fix: use GET_PRIVATE_LINK socket command for Wayland clipboard support

[DeepDiver1975]

Problem

On native Wayland sessions the ownCloud daemon has no compositor surface, so
QClipboard::setText() is silently dropped. Copy private link to clipboard never
works on Wayland from the Dolphin context menu.

Solution

When the session is Wayland (WAYLAND_DISPLAY set or XDG_SESSION_TYPE=wayland), the
plugin replaces the COPY_PRIVATE_LINK action handler: it sends GET_PRIVATE_LINK:<file>
to the client (a new socket command in owncloud/client) and waits up to 1 s for
PRIVATE_LINK:<url>. The URL is then written via QApplication::clipboard()->setText()
from within the Dolphin process, which has a valid Wayland surface.

If no response arrives within the timeout (old client), the clipboard is left unchanged —
same as the current broken behaviour, with no crash or user-visible error.

Requires: owncloud/client PR for GET_PRIVATE_LINK command.

Testing

• KDE Plasma on Wayland with Dolphin: right-click synced file →
  "Copy private link to clipboard" → clipboard contains the URL ✓
• X11 session: existing behaviour unchanged ✓
• Old client (no GET_PRIVATE_LINK): event loop times out cleanly ✓

[dj4oC]

Adds a Wayland-specific "Copy private link to clipboard" path: on Wayland, intercepts the COPY_PRIVATE_LINK action, sends the new GET_PRIVATE_LINK socket command, waits for PRIVATE_LINK: and writes to the clipboard from within the Dolphin process (which has a valid Wayland surface).

Findings

Memory safety: No raw pointer arithmetic; the helper/files/parentWidget raw-pointer captures match the existing pattern already used a few lines above in the same function, so not a new risk. The &waitLoop reference capture is safe — it's used synchronously within the same stack frame and explicitly disconnected before the function returns.

Stability/UX concern: waitLoop.exec(QEventLoop::ExcludeUserInputEvents) blocks user input processing in Dolphin for up to 1000ms per "copy private link" click while waiting for the client's reply. That's a real, if bounded, UI freeze on every invocation (not just the old-client/timeout case) — worth reducing the timeout or making it async/non-modal if possible.

Cross-repo dependency risk (blocking): This depends on GET_PRIVATE_LINK, added in owncloud/client PR #12535, which this same automated review flagged with a stability: Block finding — the client-side handler captures a raw SocketListener* in an async completion lambda, risking a use-after-free if the socket disconnects before the reply arrives (exactly the kind of disconnect this 1-second wait window makes more likely to be hit in practice, e.g. if Dolphin/the plugin is torn down mid-wait). Recommend holding this PR until the client-side UAF is fixed, to avoid shipping a shell-integration feature that can crash the sync daemon.

Platform API / syscalls: QApplication::clipboard()/QClipboard usage is standard Qt, appropriate here. No new unsafe syscalls.

REUSE: Additive changes to existing licensed files; no new files.

Verdict

Changes requested (pending the upstream client-side fix)

🤖 Automated review by Claude Code (memory-safety · platform-API · REUSE)

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Generated by Claude Code