A node was a Lua table of ~625 bytes, of which 21 keys pushed it over a
power-of-two hash boundary and eight were style copies inheritance had
splattered down from its parent. A 400 node screen cost ~250 KB and could not
coexist with wifi's buffers.
The tree now lives in src/ui/layout.h as a 16 byte struct in a flat arena, and
splits by lifetime: Node holds what hit testing and repainting need forever,
Spec holds what only measure/place read and is dropped when layout ends. Style
is sparse and resolved by walking parents, so a node naming no colours costs
nothing. Re-layout rebuilds from Lua rather than retaining the inputs.
401 nodes: 8218 B steady, 21050 B peak
Lua: ~250000 B steady
sdcard/lib/ui.lua stays the toolkit and keeps every constructor signature, but
returns integer handles: 627 lines to 374. Composition, the palette and custom
painters are still Lua on the SD card; only primitives now need a reflash.
BREAKING CHANGE: ui constructors return handles, not tables. Use
ui.setText(id, text) and keep per-node app data in a table keyed by id.
The firmware now fires on_touch_move with a 2px noise threshold; gesture
intent is the toolkit's 8px slop, since a painting app's stroke starts at
the first real pixel. Past the slop, Screen:move hands the drag to the
nearest scroll ancestor and cancels the widget under the finger.
ui.scroll leans on the app viewport for clipping, so it must reach both
panel edges. Paint and Scroll demo both halves of the gesture split.
Remove OpenFontRender, embedded Meslo assets, custom-font APIs, and their runtime allocation overhead. Keep the taller status layout and compact card grid, with used RAM, aligned faded WiFi bars, and tighter telemetry rows.
Cache font heights, release FreeType glyph state between apps, and catch renderer allocation failures before they cross Lua and abort the device. Individual low-memory draws degrade to allocation-free Font 1. Show disconnected WiFi as three faded zero-signal bars without expanding the icon footprint.
Embed a Latin-1 Meslo LG S default and use OpenFontRender for anti-aliased text with an explicit pixel size on each draw and measurement call. Apps may replace the one retained face with an SD-backed TTF and restore Meslo with nil. Refresh UI sizing, status telemetry, Settings typography, tests, documentation, and font license notices.
Make sys.launch push the current path and argument, sys.replace switch without pushing, and sys.back restore the previous route. The status-bar chevron uses the same back action, failed child apps return to their caller, and history is capped at eight routes. Remove the redundant Settings back card.
The directory name is what the status bar and the launcher cards display, so Home,
Hello and Settings read as titles without a lookup table. Updates the firmware's home
path, the launcher's self-exclusion and the host tests that load the settings app.
Also brings the bar's next repaint forward when an app renames itself or the frame
rotates. The bar still decides what changed; this only stops the answer waiting most of
a second for the next tick.
sys.launch(path, arg) carries a string to the next app's init(arg), nil when there is
none. States share no memory, so one string is the whole handoff; anything structured
travels as a Lua literal the receiver loads. This is what a screen split across apps
needs to say "collect a password for this network".
sys.setAppName() retitles the status bar, defaulting to the directory name as before. A
setter rather than a declared constant, so one app can retitle per screen. The bar needs
no new invalidation path for it -- the name joins rotation and theme in the cache key --
and clips a name wide enough to reach the memory slot.
evan