# Vendored Perspective

pf_app runs a **patched build of Perspective**. Upstream's C++ engine has always
implemented column-axis expand/collapse — `t_ctx2::set_depth(HEADER_COLUMN, …)`
and `open`/`close(HEADER_COLUMN, idx)` are fully written — but nothing above C++
could reach it: `set_column_pivot_depth()` was never called, and
`View<t_ctx2>::expand/collapse` hardcoded `HEADER_ROW`. The patch is wiring, not
new engine logic.

It buys two things the released packages cannot do at all:

- `split_by_depth` in `ViewConfig`, the `split_by` counterpart to `group_by_depth`
- `expand_column()` / `collapse_column()`, so one column branch can fold to its
  subtotal while its siblings stay expanded — the Excel behaviour

**Source:** https://github.com/fleetside72/perspective, branch
`column-axis-expand-collapse`. See `PROVENANCE.txt` for the exact commit these
tarballs were built from.

## Why tarballs and not npm

The feature is not released upstream. Until it is, the four packages are built
from the fork and committed here as npm tarballs. `npm install` expands them
exactly as it expands anything from the registry — no special tooling, and
`pf.sh deploy` works unchanged. A deploy machine needs node and nothing else:
no emscripten, no cmake, no protoc, no Rust.

All four move together, never a subset. Perspective couples loader, package
versions, data format and `apache-arrow`; vendoring a partial set reintroduces
exactly the drift that causes trouble.

## Changing the engine

    ./rebuild-perspective.sh          # builds the fork, repacks, rewrites PROVENANCE.txt
    cd .. && npm install
    git add vendor && git commit

Push the fork first — the script warns if the source tree is dirty, because a
tarball built from uncommitted code has no recoverable source.

The build itself needs cmake >= 3.29.5, protoc >= 22 (its version silently
selects which protobuf source tree gets cloned), pnpm, and the Rust nightly the
repo pins. Roughly 40 minutes cold. Only ever on a machine changing the engine.

## Getting rid of this

This is a fork, with the maintenance that implies. The exit is upstream taking
the change — the patch is small and additive, and the engine work is already
theirs. When a release ships it, delete this directory and put normal version
ranges back in `ui/package.json`.

## Pending patch: depth fields on a config update

`0001-apply-depth-fields-on-config-update.patch` is not in the vendored
tarballs yet. It fixes an upstream bug in
`rust/perspective-client/src/rust/config/view_config.rs`:
`ViewConfig::apply_update` applies ten fields and **neither `group_by_depth`
nor `split_by_depth` is among them**. So a depth can be set when a view is
created (`table.view({ group_by_depth: 1 })` — which is what the fork's own
`depth_test.mjs` exercises) but never through `restore()`, which is how a
viewer changes its own configuration. The field arrives, deserializes, and is
discarded before the engine sees it.

`group_by_depth` and the omission are both upstream; the fork mirrored
`split_by_depth` alongside it faithfully, including the omission.

Note the semantics, from `server.cpp`:

```cpp
ctx1->set_depth(row_pivot_depth - 1);                        // one-sided
ctx2->set_depth(t_header::HEADER_ROW, row_pivot_depth - 1);  // two-sided
```

The config field counts **levels to show**; `view.set_depth()` counts the
boundary below them. So `group_by_depth: n` equals `set_depth(n - 1)`, and
`Forecast.jsx` sends `d + 1`.

To apply:

```bash
cd $PSP_DIR                       # default ~/perspective
git apply /path/to/pf_app/ui/vendor/0001-apply-depth-fields-on-config-update.patch
./ui/vendor/rebuild-perspective.sh
cd ui && npm install
```

`cargo check` on this patch was clean — the 125 errors it reports without
`protoc` installed are unresolved generated protobuf modules, none of them in
`view_config.rs`.

Until the rebuild lands, `applyDepth()` in `Forecast.jsx` reads the config back
after restoring it and falls back to the imperative `view.set_depth()` when the
value did not stick. That fallback loses the depth whenever the viewer rebuilds
its view; the declarative path does not, which is the point of the patch. The
check is cheap and self-clearing — once the engine honours the field, the
fallback stops running on its own.