Schedule Design Patterns

Lessons extracted from building the /europe/schedule page — a single-file (~2000 line) React component with a 2D room×time grid, 1D session list, modal detail view, multi-axis filtering, favorites, theming, and semantic search.

Architecture

Single-file component is fine for schedule pages

The entire page lives in one .tsx file. Sub-components (TypeBadge, SpeakerPhoto, SessionModal, GridOverview, SessionCard, FilterPill, StarButton) are defined in the same file. This avoids prop-drilling across module boundaries and keeps the schedule self-contained. Extract to separate files only when reuse is needed elsewhere.

Build-time data extraction with getStaticProps

Raw JSON (with nullable/optional fields) is normalized at build time into clean ScheduleSession objects with guaranteed string fields (empty string, not null). This eliminates null checks throughout the render logic.

Synthetic plenary sessions

Plenary/logistics sessions (breakfast, lunch, expo hours) are hardcoded as a PLENARY_SESSIONS array and merged with speaker sessions at build time. They get id: 10000 + i to avoid collisions.

Theme System

Semantic token objects, not CSS variables

Define a Theme type with ~40 semantic tokens (bg, bgCard, text, textSecondary, border, accent, gridHeaderBg, starActive, etc.). Create DARK_THEME and LIGHT_THEME constants. Pass t: Theme and isDark: boolean to every sub-component.

Theme persistence across pages

Store preference in localStorage under a shared key (eu-theme). On mount, check localStorage first, then fall back to window.matchMedia('(prefers-color-scheme: light)'). This syncs theme between /europe and /europe/schedule.

Global styles must also be themed

Body background, scrollbar colors (::webkit-scrollbar-*), text selection (::selection), and any <style jsx global> blocks must reference theme tokens. Don't forget the logo image — use filter: invert(1) for light mode if the logo is white-on-transparent.

2D Grid Overview (Room × Time)

HTML <table> for the grid, not CSS grid

A real <table> with <thead>, <tr>, <th>, <td> handles column alignment, sticky headers, and horizontal scroll correctly. CSS Grid struggles with sticky columns in a scrollable container.

Sticky header and sticky first column(s)

• Day header row: position: sticky; top: 0; zIndex: 20 with colSpan={rooms.length + 1} so it spans full width on horizontal scroll.
• Room header row: position: sticky; top: 30px (offset by day header height).
• Time column: position: sticky; left: 0; zIndex: 10.
• Priority column (e.g. Plenary): position: sticky; left: 48px (offset by time column width), zIndex: 10.

Plenary column spanning

Plenary sessions span across the full day, so the Plenary column needs special logic: track which plenary sessions are "active" (started before, ending after) each time slot, and render continuing sessions with reduced opacity and a "continues" label.

Room sort order matters

Sort rooms: Plenary first → Keynote rooms → Regular rooms (alphabetical) → Special rooms (e.g. Leadership Lunch) → Expo rooms. Use a numeric group assignment for sorting.

Bright pastel grid cell colors with dark text

Grid cells use a separate GRID_COLORS palette with bright pastel backgrounds and dark text — different from the badge colors which use dark backgrounds with light text. This improves readability in the dense grid.

Cell overflow

Set maxHeight: 80 and overflowY: 'auto' on grid cell content divs so dense cells scroll rather than expanding the row.

Grid cell click → modal

Clicking a grid cell opens a SessionModal overlay (not inline expansion). The modal uses position: fixed; inset: 0 with backdrop blur, and closes on ESC, backdrop click, or close button. Lock body scroll (document.body.style.overflow = 'hidden') while modal is open.

Filter System

Type grouping for cleaner filters

Map granular types into user-friendly groups. Example: track_keynote, talk, and lightning all map to a single "talks" filter group via a TYPE_FILTER_GROUPS record and typeFilterGroup() function. Individual session badges still show the specific type — only the filter pills are grouped.

