`PKind::ScrollLeft | PKind::ScrollRight` were CLAIMED AND DROPPED in the
panel replay, with a comment assigning the axis to Stage 1b. That is the
"frontend emits, receiver discards" shape the panel-replay lane was
opened to fix, inherited for the horizontal axis. This closes it.
`scroll_window_columns` moves the side window's `view_left` by B7's
bound, stated exactly: `0 ..= widest - viewport`, saturating at zero, so
the final display column stays visible --- clamping at the widest line's
full width would let the origin pass every glyph and blank the viewport.
Wrap pins the origin to zero, matching `horizontal_follow`. It returns
whether the origin actually moved, which is lifetime clause 2's
"effective move".
The widest-line rule is SHARED. `display_width::widest_line_columns`
lives beside the module's other column helpers and both frontends use
it, for the same reason `scroll::follow_left` is shared: two frontends
that compute the right bound differently disagree about where the
document ends.
B2's row asserts the EFFECT --- `view_left` before and after --- not an
emission, and it carries the discriminating setup the bound requires: a
panel whose content fits has a maximum origin of zero, so the move is
absorbed by the clamp and a dropped event reads identical to correct
behaviour. The fixture gets a line wider than the viewport. Mutation:
restore the claimed-and-dropped arm, and the row fires.
Two mistakes of mine in this commit's history, both caught before it:
- I reverted a mutation with `git checkout -- src/editor.rs` on a file
holding UNCOMMITTED work, and destroyed the whole B2 implementation.
Re-applied, and the mutation check redone against a file snapshot ---
the discipline I had used earlier in the CRDT lane and dropped here.
- Inserting the new test above an existing one STOLE ITS `#[test]` and
its doc comment, so `r4_p1_a_chrome_press_neither_arms_nor_moves_point`
silently stopped being a test. Clippy's "never used" caught it. Both
are restored, and the suite count confirms 1994 tests rather than
1993.
Levi Neuwirth
d3d720ba8a