Support xdg-foreign-unstable-v2 protocol

[Copilot]

GTK apps (e.g. Purple Task) warn "Server is missing xdg_foreign support" because Mir lacks zxdg_exporter_v2/zxdg_importer_v2. This breaks cross-process surface parent-child relationships, making buttons like "View source code" and "Report issues" in sandboxed Flutter apps non-functional.

What's new?

• wayland-protocols/xdg-foreign-unstable-v2.xml — protocol definition for zxdg_exporter_v2, zxdg_importer_v2, zxdg_exported_v2, zxdg_imported_v2
• src/server/frontend_wayland/xdg_foreign_unstable_v2.{h,cpp} — implementation:
  • XdgForeignV2Registry: shared registry mapping opaque handle strings to exported WlSurface weak refs, with per-handle importer tracking for destroyed event delivery
  • Export path: ZxdgExportedV2 generates a random 128-bit hex handle, sends it via the handle event
  • Import path: ZxdgImportedV2::set_parent_of() resolves the handle to a scene surface and sets it as the parent via WlSurface::update_surface_spec(); defers via on_scene_surface_created if the exported surface has no scene surface yet
  • Destruction: ZxdgExportedV2 destruction (explicit or surface-driven) drains the importer list and sends destroyed to each
• wayland_default_configuration.cpp — registers the combined exporter+importer global under mw::XdgExporterV2::interface_name; both Wayland globals are created in one call
• zxdg_exporter_v2 added to get_standard_extensions() — enabled by default
• src/wayland/symbols.map — exports all four new wrapper classes under MIRWAYLAND_2.17

How to test

Run a GTK4 application (e.g. any app using GtkFileChooserNative or GtkPrintDialog) under a Mir-based compositor and verify the "Server is missing xdg_foreign support" warning no longer appears. Cross-process dialogs (portals) should now correctly set the parent window relationship.

Checklist

• Tests added and pass
• Adequate documentation added
• (optional) Added Screenshots or videos

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• dl.google.com
  • Triggering command: /usr/lib/apt/methods/https /usr/lib/apt/methods/https --local /home/REDACTED/.ca/var/lib/dpkg/reassemble.deb tar -x _amd64.deb - /usr/bin/dpkg-deb 2.1ubuntu3.2_amdrm d64.deb /usr/local/sbin/-- (dns block)
• gitlab.freedesktop.org
  • Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node /home/REDACTED/work/_temp/ghcca-node/node/bin/node --enable-source-maps /home/REDACTED/work/_temp/copilot-developer-action-main/dist/index.js (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)