docs: stage I3 -- documentation rewritten under docs/solo

Short pages by feature (getting started, messages, contacts, navigation,
tools, settings, lock, hardware) instead of one page per OLED screen, with
Wio Tracker L2 differences as notes; facts checked against the code
(keyboard scripts vs. hold-for-accents, {batt}/{dist}, L2 limits and
settings layout). Developer guides and build flags under docs/solo/developer.
Old docs/solo_features and its ~50 screenshots removed; a hero banner and
three simulator screenshots added; links updated.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
This commit is contained in:
Jakub
2026-09-29 08:41:10 +02:00
co-authored by Claude Opus 5.5
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## Build Flags
[Go back](../README.md)
Reference for the `-D` build flags a Solo build understands beyond the
per-board defaults already set in `solo/<board>/platformio.ini`. Add any of
these to your own board's `build_flags` (in `solo/<board>/platformio.ini`) to
enable optional hardware you've wired up yourself, or to tune a default.
Everything below is a no-op when left unset — adding a flag for hardware that
isn't there costs nothing and can't brick a build; the exceptions (pin
conflicts, wrong polarity) are called out per flag.
None of this needs touching to get a board running — see the
[environment list](../../../README.md#building) for the flag-free
default build for each supported board.
---
### Already part of every solo build
Set once per board in `solo/<board>/platformio.ini`, not usually touched
per-user. Listed here so the rest of this page can assume them.
| Flag | Meaning |
| --- | --- |
| `FIRMWARE_SOLO_BUILD=1` | Marks the build as Solo (full on-device UI) rather than a companion-only firmware. |
| `DUAL_SERIAL=1` | The companion app can attach over BLE *or* USB serial, whichever it finds; BLE wins if both are live. Every solo build sets this — Solo standardises on one build per board rather than splitting BLE-only / USB-only variants. |
| `MAX_CONTACTS=<n>` | Size of the contact table. Default is 32 if unset; solo builds set 350. |
| `MAX_GROUP_CHANNELS=<n>` | Size of the channel list. Required for channel support to compile in at all — not optional the way the rest of this page is. |
| `OFFLINE_QUEUE_SIZE=<n>` | How many messages queue for later delivery while the phone app is disconnected. Default 16; solo builds set 256. |
| `UI_SENSORS_PAGE=1` | Enables the on-device sensors dashboard page. |
| `BLE_PIN_CODE=<n>` | See below — not a plain fixed value in practice. |
| `DISPLAY_CLASS=<Class>` | Selects the display driver (e.g. `SSD1306Display`, `GxEPDDisplay`, `ST7789Display` — see `src/helpers/ui/` for the full set). Fixed by whatever panel the board actually has; only relevant if you're wiring on a *different* display than stock, in which case the matching driver's `.cpp` also needs adding to `build_src_filter`. |
**`BLE_PIN_CODE`** has a special case baked in: if it's left at the literal
value `123456` *and* the board has a display, pairing uses a random 6-digit
PIN generated fresh each session and shown on-device, rather than a fixed one.
Any other numeric value is used as a static PIN instead. Leaving the flag out
entirely disables the PIN prompt (BLE pairing is unauthenticated).
---
### Input hardware add-ons
Each of these assumes you're wiring something up yourself — check pins are
actually free on your board first (see the board's `variant.h` and its
existing `solo/<board>/platformio.ini` for what's already claimed).
