# Design: PWA Mobile BottomNav + Drawer

**Author:** cronus (inventor)
**Date:** 2026-04-26
**Task:** t-paliad-041
**Status:** Design complete — awaiting m's go/no-go before implementation
**Reference:** `~/dev/web/docs/pwa-baseline.md` (canonical PWA pattern across m's web surfaces)

---

## 1. Executive Summary

Paliad's current navigation is **desktop-first**: a 64px collapsed / 240px
expanded left **Sidebar** (with hover/pin) on `≥1024px`, a slide-out
drawer with a top-left hamburger on `<1024px`. This works on a laptop. On
a phone it does not — the hamburger is a long thumb-stretch and every
common action (open Agenda, create a Frist) is two taps deep behind it.

This design adds a **bottom navigation bar** for phones (`<768px`) per
the m-stack PWA baseline:

- 5-slot fixed bottom bar with thumb-reach icons.
- Center slot opens a **slide-up Quick-Add sheet** (Frist / Termin / Projekt).
- Right-most slot opens the existing **mobile sidebar drawer** (no new drawer — we reuse what already works).
- Auto-hides when the on-screen keyboard opens (`visualViewport` watcher).
- Honors `safe-area-inset-bottom` so iOS home-indicator doesn't sit on top of the buttons.

The desktop Sidebar (≥1024px) is unchanged. Tablets (768-1023px) keep
the current hamburger-drawer pattern. Only phones gain BottomNav.

PWA shell items split into "do now" (cheap, required) and "defer to a
follow-up task":

- **Now:** `viewport-fit=cover`, `theme-color`, `apple-mobile-web-app-*`
  meta tags so iOS draws under the notch and `safe-area-inset` actually
  has values.
- **Later (separate task):** `manifest.json` + icon assets, service worker,
  add-to-home-screen prompt UI.

---

## 2. Why These Choices (HLC Patent Lawyer Perspective)

The user is a litigator-in-the-hallway — between meetings, on the train,
in court anteroom. The phone use-case is overwhelmingly **read** rather
than create:

1. *"What's coming up this week?"* → Agenda, Dashboard
2. *"What's the status on this matter?"* → Projekte detail
3. *"Quickly capture a Frist I just got told about"* → create Frist
4. *"What's the Frist for replying to office action X?"* → Fristenrechner (rare on phone)
5. *"Settings / Glossar / Kostenrechner"* → desk activities, rare on phone

The bottom slots therefore optimise for read-heavy, with a single
prominent capture path in the center. Tools/Wissen/Settings live in the
drawer because phone use of those is rare and a one-tap detour is fine.

---

## 3. Slot Layout

**5 slots, decided:**

```
┌─────────────────────────────────────────────────────────┐
│                                                         │
│                  [page content]                         │
│                                                         │
├─────────────────────────────────────────────────────────┤
│                                                         │
│   [🏠]      [📁]      ╔══[+]══╗     [📅]      [☰]       │
│  Start    Projekte    Anlegen    Agenda    Menü        │
│                                                         │
└─────────────────────────────────────────────────────────┘
   ↑          ↑           ↑           ↑          ↑
 Dash      Projekte    Quick-Add   Agenda      Drawer
 (/dashboard)  (/projects)  (sheet) (/agenda)  (toggle)
```

| Slot | Label DE | Label EN | Target | Icon (reuse from Sidebar.tsx) |
|------|----------|----------|--------|-------------------------------|
| 1 | Start | Home | `/dashboard` | `ICON_GAUGE` |
| 2 | Projekte | Projects | `/projects` | `ICON_FOLDER` |
| 3 | Anlegen | New | (opens sheet) | `ICON_PLUS` (new) |
| 4 | Agenda | Agenda | `/agenda` | `ICON_AGENDA` |
| 5 | Menü | Menu | (opens drawer) | `ICON_MENU` |

### Why Dashboard + Agenda over Dashboard + Fristen

Initial brief proposed `[Dashboard / Projekte / + / Fristen / Menu]` or
`[... / Agenda / Menu]`. **Agenda wins** because:

- Agenda merges Fristen *and* Termine into one date-sorted timeline
  (shipped in t-paliad-030). On a phone you almost never want one but
  not the other — you want "what's next".
- Fristen is reachable from Agenda items (each row deep-links to
  `/deadlines/{id}`) and from the drawer.
- Dashboard already gives the high-level "traffic light" overview
  (overdue / today / week / later) — Agenda gives the actionable list
  underneath. Pairing them in the BottomNav covers ~80% of phone reads.