Inclusive multi-select with Set<string>

Each filter axis (day, type, track) uses a Set<string>. Empty set = no filter (show all). Use a toggleSet helper to add/remove values immutably.

Filter panel is collapsible, but active state must be obvious

When the filter panel is collapsed:

1. The "Filters" button turns purple/highlighted with badge count: Filters (3) ▼.
2. A compact summary strip below the header shows active filter chips.
3. The session count in the header (92/214) turns bold + accent color.

Without these, users don't realize filters are active — this was a real usability issue.

Filter layout: grouped rows with labels

Each filter axis gets its own row with an uppercase label (DAY, TYPE, TRACK). A separate row at the bottom holds "Starred", "Clear all filters", and a count summary. This is much clearer than a single inline row of mixed pills.

Starred/favorites in localStorage

Use localStorage key aie-schedule-favorites storing a JSON array of session IDs. Wrap in a useFavorites hook returning { favorites, toggleFavorite, isFavorited }. Starred items get a golden border/glow in the grid: boxShadow: '0 0 8px rgba(250,204,21,0.5)'.

Session Display

Title first, then speaker attribution

Grid cells and cards show the session title first, then speaker info below. Speaker attribution format: {name} - {company}, {role} with graceful fallbacks — omit dash/comma segments if company or role is missing.

TBD speaker detection

Use regex /^tbd\b/i to detect placeholder speaker names and render them with reduced opacity.

Speaker photos with initials fallback

SpeakerPhoto component tries to load the image, falls back to a circular badge with initials (extracted from name) on error. Use loading="lazy" on images.

URL State

Modal state syncs to URL query param

Opening a modal sets ?session=<id> via shallow router replace. On mount, check router.query.session to restore the modal. This makes session links shareable.

Persistent identity must be stable across schedule rebuilds

Never use array indexes, sort positions, or regenerated numeric ordinals as identities for detail API lookups, cache keys, favorites, or new deep links. Schedule restructuring changes those numbers and can pair a current title with another session's cached description.

• Use the stable scheduled-occurrence/assignment ID; fall back to a stable slot ID for assignment-less logistics such as lunch.
• Store stable IDs in favorites and deep links. Keep numeric-link parsing only as a temporary compatibility path.
• When session details load separately from the page payload, include the schedule version in the request/cache key and return it in the response.
• Reject a page/API schedule-version mismatch instead of merging potentially unrelated content.
• Add a regression test that reorders slots and proves each stable session ID still resolves to the same description.

Semantic Search

Debounced API call with request-ID guard

Each keystroke increments a semanticRequestIdRef. Only the response whose ID matches the latest ref is applied — stale/out-of-order responses are silently dropped. Use AbortController for cleanup. Debounce delay: 400ms.

Common Pitfalls

1. next lint doesn't work in Next.js 16 — use npx tsc --noEmit instead.
2. Sticky position in tables: position: sticky on <td> requires explicit background — otherwise transparent cells show content underneath during scroll.
3. colSpan on day headers: Without proper colSpan spanning all columns, the day header won't stretch when scrolling horizontally.
4. Plenary contrast: Dark-on-dark or light-on-light plenary badges are easy to miss. Give plenary sessions distinct, high-contrast colors in both palettes.
5. Line height in dense grid cells: Default line height is too spacious for 9-10px text in grid cells. Use lineHeight: 1.15.
6. Room name typos: Always validate room names against the source data (e.g. "Westley" vs "Wesley"). A bulk rename in the JSON source is safer than patching in rendering code.
7. Filter state invisible to users: The most common UX complaint was "I don't know why I'm seeing fewer sessions." Always make active filter state visible even when the filter panel is collapsed.
8. Ordinal IDs are not cache keys: A positional session ID may point to a different talk after any insertion, removal, or reorder. Lazy detail endpoints keyed by ordinals can transiently attach the wrong abstract to a title when page and API caches come from different schedule builds. Use stable occurrence IDs plus schedule-versioned requests.