| Flag | Adds |
| --- | --- |
| `ENV_PIN_SDA` / `ENV_PIN_SCL` | CardKB (M5Stack I2C keyboard, addr `0x5F`) on a second I2C bus (resolves to `Wire1`). Probed at boot — harmless with nothing plugged in. See [External Keyboard & Joystick](../hardware.md#external-keyboard-and-joystick). |
| `CARDKB_I2C=<Wire\|Wire1>` | Same CardKB support, naming the bus directly — for a board with no free pins for a second bus, set `CARDKB_I2C=Wire` to share the primary bus (already used by the display/RTC) instead of defining `ENV_PIN_SDA`/`ENV_PIN_SCL`. Takes precedence if both are somehow set. |
| `UI_HAS_JOYSTICK=1` + `UI_HAS_JOYSTICK_UPDOWN=1` (optional) + `JOYSTICK_UP` / `JOYSTICK_DOWN` / `JOYSTICK_LEFT` / `JOYSTICK_RIGHT` + `PIN_USER_BTN` + `PIN_BACK_BTN` | A wired joystick (four direction contacts + a press contact for Enter). Replaces single-button navigation entirely once enabled. See [External Keyboard & Joystick](../hardware.md#external-keyboard-and-joystick). |
| `PIN_GPIO1` .. `PIN_GPIO4` | Up to four general-purpose pins, each independently switchable between Off / Input / Output (GPIO1/GPIO2 also get an Analog step, if wired to an ADC-capable pin) from Tools › GPIO, and via the `!gpio1`..`!gpio4` bot commands. Not restricted to any particular board — works anywhere the pins are actually free. See [Tools › GPIO](../tools.md#gpio). |
| `PIN_HALL_SENSOR` + `HALL_ACTIVE_HIGH=1` (optional) | A Hall-effect or reed sensor for a magnetic flip cover: closing locks and blanks the screen instantly, opening unlocks and wakes it, no combo either way. `HALL_ACTIVE_HIGH` is only for a module wired to pull the pin high (rather than low) when the magnet is near. See [Screen lock › Magnetic cover](../lock.md#magnetic-cover). |
| `PIN_GPS_SWITCH` | A physical on/off switch for GPS power, read alongside the software GPS toggle — the Tools screen shows `gps off(hw)` / `gps off(sw)` when the two disagree, instead of silently trusting one over the other. |
---
### Output / feedback hardware
| Flag | Adds |
| --- | --- |
| `PIN_BUZZER` (+ `PIN_BUZZER_EN`, optional) | A passive piezo buzzer, driven by direct PWM (nRF52) or the `NonBlockingRtttl` library (everything else) for RTTTL ringtones and UI beeps. `PIN_BUZZER_EN` is an optional enable line some boards wire separately from the signal pin. |
| `PIN_VIBRATION` | A vibration motor for haptic notification, via `GenericVibration`. |
---
### GPS
| Flag | Meaning |
| --- | --- |
| `ENV_INCLUDE_GPS=1` | Compiles in GPS support (NMEA parsing, location provider) at all. |
| `GPS_BAUD_RATE=<n>` | Baud rate for the GPS module's serial link (`Serial1`). Match your module's default. |
`PIN_GPS_SWITCH` (above) is independent of both — it's a hardware kill switch
layered on top of GPS support, not a requirement for it.
---
### Display & battery tuning
| Flag | Meaning |
| --- | --- |
| `OLED_MISC_FIXED_FONT=1` | Pulls in a full Latin/Greek/Cyrillic 6×9 fixed font (~14 KB flash) so typed text in those alphabets renders as itself instead of block placeholders. Worth it on any board with a keyboard; skip it on space-constrained builds without one. |
| `DISPLAY_ROTATION=<0-3>` | Rotates the panel in 90° steps, for a board mounted sideways or upside down. |
| `ENABLE_SCREENSHOT` | Lets Solo Tools read the framebuffer over USB to capture a screenshot. |
| `KEEP_DISPLAY_ON_USB` | Refreshes the auto-off deadline continuously while externally (USB) powered, so the auto-off timer only starts counting once power is actually removed. Off by default because OLED panels burn in quickly with a permanently-lit screen — only worth enabling for an LCD/e-ink target, or a display you don't mind replacing. |
| `AUTO_OFF_MILLIS=<ms>` | How long the display stays on before auto-off. Default 15000 (15s); `0` disables auto-off entirely. |
| `UI_RECENT_LIST_SIZE=<n>` | How many entries the recent-activity lists show before scrolling. Default 4. |
---
### External PA / TX power curve
For a board with an always-on external power amplifier after the SX1262. Both
flags are needed together; leave them unset on a bare-SX1262 board.
