feat: Add ExternalLaunchActivity for custom game settings

src/android/app/src/main/AndroidManifest.xml

@@ -78,6 +78,16 @@
 
         </activity>
 
+        <activity
+            android:name="org.citra.citra_emu.features.external.ExternalLaunchActivity"
+            android:exported="true"
+            android:theme="@style/Theme.Citra.Main">
+            <intent-filter>
+                <action android:name="org.citra.citra_emu.LAUNCH_WITH_CUSTOM_CONFIG" />
+                <category android:name="android.intent.category.DEFAULT" />
+            </intent-filter>
+        </activity>
+
         <activity
             android:name="org.citra.citra_emu.features.cheats.ui.CheatsActivity"
             android:exported="false"

src/android/app/src/main/java/org/citra/citra_emu/features/external/ExternalLaunchActivity.kt

@@ -0,0 +1,156 @@
+// Copyright Citra Emulator Project / Azahar Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+package org.citra.citra_emu.features.external
+
+import android.content.Intent
+import android.net.Uri
+import android.os.Bundle
+import androidx.appcompat.app.AppCompatActivity
+import com.google.android.material.dialog.MaterialAlertDialogBuilder
+import org.citra.citra_emu.CitraApplication
+import org.citra.citra_emu.R
+import org.citra.citra_emu.activities.EmulationActivity
+import org.citra.citra_emu.features.settings.utils.SettingsFile
+import org.citra.citra_emu.model.Game
+import org.citra.citra_emu.utils.DirectoryInitialization
+import org.citra.citra_emu.utils.GameHelper
+import org.citra.citra_emu.utils.Log
+
+class ExternalLaunchActivity : AppCompatActivity() {
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+
+        // Ensure user directory is initialized
+        DirectoryInitialization.start()
+
+        val titleIdStr = intent.getStringExtra(EXTRA_TITLE_ID)
+        val iniText = intent.getStringExtra(EXTRA_CONFIG_INI) ?: ""
+        if (titleIdStr.isNullOrEmpty()) {
+            finishWithResult(success = false)
+            return
+        }
+
+        val titleId = parseTitleId(titleIdStr)
+        if (titleId == null) {
+            finishWithResult(success = false)
+            return
+        }
+
+        // If existing per-game file exists, confirm overwrite
+        val hasExisting = SettingsFile.customExists(String.format("%016X", titleId))
+        if (hasExisting) {
+            MaterialAlertDialogBuilder(this)
+                .setTitle(R.string.application_settings)
+                .setMessage(R.string.overwrite_custom_settings_prompt)
+                .setPositiveButton(android.R.string.ok) { _, _ ->
+                    proceedWithDriverCheckAndLaunch(titleId, iniText)
+                }
+                .setNegativeButton(android.R.string.cancel) { _, _ -> finishWithResult(success = false) }
+                .setOnCancelListener { finishWithResult(success = false) }
+                .show()
+        } else {
+            proceedWithDriverCheckAndLaunch(titleId, iniText)
+        }
+    }
+
+    private fun proceedWithDriverCheckAndLaunch(titleId: Long, iniText: String) {
+        val idHex = String.format("%016X", titleId)
+        val requestedBackend = extractGraphicsApi(iniText)
+
+        if (requestedBackend == GRAPHICS_BACKEND_VULKAN) {
+            MaterialAlertDialogBuilder(this)
+                .setTitle(R.string.custom_launch_backend_warning_title)
+                .setMessage(R.string.custom_launch_backend_warning_message)
+                .setPositiveButton(R.string.custom_launch_backend_option_use_vulkan) { _, _ ->
+                    writeConfigAndLaunch(titleId, iniText, idHex)
+                }
+                .setNegativeButton(R.string.custom_launch_backend_option_use_opengl) { _, _ ->
+                    val adjusted = replaceGraphicsApi(iniText, GRAPHICS_BACKEND_OPENGL)
+                    Log.info("[ExternalLaunch] Falling back to OpenGL for external launch")
+                    writeConfigAndLaunch(titleId, adjusted, idHex)
+                }
+                .setOnCancelListener { finishWithResult(success = false) }
+                .show()
+            return
+        }
+
+        writeConfigAndLaunch(titleId, iniText, idHex)
+    }
+
+    private fun writeConfigAndLaunch(titleId: Long, iniText: String, idHex: String) {
+        SettingsFile.saveCustomFileRaw(idHex, iniText)
+
+        val game = findGameByTitleId(titleId)
+        if (game == null) {
+            MaterialAlertDialogBuilder(this)
+                .setTitle(R.string.custom_launch_missing_game_title)
+                .setMessage(getString(R.string.custom_launch_missing_game_message, idHex))
+                .setPositiveButton(android.R.string.ok) { _, _ -> finishWithResult(success = false) }
+                .setOnCancelListener { finishWithResult(success = false) }
+                .show()
+            return
+        }
+
+        val launch = Intent(this, EmulationActivity::class.java)
+        launch.putExtra("game", game)
+        startActivity(launch)
+        finishWithResult(success = true)
+    }
+
+    private fun findGameByTitleId(titleId: Long): Game? {
+        // Try cached games first
+        val prefs = androidx.preference.PreferenceManager.getDefaultSharedPreferences(CitraApplication.appContext)
+        val serialized = prefs.getStringSet(GameHelper.KEY_GAMES, emptySet()) ?: emptySet()
+        if (serialized.isNotEmpty()) {
+            val games = serialized.mapNotNull {
+                try { kotlinx.serialization.json.Json.decodeFromString(org.citra.citra_emu.model.Game.serializer(), it) } catch (_: Exception) { null }
+            }
+            games.firstOrNull { it.titleId == titleId }?.let { return it }
+        }
+        // Fallback: rescan library
+        return GameHelper.getGames().firstOrNull { it.titleId == titleId }
+    }
+
+    companion object {
+        const val EXTRA_TITLE_ID = "title_id"
+        const val EXTRA_CONFIG_INI = "config_ini"
+        private const val GRAPHICS_BACKEND_OPENGL = 1
+        private const val GRAPHICS_BACKEND_VULKAN = 2
+    }
+
+    private fun parseTitleId(raw: String?): Long? {
+        if (raw.isNullOrBlank()) return null
+        val trimmed = raw.trim()
+        val withoutPrefix = if (trimmed.startsWith("0x", true)) trimmed.substring(2) else trimmed
+
+        // Prefer hexadecimal interpretation – Title IDs are traditionally provided in hex.
+        val hexValue = withoutPrefix.toLongOrNull(16)
+        if (hexValue != null) return hexValue
+
+        return withoutPrefix.toLongOrNull()
+    }
+
+    private fun extractGraphicsApi(config: String): Int? {
+        val regex = Regex(
+            "^\\s*graphics_api\\s*=\\s*(\\d+)\\s*$",
+            setOf(RegexOption.IGNORE_CASE, RegexOption.MULTILINE)
+        )
+        val match = regex.find(config) ?: return null
+        return match.groupValues.getOrNull(1)?.trim()?.toIntOrNull()
+    }
+
+    private fun replaceGraphicsApi(config: String, backend: Int): String {
+        val regex = Regex(
+            "^\\s*graphics_api\\s*=\\s*(\\d+)\\s*$",
+            setOf(RegexOption.IGNORE_CASE, RegexOption.MULTILINE)
+        )
+        return regex.replace(config) { "graphics_api = $backend" }
+    }
+
+    private fun finishWithResult(success: Boolean) {
+        setResult(if (success) RESULT_OK else RESULT_CANCELED)
+        finish()
+    }
+}