### Why Projekte not Termine

Termine alone is too narrow for a top-level slot. A patent lawyer's
mental model is "I'm working on matter X" — Projekte is the natural
hub. Termine is reachable from a project's detail page or from Agenda.

### Active-state highlighting

Same rule the Sidebar already uses (`navItem` active logic): a slot is
active when its `href` is a prefix of `currentPath`. So `/projects/abc`
keeps the Projekte slot lit, `/deadlines/{id}` lights nothing in
BottomNav (deadlines aren't a top-level slot — that's fine, the
breadcrumb still works).

---

## 4. Center Slot: Quick-Add Sheet

A **slide-up sheet** (not a navigation) with three options:

```
┌─────────────────────────────────┐
│           ─────                 │  ← drag-handle
│                                 │
│   📅  Frist anlegen           › │  → /deadlines/new
│   🗓  Termin anlegen          › │  → /appointments/new
│   📁  Projekt anlegen         › │  → /projects/new
│                                 │
│           [Abbrechen]           │
└─────────────────────────────────┘
```

### Why a sheet, not a deep-link

| Option | Pros | Cons |
|---|---|---|
| **Sheet w/ 3 options** ✅ | One predictable place; works on every page; matches "primary capture/add" idiom from baseline doc | One extra tap vs deep-link |
| Always `/deadlines/new` | Zero-tap deadline creation | Wrong default ~30% of the time (Termin/Projekt also frequent); no escape if user wanted Termin |
| Context-aware (per page) | Smart defaults | Surprising — same button does different things on different pages; harder to learn |

The sheet is also where new capture types can be added later (Quick
Note, Voice memo) without redesign. Cheap to extend.

### Sheet mechanics (mvp — does *not* fully copy otto-pwa)

- Native `<dialog>` element via `dialog.showModal()`.
- Slide-up via CSS `transform: translateY(100%) → translateY(0)`,
  `transition: transform 220ms ease-out`.
- Backdrop tap dismisses (`dialog::backdrop` click handler).
- ESC closes (native `<dialog>` behavior).
- **Drag-to-dismiss is NOT in v1.** The full otto-pwa pointer-event
  pattern (handle hit-area + pointermove transform + 120px threshold)
  is great but adds ~80 lines for a phone-only flourish. Ship without
  it; if m wants it, a follow-up task adds it copying otto-pwa
  `voice-modal` verbatim.
- `max-height: 60vh` (we have only 3 rows; 92vh from the baseline doc is
  for sheets that contain scrollable lists).

### Tapping a sheet row

Just navigates: `window.location.href = "/deadlines/new"` etc. The
existing `/deadlines/new`, `/appointments/new`, `/projects/new` pages
already work on mobile (form layout is single-column). No new endpoints.

Note: `/projects/new` requires admin in current implementation — for a
non-admin user, that row should be hidden (read `window.__PALIAD_ME__`
or whatever the page exposes; if not exposed, just always show and let
the destination page error gracefully — m's call).

---

## 5. Drawer: Reuse What's There

**No new drawer.** The existing `Sidebar.tsx` already renders into a
fixed-left aside that, at `<1024px`, is `transform: translateX(-100%)`
by default and slides to `translateX(0)` when class `mobile-open` is
toggled. The hamburger button + `.sidebar-overlay` already do the open
mechanics.

The BottomNav `[Menü]` slot wires into the same toggle that the
hamburger uses — they call the same `toggleMobileSidebar()`.

### Hamburger fate

At `<768px` (BottomNav visible): the existing top-left hamburger is
**hidden** (the BottomNav menu slot does the same job, in a thumb-reach
spot). At `768-1023px`: hamburger stays visible, BottomNav stays
hidden — current behavior preserved.

### What's in the drawer

It's the existing Sidebar — Dashboard, Übersicht (Dashboard, Agenda,
Team), Arbeit (Projekte, Fristen, Termine), Werkzeuge, Wissen,
Ressourcen, Einstellungen, plus the bottom block (Neuigkeiten, invite,
DE/EN, Logout). Nothing duplicated, nothing pruned. Items already in
the BottomNav (Dashboard, Projekte, Agenda) also still appear in the
drawer — that's intentional, the drawer is the canonical map.

