Enhanced Client (optional add-on, browser Canvas + WebSocket terminal)

Status: test version. Shaken out across multiple real Pi3 test
sessions (font legibility, menu-overlay bugs, canvas sizing all found
and fixed live), but still actively evolving. Not part of any numbered
ANetBBS release yet.

A browser-based, mouse-driven front door to ANetBBS -- real clickable
menus, color ANSI art rendered pixel-perfect on a <canvas>, and a
bolder built-in font, running alongside every existing client
(telnet, SSH, rlogin, PETSCII, SyncTerm, NetRunner, MagiTerm) rather
than replacing any of them. A caller connecting through it sees the
exact same BBS, menus, boards, doors, and chat as everyone else --
BbsSession's term_mode == 'enhanced' is just one more terminal
mode alongside ansi/ascii/petscii/wide, in the same place
those are already handled.

This is a different thing from the existing plain browser ANSI
terminal at /terminal/ (served by the anetbbs-web app, a classic
text-stream xterm.js-style view with no mouse-driven menus) -- that
stays exactly as it is; the Enhanced Client is a new, separate,
richer option next to it, not a replacement.

It's a separate, optional download -- not part of the stock release

Unlike most ANetBBS features, this does not ship inside the normal
release tarball build-release.sh produces. A sysop who wants it
fetches a small add-on package and applies it on top of an existing
install; everyone else's stock ANetBBS never carries any of these
files at all. Same reasoning as keeping the RDQ3/ANetCHESS door games
as their own separate projects rather than bundling their release
archives into ANetBBS's own distribution.

What's in the add-on (built by
tools/build_enhanced_client_addon.sh, producing
/tmp/ANetBBS-EnhancedClient-addon-<version>.tar.gz):

anetbbs/core/enhanced_server.py -- the WebSocket listener.
anetbbs/features/enhanced_protocol.py -- the JSON message protocol
between server and client.
anetbbs/enhanced_client/ -- the client itself: a single static
index.html, no build step, no framework. Its own
anetbbs/enhanced_client/README.md has the sysop-facing install
walkthrough.
anetbbs/static/fonts/Flexi_IBM_VGA_False.ttf / .woff -- the
client's embedded font (see "Font" below).

What's NOT in the add-on, because it can't be cleanly separated:
the small if self.term_mode == 'enhanced': branches threaded through
anetbbs/core/session.py, anetbbs/features/menu_engine.py,
anetbbs/features/games.py, anetbbs/main.py, and
anetbbs/config.py (ENHANCED_ENABLED/ENHANCED_HOST/
ENHANCED_PORT) -- these are the same files every other protocol's
own term_mode dispatch already lives in, so there's no way to ship
"session.py minus the enhanced branches" without maintaining a second,
diverging copy of that file. They ship with every stock ANetBBS
install already, same as PETSCII's own always-present-but-disabled-
by-default support -- completely inert unless both
ENHANCED_ENABLED=true is set and the add-on's files are actually
present. If a sysop sets that flag without having fetched the add-on,
anetbbs.service logs a clear warning and skips just that one
listener; telnet/SSH/rlogin/PETSCII/FTP all start normally regardless.

Installing

From Admin -> Add-ons (the easier path): set
ENHANCED_CLIENT_ADDON_URL to a direct-download URL for the add-on
archive (a GitHub Release asset works well, no auth needed for a
public asset), then click Download & Install on that page --
it fetches the archive and extracts it over the install automatically.
See 38 — Add-ons for how this page works and what it
checks before writing anything.

By hand:

Build or obtain ANetBBS-EnhancedClient-addon-<version>.tar.gz.
Extract it over an existing ANetBBS install, same workflow as any
other update:
tar -xzf ANetBBS-EnhancedClient-addon-<version>.tar.gz --strip-components=1 -C /path/to/anetbbs

Either way, then:

Set ENHANCED_ENABLED=true in your config (defaults:
ENHANCED_HOST=0.0.0.0, ENHANCED_PORT=6402 -- override either if
that doesn't fit).
Restart anetbbs.service.
Open http://<your-host>:6402/ in a browser.

Uninstalling / reverting to stock

Set ENHANCED_ENABLED=false and restart. The add-on's files can stay
in place (inert) or be deleted -- neither affects any other client.

Architecture

Runs inside the same asyncio event loop as telnet/SSH/rlogin/
PETSCII (anetbbs.service), not inside the separate anetbbs-web
app's eventlet-monkey-patched process -- running real asyncio
BBSSession objects inside an eventlet process would be a real
cross-event-loop risk for no benefit. The WebSocket transport is
built on aiohttp (already a hard dependency for the MRC bridge's own
browser-facing WebSocket path), so no new dependency is introduced.

A thin reader/writer-shaped adapter (_WSReaderAdapter/
_WSWriterAdapter in enhanced_server.py) bridges aiohttp's
message-oriented WebSocket API into the same byte-stream
read(n)/write(data) + stored-exception contract every other
BBSSession transport already satisfies -- BBSSession itself needed
zero changes to its I/O model to support a fourth transport.

Output is a small JSON protocol (enhanced_protocol.py): screen
messages carry a cursor-positioned grid of styled text runs (the same
persistent virtual-screen buffer every write() call in enhanced mode
feeds, so ANSI cursor-positioned partial redraws compose correctly
across separate calls, not just appended as flat scrolling text);
menu messages carry a structured button list
({hotkey, label, send}) for auto-generated clickable menus -- a
mouse click is synthesized server-side into the exact keystroke(s) a
typed choice would have produced, so menu dispatch logic elsewhere in
the codebase needs no awareness that a WebSocket is involved at all.

CP437 Block Elements (█▀▄▌▐░▒▓) are drawn as direct canvas geometric
fills, never through the font -- a font glyph's ink doesn't reliably
fill its cell edge-to-edge regardless of font choice, confirmed live
via a side-by-side SyncTerm comparison. Every other glyph (box-drawing,
text) renders through the embedded font normally.

Font

Flexi_IBM_VGA_False.ttf/.woff -- a real scalable TrueType IBM VGA
face from int10h.org's Ultimate Oldschool PC Font Pack, CC BY-SA 4.0,
(c) VileR / Screwtape. Chosen over the bitmap-derived Ac437_IBM_VGA
font used elsewhere in this project (web ANSI editor PNG export) after
a live comparison against NetRunner's own bundled font turned up the
bitmap font looking thin/blurry at this client's render size -- a
real vector face stays crisp. "False" (square-pixel, matching this
project's existing 9:16 cell convention) and the unmarked/extended-
Unicode-charset variant (matching how this project already decodes
CP437 bytes to real Unicode codepoints rather than raw CP437
byte-position glyph mapping) specifically -- see
anetbbs/static/fonts/LICENSE.txt for the full attribution and the
reasoning behind those two variant choices.

Known limitations / deferred

RIP-style sprite/image graphics, half-block art rendering beyond the
geometric block-fill handling above, and custom per-user
fonts/themes in the client are not implemented.
Mouse support is limited to clicking auto-generated menu buttons --
no drag-select, no right-click context menus.
No packaged/installable client -- it stays a URL a caller opens, not
a downloadable app.