§2a's CORRECTION 3 said where this had to land: `apply_panel_cursor_icon`
already owns the cursor and writes `Default` in its else branch, so an
I-beam at a separate site would be CLOBBERED by it on the next motion.
B5 extends that owner rather than joining it --- `desired_cursor_icon`
decides RowResize, Text and Default together or not at all, with the
divider outranking the I-beam because a drag handle is never text.
`pointer_over_text_content` is geometric, not a byte hit-test: an I-beam
belongs over the text AREA including the blank past a short line's end,
and a byte test would flicker along a ragged right margin. It excludes
the gutter, the minimap, the panel band and everything outside the
document's text rect, each for its own reason.
The icon now applies on EVERY motion rather than only when divider hover
flips. B5's transitions --- crossing the gutter, crossing the text's
right edge --- do not touch `hover_divider`, so the old gate would have
left the icon stale for exactly the cases B5 is about. The write is
idempotent against `last_cursor_icon`, so per-motion calls cost a
comparison rather than a platform round-trip.
THE FIRST VERSION OF THE ROW COULD NOT SEE ITS OWN MUTATION. With line
numbers off, `gutter_width_px` is 0 and `text_left == TEXT_LEFT`, so
"extend the I-beam over the gutter" changed nothing and the row passed a
broken build --- 0 rows fired. The fixture now turns line numbers on and
ASSERTS a gutter exists before relying on one. Both mutations fire:
I-beam over the gutter -> the coverage row
I-beam outranks divider -> the coverage row
no-pointer guesses a spot -> the no-pointer row
Levi Neuwirth
9f24dceb6a