# Rendering & UX spikes > Scope: bench experiments that retire **display/UX** risk, run after the v0.1 > hardware bring-up spikes (1–7) in > [`v0.1-mvp-technical.md`](v0.1-mvp-technical.md#hardware-bring-up-order). > Unlike 1–7, these are **not** a v0.1 integration gate, and each feeds a > different release (noted per spike). > > They ride on the `epd::Frame` `DrawTarget` and the Spike 5 partial-refresh > path. Project overview: [`../README.md`](../README.md). Vocabulary: > [`../CONTEXT.md`](../CONTEXT.md). Release sequence: [`macroplan.md`](macroplan.md). These prove display/UX risks, not stack risks, so they sit outside the 1–7 "prove before integration" gate. **Run Spike 8 first:** it partitions the panel into the writing column and the side panel that the later spikes (scrollbar, line-number gutter, status readouts) draw within and around. Each feeds a different release, but the bench experiment is worth running now to retire the risk early. | Spike | Feeds | | ----------------------------------------- | ---------------------------------------------------- | | 8 — Layout: side panel + writing column | v0.1 | | 9 — Boot splash bitmap | v0.1 | | 10 — Dark / light theme | v1.0 | | 11 — Transient panel (help / config) | v0.4 `:` · v0.5 palette · v0.9 settings (mechanism) | | 12 — Scroll position indicator | reading / `View`-mode UX | | 13 — Line-number gutter | v0.2 | | 14 — Multi-file navigation | v0.5 | 8. **Spike 8 — Layout: side panel + writing column.** Split the 792×272 landscape into a full-height **writing column** (~60 cols, left) and an always-visible **side panel** (~150 px / ~20 cols, right), per the [Screen layout](v0.1-mvp-product.md#screen-layout). Today the editor fills the full 79-col width with text and a cramped 12 px bottom status ([`firmware/src/editor.rs`](../firmware/src/editor.rs), `COLS`/`ROWS` + `draw_status`); this spike narrows the text to a legible measure and moves all metadata into the panel, retiring the header/status bands entirely. Two driver facts shape it. First, narrowing does *not* speed up typing: `update_part` already drives both controllers full width, windowed only in Y, because "the waveform time dominates, not the data clock-out" ([`firmware/src/epd.rs`](../firmware/src/epd.rs)) — the win is line length and persistent info, not latency. Second, since every partial refresh spans the full width, a keystroke's windowed-Y band repaints the panel's pixels on that row *for free* (redrawn identically), but a panel field that changes on a *different* row than the cursor costs a **second** windowed-Y band — burning the "20 partials → forced full refresh" ghosting counter twice as fast (render module). That sorts what the panel may hold: static (filename, dirty), event-driven (mode, Wi-Fi, keyboard-disconnect, publish state), and throttled (clock, word count, session) fields only — nothing that repaints per keystroke, so no live cursor *column*. The panel sits entirely in the master half (right of the `x = 396` seam), so its glyphs never split the seam; the writing column still straddles it, as today. Prove: render column + panel; type and confirm the windowed-Y refresh stays a single band (panel redraws in place, no second region); then update a throttled field (word count on a typing pause) and a discrete one (mode flip) and confirm each is one isolated band that forces no extra full refresh. Decides the column/panel split in pixels, the panel's field layout and update cadence, and whether the ghosting counter needs per-region accounting. (Feeds v0.1's screen layout — the writing column + side panel the product doc now draws.) 9. **Spike 9 — Boot splash bitmap.** Embed the Typoena logo as a 1-bit asset and blit it, with the build tag, at boot before the editor opens. Spike 2 already proved vector + font rendering, so the only new risk is the image-asset pipeline (embedding + blit) and that a large near-full-frame image takes a clean full refresh. Mostly a feature — kept as a spike only to prove the asset path. (Feeds v0.1's "e-ink shows Typoena splash + boot log".) **Built 2026-07-11 as a *vector* splash**, not a bitmap. The frame is [`display::Frame::splash`](../display/src/lib.rs) — the `typoena` wordmark centred inside a stroked `Circle`, drawn with `embedded-graphics`, one clean full refresh. It is shared by two callers: the [`splash`](../firmware/src/bin/splash.rs) bench binary (`just flash-splash`) and **`main.rs`'s boot path**, which shows it right after EPD init — replacing