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drizzli/src/routes/+layout.svelte
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Svelte

<script lang="ts">
import { tick } from 'svelte';
import { get } from 'svelte/store';
import { fade, fly } from 'svelte/transition';
import { afterNavigate, onNavigate } from '$app/navigation';
import { page } from '$app/stores';
import {
mapTransitionCover,
markPageLoading,
markPageReady,
pageContentReady
} from '$lib/stores/page-transition.svelte';
import { storedTheme } from '$lib/stores/settings';
import {
canStartViewTransition,
startViewTransition,
supportsViewTransitions
} from '$lib/utils/view-transition';
import Footer from '$lib/components/navigation/footer.svelte';
import Header from '$lib/components/navigation/header.svelte';
import WeatherNav from '$lib/components/navigation/weather-nav.svelte';
import { routePath } from '$lib/i18n';
import * as m from '$lib/paraglide/messages';
import './layout.css';
let { children } = $props();
// keep the .dark class in sync with the persisted theme; in 'system' mode
// follow the OS preference live
let themeSettled = false;
let themeTimer = 0;
$effect(() => {
const theme = $storedTheme;
const mq = window.matchMedia('(prefers-color-scheme: dark)');
const apply = () => {
const root = document.documentElement;
const dark = theme === 'dark' || (theme === 'system' && mq.matches);
const paint = () => {
root.classList.toggle('dark', dark);
};
// The very first application is just painting the stored theme - only
// an actual switch afterwards is worth cross-fading.
const reduced = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
if (!themeSettled || reduced) {
themeSettled = true;
paint();
return;
}
if (canStartViewTransition() && !onMapsPage()) {
// one cross-fade of the whole document; component transitions untouched
void startViewTransition(paint);
return;
}
// A navigation transition already owns the screen: repaint under it
// rather than skipping it (which would flash), and fall back to the
// colour transition below when the browser has none at all.
if (supportsViewTransitions()) {
paint();
return;
}
// no view transitions: fall back to fading the colours for one window
root.classList.add('theme-transition');
clearTimeout(themeTimer);
themeTimer = window.setTimeout(() => root.classList.remove('theme-transition'), 400);
paint();
};
apply();
mq.addEventListener('change', apply);
return () => mq.removeEventListener('change', apply);
});
// ── Page cross-fade ───────────────────────────────────────────────────────
// A real cross-fade needs the outgoing page still on screen while the
// incoming one appears - so the view transition is opened at navigation and
// held open for a short grace period, waiting for the new page to report that
// its data has landed. A cached or fast response lands inside that window and
// the old page fades straight into the finished one, no skeleton in between.
//
// Past the grace period the wait gives up and the loading overlay takes over:
// holding the old page frozen any longer looks like a dead click, and the
// overlay is the honest answer - something is happening, it just isn't here
// yet. Note the order: the overlay has to be in the DOM *before* the
// transition captures the incoming state, because a running view transition
// freezes the page and nothing painted after that point can appear.
//
// There is deliberately no fade for browsers without view transitions. The
// old fallback dimmed the outgoing page to nothing and brought the new one
// back up, which on a single layer is a flash of the bare background rather
// than a cross-fade. Swapping outright and letting the overlay carry the
// "loading" message is quieter and honest.
const READY_HOLD_MS = 350;
// Nothing reports ready when a fetch fails outright, so the overlay needs its
// own way out rather than sitting on top of an error message forever.
const OVERLAY_CEILING_MS = 15000;
// The map is a cross-origin iframe, and a browser does not paint one into a
// view transition snapshot - captured bare, any transition with the maps page
// on either side would animate a hole where the map is. The way out is to
// make sure the map is never what gets captured: the maps page keeps an
// opaque cover over the iframe while the map boots (so an arrival fades into
// a clean panel, and the map fades up once ready), and raises the same cover
// again just before a departure is captured (see mapTransitionCover). Both
// snapshots then hold real pixels and the maps page transitions like any
// other route.
const MAPS_ROUTE = '/weather/maps';
const onMapsPage = () => routePath(get(page).url.pathname).startsWith(MAPS_ROUTE);
let loadingOverlay = $state(false);
let overlayCeilingTimer = 0;
// A view transition freezes the page, so a Svelte in-transition started under
// one cannot play - the overlay would be captured at opacity 0 and pop in
// afterwards. Inside a transition the cross-fade does the fading instead.
let overlayFadesIn = $state(true);
function showOverlay(animate: boolean): void {
overlayFadesIn = animate;
loadingOverlay = true;
clearTimeout(overlayCeilingTimer);
overlayCeilingTimer = window.setTimeout(() => (loadingOverlay = false), OVERLAY_CEILING_MS);
}
function hideOverlay(): void {
clearTimeout(overlayCeilingTimer);
loadingOverlay = false;
}
/**
* Manual dismissal. The overlay reports on a fetch it does not control, so
* "stuck" is always a possibility (a page that never reports ready, a request
* that neither resolves nor rejects) - and the page behind it still works.
