting the XKB_CONFIG_ROOT should be enough, so we don't need to
rebuild the xserver, xkbcomp and other packages anymore.
However, the variable has to be passed explicitely to scripts running at
build time: in particular to xkbvalidate and xkb-console-keymap.

3 files changed, 14 insertions, 47 deletions

diff --git a/nixos/modules/config/console.nix b/nixos/modules/config/console.nix
index c5150305bd8..98f942ee63f 100644
--- a/nixos/modules/config/console.nix
+++ b/nixos/modules/config/console.nix
@@ -116,7 +116,11 @@ in
     { console.keyMap = with config.services.xserver;
         mkIf cfg.useXkbConfig
           (pkgs.runCommand "xkb-console-keymap" { preferLocalBuild = true; } ''
-            '${pkgs.ckbcomp}/bin/ckbcomp' -model '${xkbModel}' -layout '${layout}' \
+            '${pkgs.ckbcomp}/bin/ckbcomp' \
+              ${optionalString (config.environment.sessionVariables ? XKB_CONFIG_ROOT)
+                "-I${config.environment.sessionVariables.XKB_CONFIG_ROOT}"
+              } \
+              -model '${xkbModel}' -layout '${layout}' \
               -option '${xkbOptions}' -variant '${xkbVariant}' > "$out"
           '');
     }
diff --git a/nixos/modules/services/x11/extra-layouts.nix b/nixos/modules/services/x11/extra-layouts.nix
index 0e2edc6a530..b1c4e04975f 100644
--- a/nixos/modules/services/x11/extra-layouts.nix
+++ b/nixos/modules/services/x11/extra-layouts.nix
@@ -79,6 +79,10 @@ let
     };
   };
 
+  xkb_patched = pkgs.xorg.xkeyboardconfig_custom {
+    layouts = config.services.xserver.extraLayouts;
+  };
+
 in
 
 {
@@ -114,58 +118,14 @@ in
 
   config = mkIf (layouts != { }) {
 
-    # We don't override xkeyboard_config directly to
-    # reduce the amount of packages to be recompiled.
-    # Only the following packages are necessary to set
-    # a custom layout anyway:
-    nixpkgs.overlays = lib.singleton (self: super: {
-
-      xkb_patched = self.xorg.xkeyboardconfig_custom {
-        layouts = config.services.xserver.extraLayouts;
-      };
-
-      xorg = super.xorg // {
-        xorgserver = super.xorg.xorgserver.overrideAttrs (old: {
-          configureFlags = old.configureFlags ++ [
-            "--with-xkb-bin-directory=${self.xorg.xkbcomp}/bin"
-            "--with-xkb-path=${self.xkb_patched}/share/X11/xkb"
-          ];
-        });
-
-        setxkbmap = super.xorg.setxkbmap.overrideAttrs (old: {
-          postInstall =
-            ''
-              mkdir -p $out/share
-              ln -sfn ${self.xkb_patched}/etc/X11 $out/share/X11
-            '';
-        });
-
-        xkbcomp = super.xorg.xkbcomp.overrideAttrs (old: {
-          configureFlags = [ "--with-xkb-config-root=${self.xkb_patched}/share/X11/xkb" ];
-        });
-
-      };
-
-      ckbcomp = super.ckbcomp.override {
-        xkeyboard_config = self.xkb_patched;
-      };
-
-      xkbvalidate = super.xkbvalidate.override {
-        libxkbcommon = self.libxkbcommon.override {
-          xkeyboard_config = self.xkb_patched;
-        };
-      };
-
-    });
-
     environment.sessionVariables = {
       # runtime override supported by multiple libraries e. g. libxkbcommon
       # https://xkbcommon.org/doc/current/group__include-path.html
-      XKB_CONFIG_ROOT = "${pkgs.xkb_patched}/etc/X11/xkb";
+      XKB_CONFIG_ROOT = "${xkb_patched}/etc/X11/xkb";
     };
 
     services.xserver = {
-      xkbDir = "${pkgs.xkb_patched}/etc/X11/xkb";
+      xkbDir = "${xkb_patched}/etc/X11/xkb";
       exportConfiguration = config.services.xserver.displayManager.startx.enable
         || config.services.xserver.displayManager.sx.enable;
     };
diff --git a/nixos/modules/services/x11/xserver.nix b/nixos/modules/services/x11/xserver.nix
index ad9bd88f98a..ee190ac3cc4 100644
--- a/nixos/modules/services/x11/xserver.nix
+++ b/nixos/modules/services/x11/xserver.nix
@@ -738,6 +738,9 @@ in
       nativeBuildInputs = with pkgs.buildPackages; [ xkbvalidate ];
       preferLocalBuild = true;
     } ''
+      ${optionalString (config.environment.sessionVariables ? XKB_CONFIG_ROOT)
+        "export XKB_CONFIG_ROOT=${config.environment.sessionVariables.XKB_CONFIG_ROOT}"
+      }
       xkbvalidate "$xkbModel" "$layout" "$xkbVariant" "$xkbOptions"
       touch "$out"
     '');