Skynet CRT Screensaver

A native macOS screensaver (.saver bundle) that displays the Skynet logo on a simulated CRT monitor: scanlines, chromatic aberration, noise, a rolling bar, flicker, and periodic heavy glitches.

The screensaver renders a self-contained HTML file inside a WKWebView, hosted by a minimal ScreenSaverView subclass in Swift. An external Swift timer drives the frame loop, because WebKit would otherwise throttle the page when macOS treats the view as hidden.

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Quickinstall

1. Open build/ in Finder and double-click Skynet.saver.
2. macOS asks for this user or for all users – pick one; System Settings opens with Skynet preselected.
3. Hit Set as Screen Saver.

If Gatekeeper complains on first launch:

xattr -dr com.apple.quarantine ~/Library/Screen\ Savers/Skynet.saver

No build/Skynet.saver yet? Run ./build.sh --no-install once, then double-click.

The sections below cover the same steps in detail, plus alternatives, rebuilding, and troubleshooting.

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Requirements

• macOS 11 (Big Sur) or newer
• Xcode Command Line Tools – install them if missing:

  xcode-select --install

  Verify with swiftc --version (it must print a version).
• No other dependencies. No Xcode project, no Homebrew – just Swift and a shell script.

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Project layout

skynet-screensaver/
├── build.sh                # Compiles, signs, installs
├── skynet.html             # Self-contained HTML with SVG logo + CRT effects
├── src/
│   ├── SkynetView.swift    # ScreenSaverView subclass, loads HTML in WKWebView
│   └── Info.plist          # Bundle metadata
├── build/
│   └── Skynet.saver/       # Compiled bundle (produced by build.sh)
├── README.md
└── LICENSE

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Installation – step by step

1. Get the repository

git clone <repo-url> skynet-screensaver
cd skynet-screensaver

Or just copy the folder if you're not using Git.

2. Build the bundle

./build.sh --no-install

The script, in one go:

1. Wipes build/Skynet.saver
2. Copies Info.plist and skynet.html into the bundle
3. Compiles src/SkynetView.swift against the ScreenSaver, WebKit and Cocoa frameworks
4. Ad-hoc signs the bundle (codesign --sign -) so Gatekeeper stops complaining

The finished bundle ends up at build/Skynet.saver.

3. Install – pick one

Option A – double-click in Finder (simplest):

1. Open build/ in Finder
2. Double-click Skynet.saver
3. macOS asks whether to install it for this user or for all users – pick one
4. System Settings opens with Skynet preselected

Option B – let the build script install it:

./build.sh

Same as --no-install, but additionally copies the bundle to ~/Library/Screen Savers/Skynet.saver. Handy during development when you rebuild often.

Option C – open from the Terminal:

open build/Skynet.saver

Triggers the same install dialog as double-clicking in Finder.

4. Activate it in System Settings

• macOS 14 Sonoma and newer: System Settings → Screen Saver → scroll to the Other group → pick Skynet.
• macOS 13 Ventura and older: System Preferences → Desktop & Screen Saver → Screen Saver → pick Skynet.

Click the preview image to start a fullscreen preview.

Tip: if Skynet doesn't show up, close System Settings completely and open it again.

5. If Gatekeeper blocks the screensaver

On first launch you may see a warning like "Skynet.saver can't be opened because Apple cannot check it for malicious software."

Option A – via the UI: System Settings → Privacy & Security → at the bottom you'll see "Skynet was blocked…" → Open Anyway.

Option B – via Terminal (faster):

xattr -dr com.apple.quarantine ~/Library/Screen\ Savers/Skynet.saver

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Modifying and rebuilding

If you change the HTML, the logo, or the Swift code:

./build.sh

Then, in System Settings, switch to a different screensaver and back to Skynet – otherwise macOS serves the cached version.

If the new build still isn't picked up:

# Kill the screen saver engine; macOS will relaunch it on demand
killall ScreenSaverEngine legacyScreenSaver 2>/dev/null || true

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Test the HTML in a browser

To iterate on the visuals without rebuilding the bundle:

open -a Safari skynet.html

Same file that ships inside the bundle – useful for fast CSS/JS tweaks.

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Uninstall

rm -rf ~/Library/Screen\ Savers/Skynet.saver

Then pick a different screensaver in System Settings.

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Tuning the effects

All visual parameters live in skynet.html:

Effect	Where	Parameter
Scanline strength	CSS .scanlines	alpha value 0.38
Noise intensity	CSS #noise	opacity: 0.12
Small glitches	JS scheduleGlitch()	interval 2500 + rand*9000 ms
Heavy glitch	JS scheduleHeavyGlitch()	first fires 40–90 s in, then every 2–5 min
Roll-bar speed	CSS animation: roll	8.5s (smaller = faster)
Colors	CSS vars / fills	#c20000 (red), #d8d8d8 (text), #8a0000

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Troubleshooting

"Skynet" doesn't appear in the list Check that the bundle is actually installed:

ls -la ~/Library/Screen\ Savers/Skynet.saver/Contents/MacOS/Skynet

The binary must exist and be executable. If not, run ./build.sh again.

Black screen instead of the logo Usually skynet.html is missing from the bundle. Verify:

ls ~/Library/Screen\ Savers/Skynet.saver/Contents/Resources/

The screensaver stops animating after a few seconds macOS throttles WKWebView in the background. The external Swift timer in SkynetView.swift already works around that – if it stops working, check whether forcePageVisible() still hits the private selector. (Apple occasionally changes the signature between major versions.)

Build script fails with "swiftc: command not found" Command Line Tools are missing: xcode-select --install.

codesign fails Ad-hoc signing (--sign -) needs no certificate. If it still errors out, this usually helps:

sudo xcode-select -r

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How it works (short version)

1. SkynetView is a ScreenSaverView subclass that hosts a WKWebView as its only subview.
2. skynet.html is loaded into that WebView from the bundle resources.
3. A WKUserScript injected at documentStart overrides document.hidden / visibilityState, so requestAnimationFrame and CSS animations don't get throttled.
4. In addition, a Swift Timer runs at 30 Hz and calls window.__sk.update(performance.now()) via evaluateJavaScript on every tick. That's the external frame driver WebKit can't throttle.
5. forcePageVisible() uses a private API (_setVisibilityState:isInitialState: or _setVisibilityState:) to pin the WebView as visible, so the compositor keeps drawing even when the screensaver host flags the view as hidden.

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License

MIT – see LICENSE.