The HTML→PDF path produced PDFs where content extended past the
right margin of each letter page. Two contributing causes in
viewer-template.html's @media print rules:
1. .content-wrapper carries max-width: min(900px, 100%) from the
screen layout. The print override set width: 100% but didn't reset
max-width. Chromium's --print-to-pdf renders at the full page
width (816px for letter at 96dpi) and only clips at print time,
so without max-width: none the element actually extends past the
~624px printable area.
2. Tables, preformatted blocks, and long URLs had no print
containment. A wide <pre> or a <table> with many columns would
blow out the right edge even when the parent constraints held.
Fixes applied to @media print:
- html, body, .app-container: explicit width: 100% + max-width: 100%
to be sure the print viewport flows top-down with no horizontal
creep at the layout root.
- .content-wrapper: max-width: none + width: 100% (was just width).
- .content-page: width: 100% added (was just max-width: none).
- .document-content: max-width: 100% + box-sizing: border-box so
the existing 0.5in horizontal padding stays inside the page.
- pre/code/table/blockquote/img/video: max-width: 100% +
overflow-wrap: break-word; <pre> additionally white-space:
pre-wrap + word-break: break-word so unbreakable token runs
(URLs, paths, command lines) wrap instead of overflowing.
- table: table-layout: fixed so columns shrink to fit rather than
forcing horizontal scroll/overflow.
Both source files (pandoc/viewer-template.html and the embed copy at
zddc/internal/convert/viewer-template.html) updated and verified
identical with diff -q.
New endpoint GET /<path>/foo.md?convert=docx|html|pdf renders a markdown
source on demand. Surfaced as the Download buttons in browse's markdown
editor (separate commit).
Execution model — two upstream container images, lazy-pulled:
• docker.io/pandoc/latex:latest — MD→DOCX, MD→HTML (entrypoint pandoc)
• docker.io/zenika/alpine-chrome — HTML→PDF (entrypoint chromium-browser)
No custom image build. The runner passes --pull=missing on every podman/
docker invocation so the operator only needs the runtime installed —
first request pulls the image, subsequent requests use the local cache.
Overrides: --convert-pandoc-image / --convert-chromium-image (and the
matching ZDDC_CONVERT_* env vars). Engine: --convert-engine (podman
preferred, docker fallback). Resource caps: --convert-mem-mib (512),
--convert-cpus (2), --convert-pids (100), --convert-timeout (30s).
PDF flow is two-stage: pandoc renders the markdown through the embedded
viewer-template.html to standalone HTML, then chromium prints that HTML
via --print-to-pdf. Preserves the print-media CSS already authored in
viewer-template.html rather than going through pandoc's LaTeX template.
Each conversion runs in a throw-away container with --rm --network=none
--read-only --tmpfs=/tmp --cap-drop=ALL --security-opt=no-new-privileges
--env=HOME=/tmp plus a bind-mounted scratch dir for I/O. Pandoc reads
markdown from stdin / writes to stdout; the viewer template lives at
/tpl (ro). Chromium reads HTML from a read-write bind mount at /pdf
and writes the PDF to the same mount; the host reads it back. No shell
wrappers, no shell quoting — argv flows straight into each image's
entrypoint.
On-disk cache at <dir>/.converted/<base>.<ext> with mtime synced to the
source. Fast path is a stat-and-serve with no exec; slow path
singleflights concurrent requests for the same target. PUT/DELETE/MOVE
on the source .md purges the .converted/ sidecars.
Per-project template variables (client/project/contractor/project_number)
come from a new .zddc `convert:` cascade block, walked leaf→root with
per-key latest-wins. Filename-derived variables (title, tracking_number,
revision, status, is_draft) come from a new zddc.ParseFilename helper.
If neither podman nor docker is on PATH, the endpoint serves 503 with
a clear Retry-After. The rest of the server keeps working.
This is the first os/exec site in the codebase. The hardening in
internal/convert/runner.go — context.CancelFunc → process kill,
cmd.WaitDelay, platform-specific SysProcAttr (Setpgid + Pdeathsig on
Linux), minimal env, stdout cap via limitWriter, stderr ring buffer —
sets the pattern for any future shell-outs.
Public surface:
convert.ToDocx(ctx, source, meta) / .ToHTML / .ToPDF
convert.Probe(ctx, engineOverride) → install Runner if engine present
convert.SetImages(pandoc, chromium)
convert.ConfigureLimits(memMiB, cpus, pids, timeout)
convert.Available()
Container handler at internal/handler/converthandler.go; dispatcher
branch in cmd/zddc-server/main.go inserts the convert lookup after the
existing ACL gate, reusing the source file's read policy verbatim.
