flutter_example_template 0.1.0

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First release. The shell was built inside the example app of a Flutter table package over roughly a dozen tickets, extracted once it had been proven portable, and rebuilt here around three ports.

What a consumer gets

• ShellPage — a category menu, a preview stage and a knob region, holding one destination at a time.
• PreviewStage, PreviewFrame and ViewportSpec — a subtree rendered as if it were running at desktop, tablet or phone size: constrained, told that is the whole screen, and given its own Overlay so tooltips and drags stay inside the frame.
• DeviceWall — all three viewports at once, live, over one shared state. The single-viewport modes answer what something looks like at a width; the wall answers what changed between them.
• CodePane — a recipe's own source, read out of the asset bundle so what is on screen and what executes cannot disagree. flutter_syntax_highlight tokenizes it into a partition, so concatenating every token reproduces the file byte for byte, and this package decides only what a kind looks like.
• PresetBar, FeatureListPane, FeatureDetailPane — a settings panel drawn from a description of groups, features, options and the interactions between them, with search over control labels.
• MetricsPanel and MetricsChip — named readings the consumer formats and assigns a severity, since the thresholds belong to whoever knows what is being measured.
• exampleTheme — chrome that carries no hue, so the only colour on screen is the one your package is wearing. The font family is a parameter; this package ships no typeface and names none. The palette is not a parameter, and ADR-0013 says what that buys.

The three ports

ShellDestinations carries what the menu points at and its lifetime. SettingsHost is five members, each read off a real call site. PresetSummary carries a preset's name and what to watch for, and deliberately not what it turns on. Writes across the seam are commands — setSwitch(id, on), applyPreset(id) — never a settings object, because constructing one means knowing its type.

The property, and what enforces it

Nothing in lib/ names what it demonstrates. Three rules hold what the compiler will not, all of them legal Dart when violated: nothing under lib/ imports outside dart:, package:flutter/ and flutter_syntax_highlight; nothing outside lib/src/ reaches into it; and the barrel and the tree name the same files, both ways. A fourth lives in example/ — a file the Code pane shows imports no shell.

Also in this release

• example/ demonstrates an adaptive action bar, deliberately not a table.
• docs/adr/ records thirteen decisions, including the ones most likely to be re-proposed: no demo framework, the font as a parameter but not the palette, no line numbers in the Code pane, why this package is depended on rather than copied, why the SDK floor is 3.27.0 and not the 3.22 the code alone would reach, and why the import allow-list grew to three.
• The Dart tokenizer is flutter_syntax_highlight rather than 485 lines under src/. Measured before it was decided: the two disagree on 1,821 characters of 38,492, every one of them the package being finer — string interpolation most of all, which the copy painted as one flat literal.
• .github/workflows/ci.yml runs both suites on four legs — the declared floor and the current stable, on Linux and on Windows. The platform axis is there because a property in portable_seam_test.dart had been red on Windows since the day it was written, and nothing was looking.
• .github/workflows/screenshots.yml runs tool/screenshots.sh when lib/, example/ or tool/ moves, and weekly besides. It gates on the script's own exit code — a shot it could not reach — and uploads what it captured rather than committing it, because a bot that commits screenshots is a bot that can quietly replace the front page.
• tool/screenshots.sh regenerates the README images by driving the example in headless Chrome, pressing controls by their semantics label and checking the state it reached before capturing. The Code pane's shot also checks the picture, because its content is painted to a canvas that no label can see.

Runs on Flutter 3.27.0 and up, and that floor was measured rather than inherited from whatever built it: both suites — 23 tests here, 11 in the example — pass and analyse clean on 3.27.0 and on 3.41.9, and 3.24.5 fails with exactly one error, CardThemeData in example_theme.dart. pubspec.yaml names that line, and says why it is not swapped for the older spelling that would reach lower still. The upper end is held by CI rather than by memory: the latest stable legs resolve 3.47.2 and run the same suites on every push.