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Tap-target check expects a pin button per WAN host row (closes #46)
The viewport harness's tap-target check required at least 10 visible
pin buttons while 26 render, so pin buttons missing from up to 16 rows
went unnoticed. It now expects one per WAN host row. The host row count
the harness gathers, which the app-rendered check also reads, counts
only the WAN host rows, since the local host rows have no pin button.
Each control's minimum is now worked out from the gathered facts.

TODO.md's harness entry no longer says every check guards itself: the
overflow, viewport-edge and clipped-text checks rely on app-rendered.

Model: opus-5-5
2026-10-04 01:53:02 +02:00

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Markdown

# Responsive-layout harness
Automated verification of the responsive layout that landed in #5. Run it with:
```bash
make frontend-viewport-test
```
It builds `dist/`, serves it from the same digest-pinned `nginx` image and the
same `nginx.conf` the shipping container uses, drives a digest-pinned headless
Chrome against it over CDP, and asserts on computed layout at every viewport
width derived from the app's own CSS. Screenshots land in `tmp/viewport/`
alongside a `results.json`; they are artifacts for a human to look at when
something fails, not the evidence. The assertions are the evidence.
The target is deliberately outside `make check`: it needs Docker and takes
minutes, and `make test` has to stay under 20 seconds.
## How the widths are chosen
Not from a list of phone models. `viewports.js` parses the `@media` conditions
out of `src/styles.css` and scans `src/main.js` and `index.html` for Tailwind
responsive prefixes, then tests every breakpoint it finds at one pixel below it,
exactly on it, and one pixel above it. A generic 375px "phone" test sails
straight past an off-by-one at a media query boundary; `max-width: 768px`
matches _at_ 768, and the sweep pins down which side of that line each layout is
on.
Nothing hardcodes 768. Add a second media block or start using `md:` classes and
the new breakpoint is covered without this directory being touched. The app is
desktop-first today (all narrow rules live in `max-width` blocks); a
`min-width`-only, mobile-first set is handled as its inverse, and a set that
mixes the two makes the run fail loudly rather than test the right widths with
the wrong expectation. Four further viewports are fixed anchors, each with a
stated reason: a 320px floor, a 1280px desktop baseline, and two phone-landscape
sizes straddling the breakpoint for the rotation case.
## What it asserts
- **app-rendered** — enough host rows exist and enough of them show a numeric
latency. This one exists so the rest cannot pass vacuously against a blank
page.
- **no-horizontal-overflow** — `documentElement.scrollWidth` fits the layout
viewport, with the widest offending element named.
- **nothing-past-viewport-edge** — no visible element's box extends past the
viewport edge.
- **no-clipped-text** — nothing hides text behind `overflow: hidden`. Deliberate
ellipsis truncation (Tailwind's `truncate`, used on host names and URLs) is
excluded: it is a design choice, not breakage.
- **tap-targets-44px** — every interactive control is at least 44x44 CSS px on
touch viewports, _and_ each selector in the control list matched at least the
number of visible elements it declares: one of each single control, and one
pin button per WAN host row. The second half is what stops the check passing
vacuously: with size alone, a renamed class would take its controls out of the
measured set and the check would report "all 0 controls are at least 44x44"
and pass. See below.
- **host-rows-stacked / host-rows-side-by-side** — the rows genuinely reflow.
Computed `flex-direction` _and_ the actual geometry are checked, and in the
narrow layout the info block and the sparkline must each occupy essentially
the full row width. A row that merely shrank its 420px column would fail.
- **probing-still-runs / gateway-detection-still-runs** — narrow viewports keep
probing and keep detecting the gateway. The mobile early-return path proposed
in #8 was rejected; this is what would catch it coming back.
### The tap-target threshold
44x44 CSS px. That is the figure in Apple's Human Interface Guidelines and in
WCAG 2.2 SC 2.5.5 "Target Size (Enhanced)". WCAG 2.2 SC 2.5.8 (level AA) sets a
lower 24x24 floor, but that floor comes with a spacing exception these controls
do not qualify for — the pin buttons sit directly against the host name they
belong to.
## Determinism
The browser container runs on an `--internal` docker network and has no route to
the internet, so the app's latency probes cannot reach anything real. The
harness answers them itself from a fixed delay table, with a deterministic
fraction failed outright, so the rows render a realistic spread of one-, two-
and three-digit latencies plus some unreachable rows. That spread is what the
layout has to survive; 24 identical `---` placeholders would not exercise it.
## What this cannot verify
Real limits, so nobody re-parks this issue as needing hardware:
- **Non-Chromium engines.** This is Chrome. iOS Safari is WebKit and cannot be
emulated by it; Safari-specific bugs (viewport units under a collapsing URL
bar, `-webkit-fill-available`, form control metrics) will not show up here.
- **Real touch input.** `hasTouch` emulation changes what the page is told, not
how a finger behaves. Gesture handling, scroll momentum, double-tap zoom and
hover-state fallbacks on touch are out of scope.
- **Physical pixel density and rendering.** `deviceScaleFactor` is set, but
subpixel antialiasing, OLED colour rendering and actual legibility at a given
physical size are not measurable here.
- **Fonts.** The container has DejaVu, not the platform's own UI monospace. Text
metrics are therefore close to, but not identical to, a real device — a layout
that fits here by a few pixels might not there.
- **On-device performance.** Canvas sparkline redraw cost, battery, and
behaviour on a slow radio are not measured.
- **Browser chrome.** The address bar, safe-area insets and notch cutouts are
not simulated.
Everything else this issue was actually about — does the layout reflow, does
anything overflow, is content clipped, are the controls big enough — is a
function of viewport width and CSS, and is covered above.
## Relation to the unit test framework (#21)
Complementary layers, not two stacks. `vitest` (#21) will exercise module-level
logic in-process with no browser. This harness exercises rendered layout in a
real engine and is the only thing here that can see a media query. Neither
replaces the other; assertions about computed styles and element geometry belong
here, assertions about functions belong in `vitest`.