| Flag | Meaning |
| --- | --- |
| `LORA_TX_POWER=<dBm>` / `MAX_LORA_TX_POWER=<dBm>` | Default and ceiling for the TX power the app/CLI may request. The SX1262 alone tops out at 22; a board with a PA sets these to what the PA really delivers (the GAT562 30S sets 30). |
| `NUM_PA_POINTS=<n>` + `TX_GAIN_LORA=<g0,g1,…>` | The PA's measured gain in dB for each SX1262 register setting `0 … n-1`. Requesting *X* dBm picks the lowest register setting whose `setting + gain` reaches *X*, clamped at the last entry once the PA saturates — so the reported power matches the radiated one. A request below the PA's floor gain still radiates at that floor, and the value stored/reported back is the power actually applied. |
The GAT562 30S uses the vendor-measured 869 MHz curve from
[meshtastic/firmware#11212](https://github.com/meshtastic/firmware/pull/11212).
Note the on-device **Settings › Radio › TX Pwr** row is still capped at 22 dBm;
values above that are set from the phone app or the CLI.
---
### Misc
| Flag | Meaning |
| --- | --- |
| `ADVERT_NAME='"name"'` | Sets the default node name baked into a fresh device, instead of the hex of the first 4 bytes of its public key. Note the doubled quoting — it's a C string literal passed through a build flag. |
| `MESHCORE_VERSION='"x.y"'` | Overrides the upstream MeshCore base-version string shown in diagnostics, for boards whose port hasn't been rebased onto the latest yet. Cosmetic only — doesn't change protocol behaviour. |
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# Solo UI framework — a guide for adding features
[Go back](../README.md)
This is a developer guide to the reusable building blocks behind the
`companion_radio` **solo** firmware UI (the `ui-new` screens). It is not a
user manual — for what each screen *does*, see the [documentation](../README.md).
The goal here is so that adding a new screen or feature means *wiring together
existing helpers*, not reinventing list scrolling, text wrapping, or persistence.
Everything below lives under `examples/companion_radio/` unless a path says
otherwise. The screen fragments (`ui-new/*.h`) are all `#include`d, in order,
into one translation unit (`ui-new/UITask.cpp`) — so a `static inline` helper in
an earlier header is visible to later ones. Header-include order in `UITask.cpp`
therefore matters; new screens go near the others.
> **Single-TU only.** These fragments compile *only* as part of `UITask.cpp`.
> Some define external-linkage symbols at file scope (e.g.
> `NearbyScreen::FILTER_LABELS`), so including a fragment from a second `.cpp`
> is a duplicate-symbol link error. Anything genuinely shared across TUs must
> live in a real header (`icons.h`, `GeoUtils.h`, `DisplayDriver.h`), not a
> screen fragment.
---
## 1. The screen model
Every screen implements `UIScreen` (`src/helpers/ui/UIScreen.h`):
```cpp
class UIScreen {
public:
virtual int render(DisplayDriver& display) = 0; // returns ms until the next render
virtual bool handleInput(char c) { return false; }
virtual void poll() { }
virtual void onShow() { } // reset per-visit state
};
```
- **`render()`** draws one frame and returns *how long until it wants to be
drawn again*, in milliseconds. Return a big number (`2000`) for a static
screen, a small one (`50`–`200`) while something animates or a popup is open.
This return value is the main lever for the e-ink cost/latency trade-off — see
§9. `UITask` owns `startFrame()`/`endFrame()`; **`render()` must not call them.**
- **`handleInput(c)`** gets one key (`KEY_*`, see §7). Return `true` if consumed.
- **`poll()`** runs every loop tick regardless of focus — rare, for background
housekeeping (e.g. the shutdown button).