### Drawer trigger options considered

| Trigger | Verdict |
|---|---|
| BottomNav `[Menü]` slot ✅ | Standard, discoverable, thumb-reach |
| Top-left hamburger (legacy) | Hidden on phones; lives on for tablets |
| Edge-swipe from left | **No** — conflicts with project-detail tabs that already overflow-scroll horizontally on mobile |
| ESC closes | Already implemented via `closeMobile()` |

Matches mBrian/otto pattern: button-triggered, no swipe.

---

## 6. Breakpoints

```
 ≥1024px        : Desktop sidebar (hover-expand, pin)
 768-1023px     : Slide-out drawer + top-left hamburger (current behavior)
 <768px         : Slide-out drawer + BottomNav (hamburger hidden)
```

Two distinct thresholds because they answer different questions:

- **1024px** = "is there room for a persistent collapsed sidebar?"
- **768px**  = "is this a phone — do we need a thumb-reach bar?"

The existing `1023px` breakpoint stays. We add a new `767px` breakpoint
specifically for showing/hiding BottomNav and hiding the legacy
hamburger.

The pwa-baseline doc says 768px throughout — that's the BottomNav
breakpoint. The doc doesn't mandate the 1024 sidebar threshold; that's
a paliad-specific affordance worth preserving.

---

## 7. Visual Spec

### Bar dimensions

- Height: `56px` (`--bottom-nav-height`, matches baseline doc).
- Background: `var(--color-surface)` (`#ffffff`).
- Top border: `1px solid var(--color-border)`.
- Box-shadow: subtle upward `0 -1px 3px rgba(0,0,0,0.04)` — looks
  attached to the screen edge, not floating.
- Position: `fixed; bottom: 0; left: 0; right: 0;`
- Padding-bottom: `env(safe-area-inset-bottom)` — additive to the 56px,
  so on iPhone X+ the bar effectively grows to account for the home
  indicator without overlapping it.
- Width: 100%, slots `flex: 1`.
- Z-index: `30` (above content, below sidebar overlay z=35 so the drawer
  always covers BottomNav, below modals z=100).

### Slot

- 56px tall, full-width slot, vertical icon (~22px) + label (10-11px).
- Active slot: lime accent `var(--color-accent)` icon + label, with a
  thin lime top-bar (3px tall) at the slot top edge.
- Inactive slot: `var(--color-text-muted)` icon + label.
- Tap target: full slot — no inner padding gymnastics. iOS HIG ≥44pt;
  56px height + ~70px wide slot easily clears that.

### Center slot ([+])

- Visually elevated: a 48px circular lime button raised ~4px above the
  bar (negative margin-top), white plus-icon, subtle `box-shadow:
  var(--shadow-md)`.
- Same width slot underneath; the circle is decoration, the whole slot
  is the tap target.
- This is the only "loud" pattern; matches the baseline doc's
  "primary capture/add action" emphasis.

### Quick-Add sheet

- Width: 100vw on mobile, max 480px on tablet (the sheet should never
  appear on desktop because the [+] slot only exists on phones, but
  cap width as belt-and-braces).
- Border-radius: `16px 16px 0 0` (top corners rounded, bottom flush).
- Padding-bottom: `env(safe-area-inset-bottom)` so the cancel row sits
  above the home indicator.
- Backdrop: `rgba(0,0,0,0.5)` via `<dialog>::backdrop`.

### Layout reflow

Pages with `body.has-sidebar` need extra bottom padding on mobile so
the BottomNav doesn't cover the last row of content. New CSS rule:

```css
@media (max-width: 767px) {
    body.has-sidebar main {
        padding-bottom: calc(var(--bottom-nav-height) + 1rem
                             + env(safe-area-inset-bottom));
    }
}
```

`main` gets the padding rather than `body` so the BottomNav's own
fixed-position remains glued to the viewport edge.

### Keyboard-open hide

```css
body.keyboard-open .bottom-nav {
    transform: translateY(120%);
    transition: transform 200ms ease-out;
}
```

Toggle from JS via `visualViewport.height` delta > 100px (see §9).

