Plugin Authoring
WebToApp stays extensible after an app ships. Three kinds of plugins share one management surface and one injection pipeline:
| Type | What it is | Good for |
|---|---|---|
| HCJ Plugin | A plugin.json + single plugin.html package — plain HTML + CSS + JS, no DSL | Custom features, panels, settings UIs |
| Userscript | Tampermonkey/Greasemonkey-style .user.js | Porting existing userscripts; GM_* APIs |
| Chrome MV3 | A Manifest V3 Chrome extension | Porting browser extensions; chrome.* APIs |
| NativeBridge | window.NativeBridge on the system WebView | Clipboard, vibration, share, files, screen, and key events |
HCJ (HTML+CSS+JS) is the native format — think of it as a userscript upgraded with a real UI surface.
How injection works
Script plugins are injected at their configured run time:
| Run time | Fires at |
|---|---|
document_start | onPageStarted, before page scripts |
document_end | DOMContentLoaded (default) |
document_idle | after load |
hcj.addStyle() (or a legacy style.css) injects page CSS at document-start so visual plugins apply before first paint. URL match rules (Chrome-style globs or /regex/) decide which pages a plugin runs on. Chrome extensions run through the MV3 engine — a hidden WebView for the background service worker plus dynamically registered content scripts.
Where plugins live
Every plugin gets an entry on the plugin surface. The user picks the host style per app (or globally):
- Toolbar — a plugins button in the native toolbar; tap to open the plugin drawer
- Floating handle — a draggable native handle that auto-collapses (works with the toolbar hidden)
- Menu — an item inside the overflow menu
A plugin whose plugin.html carries panel markup opens it in the user-chosen panel host — bottom sheet, floating window, or fullscreen. A page-only plugin fires its hcj.on('action') handler instead. Chrome extension action.popup pages are hosted in the same panel surface.
Accuracy notes
- Userscript
GM_*functions are not gated by@grant— all are exposed unconditionally. - Chrome
ISOLATEDvsMAINworld is not truly isolated — Android WebView has a single JS context; isolation is simulated. - The MV3 "background service worker" is a hidden WebView, not a real service worker.
Where to go next
- HCJ Plugins — the native package format.
- CSS Plugins — pure style overrides.
- Userscripts — the
GM_*/GM.*API reference. - Chrome MV3 — the supported
chrome.*surface. - Publish to the Market — share plugins with the community.