62 lines
2.7 KiB
Markdown
62 lines
2.7 KiB
Markdown
# FieldLens Print Capture Architecture
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## Target architecture
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### Linux
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```text
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original document
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-> FieldLens Print CUPS queue
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-> FieldLens CUPS pre-filter
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-> /var/lib/fieldlens-print/capture
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-> FieldLens watcher / decode / sync
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-> normal CUPS rendering
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-> physical printer
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```
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The production Linux path does not depend on the RAW 9100 proxy. The CUPS pre-filter is authoritative for original-document capture.
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The no-paper self-test uses the same CUPS pre-filter, then sends the rendered output to a local discard sink on 127.0.0.1:9101. Self-test success means the exact submitted document was observed by the FieldLens watcher, not merely accepted by CUPS.
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### Windows
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Target:
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```text
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original spool/document
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-> FieldLens native capture backend
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-> FieldLens capture / decode / sync
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-> normal Windows print pipeline
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-> physical printer
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```
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The current localhost:9100 RAW proxy remains a compatibility backend only until the native Windows backend is complete.
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## Windows native backend implementation track
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1. Spike the supported Windows spool interception options:
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- custom port monitor,
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- print processor,
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- virtual printer / print support backend.
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2. Prefer the least-privileged option that can capture the spool/document before final device rendering while returning the job to the normal Windows print pipeline.
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3. Package and register the native component from the FieldLens installer with repair/remove support.
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4. Preserve the existing FieldLens capture event contract so OCR/barcode, history, sync, and UI do not care which platform backend produced the job.
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5. Support USB, WSD, locally installed, and network printers without requiring destination TCP/9100.
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6. Add health checks that verify the native backend is installed, loadable, and attached to the FieldLens queue.
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7. Add an end-to-end self-test that proves a submitted document creates a FieldLens capture event and reaches the downstream Windows print pipeline.
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8. Remove the localhost:9100 compatibility backend after native backend rollout and migration are verified.
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## Health invariants
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FieldLens must not report Ready unless the active platform capture backend is actually operational.
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Linux Ready requires:
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- FieldLens Print queue present, enabled, and accepting jobs;
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- FieldLens Test Capture queue present, enabled, and accepting jobs;
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- installed FieldLens CUPS filter present and Python-syntax-valid;
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- production capture watcher running.
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Linux self-test passes only when the exact submitted test document creates a matching `cups-test` capture event.
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Windows Ready will eventually require the equivalent native-backend registration/load/queue checks, rather than only queue existence.
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