fix(niri): route Zoom screen sharing through xdg-desktop-portal-wlr 0.8.2

niri 26.04 exposes DMA-BUF only, which Zoom 7.2.1 rejects. xdg-desktop-portal-wlr 0.8.2 provides the working SHM path; 0.8.4 regresses Zoom SelectSources.

Assisted-by: DeepSeek Harness (deepseek-flash)

modules/nixos/desktop/xdg.nix

@@ -1,4 +1,9 @@
-{ lib, pkgs, ... }:
+{
+  lib,
+  pkgs,
+  pkgs-stable,
+  ...
+}:
 {
   xdg.terminal-exec = {
     enable = true;
@@ -33,12 +38,13 @@
 
     config = {
       common = {
-        # Use xdg-desktop-portal-gtk for every portal interface...
+        # Prefer the GTK portal for interfaces it implements.
         default = [
           "gtk"
           "gnome"
         ];
       };
+      niri."org.freedesktop.impl.portal.ScreenCast" = "wlr";
     };
 
     # Sets environment variable NIXOS_XDG_OPEN_USE_PORTAL to 1
@@ -50,8 +56,10 @@
 
     # ls /run/current-system/sw/share/xdg-desktop-portal/portals/
     extraPortals = with pkgs; [
-      xdg-desktop-portal-gtk # for provides file picker / OpenURI
-      xdg-desktop-portal-gnome # for screensharing
+      xdg-desktop-portal-gtk # file picker and OpenURI
+      xdg-desktop-portal-gnome # screenshot and remaining GNOME services
+      # xdg-desktop-portal-wlr 0.8.4 regresses Zoom; 0.8.2 works with niri.
+      pkgs-stable.xdg-desktop-portal-wlr
     ];
   };
 
@@ -68,8 +76,8 @@
     overrideStrategy = "asDropin";
     text = ''
       [Unit]
-      After=xdg-desktop-portal.service xdg-desktop-portal-gtk.service xdg-desktop-portal-gnome.service
-      Wants=xdg-desktop-portal.service xdg-desktop-portal-gtk.service xdg-desktop-portal-gnome.service
+      After=xdg-desktop-portal.service xdg-desktop-portal-gtk.service xdg-desktop-portal-gnome.service xdg-desktop-portal-wlr.service
+      Wants=xdg-desktop-portal.service xdg-desktop-portal-gtk.service xdg-desktop-portal-gnome.service xdg-desktop-portal-wlr.service
     '';
   };
 }