[Modules] Handle WM_ENDSESSION in run_message_loop daemons (GrabAndMove, AlwaysOnTop, FancyZones)

[Gordon Lam (yeelam-gordon)]

Summary

Companion PR to #48378 (runner). Fixes the same APPLICATION_HANG_QUIESCE_*_PowerToys.exe!run_message_loop WER bucket in the other PowerToys daemons whose top-level windows ignored WM_ENDSESSION.

Root cause (same as #48378)

run_message_loop (src/common/utils/window.h) calls GetMessageW which only returns 0 on WM_QUIT. If a daemon's WndProc lets WM_ENDSESSION fall through to DefWindowProc, no WM_QUIT is ever posted on logoff/shutdown, the loop blocks, CSRSS hits the quiesce timeout (~5s), TerminateProcess fires, and Watson logs APPLICATION_HANG_QUIESCE.

run_message_loop callsite audit

8 production callsites. Persistent daemons that own a top-level window and were affected:

Module	Status before	Fix here
runner	hang	Fixed in #48378
GrabAndMove	hang (tray icon, NIM_DELETE in WM_DESTROY)	✅ main.cpp
AlwaysOnTop	hang	✅ AlwaysOnTop.cpp
FancyZones	hang	✅ FancyZones.cpp
KeyboardManagerEngine	n/a	No top-level window → OS skips WM_ENDSESSION and TerminateProcess directly; no hang bucket possible
ZoomIt	already handled	SysInternals heritage
PowerLauncher	already handled	Managed SessionEnding event
MeasureTool, Notifications	transient/spawned on demand	Not a shutdown-time daemon

Fix pattern

For AlwaysOnTop and FancyZones (no tray icon to clean up) — minimal:

case WM_ENDSESSION:
    if (wparam) PostQuitMessage(0);  // wparam==FALSE => shutdown vetoed
    return 0;

For GrabAndMove (has Shell_NotifyIcon cleanup in WM_DESTROY that must not run on shutdown) — use a g_session_ending flag and skip the tray-icon delete in WM_DESTROY, mirroring runner's tray_icon.cpp pattern from #48378.

No shared header: each module's WM_DESTROY cleanup is module-specific; the abstraction would be too thin and would hide the variance in what to skip.

Why no logging on the shutdown path

Same reasoning as #48378 review feedback — spdlog::flush_on(info) synchronously flushes to disk; emitting log lines from WM_ENDSESSION/WM_DESTROY burns the ~5s quiesce budget for no diagnostic value (Watson already records the bucket on failure).

Verification

• Built clean (Debug|x64): GrabAndMove.vcxproj, AlwaysOnTop.vcxproj, FancyZonesLib.vcxproj — all exit 0.
• Runner counterpart fix (Fix runner APPLICATION_HANG_QUIESCE without bypassing WM_CLOSE or blocking on shutdown #48378) verified end-to-end with real reboot + WM_ENDSESSION injection; quiesce 1–8 ms. Same OS-level mechanism applies here.

Related

• Fix runner APPLICATION_HANG_QUIESCE without bypassing WM_CLOSE or blocking on shutdown #48378 — runner fix (this PR's companion)
• Fix runner APPLICATION_HANG_QUIESCE: handle WM_ENDSESSION and skip blocking shutdown cleanup #48363 — original community fix (over-engineered; this approach is the minimal correct one)

[Copilot]

Pull request overview

This PR updates several PowerToys module daemons that run a top-level GetMessageW loop so they respond to WM_ENDSESSION and can unwind promptly during OS logoff/shutdown, avoiding the APPLICATION_HANG_QUIESCE_*_PowerToys.exe!run_message_loop WER bucket.

Changes:

• GrabAndMove: adds a g_session_ending flag, routes WM_ENDSESSION through WM_CLOSE, and skips tray-icon deletion in WM_DESTROY during OS shutdown.
• FancyZones: handles WM_ENDSESSION and posts WM_QUIT (only when wparam indicates shutdown is proceeding).
• AlwaysOnTop: handles WM_ENDSESSION and posts WM_QUIT (only when wparam indicates shutdown is proceeding).

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
src/modules/GrabAndMove/GrabAndMove/main.cpp	Add WM_ENDSESSION handling + shutdown flag to avoid shutdown-time work in WM_DESTROY.
src/modules/fancyzones/FancyZonesLib/FancyZones.cpp	Post WM_QUIT on confirmed session end so the message loop exits.
src/modules/alwaysontop/AlwaysOnTop/AlwaysOnTop.cpp	Post WM_QUIT on confirmed session end so the message loop exits.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.

[Gordon Lam (yeelam-gordon)]

/acp run

[Gordon Lam (yeelam-gordon)]

/azp run

[azure-pipelines]

Azure Pipelines could not run because the pipeline triggers exclude this branch/path.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.