Introduce rememberGlobally

app/src/main/java/com/hippo/ehviewer/ui/compose/RememberGlobally.kt

@@ -0,0 +1,34 @@
+package com.hippo.ehviewer.ui.compose
+
+import androidx.collection.lruCache
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.currentCompositeKeyHash
+import androidx.compose.runtime.remember
+
+private val remembered = lruCache<String, Any>(1)
+
+@Composable
+fun <T : Any> rememberGlobally(
+    vararg inputs: Any?,
+    key: String? = null,
+    init: () -> T,
+): T {
+    // key is the one provided by the user or the one generated by the compose runtime
+    val finalKey = if (!key.isNullOrEmpty()) {
+        key
+    } else {
+        currentCompositeKeyHash.toString(36)
+    }
+    // value is restored using the registry or created via [init] lambda
+    val value = remember(*inputs) {
+        @Suppress("UNCHECKED_CAST")
+        val restored = remembered[finalKey] as? T
+        restored ?: init()
+    }
+
+    LaunchedEffect(finalKey) {
+        remembered.put(finalKey, value)
+    }
+    return value
+}

app/src/main/java/com/hippo/ehviewer/ui/scene/GalleryPreviewScreen.kt

@@ -57,6 +57,7 @@ import com.hippo.ehviewer.coil.imageRequest
 import com.hippo.ehviewer.coil.justDownload
 import com.hippo.ehviewer.ui.compose.data.EhPreviewItem
 import com.hippo.ehviewer.ui.compose.rememberDialogState
+import com.hippo.ehviewer.ui.compose.rememberGlobally
 import com.hippo.ehviewer.ui.compose.setMD3Content
 import com.hippo.ehviewer.ui.legacy.recyclerview.calculateSuitableSpanCount
 import com.hippo.ehviewer.ui.navToReader
@@ -118,7 +119,7 @@ class GalleryPreviewScreen : Fragment() {
                     initialKey = goto
                 }
 
-                val previewPagesMap = remember { mutableMapOf<Int, PreviewPage>().apply { put(1, galleryDetail.previewList) } }
+                val previewPagesMap = rememberGlobally { mutableMapOf<Int, PreviewPage>().apply { put(1, galleryDetail.previewList) } }
                 val data = remember(initialKey) {
                     Pager(PagingConfig(1, prefetchDistance = 4, enablePlaceholders = false, initialLoadSize = 1), initialKey) {
                         object : PagingSource<Int, PreviewPage>() {