fix(xwayland): X11 apps cannot connect after treeland restart

[wineee]

When treeland restarts, Xwayland generates a new MIT-MAGIC-COOKIE-1 but treeland-sd (xwayland helper) does not update the user's XAUTHORITY, causing "Invalid MIT-MAGIC-COOKIE-1 key" errors for all X11 apps.

Root cause: sessionChanged() was only emitted on user switch, not when the same session's Xwayland was recreated after a restart. treeland-sd listens for this signal to refresh DISPLAY/XAUTHORITY.

Changes:

• Emit sessionChanged() in WXWayland::ready callback to ensure the xauth cookie is valid before notifying treeland-sd
• Add Restart=on-failure to treeland-xwayland.service so the helper recovers automatically if treeland restarts causes D-Bus disconnection
• Add ExecStartPre to treeland.service to kill orphaned Xwayland processes from a crashed previous instance

Fix: #1071

Summary by Sourcery

Improve Xwayland activation robustness and recovery when treeland restarts.

Bug Fixes:

• Ensure Xwayland activation retries when the compositor D-Bus interface is temporarily unavailable, preventing X11 connection failures after treeland restarts.

Enhancements:

• Add delayed retry logic for Xwayland activation when the compositor D-Bus interface is not yet ready.

Deployment:

• Update treeland systemd units to restart the Xwayland helper on failure and clean up orphaned Xwayland processes on treeland startup.

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[deepin-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: wineee

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• debian/deepin/OWNERS

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[deepin-bot]

TAG Bot

New tag: 0.8.13
DISTRIBUTION: unstable
Suggest: synchronizing this PR through rebase #1063

[sourcery-ai]

Reviewer's guide (collapsed on small PRs)

Reviewer's Guide

Ensures Xwayland helper and environment are correctly updated and resilient after treeland restarts, fixing invalid X11 auth cookies and orphaned processes.

Sequence diagram for treeland-sd retrying XWaylandName after restart

sequenceDiagram
    participant treeland_sd as treeland_sd
    participant Compositor1 as org_deepin_Compositor1
    participant QTimer as QTimer
    participant Systemd as systemd

    loop retry_activateFd
        treeland_sd->>Compositor1: XWaylandName
        alt reply is valid
            treeland_sd->>Compositor1: UpdateActivationEnvironment
            treeland_sd->>Systemd: sd_notify READY=1
        else reply is error
            treeland_sd->>QTimer: QTimer::singleShot(500, app, activateFd)
        end
    end

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File-Level Changes

Change	Details	Files
Make systemd socket activator resilient to transient Xwayland D-Bus failures so Xwayland name registration is retried.	Capture app and self-recursive lambda in active() closure to support delayed re-invocation Handle QDBusMessage::ErrorMessage from XWaylandName call and log detailed warning Schedule a 500ms QTimer retry for type=="xwayland" when the D-Bus interface is invalid, reusing the same activateFd logic	src/systemd-socket.cpp
Harden treeland/xwayland systemd units so helper recovers on compositor restart and cleans up stale Xwayland processes.	Add Restart=on-failure to treeland-xwayland.service to auto-recover helper after D-Bus disconnects or crashes Add ExecStartPre to treeland.service that kills orphaned Xwayland instances from previous crashed treeland runs Ensure unit ordering keeps helper and compositor restart semantics aligned with Xwayland lifecycle	misc/systemd/dde-session-pre.target.wants/treeland-xwayland.service.in misc/systemd/treeland.service.in

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[sourcery-ai]

Hey - I've found 1 issue, and left some high level feedback:

• The recursive use of activateFd with QTimer::singleShot(500, &app, activateFd) for the xwayland case has no retry limit or backoff, so consider adding a maximum retry count or exponential backoff to avoid an infinite retry loop if the compositor never comes up.
• You're capturing app and activateFd by reference into a lambda that is scheduled for later execution; double-check that their lifetimes are clearly bounded by main and that treeland-sd cannot exit while timers are still queued, or consider encapsulating this logic in an object with explicit lifetime management.
• The error handling path logs XWaylandName failures but then immediately retries only when updateFd is invalid; consider distinguishing between transient D-Bus errors and permanent failures to avoid noisy retries in cases where the service is misconfigured or unavailable.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- The recursive use of `activateFd` with `QTimer::singleShot(500, &app, activateFd)` for the xwayland case has no retry limit or backoff, so consider adding a maximum retry count or exponential backoff to avoid an infinite retry loop if the compositor never comes up.
- You're capturing `app` and `activateFd` by reference into a lambda that is scheduled for later execution; double-check that their lifetimes are clearly bounded by `main` and that treeland-sd cannot exit while timers are still queued, or consider encapsulating this logic in an object with explicit lifetime management.
- The error handling path logs `XWaylandName` failures but then immediately retries only when `updateFd` is invalid; consider distinguishing between transient D-Bus errors and permanent failures to avoid noisy retries in cases where the service is misconfigured or unavailable.

## Individual Comments

### Comment 1
<location path="src/systemd-socket.cpp" line_range="77-79" />
<code_context>

-    auto active = [unixFileDescriptor, type, &tmpFiles](QDBusConnection connection) {
-        auto activateFd = [unixFileDescriptor, type, &connection, &tmpFiles] {
+    auto active = [unixFileDescriptor, type, &tmpFiles, &app](QDBusConnection connection) {
+        std::function<void()> activateFd;
+        activateFd = [unixFileDescriptor, type, connection, &tmpFiles, &app, &activateFd] {
             QDBusInterface updateFd("org.deepin.Compositor1",
                                     "/org/deepin/Compositor1",
</code_context>
<issue_to_address>
**issue (bug_risk):** Recursive lambda captures its own std::function by reference, leading to a dangling reference when used with QTimer::singleShot.

Because the lambda captures `&activateFd`, the `std::function` stored in `activateFd` closes over a stack variable that is destroyed when `active()` returns. Any callbacks scheduled via `QTimer::singleShot` will then invoke a dangling reference, causing undefined behavior.

For safe recursion with `QTimer::singleShot`, ensure the callback does not capture stack references that outlive `active()`. For example, capture by value and move into `singleShot`, or restructure using a helper QObject/free function or a heap-allocated callable (e.g., `std::shared_ptr<std::function<void()>>`) with a lifetime that exceeds `active()`.
</issue_to_address>

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