* Whatever was loading carries on; only the veil goes.
*/
function dismissOverlay(): void {
hideOverlay();
}
function onWindowKeydown(event: KeyboardEvent): void {
if (event.key === 'Escape' && loadingOverlay) dismissOverlay();
}
/** The page that just mounted has its data: whatever we were waiting for is in. */
$effect(() => {
if ($pageContentReady) hideOverlay();
});
// Routes that are not finished on arrival: the five that fetch a forecast
// after mounting, the maps page (whose map is a cross-origin iframe that has
// to load first), and the redirect stubs, which render nothing at all and
// bounce to a located URL from `onMount`. Knowing this up front is what makes
// the wait reliable - the layout clears the ready flag before the swap rather
// than trusting the incoming page to have done it.
const PENDING_ROUTES = new Set([
'/',
'/weather/week',
'/weather/14-day',
'/weather/compare',
'/weather/seasonal',
'/weather/historical',
'/weather/maps',
'/weather/week/[location]',
'/weather/14-day/[location]',
'/weather/compare/[location]',
'/weather/seasonal/[location]',
'/weather/historical/[location]'
]);
/**
* Resolves once the freshly mounted page has its data, or once the grace
* period is up - in which case the overlay goes up first, so it is part of
* the state the transition is about to snapshot.
*/
async function waitForContent(underTransition: boolean): Promise<void> {
const deadline = Date.now() + READY_HOLD_MS;
while (!get(pageContentReady) && Date.now() < deadline) {
await new Promise((resolve) => setTimeout(resolve, 20));
}
if (!get(pageContentReady)) showOverlay(!underTransition);
// one more frame so the page paints its data before the snapshot is taken
await tick();
}
/**
* True when the navigation lands on the route and params the page is already
* showing - the sidebar's home link from the week page it points at, or a
* link that differs only in the query string.
*
* SvelteKit keeps the page component mounted for those, and nothing it holds
* changes: its forecast is already fetched, so the readiness effect it
* registered never re-runs and never re-announces. Clearing the flag for such
* a navigation strands it cleared, and the overlay sits there until its
* ceiling. There is genuinely nothing to wait for, so don't clear it.
*/
function landsOnCurrentPage(navigation: {
from: { route: { id: string | null }; params: Record<string, string> | null } | null;
to: { route: { id: string | null }; params: Record<string, string> | null } | null;
}): boolean {
const from = navigation.from;
const to = navigation.to;
if (!from?.route.id || from.route.id !== to?.route.id) return false;
return JSON.stringify(from.params ?? {}) === JSON.stringify(to.params ?? {});
}
onNavigate(async (navigation) => {
const pending =
PENDING_ROUTES.has(navigation.to?.route?.id ?? '') && !landsOnCurrentPage(navigation);
// Either way the flag is set explicitly: leaving a page that never resolved
// for one that has nothing to load would otherwise strand the overlay.
if (pending) markPageLoading();
else markPageReady();
// `startViewTransition` decides whether a transition is possible at all
// (support, reduced motion, one already capturing) and runs the update
// inline when it is not - so there is exactly one path from here down.
const underTransition = canStartViewTransition();
// Leaving the maps page: cover the iframe before the outgoing state is
// captured, so the snapshot holds a clean panel instead of a hole where
// the map was. The tick makes sure the cover is actually in the DOM by
// the time the capture reads it.
if (underTransition && navigation.from?.route?.id === MAPS_ROUTE) {
mapTransitionCover.set(true);
await tick();
}
return new Promise<void>((swap) => {
void startViewTransition(
async () => {
// hand control back so SvelteKit swaps the DOM underneath the
// frozen snapshot of the old page
swap();
// A superseded navigation (a redirect, or a fast second click)
// rejects this promise; that is not an error worth surfacing,
// and leaving it unhandled shows up as "navigation aborted".
await navigation.complete.catch(() => {});
if (pending) await waitForContent(underTransition);
},
// pins the chrome that is the same on both sides (routes/layout.css)
{ rootClass: 'page-switch', enabled: underTransition }
);
});
});
let mainEl = $state<HTMLElement | null>(null);
afterNavigate((navigation) => {
// The departure snapshot (if any) is taken by now, so the maps cover has
// done its job; lowering it here also means a later visit to the maps page
// starts from its own boot cover rather than a stuck one.
mapTransitionCover.set(false);
// The page scrolls inside <main>, not the window, so SvelteKit's own scroll
// handling never touches it and a new page would open half way down.
