Caches translations to avoid blinking text every time the user comes back to an older screen.

amethyst/src/play/java/com/vitorpamplona/amethyst/service/lang/TranslationsCache.kt

@@ -0,0 +1,37 @@
+/**
+ * Copyright (c) 2024 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.service.lang
+
+import android.util.LruCache
+import com.vitorpamplona.amethyst.ui.components.TranslationConfig
+
+object TranslationsCache {
+    val cache = LruCache<String, TranslationConfig>(100)
+
+    fun get(content: String): TranslationConfig = cache.get(content) ?: TranslationConfig(content, null, null, false)
+
+    fun set(
+        content: String,
+        config: TranslationConfig,
+    ) {
+        cache.put(content, config)
+    }
+}

amethyst/src/play/java/com/vitorpamplona/amethyst/ui/components/TranslatableRichTextViewer.kt

@@ -54,6 +54,7 @@ import androidx.compose.ui.unit.dp
 import androidx.core.os.ConfigurationCompat
 import com.vitorpamplona.amethyst.R
 import com.vitorpamplona.amethyst.service.lang.LanguageTranslatorService
+import com.vitorpamplona.amethyst.service.lang.TranslationsCache
 import com.vitorpamplona.amethyst.ui.actions.CrossfadeIfEnabled
 import com.vitorpamplona.amethyst.ui.navigation.INav
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
@@ -80,18 +81,7 @@ fun TranslatableRichTextViewer(
     accountViewModel: AccountViewModel,
     nav: INav,
 ) {
-    var translatedTextState by
-        remember(id) { mutableStateOf(TranslationConfig(content, null, null, false)) }
-
-    TranslateAndWatchLanguageChanges(content, accountViewModel) { result ->
-        if (
-            !translatedTextState.result.equals(result.result, true) ||
-            translatedTextState.sourceLang != result.sourceLang ||
-            translatedTextState.targetLang != result.targetLang
-        ) {
-            translatedTextState = result
-        }
-    }
+    var translatedTextState by translateAndWatchLanguageChanges(content, id, accountViewModel)
 
     CrossfadeIfEnabled(targetState = translatedTextState, accountViewModel = accountViewModel) {
         RenderText(
@@ -333,6 +323,31 @@ private fun TranslationMessage(
     }
 }
 
+@Composable
+fun translateAndWatchLanguageChanges(
+    content: String,
+    id: String,
+    accountViewModel: AccountViewModel,
+): MutableState<TranslationConfig> {
+    var translatedTextState = remember(id) { mutableStateOf(TranslationsCache.get(content)) }
+
+    TranslateAndWatchLanguageChanges(
+        content,
+        accountViewModel,
+    ) { result ->
+        if (
+            !translatedTextState.value.result.equals(result.result, true) ||
+            translatedTextState.value.sourceLang != result.sourceLang ||
+            translatedTextState.value.targetLang != result.targetLang
+        ) {
+            TranslationsCache.set(content, result)
+            translatedTextState.value = result
+        }
+    }
+
+    return translatedTextState
+}
+
 @Composable
 fun TranslateAndWatchLanguageChanges(
     content: String,