feat: add GET_PRIVATE_LINK socket command for Wayland clipboard support

[DeepDiver1975]

Problem

On native Wayland sessions the ownCloud daemon has no compositor surface.
QApplication::clipboard()->setText() requires a valid Wayland wl_data_device serial
from a recent input event, but a tray-only app (system tray via StatusNotifierItem)
never receives seat events and so never has one. The compositor silently drops the
clipboard write. Copy private link to clipboard is broken for all users on Wayland.

Qt 6.9+ added zwlr-data-control support as a partial fix (QT_WAYLAND_USE_DATA_CONTROL=1),
but it requires an environment variable and only works on KDE/wlroots compositors — not on
GNOME/Mutter, which is the primary affected environment.

Solution

Add GET_PRIVATE_LINK:<file> → PRIVATE_LINK:<url> to the socket protocol. File manager
extensions that run inside processes with a real Wayland surface (Nautilus, Dolphin) can
request the URL and write to the clipboard themselves.

The command reuses fetchPrivateLinkUrlHelper() — ~7 lines of new production code.
COPY_PRIVATE_LINK is unchanged for X11 and for extensions that do not yet use the new
command.

Related

• fix: Wayland clipboard support for COPY_PRIVATE_LINK client-desktop-shell-integration-nautilus#11 (closed — this PR is the correct server-side fix)
• Nautilus extension fix: fix: use GET_PRIVATE_LINK socket command for Wayland clipboard support client-desktop-shell-integration-nautilus#12
• Dolphin plugin fix: fix: use GET_PRIVATE_LINK socket command for Wayland clipboard support client-desktop-shell-integration-dolphin#5

Backward compatibility

Scenario	Behaviour
New client + new Nautilus/Dolphin, Wayland	✅ Fixed
New client + new Nautilus/Dolphin, X11	✅ Unchanged
Old client + new Nautilus, Wayland	Graceful: GET_PRIVATE_LINK times out (3 s), falls through to COPY_PRIVATE_LINK
New client + old Nautilus/Dolphin, Wayland	Unchanged (old extension still sends COPY_PRIVATE_LINK)

[update-docs]

Thanks for opening this pull request! The maintainers of this repository would appreciate it if you would create a changelog item based on your changes.

[dj4oC]

Adds a new GET_PRIVATE_LINK socket-API command so shell-integration extensions can retrieve a private-link URL directly (for platforms where clipboard write is unreliable, e.g. Wayland), plus a new unit test.

Findings

Security: Clean — reuses the existing fetchPrivateLinkUrlHelper already used by COPY_PRIVATE_LINK/EMAIL_PRIVATE_LINK; any peer already authorized to reach the socket can already obtain this URL via those commands, so this adds a delivery mechanism rather than new attack surface. The socket's peer-auth model (0700 runtime-dir socket / per-user named pipe) is untouched. The new OWNCLOUDGUI_EXPORT on socketApiSocketPath() is a visibility annotation for the test binary, not a new external interface.

Stability: Block — command_GET_PRIVATE_LINK captures a raw SocketListener *listener pointer in a lambda passed to the asynchronous fetchPrivateLinkUrlHelper (a PROPFIND round-trip). Every existing V1 handler only touches listener synchronously; if the socket disconnects before the async reply arrives, _listeners.remove(socket) drops the last QSharedPointer<SocketListener> and frees the object, and the pending lambda's listener->sendMessage(...) becomes a use-after-free. Recommend retaining a QSharedPointer<SocketListener> by value in the capture (as SocketApiJobV2 already does for exactly this problem) instead of a raw pointer, or implementing this as a V2 command.

Performance: Clean — same async, non-blocking pattern as sibling commands; no new UI-thread blocking or polling.

Coverage: Gap — the two added tests cover the happy path and "file not synced," but not: capability disabled (privateLinkPropertyAvailable() == false, which silently no-ops), PROPFIND failure/timeout, or an empty privatelink property — all of which currently collapse to the same silent "no message sent" as the tested negative case. Since this directly backs Wayland clipboard UX, at least a disabled-capability and a PROPFIND-error test should be added.

Cross-platform check

Clean — additive Q_INVOKABLE command, no wire-format change to existing commands; old clients unaffected.

Verdict

Changes requested

🤖 Automated review by Claude Code (security · stability · performance · coverage)

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Generated by Claude Code