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docs: drop relative line numbering from the v0.2 gutter

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Relative numbering renumbers the whole gutter on every j/k, a tall partial
refresh per cursor move that eats the e-ink ghosting budget for no
proportionate gain. Gutter is now absolute-only; Spike 13 downgrades from a
genuine e-ink risk to a layout decision.
This commit is contained in:
Julien Calixte
2026-07-11 18:31:33 +02:00
parent a817229ae1
commit 491dc57144
2 changed files with 18 additions and 19 deletions
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31
docs/spikes.md
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@@ -114,23 +114,20 @@ risk early.
a design decision this spike hands data to.)
13. **Spike 13 — Line-number gutter.** Draw a fixed-width digit column left of
the text area. The v0.2 spec is the hard case: **relative** numbers in
Normal mode (current line as its absolute number), **absolute** in Insert.
The naive part — reserving columns and drawing digits — is trivial; the
e-ink risk is churn. Relative numbering renumbers the *entire visible gutter
on every `j`/`k`*, so a single cursor move becomes a partial refresh of a
tall digit column, straight into the Spike 5 windowed-Y path and the "20
partials → forced full refresh" ghosting counter
([`firmware/src/epd.rs`](../firmware/src/epd.rs), render module). Absolute
numbering is cheap by comparison — only the rows below an inserted/deleted
line renumber. Two more interactions: the gutter steals horizontal columns
from the render-time soft-wrap, and wrapped continuation rows have no number
(blank vs. tilde — a layout decision). Prove: measure gutter partial-refresh
cost for (a) a held-`j` scan that renumbers the whole relative gutter vs.
(b) a single-line absolute edit, and confirm neither blows the ghosting
budget or forces extra full refreshes. Decides whether relative numbering is
viable on this panel or must be gated (absolute-only, or a batched/coalesced
gutter repaint). (Feeds v0.2's line-number gutter; genuine new e-ink risk.)
the text area. **Absolute numbering only** — relative numbering was dropped
(2026-07-11). It renumbered the *entire visible gutter on every `j`/`k`*, so
a single cursor move became a partial refresh of a tall digit column,
straight into the Spike 5 windowed-Y path and the "20 partials → forced full
refresh" ghosting counter ([`firmware/src/epd.rs`](../firmware/src/epd.rs),
render module) — real e-ink cost for no proportionate gain on a
distraction-first panel. Dropping it removes the genuine e-ink risk this
spike existed to prove: absolute numbering is cheap — only the rows below an
inserted/deleted line renumber. What remains is a **layout decision**, not a
latency one: the gutter steals horizontal columns from the render-time
soft-wrap, and wrapped continuation rows have no number (blank vs. tilde).
Prove: reserve the gutter width, then confirm a single-line edit repaints
only the rows at/below the change and forces no extra full refresh. (Feeds
v0.2's line-number gutter; now low-risk after the relative drop.)
14. **Spike 14 — Multi-file navigation (open / switch / new / delete).** The
panel *mechanism* is already Spike 11 (which names this v0.5 file palette),