enhance(frontend): 季節に応じた画面の演出を南半球に対応させる (#12838)

* (enhance) 季節に応じた画面の演出を南半球に対応させる

* Update Changelog

* (add) 半球の簡易自動判定

---------

Co-authored-by: syuilo <Syuilotan@yahoo.co.jp>

4 files changed, 30 insertions, 3 deletions

diff --git a/packages/frontend/src/boot/main-boot.ts b/packages/frontend/src/boot/main-boot.ts
index c99118f9b2..eb0ac43da7 100644
--- a/packages/frontend/src/boot/main-boot.ts
+++ b/packages/frontend/src/boot/main-boot.ts
@@ -77,9 +77,18 @@ export async function mainBoot() {
 
 	if (defaultStore.state.enableSeasonalScreenEffect) {
 		const month = new Date().getMonth() + 1;
-		if (month === 12 || month === 1) {
-			const SnowfallEffect = (await import('@/scripts/snowfall-effect.js')).SnowfallEffect;
-			new SnowfallEffect().render();
+		if (defaultStore.state.hemisphere === 'S') {
+			// ▼南半球
+			if (month === 7 || month === 8) {
+				const SnowfallEffect = (await import('@/scripts/snowfall-effect.js')).SnowfallEffect;
+				new SnowfallEffect().render();
+			}
+		} else {
+			// ▼北半球
+			if (month === 12 || month === 1) {
+				const SnowfallEffect = (await import('@/scripts/snowfall-effect.js')).SnowfallEffect;
+				new SnowfallEffect().render();
+			}
 		}
 	}
 
diff --git a/packages/frontend/src/pages/settings/general.vue b/packages/frontend/src/pages/settings/general.vue
index bbc910a32a..8b489c7a11 100644
--- a/packages/frontend/src/pages/settings/general.vue
+++ b/packages/frontend/src/pages/settings/general.vue
@@ -17,6 +17,13 @@ SPDX-License-Identifier: AGPL-3.0-only
 		</template>
 	</MkSelect>
 
+	<MkRadios v-model="hemisphere">
+		<template #label>{{ i18n.ts.hemisphere }}</template>
+		<option value="N">{{ i18n.ts._hemisphere.N }}</option>
+		<option value="S">{{ i18n.ts._hemisphere.S }}</option>
+		<template #caption>{{ i18n.ts._hemisphere.caption }}</template>
+	</MkRadios>
+
 	<MkRadios v-model="overridedDeviceKind">
 		<template #label>{{ i18n.ts.overridedDeviceKind }}</template>
 		<option :value="null">{{ i18n.ts.auto }}</option>
@@ -260,6 +267,7 @@ async function reloadAsk() {
 	unisonReload();
 }
 
+const hemisphere = computed(defaultStore.makeGetterSetter('hemisphere'));
 const overridedDeviceKind = computed(defaultStore.makeGetterSetter('overridedDeviceKind'));
 const serverDisconnectedBehavior = computed(defaultStore.makeGetterSetter('serverDisconnectedBehavior'));
 const showNoteActionsOnlyHover = computed(defaultStore.makeGetterSetter('showNoteActionsOnlyHover'));
@@ -322,6 +330,7 @@ watch(useSystemFont, () => {
 });
 
 watch([
+	hemisphere,
 	lang,
 	fontSize,
 	useSystemFont,
diff --git a/packages/frontend/src/scripts/intl-const.ts b/packages/frontend/src/scripts/intl-const.ts
index ea16c9c2ae..d2d939af1f 100644
--- a/packages/frontend/src/scripts/intl-const.ts
+++ b/packages/frontend/src/scripts/intl-const.ts
@@ -33,6 +33,10 @@ try {
 }
 export const dateTimeFormat = _dateTimeFormat;
 
+export const timeZone = dateTimeFormat.resolvedOptions().timeZone;
+
+export const hemisphere = /^(australia|pacific|antarctica|indian)\//i.test(timeZone) ? 'S' : 'N';
+
 let _numberFormat: Intl.NumberFormat;
 try {
 	_numberFormat = new Intl.NumberFormat(versatileLang);
diff --git a/packages/frontend/src/store.ts b/packages/frontend/src/store.ts
index 5635e99650..afc35bb825 100644
--- a/packages/frontend/src/store.ts
+++ b/packages/frontend/src/store.ts
@@ -8,6 +8,7 @@ import * as Misskey from 'misskey-js';
 import { miLocalStorage } from './local-storage.js';
 import type { SoundType } from '@/scripts/sound.js';
 import { Storage } from '@/pizzax.js';
+import { hemisphere } from '@/scripts/intl-const.js';
 
 interface PostFormAction {
 	title: string,
@@ -429,6 +430,10 @@ export const defaultStore = markRaw(new Storage('base', {
 			sfxVolume: 1,
 		},
 	},
+  hemisphere: {
+		where: 'device',
+		default: hemisphere as 'N' | 'S',
+  },
 	enableHorizontalSwipe: {
 		where: 'device',
 		default: true,