- **`onShow()`** is called by `setCurrScreen()` every time the screen becomes
current — override it to reset per-visit state (`_sel = 0`, `_dirty = false`,
sub-views). Default no-op for screens that keep state across visits. Because
it's invoked centrally, a navigator can't forget to reset on show.
### Wiring a screen into UITask
1. Add a `UIScreen* my_screen;` member in `UITask.h` (near the others).
2. Construct it in `UITask::begin()` (`UITask.cpp`):
`my_screen = new MyScreen(this, …);`
3. Add a navigator — usually just the one line (the cast-free `onShow()` runs
inside `setCurrScreen`):
```cpp
void UITask::gotoMyScreen() { setCurrScreen(my_screen); }
```
Only screens needing a *parameter* at entry add a typed call after it (e.g.
`gotoRingtoneEditor` → `selectSlot(slot)`, `gotoMapScreen` → `showMapView()`).
4. Reach it from somewhere — usually a row in `ToolsScreen.h` (add an `Action`
enum value, a row in the right section table, and a `dispatch()` case).
That's the whole contract. Steps 1, 3 and 4 are compiler-checked (a mismatch
won't link); only a forgotten step 2 can slip through — every screen pointer is
nullptr-initialised in `UITask.h` and `setCurrScreen()` bails on null, so a
missed `new` is an inert no-op rather than a null deref.
The constructor takes `UITask* task` plus whatever it needs (`NodePrefs*`,
`KeyboardWidget*`, …); the task back-pointer is how a screen calls shared
services (`_task->showAlert(...)`, `_task->waypoints()`, …).
---
## 2. Layout metrics & text (DisplayDriver)
`DisplayDriver` (`src/helpers/ui/DisplayDriver.h`) abstracts OLED vs e-ink and,
crucially, font scale: landscape e-ink renders text at 2×, so **never hard-code
pixel sizes** — derive everything from these:
| Call | Meaning |
| --- | --- |
| `getLineHeight()` | pixel rows per text line (8 at 1×, 16 at 2×) |
| `lineStep()` | row pitch = line height + gap; use for row `y` stepping |
| `getCharWidth()` / `getTextWidth(s)` | advance width; `getTextWidth` is font-accurate |
| `headerH()` / `listStart()` | title-bar height / first content row `y` |
| `listVisible(itemH)` | how many rows fit below the header |
| `valCol()` | conventional x for a right-hand value column |
| `width()` / `height()` | panel size in px |
| `isEink()` | true only on landscape e-ink; branch on this, not on pixel counts |
Drawing helpers (all clip/measure for you):
- `drawCenteredHeader(title, menu_hint=false, menu_open=false)` — plain centered
title + separator.
- `drawInvertedHeader(label, menu_hint=false, menu_open=false)` — filled title
bar (used by detail views).
- Both take an optional `menu_hint`: pass `true` on a screen with a Hold-Enter
context menu to reserve a `≡` glyph (`menuHintWidth()`/`drawContextMenuHint()`)
in the header, so the menu is discoverable without already knowing the
shortcut; `menu_open` highlights it while the menu is actually up.
- `drawSelectionRow(x, y, w, h, sel)` — the highlight bar behind a list row.
- `drawTextEllipsized(x, y, max_w, str, selected=false)` — truncates with `…`;
**use this for any user string** (names, labels) so long/UTF-8 text can't
overrun. Pass `selected=true` for the currently-selected row and the text
that doesn't fit marquee-scrolls into view (pause → scroll to the end →
pause → scroll back), instead of just sitting behind the ellipsis; returns
the ms until the next redraw is needed for that animation to stay smooth
(0 when nothing is scrolling) — thread it into your screen's own `render()`
return value the same way you already clamp for anything else that needs a
faster redraw. Only one row UI-wide marquees at a time (whichever is
currently selected), so there's no risk of two animations racing each
other for the shared timing state.
- `drawTextCentered(mid_x, y, str)`.
- `translateUTF8ToBlocks(dst, src, n)` — map UTF-8 to the panel's glyph set for
*display only*. Never run text through it before sending it over the air or
storing it (it is lossy) — see the reply-prefix note in §5.
