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Add whiteboard frame mode (Nextcloud Whiteboard / Excalidraw over WebDAV)
New third mode alongside photos/calendar: fetches a .whiteboard file
over plain WebDAV (Basic auth -- generic, not Nextcloud-specific) and
renders it via a small Node.js sidecar using Excalidraw's own real
export code (@excalidraw/utils + @resvg/resvg-js, no headless browser),
since a .whiteboard file turns out to be Excalidraw scene JSON, not an
image. The sidecar runs as a second process inside this same container
(Dockerfile installs Node, start.sh backgrounds it before exec'ing
uvicorn) rather than a separate docker-compose service -- lightweight,
stateless, reachable only at 127.0.0.1 from the Python process, nothing
worth independently scaling.

The rendered PNG is treated exactly like a photo from there on --
composed/quantized through the existing image_pipeline (letterboxed,
never cropped) rather than a second parallel rendering pipeline.

WebDAV credentials support the common "it's actually the same Nextcloud
account as my CalDAV" case (an explicit opt-in checkbox, not silently
inferred) while still working with any WebDAV server generically.
Frame-level source (URL + owning account) follows the same owner-
controls-their-own-data permission split as calendar sources and the
week view's task list: only the account owner can point a frame at it,
anyone linked can clear it.

Honest limitation: this environment has no Node.js/npm, so
render-service/ is written carefully against each library's documented
API (verified via the npm registry, including transitive dependency
licenses after the CalDAV/AGPL surprise earlier this session) but has
never actually been executed. First real docker build is the first
true test -- see render-service/README.md.
2026-07-23 17:02:08 -04:00

76 lines
2.9 KiB
Python

"""Whiteboard frame mode: fetches a Nextcloud Whiteboard (or any other
WebDAV server's) .whiteboard file and renders it via the local
render-service sidecar (server/render-service/, own README there) --
Excalidraw's real export code, not a hand-rolled reimplementation of its
element types/styling/fonts.
Deliberately renders at a fixed generous width, not the panel's exact
target size -- the resulting PNG then runs through
image_pipeline.compose_into exactly like a photo would (crop/letterbox
per the frame's own display_mode setting), so this module doesn't need
to know anything about panel dimensions/orientation, and whiteboard mode
reuses the same fit logic photos mode already has instead of a second
parallel implementation of it.
Pure functions -- no ORM, no FastAPI Depends -- same testability
philosophy as calendar_feed.py/weather.py.
"""
from __future__ import annotations
import json
import httpx
from . import webdav_client
RENDER_SERVICE_URL = "http://127.0.0.1:3001/render"
# Rendering (not just fetching) can take a moment for a busy board --
# more generous than a typical fetch timeout.
HTTP_TIMEOUT_S = 30.0
# Fixed render width regardless of the target frame's orientation/size --
# see module docstring. Comfortably above this panel's 800px long edge
# so downstream cropping isn't working from an upscaled source.
RENDER_WIDTH = 1600
CHECK_INTERVAL_S = 20 * 60 # same cadence as calendar_feed's merge-fetch throttle
class WhiteboardRenderError(Exception):
"""Fetch or render failed -- network, auth, an invalid/non-JSON
file, or the render sidecar itself erroring. Raised loudly; callers
decide what to do."""
def fetch_and_render(url: str, username: str, password: str) -> bytes:
"""Fetches the .whiteboard file at `url` and renders it to a PNG via
the local render-service sidecar. Returns raw PNG bytes at
RENDER_WIDTH wide, natural aspect ratio."""
try:
raw = webdav_client.fetch_file(url, username, password)
except webdav_client.WebDavError as e:
raise WhiteboardRenderError(f"Could not fetch whiteboard file: {e}") from e
try:
scene = json.loads(raw)
except ValueError as e:
raise WhiteboardRenderError(f"Not a valid whiteboard file (not JSON): {e}") from e
if not isinstance(scene.get("elements"), list):
raise WhiteboardRenderError('Not a valid whiteboard file (no "elements" array)')
try:
resp = httpx.post(
RENDER_SERVICE_URL,
json={
"elements": scene.get("elements", []),
"appState": scene.get("appState", {}),
"files": scene.get("files", {}),
"width": RENDER_WIDTH,
},
timeout=HTTP_TIMEOUT_S,
)
resp.raise_for_status()
return resp.content
except httpx.HTTPError as e:
raise WhiteboardRenderError(f"Render sidecar failed: {e}") from e