# 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`.