---

## 8. Files to Add / Change

### New files

| File | Purpose |
|---|---|
| `frontend/src/components/BottomNav.tsx` | TSX component, exports `BottomNav({currentPath, role?})` |
| `frontend/src/client/bottom-nav.ts` | `initBottomNav()` — drawer toggle wiring, sheet open/close, visualViewport keyboard watcher |

### Modified files

| File | Change |
|---|---|
| `frontend/src/components/Sidebar.tsx` | Hamburger button gains a class so CSS can hide it `<768px` (`.sidebar-hamburger.hide-on-phone` or just by media query — no markup change needed). Add `id` on the toggle target so bottom-nav.ts can find/share it. |
| `frontend/src/client/sidebar.ts` | Export `toggleMobileSidebar()` so bottom-nav.ts re-uses the exact same open/close/overlay code (don't duplicate). |
| `frontend/src/client/index.ts` | Add `import { initBottomNav } from "./bottom-nav"; initBottomNav();` |
| `frontend/src/styles/global.css` | Add ~120 lines: `--bottom-nav-height` token, `.bottom-nav` + slot styles, `<768px` media query showing BottomNav and hiding hamburger, keyboard-open transform, `body.has-sidebar main` padding-bottom rule, sheet styles. |
| All page `*.tsx` files (~25) | (a) Replace `<meta name="viewport" content="width=device-width, initial-scale=1.0" />` with `<meta name="viewport" content="width=device-width, initial-scale=1, viewport-fit=cover" />`. (b) Add `<BottomNav currentPath="..." />` next to existing `<Sidebar currentPath="..." />` in each page. Easiest as a sed for (a); each page is touched once for (b). |
| `frontend/build.ts` | Add `bottom-nav.ts` entry... — actually `bottom-nav.ts` is imported by `index.ts` so it gets bundled into `index.js` — no separate entry needed. |

### Optionally (low-cost, highly recommended)

| File | Change |
|---|---|
| All page `*.tsx` `<head>` | Add `<meta name="theme-color" content="#65a30d" />` (lime, matches accent) so iOS Safari paints the URL bar lime in standalone mode. |
| All page `*.tsx` `<head>` | Add `<meta name="apple-mobile-web-app-capable" content="yes" />` and `<meta name="apple-mobile-web-app-status-bar-style" content="default" />`. Cheap, no asset dependency. |

These three meta-tag rows are a one-time sed across 25 files; adding
them now means we don't need a follow-up just to redo the sweep.

### NOT in this task

- `manifest.json` and icon assets (192/512 maskable PNGs) → follow-up.
- Service worker / `sw.js` / app-shell caching → follow-up.
- `beforeinstallprompt` add-to-home-screen UI → follow-up.

These are tracked under §11 below as proposed `t-paliad-04*` follow-ups.

---

## 9. Behavior Spec (`bottom-nav.ts`)

```ts
// Pseudo-shape (real impl will follow paliad style — no narration comments).
import { toggleMobileSidebar } from "./sidebar";

export function initBottomNav() {
  initDrawerSlot();      // [Menü] tap → toggleMobileSidebar()
  initQuickAddSheet();   // [+] tap → dialog.showModal(); rows nav
  initKeyboardWatcher(); // visualViewport resize → body.keyboard-open
}
```

### Keyboard watcher (the one tricky bit)

```ts
function initKeyboardWatcher() {
  if (!window.visualViewport) return;            // older browsers: no-op
  const baseHeight = window.innerHeight;
  const KEYBOARD_THRESHOLD = 100;                // px shrink == keyboard
  window.visualViewport.addEventListener("resize", () => {
    const delta = baseHeight - window.visualViewport!.height;
    document.body.classList.toggle("keyboard-open", delta > KEYBOARD_THRESHOLD);
  });
}
```

`baseHeight` is captured once at init — re-orientation events update it
via a `window.orientationchange` handler. Edge case: a user who rotates
the phone while the keyboard is open will see the bar reappear briefly
until the keyboard re-deploys. Acceptable.

### Active-tab class on navigation

The TSX component renders the active class server-side from
`currentPath`, identical to Sidebar. No client-side recomputation
needed.

---

## 10. Z-index Map (post-change)

| Layer | z-index | Notes |
|---|---|---|
| Page content | auto | |
| Header | 10 | Existing `.header` |
| **BottomNav** | **30** | New |
| Sidebar overlay (drawer backdrop) | 35 | Existing |
| Sidebar drawer | 40 | Existing |
| Top-left hamburger (legacy, tablet) | 50 | Existing — hidden <768px |
| Quick-Add sheet backdrop | 90 | New (or just rely on `<dialog>::backdrop`) |
| Quick-Add sheet card | 100 | New, same tier as `.modal-overlay` |
| Existing modal-overlay (invite, etc.) | 100 | Existing |

