xdg-desktop-portal-gnome: get working as a xdp backend, on lappy

probably needs some porting to moby before it works there

hosts/common/programs/default.nix

@@ -180,6 +180,7 @@
     ./wvkbd.nix
     ./xarchiver.nix
     ./xdg-desktop-portal.nix
+    ./xdg-desktop-portal-gnome
     ./xdg-desktop-portal-gtk.nix
     ./xdg-desktop-portal-wlr.nix
     ./xdg-terminal-exec.nix

hosts/common/programs/sway/default.nix

@@ -172,6 +172,7 @@ in
       "wireplumber"  # used by sway config
       "wl-clipboard"
       "xdg-desktop-portal"
+      # "xdg-desktop-portal-gnome"
       # xdg-desktop-portal-gtk provides portals for:
       # - org.freedesktop.impl.portal.Access
       # - org.freedesktop.impl.portal.Account
@@ -226,7 +227,7 @@ in
     fs.".config/xdg-desktop-portal/sway-portals.conf".symlink.text = ''
       # portals.conf docs: <https://flatpak.github.io/xdg-desktop-portal/docs/portals.conf.html>
       [preferred]
-      default=wlr;gtk
+      default=wlr;gnome;gtk
     '';
 
     fs.".config/sway/config".symlink.target = pkgs.substituteAll {

hosts/common/programs/xdg-desktop-portal-gnome/default.nix

@@ -0,0 +1,30 @@
+# XXX(2024-08-07): xdg-desktop-portal-gnome has a nicer filechooser than xdg-desktop-portal-gtk.
+# especially, mobile friendly.
+# but starting with 47.0 (unreleased), it will switch to Nautilus. so expect some work in porting.
+{ config, pkgs, ... }:
+let
+  cfg = config.sane.programs.xdg-desktop-portal-gnome;
+in
+{
+  sane.programs.xdg-desktop-portal-gnome = {
+    packageUnwrapped = pkgs.xdg-desktop-portal-gnome.overrideAttrs (base: {
+      patches = (base.patches or []) ++ [
+        ./init_display_no_mutter.diff
+      ];
+    });
+
+    fs.".config/xdg-desktop-portal/portals/gnome.portal".symlink.target =
+      "${cfg.packageUnwrapped}/share/xdg-desktop-portal/portals/gnome.portal";
+    # XXX: overcome bug when manually setting `$XDG_DESKTOP_PORTAL_DIR`
+    #      which causes *.portal files to be looked for in the toplevel instead of under `portals/`
+    fs.".config/xdg-desktop-portal/gnome.portal".symlink.target = "portals/gnome.portal";
+
+    services.xdg-desktop-portal-gnome = {
+      description = "xdg-desktop-portal-gnome backend (provides file chooser and other functionality for xdg-desktop-portal)";
+      dependencyOf = [ "xdg-desktop-portal" ];
+
+      command = "XDG_SESSION_TYPE=wayland ${cfg.package}/libexec/xdg-desktop-portal-gnome";
+      readiness.waitDbus = "org.freedesktop.impl.portal.desktop.gnome";
+    };
+  };
+}

hosts/common/programs/xdg-desktop-portal-gnome/init_display_no_mutter.diff

@@ -0,0 +1,38 @@
+diff --git a/src/externalwindow-wayland.c b/src/externalwindow-wayland.c
+index 4ed62c7..329b9a8 100644
+--- a/src/externalwindow-wayland.c
++++ b/src/externalwindow-wayland.c
+@@ -259,33 +259,6 @@ init_external_window_wayland_display (GError **error)
+   g_autofree char *fd_str = NULL;
+   GdkDisplay *display;
+ 
+-  proxy = org_gnome_mutter_service_channel_proxy_new_for_bus_sync (
+-    G_BUS_TYPE_SESSION,
+-    (G_DBUS_PROXY_FLAGS_DO_NOT_AUTO_START |
+-     G_DBUS_PROXY_FLAGS_DO_NOT_LOAD_PROPERTIES |
+-     G_DBUS_PROXY_FLAGS_DO_NOT_CONNECT_SIGNALS),
+-    "org.gnome.Mutter.ServiceChannel",
+-    "/org/gnome/Mutter/ServiceChannel",
+-    NULL, error);
+-  if (!proxy)
+-    return NULL;
+-
+-  if (!org_gnome_mutter_service_channel_call_open_wayland_service_connection_sync (
+-        proxy,
+-        SERVICE_CLIENT_TYPE_PORTAL_BACKEND,
+-        NULL,
+-        &fd_variant,
+-        &fd_list,
+-        NULL, error))
+-    return NULL;
+-
+-  fd = g_unix_fd_list_get (fd_list, g_variant_get_handle (fd_variant), error);
+-  if (fd < 0)
+-    return NULL;
+-
+-  fd_str = g_strdup_printf ("%d", fd);
+-
+-  g_setenv ("WAYLAND_SOCKET", fd_str, TRUE);
+   gdk_set_allowed_backends ("wayland");
+   display = gdk_display_open (NULL);
+   g_assert (display);