From e1b6e9d4b6fd261a4d38c4760d8bc5dcd43b35fe Mon Sep 17 00:00:00 2001
From: syuilo <4439005+syuilo@users.noreply.github.com>
Date: Mon, 1 Dec 2025 08:21:30 +0900
Subject: [PATCH] =?UTF-8?q?fix(frontend):=20visibilityState=E3=81=8Chidden?=
 =?UTF-8?q?=E3=81=AA=E7=8A=B6=E6=85=8B=E3=81=A7startViewTransition?=
 =?UTF-8?q?=E3=81=97=E3=81=AA=E3=81=84=E3=82=88=E3=81=86=E3=81=AB?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
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---
 packages/frontend/src/theme.ts | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/packages/frontend/src/theme.ts b/packages/frontend/src/theme.ts
index fc3f5f55f2..e001bed8f3 100644
--- a/packages/frontend/src/theme.ts
+++ b/packages/frontend/src/theme.ts
@@ -144,7 +144,9 @@ export function applyTheme(theme: Theme, persist = true) {
 	if (theme.id === currentThemeId && miLocalStorage.getItem('themeCachedVersion') === version) return;
 	currentThemeId = theme.id;
 
-	if (window.document.startViewTransition != null) {
+	// visibilityStateがhiddenな状態でstartViewTransitionするとブラウザによってはエラーになる
+	// 通常hiddenな時に呼ばれることはないが、iOSのPWAだとアプリ切り替え時に(何故か)hiddenな状態で(何故か)一瞬デバイスのダークモード判定が変わりapplyThemeが呼ばれる場合がある
+	if (window.document.startViewTransition != null && window.document.visibilityState === 'visible') {
 		window.document.documentElement.classList.add('_themeChanging_');
 		try {
 			window.document.startViewTransition(async () => {