ce6d44e69f
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.
133 lines
5.4 KiB
Markdown
133 lines
5.4 KiB
Markdown
# EventSaver
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A rotating-image screensaver for shop-floor PCs. Idle bays show the slides
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managed in ShopDB, so a safety notice or a shift message reaches the floor
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without anyone walking to each machine.
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It is a small C# WinForms screensaver (`.scr`), not part of the ShopDB server.
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It is documented here because ShopDB serves its content and because a site
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adopting the fleet tools needs to know how it is configured.
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For how to deploy it at a new site, see
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[ADOPTING-AT-ANOTHER-SITE.md](ADOPTING-AT-ANOTHER-SITE.md). This page is what it
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is, how it decides what to show, and how to diagnose it.
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## Two sources, one of them preferred
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EventSaver reads `EventSaver.ini` from the directory it lives in, **on every
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launch**. Retargeting it never needs a recompile.
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```ini
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# HTTP mode: pull the playlist from ShopDB and cache it locally.
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url=https://shopdb.example.net/api/slides/feed?surface=shopfloor
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# Folder mode: used only when url is blank. SMB or local path.
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# folder=\\fileserver\shopfloor\tv
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interval=10 # seconds per image, unless a slide carries its own time
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shuffle=0 # 1 = random order, 0 = ordered
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fadems=600 # crossfade length in ms, reserved (v1 hard-cuts)
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```
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**HTTP mode is the one to use.** Slides are managed in ShopDB (Slides), the
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feed is public so the screensaver needs no credentials, and each PC caches what
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it fetched under its own `LocalApplicationData`. A bay that cannot reach the
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server keeps showing the last set it saw instead of going black - which matters,
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because the failure would otherwise be visible to the whole floor.
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**Folder mode** predates the server and stays as a fallback for a site with no
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ShopDB instance yet, or for content nobody wants in the database.
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> If `EventSaver.ini` is missing, or both `url` and `folder` are blank, the
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> binary falls back to a path compiled into `EventSaver.cs` - and that path
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> belongs to the site it was first built for. Ship the ini. A missing ini is not
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> a neutral default.
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## What decides the running order
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| Situation | Behaviour |
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|---|---|
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| No `order.txt` | Every image shows, sorted by filename. Number them `001_`, `002_` to sequence. |
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| `shuffle=1` | Random order, ignored when a playlist is present. |
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| `order.txt` present | ONLY the listed files show, in the listed order, looped. |
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`order.txt` is the strict-sequence option and is the whole playlist - a file not
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listed does not appear. Per-slide duration is appended with a pipe:
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```
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# Lines starting with # or ; are ignored.
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001_welcome.jpg
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002_safety_week.jpg|15
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003_quality_board.jpg
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```
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In HTTP mode you do not write `order.txt` by hand: ShopDB's feed carries the
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order and each slide's own seconds, and EventSaver writes the equivalent
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`order.txt` into its cache so the same playlist logic runs either way.
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A running screensaver rescans about every 30 seconds, so a slide change reaches
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the floor without touching any PC.
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## Command-line switches
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Windows calls a screensaver with these, and EventSaver answers all three:
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| Switch | Meaning |
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| `/s` | Show fullscreen. What Windows uses on idle. |
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| `/c` | Configuration. Reports the resolved source and cache directory, and points at the ini. |
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| `/p <hwnd>` | Preview pane. Deliberately a no-op - it keeps the Settings dialog happy without drawing a thumbnail nobody looks at. |
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`EventSaver.scr /c` is the first diagnostic: it says which source it resolved
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and where it is caching, which answers most "why is it showing the wrong thing"
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questions immediately.
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## Where it should and should not run
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A screensaver over a live display is a defect, not a feature. The reference
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fleet excludes:
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- **Kiosks and lobby displays**, which show a live dashboard.
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- **Metrology bays** - CMM, Genspect, Keyence, wax-trace - where an operator
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watches a measurement run.
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- **Bays that sleep**, where the screensaver never wins anyway.
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Targeting is per PC type in the GE-Enforce manifest, or by group assignment in
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Intune. Decide it deliberately: the cost of getting it wrong is a screensaver
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covering something someone needed to see.
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## Building it
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No SDK required - it compiles with the in-box .NET Framework compiler on any
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Windows 10 or 11 machine:
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```
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C:\Windows\Microsoft.NET\Framework64\v4.0.30319\csc.exe ^
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/target:winexe /out:EventSaver.scr ^
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/reference:System.dll,System.Drawing.dll,System.Windows.Forms.dll ^
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EventSaver.cs
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```
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Ship `EventSaver.scr` and `EventSaver.ini` together. A `.scr` is an executable
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with a different extension, so it goes to `C:\Windows\System32\`.
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## Diagnosing it
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| Symptom | Cause to check first |
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|---|---|
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| Blank screen, no images | Source unreachable and cache empty. Run `/c` and open the `url` in a browser on that PC. |
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| Old slides only | Feed reachable at first run, not since. The cache is doing its job; fix the network path. |
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| Wrong content | Pointing at another surface, or another site's server. `/c` reports which. |
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| Local ini edits revert | Correct behaviour if the config is enforced by hash. Edit the copy on the share and update its `DetectionValue`. |
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| Screensaver never starts | Per-user setting missing. Check `HKCU:\Control Panel\Desktop` for `SCRNSAVE.EXE`, `ScreenSaveActive` and `ScreenSaveTimeOut`. |
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The feed is a plain public endpoint, so it can always be checked from the PC
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itself:
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```
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https://shopdb.example.net/api/slides/feed?surface=shopfloor
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```
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An empty `slides` array means no slides have been uploaded for that surface -
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the PC is configured correctly and there is nothing to show.
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