src/android/app/src/main/java/org/citra/citra_emu/features/settings/utils/SettingsFile.kt

@@ -170,6 +170,19 @@ object SettingsFile {
         }
     }
 
+    fun saveCustomFileRaw(gameId: String, contents: String) {
+        val ini = getOrCreateCustomGameSettingsFile(gameId)
+        val context: Context = CitraApplication.appContext
+        context.contentResolver.openOutputStream(ini.uri, "wt").use { out ->
+            out?.write(contents.toByteArray())
+            out?.flush()
+        }
+    }
+
+    fun customExists(gameId: String): Boolean {
+        return findCustomGameSettingsFile(gameId) != null
+    }
+
     fun saveFile(
         fileName: String,
         setting: AbstractSetting

src/android/app/src/main/res/values/strings.xml

@@ -496,6 +496,14 @@
     <string name="menu_emulation_amiibo_remove">Remove</string>
     <string name="application_settings">Custom Settings</string>
     <string name="use_default">Use default</string>
+    <string name="overwrite_custom_settings_prompt">Custom settings for this game already exist. Overwrite them and proceed?</string>
+    <string name="custom_launch_missing_game_title">Game not found</string>
+    <string name="custom_launch_missing_game_message">This title isn\'t in your Azahar library (ID: %1$s). Add it to the library and try again.</string>
+    <string name="custom_launch_backend_warning_title">Vulkan backend requested</string>
+    <string name="custom_launch_backend_warning_message">This configuration asks Azahar to use the Vulkan renderer. Some devices crash when launching games externally with Vulkan. Keep Vulkan, or switch this launch to OpenGL for safety?</string>
+    <string name="custom_launch_backend_option_use_vulkan">Use Vulkan</string>
+    <string name="custom_launch_backend_option_use_opengl">Use OpenGL</string>
+    <string name="required_driver_missing">Missing required driver: %1$s. Please install it and try again.</string>
     <string name="select_amiibo">Select Amiibo File</string>
     <string name="amiibo_load_error">Error Loading Amiibo</string>
     <string name="amiibo_load_error_message">While loading the specified Amiibo file, an error occurred. Please check that the file is correct.</string>