♻️ refactor(client): 浏览器半拆成 src 模块，client.js 改由构建产出

src/client/ui/hooks.js

@@ -0,0 +1,49 @@
+/**
+ * The React seams the components share: two subscriptions this plugin needs
+ * beyond the ones the slot owner already provides, plus the seat rule for
+ * translation.
+ *
+ * @module @dsh-plugin/session-notify/client/ui/hooks
+ */
+
+import * as React from 'react'
+import { windowIsAway } from '../platform.js'
+
+/** Subscribe to this plugin's own store from inside a component. */
+export function useOwnStore(source) {
+  return React.useSyncExternalStore(source.subscribe, source.getSnapshot, source.getSnapshot)
+}
+
+/**
+ * Subscribe to every browser signal that says whether the app is visible:
+ * the window's focus events and the document's visibility change. The value
+ * itself is a boolean, so the observer re-renders once per transition.
+ */
+export function useWindowState() {
+  const subscribe = React.useCallback((listener) => {
+    try {
+      window.addEventListener('focus', listener)
+      window.addEventListener('blur', listener)
+      document.addEventListener('visibilitychange', listener)
+    } catch {
+      return () => {}
+    }
+    return () => {
+      window.removeEventListener('focus', listener)
+      window.removeEventListener('blur', listener)
+      document.removeEventListener('visibilitychange', listener)
+    }
+  }, [])
+  return React.useSyncExternalStore(subscribe, () => !windowIsAway(), () => true)
+}
+
+/**
+ * Every component translates through this: the slot's own seat when the owner
+ * supplies one, else this package's own translator.
+ * @param props - the slot entry's props, which carry the owner's `t` when it has one.
+ * @param fallback - the plugin's own translator, used when the seat has none.
+ * @returns the translate function this render should use.
+ */
+export function seatTranslator(props, fallback) {
+  return typeof props.t === 'function' ? props.t : fallback
+}