1 files changed, 32 insertions, 13 deletions
diff --git a/nixos/modules/services/x11/display-managers/sddm.nix b/nixos/modules/services/x11/display-managers/sddm.nix
index 2d4cb8aa20a5..426b899586f5 100644
--- a/nixos/modules/services/x11/display-managers/sddm.nix
+++ b/nixos/modules/services/x11/display-managers/sddm.nix
@@ -19,17 +19,6 @@ let
 
   Xsetup = pkgs.writeScript "Xsetup" ''
     #!/bin/sh
-
-    # Prior to Qt 5.9.2, there is a QML cache invalidation bug which sometimes
-    # strikes new Plasma 5 releases. If the QML cache is not invalidated, SDDM
-    # will segfault without explanation. We really tore our hair out for awhile
-    # before finding the bug:
-    # https://bugreports.qt.io/browse/QTBUG-62302
-    # We work around the problem by deleting the QML cache before startup. It
-    # will be regenerated, causing a small but perceptible delay when SDDM
-    # starts.
-    rm -fr /var/lib/sddm/.cache/sddm-greeter/qmlcache
-
     ${cfg.setupScript}
   '';
 
@@ -65,6 +54,10 @@ let
     XauthPath=${pkgs.xorg.xauth}/bin/xauth
     DisplayCommand=${Xsetup}
     DisplayStopCommand=${Xstop}
+    EnableHidpi=${if cfg.enableHidpi then "true" else "false"}
+
+    [Wayland]
+    EnableHidpi=${if cfg.enableHidpi then "true" else "false"}
 
     ${optionalString cfg.autoLogin.enable ''
     [Autologin]
@@ -95,6 +88,17 @@ in
         '';
       };
 
+      enableHidpi = mkOption {
+        type = types.bool;
+        default = true;
+        description = ''
+          Whether to enable automatic HiDPI mode.
+          </para>
+          <para>
+          Versions up to 0.17 are broken so this only works from 0.18 onwards.
+        '';
+      };
+
       extraConfig = mkOption {
         type = types.lines;
         default = "";
@@ -253,7 +257,7 @@ in
       '';
     };
 
-    users.extraUsers.sddm = {
+    users.users.sddm = {
       createHome = true;
       home = "/var/lib/sddm";
       group = "sddm";
@@ -262,7 +266,7 @@ in
 
     environment.etc."sddm.conf".source = cfgFile;
 
-    users.extraGroups.sddm.gid = config.ids.gids.sddm;
+    users.groups.sddm.gid = config.ids.gids.sddm;
 
     environment.systemPackages = [ sddm ];
     services.dbus.packages = [ sddm ];
@@ -270,5 +274,20 @@ in
     # To enable user switching, allow sddm to allocate TTYs/displays dynamically.
     services.xserver.tty = null;
     services.xserver.display = null;
+
+    systemd.tmpfiles.rules = [
+      # Prior to Qt 5.9.2, there is a QML cache invalidation bug which sometimes
+      # strikes new Plasma 5 releases. If the QML cache is not invalidated, SDDM
+      # will segfault without explanation. We really tore our hair out for awhile
+      # before finding the bug:
+      # https://bugreports.qt.io/browse/QTBUG-62302
+      # We work around the problem by deleting the QML cache before startup.
+      # This was supposedly fixed in Qt 5.9.2 however it has been reported with
+      # 5.10 and 5.11 as well. The initial workaround was to delete the directory
+      # in the Xsetup script but that doesn't do anything.
+      # Instead we use tmpfiles.d to ensure it gets wiped.
+      # This causes a small but perceptible delay when SDDM starts.
+      "e ${config.users.users.sddm.home}/.cache - - - 0"
+    ];
   };
 }