When the drawer is open over the BottomNav: the drawer (z=40) is wider
than the BottomNav (z=30), and its overlay (z=35) sits above the
BottomNav — so the BottomNav is fully covered. ✓

When the Quick-Add sheet is open over the BottomNav: sheet (z=100)
sits above; backdrop dims everything below including BottomNav. ✓

---

## 11. Rollout Plan

**Single PR, single coherent commit per phase per task convention:**

1. *Phase 1 (this task, after m's go):* land BottomNav + Quick-Add sheet
   + drawer wiring + viewport-fit meta + theme-color meta. One commit
   on this worktree's branch (`mai/cronus/pwa-mobile-bottom-nav`),
   self-merge to `main` per t-paliad-038/039/040 precedent.
2. *Verify on mobile breakpoint:* Playwright (`browser_resize` to
   375×812 iPhone X) — confirm: BottomNav renders, sheet opens, drawer
   opens from `[Menü]`, no double-hamburger, content padding leaves the
   last item visible above the bar. Login as `tester@hlc.de` to test
   the authenticated paths.
3. *Build green:* `bun run build` and `go build ./... && go vet ./... && go test ./...`.

### Follow-up tasks proposed (NOT in this task)

- `t-paliad-04X` — `manifest.json` + 192/512 maskable icons + `<link rel="apple-touch-icon">` on every page → installable PWA.
- `t-paliad-04Y` — `sw.js` network-first cache app-shell strategy (copy from mBrian; keep tiny — just `/dashboard` and `/assets/global.css`).
- `t-paliad-04Z` — `beforeinstallprompt` UI: a one-time toast ("Add Paliad to your Home Screen?") gated by a localStorage `paliad-pwa-prompt-dismissed` flag.
- `t-paliad-04W` — Drag-to-dismiss for Quick-Add sheet (otto-pwa pattern verbatim).
- `t-paliad-04V` — Project-detail tabs horizontal-overflow polish (already-known tablet/phone problem; surfaced again here but out of scope).

---

## 12. Open Questions for m

1. **Slot 4: Agenda or Fristen?** Design picks Agenda. Brief offered
   either. If you prefer the more old-school Fristen (deadlines only,
   no Termine), it's a one-line swap. Recommendation: **Agenda**.
2. **Center [+] slot: sheet or deep-link?** Design picks the 3-option
   slide-up sheet. If you prefer to skip the sheet and have [+] always
   go to `/deadlines/new` (the most-frequent capture), say so —
   simpler, no `<dialog>`. Recommendation: **sheet**.
3. **PWA shell items:** Add the 3 meta tags now (viewport-fit,
   theme-color, apple-mobile-web-app-capable) but defer manifest +
   service worker + install prompt to follow-up tasks?
   Recommendation: **yes — meta now, manifest/SW/prompt later.**
4. **`/projects/new` quick-add row visibility:** non-admins can't create
   projects. Hide the row for them, or always show and let the page
   gracefully error? Recommendation: **always show**, defer the
   permission-aware row to a follow-up — keeps this PR self-contained
   and matches what the Sidebar already does (`Projekte` is shown to
   everyone; admin-gating happens on the destination page).
5. **Badge counts on BottomNav slots** (e.g. red-dot on Agenda when an
   overdue Frist is due today)? Nice-to-have, not in v1. Out of scope
   here. Confirm: **defer to follow-up.**
6. **Tablet (768-1023px) behavior:** keep as-is (hamburger drawer, no
   BottomNav)? The pwa-baseline doc draws the line at 768 — we honor
   it on the BottomNav side. Confirm: **yes, no BottomNav on tablet.**

---

## 13. Acceptance Mapping

| Requirement | How design satisfies |
|---|---|
| Design doc at `docs/design-pwa-bottom-nav.md` | This file |
| BottomNav renders <768px, hidden ≥768px | §6 + media query in §8 |
| Mobile drawer slides out, mirrors desktop Sidebar | §5 — reuses existing Sidebar.tsx + slide-out CSS |
| Keyboard-open hides BottomNav | §9 visualViewport watcher + `body.keyboard-open` CSS |
| safe-area-inset-bottom padding on iOS | §7 dimensions + §8 viewport-fit=cover meta |
| No regression in desktop layout | Desktop ≥1024px untouched; only `<768px` adds BottomNav and hides hamburger; tablet 768-1023px unchanged |
| Single commit per phase | §11 rollout |