nixos/tests/keymap: use SLIM theme from nixos/tests/slim

nixos/tests/keymap.nix

@@ -49,6 +49,38 @@ let
     machine.i18n.consoleKeyMap = mkOverride 900 layout;
     machine.services.xserver.layout = mkOverride 900 layout;
     machine.imports = [ ./common/x11.nix extraConfig ];
+    machine.services.xserver.displayManager.slim = {
+      enable = true;
+
+      # Use a custom theme in order to get best OCR results
+      theme = pkgs.runCommand "slim-theme-ocr" {
+        nativeBuildInputs = [ pkgs.imagemagick ];
+      } ''
+        mkdir "$out"
+        convert -size 1x1 xc:white "$out/background.jpg"
+        convert -size 200x100 xc:white "$out/panel.jpg"
+        cat > "$out/slim.theme" <<EOF
+        background_color #ffffff
+        background_style tile
+
+        input_fgcolor #000000
+        msg_color #000000
+
+        session_color #000000
+        session_font Verdana:size=16:bold
+
+        username_msg Username:
+        username_font Verdana:size=16:bold
+        username_color #000000
+        username_x 50%
+        username_y 40%
+
+        password_msg Password:
+        password_x 50%
+        password_y 40%
+        EOF
+      '';
+    };
 
     testScript = ''
       sub waitCatAndDelete ($) {