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cproudlock ce6d44e69f docs: EventSaver, and how GE-Enforce reaches a bay in the first place

EventSaver was undocumented anywhere a reader could find it. What it is, the two
source modes and why HTTP is the one to use, how order.txt and the ShopDB feed
each decide the running order, the three command-line switches Windows calls it
with, where it must NOT run (a screensaver over a live dashboard or a metrology
run is a defect), how to build it with the in-box compiler, and a table of
symptoms with the first thing to check.

The adoption guide also stopped short of the question it invites: the fleet
tools assume GE-Enforce is already on the PC, so how does GE-Enforce get there.
Both real paths are now written down - imaging time, which is how the shop-floor
pipeline does it, and Intune, which is how the display cohort is deployed today
because those PCs are Entra-joined with no share. Machine Configuration is
possible and unshipped, with the caveat that matters: DSC and GE-Enforce are
both convergence loops, so give each a layer to own rather than pointing them at
the same configuration.

2026-08-14 14:19:16 -04:00

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EventSaver

A rotating-image screensaver for shop-floor PCs. Idle bays show the slides managed in ShopDB, so a safety notice or a shift message reaches the floor without anyone walking to each machine.

It is a small C# WinForms screensaver (.scr), not part of the ShopDB server. It is documented here because ShopDB serves its content and because a site adopting the fleet tools needs to know how it is configured.

For how to deploy it at a new site, see ADOPTING-AT-ANOTHER-SITE.md. This page is what it is, how it decides what to show, and how to diagnose it.

Two sources, one of them preferred

EventSaver reads EventSaver.ini from the directory it lives in, on every launch. Retargeting it never needs a recompile.

# HTTP mode: pull the playlist from ShopDB and cache it locally.
url=https://shopdb.example.net/api/slides/feed?surface=shopfloor

# Folder mode: used only when url is blank. SMB or local path.
# folder=\\fileserver\shopfloor\tv

interval=10     # seconds per image, unless a slide carries its own time
shuffle=0       # 1 = random order, 0 = ordered
fadems=600      # crossfade length in ms, reserved (v1 hard-cuts)

HTTP mode is the one to use. Slides are managed in ShopDB (Slides), the feed is public so the screensaver needs no credentials, and each PC caches what it fetched under its own LocalApplicationData. A bay that cannot reach the server keeps showing the last set it saw instead of going black - which matters, because the failure would otherwise be visible to the whole floor.

Folder mode predates the server and stays as a fallback for a site with no ShopDB instance yet, or for content nobody wants in the database.

If EventSaver.ini is missing, or both url and folder are blank, the binary falls back to a path compiled into EventSaver.cs - and that path belongs to the site it was first built for. Ship the ini. A missing ini is not a neutral default.

What decides the running order

Situation	Behaviour
No `order.txt`	Every image shows, sorted by filename. Number them `001_`, `002_` to sequence.
`shuffle=1`	Random order, ignored when a playlist is present.
`order.txt` present	ONLY the listed files show, in the listed order, looped.

order.txt is the strict-sequence option and is the whole playlist - a file not listed does not appear. Per-slide duration is appended with a pipe:

# Lines starting with # or ; are ignored.
001_welcome.jpg
002_safety_week.jpg|15
003_quality_board.jpg

In HTTP mode you do not write order.txt by hand: ShopDB's feed carries the order and each slide's own seconds, and EventSaver writes the equivalent order.txt into its cache so the same playlist logic runs either way.

A running screensaver rescans about every 30 seconds, so a slide change reaches the floor without touching any PC.

Command-line switches

Windows calls a screensaver with these, and EventSaver answers all three:

Switch	Meaning
`/s`	Show fullscreen. What Windows uses on idle.
`/c`	Configuration. Reports the resolved source and cache directory, and points at the ini.
`/p <hwnd>`	Preview pane. Deliberately a no-op - it keeps the Settings dialog happy without drawing a thumbnail nobody looks at.

EventSaver.scr /c is the first diagnostic: it says which source it resolved and where it is caching, which answers most "why is it showing the wrong thing" questions immediately.

Where it should and should not run

A screensaver over a live display is a defect, not a feature. The reference fleet excludes:

Kiosks and lobby displays, which show a live dashboard.
Metrology bays - CMM, Genspect, Keyence, wax-trace - where an operator watches a measurement run.
Bays that sleep, where the screensaver never wins anyway.

Targeting is per PC type in the GE-Enforce manifest, or by group assignment in Intune. Decide it deliberately: the cost of getting it wrong is a screensaver covering something someone needed to see.

Building it

No SDK required - it compiles with the in-box .NET Framework compiler on any Windows 10 or 11 machine:

C:\Windows\Microsoft.NET\Framework64\v4.0.30319\csc.exe ^
  /target:winexe /out:EventSaver.scr ^
  /reference:System.dll,System.Drawing.dll,System.Windows.Forms.dll ^
  EventSaver.cs

Ship EventSaver.scr and EventSaver.ini together. A .scr is an executable with a different extension, so it goes to C:\Windows\System32\.

Diagnosing it

Symptom	Cause to check first
Blank screen, no images	Source unreachable and cache empty. Run `/c` and open the `url` in a browser on that PC.
Old slides only	Feed reachable at first run, not since. The cache is doing its job; fix the network path.
Wrong content	Pointing at another surface, or another site's server. `/c` reports which.
Local ini edits revert	Correct behaviour if the config is enforced by hash. Edit the copy on the share and update its `DetectionValue`.
Screensaver never starts	Per-user setting missing. Check `HKCU:\Control Panel\Desktop` for `SCRNSAVE.EXE`, `ScreenSaveActive` and `ScreenSaveTimeOut`.

The feed is a plain public endpoint, so it can always be checked from the PC itself:

https://shopdb.example.net/api/slides/feed?surface=shopfloor

An empty slides array means no slides have been uploaded for that surface - the PC is configured correctly and there is nothing to show.

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