---
## 3. Lists — `drawList`
`drawList` (`ui-new/icons.h`) is the workhorse for any scrolling list. It
computes the visible window from font metrics, keeps `sel` in view, reserves the
scrollbar column, draws each visible row through your callback, and draws the
indicator:
```cpp
drawList(display, count, _sel, _scroll, [&](int idx, int y, bool sel, int reserve) {
drawRowSelection(display, y, sel, reserve); // canonical highlight bar
display.drawTextEllipsized(2, y, display.width() - reserve - 4, items[idx].name);
});
```
`reserve` is the width the scrollbar took (0 when the list fits) — subtract it
from any right-aligned content so nothing slides under the indicator. The row
callback owns its own selection bar: `drawRowSelection(d, y, sel, reserve)`
(`ui-new/icons.h`) draws the standard one (full row minus reserve, one pixel
short); call `display.drawSelectionRow()` directly only when a row needs a
non-standard geometry (full-width, custom height). For the
fold-in-place pattern (sections that expand/collapse) use `AccordionList`
instead (`ui-new/AccordionList.h`) — same idea, two callbacks (header + item).
Standalone scroll indicators (`drawScrollIndicator`, `…Px`) and the reserve
calculator (`scrollIndicatorReserve`) are exposed for hand-laid lists.
---
## 4. Reusable components
| Component | Header | Use for |
| --- | --- | --- |
| `PopupMenu` | `PopupMenu.h` | a modal action menu over any screen |
| `AccordionList` | `AccordionList.h` | collapsible sectioned lists (Tools, Settings) |
| `KeyboardWidget` | `KeyboardWidget.h` | on-screen text entry |
| `DigitEditor` | `DigitEditor.h` | scroll-edit one number, digit by digit |
| `FullscreenMsgView` | `FullscreenMsgView.h` | scrollable full-message reader + word wrap |
| `NavView` | `NavView.h` | bearing/distance/ETA "navigate to a point" view |
All follow the same shape: a `begin(...)` to open, an `active` flag, a
`handleInput(c)` returning a small `Result` enum, and a `render()`/`draw()`.
Typical embedding:
```cpp
if (_menu.active) { // popup eats input while open
auto r = _menu.handleInput(c);
if (r == PopupMenu::SELECTED) runAction(_menu.selectedIndex());
return true;
}
...
_menu.begin("Options", 6); // open it
_menu.addItem("Navigate"); _menu.addItem("Ping");
_menu.active = true;
```
`KeyboardWidget` additionally supports **placeholders** (`{loc}`, `{time}`,
sensor tokens) via `addPlaceholder()` / `clearPlaceholders()`; the shared
`kbAddSensorPlaceholders()` (`ui-new/SensorPlaceholders.h`) adds only the tokens
the board's sensors actually provide. Expand them with `expandMsg()` at send time.
Two layouts share every grid: **ABC** (one key per letter) and **T9**
(phone-keypad multi-tap — repeated Enter within `KB_T9_TIMEOUT_MS` cycles a
cell's letter group, then its digit). Page 0 is no longer hardcoded to Latin:
`NodePrefs::keyboard_main_alphabet`/`keyboard_alt_alphabet` (Settings >
Keyboard's Main/Additional rows) each pick a script — Latin, Cyrillic, or
Greek — for page 0 and page 1 respectively (`KeyboardWidget::mainScript()`/
`altScript()`); equal values collapse to a single script + Symbols (2 pages
instead of 3, see `hasAltAlphabet()`). `scriptCellStr()`/`scriptT9GroupStr()`
dispatch each script to its own ABC grid (`KB_CHARS`/`KB_CYRILLIC_CHARS`/
`KB_GREEK_CHARS`) and T9 group table (`KB_T9_GROUPS`/`KB_T9_GROUPS_CYRILLIC`/
`_GREEK`) so the two layouts always offer the same letters regardless of which
page they're on. Latin-diacritic letters (Polish, Czech, German, etc.) aren't
alt-alphabet pages — they're reached by Hold-Enter on whichever page currently
shows Latin instead (see `KB_ACCENT_VARIANTS` below).
