78 lines
2.7 KiB
Markdown
78 lines
2.7 KiB
Markdown
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# `plugin-template-v2` — Shared-memory `DocumentReader` example
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This crate is a runnable plugin template that demonstrates the V2 host/plugin
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contract:
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- **Zero-copy reads** through [`ocs_plugin_api::host::DocumentReader`].
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- **Validated writes** through the existing `HostApi` RPCs (`add_entity`,
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`write_record`).
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- **Read→write round-trips**: read an entity handle from the shared document
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view and attach XDATA to it.
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It lives under `docs/` (not `crates/`) because it is documentation/example code
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rather than a runtime dependency of the host.
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---
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## Commands
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| Command | Purpose |
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|---|---|
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| `COUNT_SURVEY_POINTS` | Count point entities on the `SURVEY` layer via `document_reader()`. |
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| `ADD_SURVEY_POINT` | Add a new point entity on the `SURVEY` layer via `host.add_entity()`. |
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| `MARK_FIRST_SURVEY_POINT` | Read the first `SURVEY` point and mark it with an XDATA record. |
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| `COUNT_MARKED_SURVEY_POINTS` | Count `SURVEY` points that carry the `SURVEYMARK` XDATA record. |
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---
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## Design notes
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### Reads are zero-copy; writes are RPCs
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`document_reader()` returns a read-only view backed by host-owned shared memory
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(for out-of-process plugins) or by `&CadDocument` (for in-process plugins). The
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plugin iterates entities without copying the model.
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All mutations still cross the validated RPC boundary. This preserves the
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host's crash-safety boundary: a buggy plugin cannot corrupt the host document
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because it never holds a mutable reference to host memory.
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### Entity handles bridge reads and writes
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Each [`ReaderEntity`](ocs_plugin_api::host::ReaderEntity) exposes the entity
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`handle`. A plugin can therefore:
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1. Find an entity of interest with `document_reader().for_each_entity(...)`.
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2. Use that handle with `host.write_record(handle, record)` to attach XDATA.
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3. Read the record back later with `host.read_record(handle, app_name)`.
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This is the primary read→write round-trip pattern the template demonstrates.
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### Ribbon integration
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The plugin registers one ribbon module (`SurveyTools`) with one group
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(`Survey`). Each tool emits a `ModuleEvent::Command(...)` carrying the command
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name. The host routes the command to `BuiltinPlugin::dispatch`.
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---
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## Building and running
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From the workspace root:
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```bash
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cargo build -p plugin-template-v2
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```
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The resulting cdylib plus `plugin.toml` can be installed into the host's
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plugins folder (see `docs/plugin-architecture.md`).
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---
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## Compatibility
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The template is built against the current `ocs_plugin_api` and declares
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`ApiVersion::CURRENT`. Older plugins compiled against API v2 continue to load
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on an API v3 host because new `HostApi` methods are appended at the end of the
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trait and the host accepts plugin majors from `API_VERSION_MIN_SUPPORTED` up to
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`API_VERSION`.
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