The runtime kept a back stack, a launcher fallback, an app id and a title
because a teardown destroys the Lua that would otherwise hold them. Only
the first of those is true: everything about where an app came from can
ride in the arguments, and the arguments are the one value that has to
outlive the VM.
So the runtime now does four things -- close the state, load a path, hand
the next state its arguments, defer the swap to a batch boundary -- and
sys.startApp(path, args) is the whole of navigation. Routing, history,
titles and data directories move to the Lua file a firmware boots, where
they can differ per product without a flag on Runtime.
Arguments cross as JSON, encoded while the sending state still holds the
table, so a function or a cycle raises at the call rather than stranding
a launch. start(args) receives the decoded table, or nil at boot, which
is how the entry file knows to open its own launcher.
Removes launch, replace, back, canGoBack, getAppID, getAppTitle,
setAppTitle and getAppDataPath, along with the home and data fields.
LANDSCAPE.md goes with them: it recorded a divergence from firmwares that
have since migrated.
lua-cjson decodes straight onto the Lua stack, so a response costs its
text plus the table it becomes rather than a document in between, and it
brings the encode half that a C tokenizer would have left to write here.
It is a module rather than a global: a global namespace is a contract a
firmware implements, and nothing about this needs a provider. Registering
into package.preload also puts it ahead of the SD-card searcher, so an
implementation cannot be shadowed, and an app that never requires it
never pays for the module.
Depth is capped at 32 through the module's own knobs rather than by
patching the vendored source. Decoding recurses on the C stack and
upstream defaults to 1000, which assumes a server rather than a FreeRTOS
task.
The runtime has always called fields on the table main.lua returns, but
@lua-global declared them as loose functions, so the stubs type-checked
something that does not exist and read as "define a global".
Callbacks are now @lua-app blocks that generate a class: App for the core
contract, TouchHandlers and ButtonHandlers beside the namespaces they belong
to. An app composes what it implements:
---@class PaintApp : App, TouchHandlers
Names follow the rest of the surface: onTouchDown rather than on_touch_down,
with the field names the runtime looks up renamed to match. @lua-field carries
the plain fields (home, data) that were prose in a preamble before.
Namespaces were shared across features: `settings` was written by core, the
panel and touch, and `input` by touch and buttons. That made "does this
firmware implement the whole feature?" a question no pointer could answer.
Each namespace now belongs to exactly one feature or to core, so a feature is
a provider pointer and the compiler validates completeness:
gui, node -> screen, tree, under the screen feature
settings -> screen (rotation, theme), sys (timezone),
touch (calibration)
input -> touch, buttons
Runtime::open() no longer requires a GuiProvider; a firmware without one runs
with no screen/tree globals and reports sys.hasFeature("screen") false.
Rotation is one value again: GuiProvider::setRotation applies and persists, so
an app rotating the panel transiently puts the old value back itself.
A build allocates a spec table per node and drops them all at once, so an
app that scans WiFi right after a screen change met whatever the incremental
GC had got around to. Costs a few ms on a screen change; recovers ~24 KB.
Chrome takes the top of the panel before an app builds anything, and layout
has not run yet when it does, so ui.frame() reports what the mount left it.
Fullscreen was the firmware surrendering a strip it clipped apps out of.
The strip is a sibling node now, so an app that wants the panel is chrome
choosing not to build itself.
Chrome and the app now share a tree, so a screen is no longer something an
app constructs and holds: ui.mount() takes the function that builds the
whole thing and ui.rebuild() runs it again. Building a node after layout
is refused rather than silently resetting the arena under the panel.
The firmware knew four paths and called four globals, so the card could
not change its own layout or put anything around an app. It now loads one
file, and the table that file returns owns the rest: start() mounts the
route, home and data name the tree, and every callback is a field on it
rather than a global the app and its chrome would have to share.
The Lua modules were split between tabs and spaces because nothing pinned a
style; .editorconfig is what lua-language-server reads on save, so the editor
and the tree now agree. clang-format already had a config and left native/
unchanged. Embedded modules regenerate from the reformatted ui.lua.
The controller and the WiFi driver each need a large aggregate allocation,
which a live app sitting on garbage can deny - that is why a failed connect
often succeeded on retry. Both bindings now collect before initializing, and
the tree reserves its node and spec capacity so a build does not reallocate
into a tight heap.
Two columns portrait and three landscape read better than 3/4 on a 320x480
panel. The new disabled palette role sits between face and muted, for a
control that is present but inactive.
ui.lua and hints.lua are compiled to LUA_32BITS bytecode (matching the
firmware's Lua build) and linked into the binary. A new package.searchers
entry checks them as the fallback after the SD card, so a local
/.lua/lib/ui.lua still shadows the packaged one for debugging.
Bytecode is ~40% smaller than source and loads without parsing. A fresh
SD card with no make sdcard now has the platform available.
evan