Shift is one-shot by default (capitalises the next letter, including whichever
candidate a T9 multi-tap cycle settles on) or Hold-Enter to toggle caps-lock;
Hold-Clear erases the whole field. **UP from the top letter row** enters
**cursor mode** (LEFT/RIGHT move the insertion point; UP/DOWN jump to
start/end, then — pressed again once already at that boundary — continue on
to the special row / letter grid, the same destinations the plain grid wrap
used to reach directly) so edits/inserts can target any point in the typed
text, not just the end; Enter/Cancel exit immediately from anywhere.
Hold-Enter on a Latin-page letter cell with accented variants instead opens
the **accent popup**: one horizontal row of `KB_ACCENT_VARIANTS[group]`
(a UTF-8 string per base letter, same shape as a T9 group string), LEFT/RIGHT
to pick, Enter to insert via the shared `insertGlyph()` helper, Cancel to
dismiss. Holding a letter with no variants, or any T9/alt-alphabet/symbols
cell, is a no-op.
`FullscreenMsgView::wrapLines()` is a standalone pixel-accurate word-wrapper
(O(n), variable-width-font aware) reusable by any multi-line layout; it writes
into the shared `s_wrap_trans` / `s_wrap_lines` scratch (single-threaded render,
never held across a yield — see §9).
---
## 5. Domain helpers
**Geo (`GeoUtils.h`, namespace `geo`, all pure/header-inline):**
- `haversineKm(lat1,lon1,lat2,lon2)`, `bearingDeg(...)`, `bearingCardinal(deg)`.
- `fmtDist(buf,n,km,imperial)` — "850m"/"2.3km" or feet/miles.
- `fmtAgeShort(buf,n,now,ts)` — compact "12s"/"5m"/"3h"/"2d" tag, "" for unknown.
**This is the one age formatter** — don't reimplement the s/m/h ladder.
- `parseLatLon(text, lat, lon, label?, n?)` — pull a `lat,lon` out of message
text; reads the `[WAY]` label if tagged.
- `parseLocShare(text, lat, lon)` — true only for an explicit `[LOC]` share.
Coordinates are **int32 degrees × 1e6** everywhere (GPS, contacts, trail,
prefs). The message tags are `LOCATION_MSG_TAG` (`[LOC]`, the sender's own live
position) and `WAYPOINT_MSG_TAG` (`[WAY]`, a saved point to share); both stay
human-readable on clients that don't know them.
**State stores:** `TrailStore` (`Trail.h`, GPS breadcrumb ring + GPX export),
`LiveTrackStore` (`LiveTrack.h`, RAM table of others' `[LOC]` positions, expiring),
`WaypointStore` (`Waypoint.h`, persisted saved points). Reach them via the task
(`_task->trail()`, `_task->liveTrack()`, `_task->waypoints()`).
**Message reply prefix:** `msgReplyBody(text, nick?, n?)` (`FullscreenMsgView.h`)
parses a leading `@[nick] ` reply marker, returning the body and optionally the
addressee. Use it instead of re-scanning for `@[`. The stored/sent prefix is raw
UTF-8 (it goes over the air) — never transliterate it.
---
## 6. Mini-icons & the status bar
Small glyphs are authored as ASCII art and packed at compile time
(`ui-new/icons.h`):
```cpp
MINI_ICON(ICON_FOO, 5,
packRow("..#.."),
packRow(".###."),
packRow("#####"));
```
Draw with `miniIconDraw(display, x, topY, ICON_FOO)` (auto-scaled & centered),
`miniIconDrawTop` (exact placement), or the boxed/slot variants
(`drawBoxedIcon` = lit when active, `drawSlotIcon` = plain). Bigger page glyphs
use `BIG_ICON` / `bigIconDraw`. The home status bar composes these right-to-left
with a `blinkOn()` cadence for "leave it on and forget" broadcasts (auto-advert,
Live Share, trail, repeater) — follow that pattern when adding an indicator:
always shown on e-ink, blinking on OLED.