// Back/forward and in-page anchors keep their position.
if (navigation.type !== 'popstate' && !navigation.to?.url.hash) {
mainEl?.scrollTo({ top: 0 });
}
});
// the maps page embeds a full-bleed map: no padding, no scrolling
let fullBleed = $derived(routePath($page.url.pathname).startsWith('/weather/maps'));
let sidebarCollapsed = $state(false);
let mobileMenuOpen = $state(false);
const toggleSidebar = () => {
sidebarCollapsed = !sidebarCollapsed;
};
const toggleMobileMenu = () => {
mobileMenuOpen = !mobileMenuOpen;
};
const closeMobileMenu = () => {
mobileMenuOpen = false;
};
</script>
<svelte:head>
<!-- the icon itself lives in app.html, so the SPA fallback carries it too -->
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1" />
</svelte:head>
<!-- Page-wide loading veil. Deliberately `pointer-events-none`: it is a status
indicator, not a modal, so the nav and the search stay usable while a slow
forecast is still on its way. It is also always dismissable - Escape or the
close button - because a veil nobody can get rid of is worse than no veil,
and the page underneath is perfectly usable either way. -->
<svelte:window onkeydown={onWindowKeydown} />
{#if loadingOverlay}
<div
class="pointer-events-none fixed inset-0 z-60 flex items-center justify-center bg-background/55 backdrop-blur-[2px]"
in:fade={{ duration: overlayFadesIn ? 120 : 0 }}
out:fade={{ duration: 280 }}
role="status"
aria-live="polite"
>
<button
type="button"
class="pointer-events-auto absolute top-3 right-3 flex h-9 w-9 cursor-pointer items-center justify-center rounded-full border border-border bg-card text-muted-foreground shadow-lg transition-colors hover:bg-muted hover:text-foreground md:top-4 md:right-4"
onclick={dismissOverlay}
aria-label={m.page_loading_dismiss()}
title={m.page_loading_dismiss()}
>
<svg
class="h-4 w-4"
fill="none"
stroke="currentColor"
viewBox="0 0 24 24"
stroke-width="2"
aria-hidden="true"
>
<path stroke-linecap="round" d="M6 6l12 12M18 6L6 18" />
</svg>
</button>
<div
class="flex items-center gap-2.5 rounded-full border border-border bg-card px-4 py-2 shadow-lg"
>
<svg
class="h-4 w-4 animate-spin text-primary"
fill="none"
stroke="currentColor"
viewBox="0 0 24 24"
stroke-width="2.5"
aria-hidden="true"
>
<path stroke-linecap="round" d="M21 12a9 9 0 1 1-6.219-8.56" />
</svg>
<span class="text-sm font-semibold">{m.page_loading()}</span>
</div>
</div>
{/if}
<div class="flex h-screen overflow-hidden bg-background text-foreground">
<!-- Desktop sidebar -->
<div class="sidebar-region hidden h-full shrink-0 md:block">
<WeatherNav collapsed={sidebarCollapsed} onToggle={toggleSidebar} />
</div>
<!-- Mobile overlay -->
{#if mobileMenuOpen}
<div class="fixed inset-0 z-50 md:hidden" role="presentation">
<!-- svelte-ignore a11y_no_static_element_interactions -->
<div
class="absolute inset-0 bg-black/30"
transition:fade={{ duration: 150 }}
onclick={closeMobileMenu}
onkeydown={closeMobileMenu}
></div>
<div
class="relative z-1 h-full w-55 shadow-lg"
transition:fly={{ x: -220, duration: 200, opacity: 1 }}
>
<WeatherNav collapsed={false} onMobileClose={closeMobileMenu} />
</div>
</div>
{/if}
<!-- Main area: topbar + content -->
<div class="flex min-w-0 flex-1 flex-col h-full">
<Header onMenuToggle={toggleMobileMenu} />
<!-- The padding stays on <main> itself: the day strip sticks with a
negative offset that exactly cancels it, so moving it to an inner
wrapper would dock the strip too high and clip its top row.
flex-col + flex-1 below keeps the footer on the bottom edge even when
the page is too short to fill the viewport. -->
<main
bind:this={mainEl}
class={fullBleed
? 'flex-1 overflow-hidden'
: 'flex flex-1 flex-col overflow-y-auto p-3 lg:px-8 lg:py-6'}
>
{#if fullBleed}
{@render children()}
{:else}
<!-- cap the content width on very large screens; the footer below
gives the page its ending, so only modest bottom room is needed -->
<div class="mx-auto w-full max-w-[1536px] flex-1 pb-24">
{@render children()}
</div>
<!-- full-bleed footer inside the scroll area (its own inner max-w),
cancelling main's padding so it sits flush with the edges -->
<div class="-mx-3 -mb-3 lg:-mx-8 lg:-mb-6">
<Footer />
</div>
{/if}
</main>
</div>
</div>