qutebrowser: Force Qt to use XCB as QPA platform

This somewhat alleviates the memory leaks, though it also creates new
issues, like problems with context menus on multi-monitor setups.

Meh…

users/simon/modules/qutebrowser/default.nix

@@ -197,6 +197,9 @@ in
       url.default_page = "about:blank";
       url.start_pages = [ "about:blank" ];
 
+      # hack to circumvent memory leak (https://github.com/qutebrowser/qutebrowser/issues/1476)
+      qt.force_platform = "xcb";
+
       # Privacy
       content.cookies.accept = "no-3rdparty";
       content.headers.user_agent = "Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Firefox/91.0";

users/simon/modules/sway/default.nix

@@ -169,6 +169,7 @@ in
         "2" = [
           { app_id = "firefox"; }
           { app_id = "org.qutebrowser.qutebrowser"; }
+          { class = "qutebrowser"; } # workaround for qutebrowser running under Xwayland
           #{ class="Chromium"; }
         ];
         "3" = [