Icons are drawn from a fixed priority-ordered table (`HomeScreen::renderBatteryIndicator()`,
`UITask.cpp`); once the row runs out of horizontal space the loop just stops,
so the lowest-priority icons silently drop first rather than the whole bar
crushing the node name. A blinking icon still reserves its width on the
off-phase of its blink, so the row's layout can't visibly shift width as icons
blink in and out.
Screens with a Hold-Enter context menu (Nodes, Bot, Admin, Diagnostics, …) pass
`menu_hint=true` to their header call (see §2) so a `≡` glyph advertises the
menu; `KEY_CONTEXT_MENU` (Hold-Enter) opens it.
---
## 7. Input
Keys arrive as the `KEY_*` codes in `UIScreen.h`: `KEY_UP/DOWN/LEFT/RIGHT`,
`KEY_ENTER`, `KEY_CANCEL`, `KEY_CONTEXT_MENU` (the "Hold Enter" menu key).
Use the **prev/next convention** for value changes so the rotary encoder and the
D-pad agree: `keyIsPrev(c)` (LEFT or encoder-prev) and `keyIsNext(c)` (RIGHT or
encoder-next). `KEY_CANCEL` and `KEY_CONTEXT_MENU` stay screen-specific. Joystick
rotation is handled upstream (`rotateJoystickKey`) — screens see already-rotated
keys.
### From hardware to `handleInput`
Each physical button is a `MomentaryButton` (`src/helpers/ui/MomentaryButton.h`);
`UITask::begin()` must call `begin()` on **every** one (the joystick directions
and Back included, not just the user button) — that sets `pinMode` and, where
enabled, claims the interrupt. `UITask::loop()` polls each button, maps its event
to a `KEY_*` code, and dispatches it to the current screen.
Two mechanisms keep input responsive when **`endFrame()` blocks the loop** for a
slow e-ink refresh:
- **IRQ edge capture** (`-D BUTTON_USE_INTERRUPTS`, e-ink boards). A GPIO
interrupt latches each press/release edge into a per-button ring buffer with
its own timestamp, so taps that land *during* a refresh aren't lost; `check()`
replays them afterwards. The nRF52 has only 8 GPIOTE channels (the radio takes
one) — if none is free a button silently falls back to polling, so it still
works, just without mid-refresh capture.
- **Key queue + coalesced redraw.** `loop()` drains *all* pending events from the
buttons into a small key FIFO, applies the whole burst (`handleInput` per key),
then redraws **once**. So three joystick flicks captured during one refresh move
the selection three steps for the cost of a single panel update, instead of
collapsing into an ignored multi-click or one-step-per-refresh. Buttons created
with `multiclick=false` therefore emit one discrete `CLICK` per release;
`multiclick=true` buttons still report double/triple-click.
---
## 8. Persistence
Device settings live in one `NodePrefs` struct (`NodePrefs.h`), saved via
`the_mesh.savePrefs()` and loaded by `DataStore.cpp`. Rules when adding a field:
- **Append only**, and bump `NodePrefs::SCHEMA_SENTINEL`. Serialization is
binary-positional, so order is the on-disk format; never insert in the middle.
- Add a matching `rd(...)` in `DataStore::loadPrefsInt()` and a `file.write(...)`
in `savePrefs()`, in the same position, and **clamp on load** (an upgrader's
file lacks the field and reads stray bytes — clamp to a sane default). Saves
are atomic (temp-file + rename), so a crash mid-save can't corrupt settings.
