Three smaller findings at the plot/figure seam:
* `Plot::remove_region()` re-indexed `region_stats_` but left `hot_.region`
naming the old index, so a frame after a removal highlighted the wrong
region's bound and an open drag edited a different region. The published
handle (and its zone) is now cleared or decremented with the cache, and the
contract documents that a host must not remove a region mid-drag.
* `Figure`'s `kMinRowHeightPx` was applied as a *device*-pixel floor while
chrome is logical, so at 2x the guarantee was half as strong exactly where
the chrome is twice as large. It is now a logical constant converted through
the row's own `ui_scale()`, 1:1 for a non-positive scale as `Style::device()`
does.
* `Figure::link_x()` refused a member whose axis 0 was `XFollow::Live`, but
nothing refused `set_x_follow(0u, XFollow::Live)` *after* linking. The group
then wrote its range into an axis that reinterpreted it against its own live
edge, read it back as an external change, and tracked one member instead of
the union. `Plot` now carries a linkage flag (`set_x_link_member()`), set by
`link_x()` and cleared by `unlink_row()`, and `set_x_follow()` refuses `Live`
on a linked axis.
Tests: arming `Live` on a linked member leaves it `Off` and unlinking restores
the ability to arm it; the row-height floor is 24 and 48 device pixels at 1x
and 2x respectively.
The repository had no licence at all, so every source was all-rights-reserved
by default. Add the verbatim MIT text at LICENSE (Copyright (c) 2026 Martino
Ferrari) and a two-line SPDX header to each of the 113 first-party sources --
48 include/plot, 26 src, 10 adapters, 5 examples, 21 tests, 3 tools -- so the
grant travels with each file rather than relying on the root document alone.
Scripts keep their shebang on line 1; the SPDX lines follow it. Genuinely
vendored code is untouched: third_party/stb_truetype.h carries no header of
ours. src/render/embedded_mono_font.cpp is generated, so tools/fonts/gen_atlas.py
emit() now writes the two lines into its header comment and the file was
regenerated -- gen_atlas.py --check passes and the regeneration adds only those
comment lines to the previously committed file.
README's provenance section now states MIT and links LICENSE.
No code, test or public API change.
The figure sync learns which row the pointer is in and that row's local y, so the
shared x goes to every row and the horizontal line only to the hovered one -- a
crosshair that finally marks a row where its y means something. The stroke gains
Style::crosshair_width/_dash_on/_dash_off (logical; 0.75 / 4 / 4), a per-Crosshair
override, and a fragment-shader dash on v_along (off == 0 is solid), anchored to the
axes edge each line is staged from so the phase does not crawl.
Martino Ferrari