the old white-clear baseline — while the SD mounts and the note loads, then a second full refresh brings up the editor. Nothing is embedded, so the image-asset pipeline named above is deliberately **left unproven** — an acceptable trade because Spike 2 already covered vector + font rendering. **Proposition, deferred to end-of-project polish (v1.0):** replace the vector mark with an embedded 1-bit raster logo, which is when the asset-embed/blit path would finally be exercised. **Confirmed on the panel 2026-07-11** — the splash renders cleanly at boot, then the editor comes up. This closed the last v0.1 display gate; v0.1 shipped the same day. 10. **Spike 10 — Dark / light theme.** Invert the 1-bit framebuffer (white on black) and refresh. The invert is trivial (XOR at blit); the real unknowns are (a) ghosting and refresh time on a predominantly-black panel — full-black waveforms stress the panel differently — and (b) whether partial-refresh ghosting accumulates faster in dark mode, forcing a more frequent full refresh. Prove: legible inverted text, acceptable ghosting, and partial-refresh latency unchanged from Spike 5. (Feeds v1.0's light/dark theme.) 11. **Spike 11 — Transient panel (help / config).** Prove a modal full-screen view that swaps in over the editor and restores the buffer exactly on exit — the shared primitive behind a help screen, the v0.9 settings screen, the v0.5 file palette (`Ctrl-P`), and the v0.4 `:` command line. The risk is e-ink-specific: entering/leaving with partial refresh leaves ghosting, and the editor viewport underneath must return artifact-free. Prove with a static help screen (trivial content): a full refresh on enter and on exit restores the prior text exactly; measure in/out latency. Decides overlay-box vs. full-screen swap — recommend the swap, since a dimmed partial overlay is both slow and ghost-prone at ~630 ms. Panel *content* (which config keys, help text) is feature work deferred to the owning release; this spike proves only the mechanism. 12. **Spike 12 — Scroll position indicator.** The buffer already scrolls (`View` mode `j`/`k`/`space`); this spike proves how to *show* position without wrecking latency. Measure two affordances on the bench: (a) a right-edge scrollbar repainted each scroll step, and (b) a compact side-panel readout (`34/128` or `27%`). Risk: the scrollbar is a tall pixel column repainted on every scroll — measure its partial-refresh cost against the small side-panel field, on the windowed-Y path, during held-key scroll. Prove: pick the affordance whose refresh cost is acceptable and confirm it forces no extra full refreshes. (Feeds the reading/`View`-mode UX; the a-vs-b choice is 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. **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.) **VERIFIED on the panel 2026-07-11** — a single-line edit repaints only the rows at/below the change, no extra full refresh; closes the last v0.2 gate. 14. **Spike 14 — Multi-file navigation (open / switch / new / delete).** The panel *mechanism* is already Spike 11 (which names this v0.5 file palette), and filename entry reuses the v0.4 `:` command line — so this spike proves neither, and depends on both. What is genuinely new is **persistence and buffer lifecycle**, not rendering: enumerate a FAT directory across *both* `/sd/repo` and `/sd/local`, keep ≤ 3 ropes resident, and on switch swap the active rope + cursor + soft-wrap after an atomic save-of-current (persistence module). Two sharp edges. **New file** (`:enew`) must prompt for scope — tracked (`/sd/repo`, pushed) vs. local (`/sd/local`, `Ctrl-G` disabled). **Delete** extends v0.5 scope (the roadmap lists `:enew` but not delete): removing the currently-open buffer must close it and fall back to another resident buffer or an empty one, and — the load-bearing check — the FAT unlink must reach the next Publish's *staged* set, which the git module's `git add .`-equivalent staging may not catch for removals (needs `git rm` / `add -A` semantics — [`git` module](v0.1-mvp-technical.md#git--commit--push)). Prove: open/switch/new/delete across both roots with a correct ≤ 3-buffer lifecycle, a delete that propagates into the following commit, and an artifact-free full-refresh swap on every buffer change (leaning on Spike 11). Latency is not the risk here; buffer-state and git-staging correctness are. (Feeds v0.5 multi-file, delete included — now authorized in [macroplan](macroplan.md#v05--file-palette--multi-file--) v0.5.)