**The `_dirty` convention:** a multi-field editor screen mutates `_node_prefs`
live for instant feedback but only persists once, on exit, gated by a `_dirty`
flag — so LEFT/RIGHT value-cycling doesn't thrash flash. Set `_dirty = true` at
each edit site, then on the exit path call `_task->savePrefsIfDirty(_dirty)`
(`UITask`) — it saves once *iff* dirty and clears the flag, so every screen's
save-on-exit reads the same and the "did we touch flash?" decision lives in one
place. A one-shot action from a popup (no exit hook) calls `the_mesh.savePrefs()`
immediately. Follow whichever matches your screen.
**The shared "active target"** (Locator/Nav destination) is set through
`UITask::setTarget()` (defines it), `setTargetNow()` (defines + saves + toast),
or `clearTarget()` — one definition used by the Locator screen, the map, and the
Nearby/Waypoints "Set as target" actions. Resolve a person's current position
with `resolvePersonPos()` (live `[LOC]` share, else last-advertised fix).
---
## 9. Conventions & gotchas
- **Single-threaded render.** Rendering and input run on one thread, so shared
static scratch (`s_wrap_*`) is safe *as long as it's never held across a
yield*. Don't add scratch that outlives one `render()`.
- **e-ink blocks.** `endFrame()` on e-ink stalls the main loop for hundreds of
ms. Keep `render()`'s return value honest so the panel isn't redrawn more than
needed, and don't depend on `loop()` cadence for timing that must be exact
(the ringtone player moved to a hardware timer for this reason).
- **Reference cleanup.** Anything that remembers a contact by pubkey (favourite
slot, Locator/Live-Share target, per-contact mute/melody) or a channel by
index must drop that reference when the entity goes away. The UI Core does
it for every frontend: `UiCore::cleanupContactPrefs()` (ui-core/UiCore.h) and
`chanctl::onRemoved()` (ui-core/ChannelControl.h). New per-contact or
per-channel state should clear there too.
- **Toasts:** `_task->showAlert("msg", duration_ms)` overlays a transient banner
over any screen; no redraw plumbing needed.
- **Strings:** always `strncpy`+NUL or `snprintf`; treat every name/label as
untrusted-length and render through `drawTextEllipsized`.
---
## 10. Worked example — a new Tools screen
```cpp
// ui-new/MyToolScreen.h — included by UITask.cpp near the other screens
#pragma once
#include "icons.h" // drawList + mini-icons
#include "../NodePrefs.h"
class MyToolScreen : public UIScreen {
UITask* _task;
NodePrefs* _prefs;
int _sel = 0, _scroll = 0;
bool _dirty = false;
static const int ROWS = 3;
public:
MyToolScreen(UITask* t, NodePrefs* p) : _task(t), _prefs(p) {}
void onShow() override { _sel = 0; _scroll = 0; _dirty = false; }
int render(DisplayDriver& d) override {
d.setTextSize(1);
d.drawCenteredHeader("MY TOOL");
drawList(d, ROWS, _sel, _scroll, [&](int i, int y, bool sel, int reserve) {
drawRowSelection(d, y, sel, reserve);
d.setCursor(4, y);
d.print(i == 0 ? "Alpha" : i == 1 ? "Bravo" : "Charlie");
});
return 500;
}
bool handleInput(char c) override {
if (c == KEY_CANCEL) {
_task->savePrefsIfDirty(_dirty); // saves once iff dirty, then clears
_task->gotoToolsScreen();
return true;
}
if (c == KEY_UP) { _sel = (_sel + ROWS - 1) % ROWS; return true; }
if (c == KEY_DOWN) { _sel = (_sel + 1) % ROWS; return true; }
if (keyIsPrev(c) || keyIsNext(c) || c == KEY_ENTER) {
/* mutate _prefs…, set _dirty = true */ return true;
}
return false;
}
};
```
Then: `#include "MyToolScreen.h"` in `UITask.cpp`, add the member + constructor +
`gotoMyToolScreen()` (§1), and add a row in `ToolsScreen.h`. Done — scrolling,
the scrollbar, font scaling, e-ink pacing and persistence batching all come from
the framework.