Link new device using QrCode.

libraries/androidutils/src/main/kotlin/io/element/android/libraries/androidutils/system/Brightness.kt

@@ -0,0 +1,27 @@
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.androidutils.system
+
+import android.app.Activity
+import android.view.WindowManager
+
+/**
+ * Set the screen brightness for the given activity.
+ *
+ * @receiver current Activity.
+ * @param full If true, override brightness to full; otherwise, set to none (default).
+ */
+fun Activity.setFullBrightness(full: Boolean) {
+    window.attributes = window.attributes.apply {
+        screenBrightness = if (full) {
+            WindowManager.LayoutParams.BRIGHTNESS_OVERRIDE_FULL
+        } else {
+            WindowManager.LayoutParams.BRIGHTNESS_OVERRIDE_NONE
+        }
+    }
+}

libraries/designsystem/src/main/kotlin/io/element/android/libraries/designsystem/atomic/atoms/LoadingButtonAtom.kt

@@ -0,0 +1,26 @@
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.designsystem.atomic.atoms
+
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.res.stringResource
+import io.element.android.libraries.designsystem.theme.components.Button
+import io.element.android.libraries.ui.strings.CommonStrings
+
+@Composable
+fun LoadingButtonAtom(
+    modifier: Modifier = Modifier,
+) = Button(
+    modifier = modifier.fillMaxWidth(),
+    enabled = false,
+    showProgress = true,
+    text = stringResource(CommonStrings.common_loading),
+    onClick = {},
+)

libraries/designsystem/src/main/kotlin/io/element/android/libraries/designsystem/utils/ForceMaxBrightness.kt

@@ -0,0 +1,24 @@
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.designsystem.utils
+
+import androidx.activity.compose.LocalActivity
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.DisposableEffect
+import io.element.android.libraries.androidutils.system.setFullBrightness
+
+@Composable
+fun ForceMaxBrightness() {
+    val activity = LocalActivity.current ?: return
+    DisposableEffect(Unit) {
+        activity.setFullBrightness(true)
+        onDispose {
+            activity.setFullBrightness(false)
+        }
+    }
+}

libraries/featureflag/api/src/main/kotlin/io/element/android/libraries/featureflag/api/FeatureFlags.kt

@@ -125,4 +125,11 @@ enum class FeatureFlags(
         defaultValue = { true },
         isFinished = false,
     ),
+    QrCodeLogin(
+        key = "feature.qr_code_login",
+        title = "QR Code Login",
+        description = "Allow logging in on other devices using a QR code.",
+        defaultValue = { false },
+        isFinished = false,
+    ),
 }

libraries/matrix/api/src/main/kotlin/io/element/android/libraries/matrix/api/MatrixClient.kt

@@ -19,6 +19,8 @@ import io.element.android.libraries.matrix.api.core.SessionId
 import io.element.android.libraries.matrix.api.core.UserId
 import io.element.android.libraries.matrix.api.createroom.CreateRoomParameters
 import io.element.android.libraries.matrix.api.encryption.EncryptionService
+import io.element.android.libraries.matrix.api.linknewdevice.LinkDesktopHandler
+import io.element.android.libraries.matrix.api.linknewdevice.LinkMobileHandler
 import io.element.android.libraries.matrix.api.media.MatrixMediaLoader
 import io.element.android.libraries.matrix.api.media.MediaPreviewService
 import io.element.android.libraries.matrix.api.notification.NotificationService
@@ -195,6 +197,21 @@ interface MatrixClient {
      */
     suspend fun markRoomAsFullyRead(roomId: RoomId, eventId: EventId): Result<Unit>
 
+    /**
+     * Check if linking a new device using QrCode is supported by the server.
+     */
+    suspend fun canLinkNewDevice(): Result<Boolean>
+
+    /**
+     * Create a handler to link a new mobile device, i.e. a device capable of scanning QrCodes.
+     */
+    fun createLinkMobileHandler(): Result<LinkMobileHandler>
+
+    /**
+     * Create a handler to link a new desktop device, i.e. a device not capable of scanning QrCodes.
+     */
+    fun createLinkDesktopHandler(): Result<LinkDesktopHandler>
+
     suspend fun performDatabaseVacuum(): Result<Unit>
 }
 

libraries/matrix/api/src/main/kotlin/io/element/android/libraries/matrix/api/linknewdevice/CheckCodeSender.kt

@@ -0,0 +1,22 @@
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.matrix.api.linknewdevice
+
+interface CheckCodeSender {
+    /**
+     * Validates the given [code]. Returns true if the code is valid, false otherwise.
+     * This method can be called multiple times to validate different codes.
+     */
+    suspend fun validate(code: UByte): Boolean
+
+    /**
+     * Sends the given [code].
+     * This method can be called only once.
+     */
+    suspend fun send(code: UByte): Result<Unit>
+}

libraries/matrix/api/src/main/kotlin/io/element/android/libraries/matrix/api/linknewdevice/ErrorType.kt

@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.matrix.api.linknewdevice
+
+sealed class ErrorType(message: String) : Exception(message) {
+    /**
+     * The requested device ID is already in use.
+     */
+    class DeviceIdAlreadyInUse(message: String) : ErrorType(message)
+
+    /**
+     * The check code was incorrect.
+     */
+    class InvalidCheckCode(message: String) : ErrorType(message)
+
+    /**
+     * The other client proposed an unsupported protocol.
+     */
+    class UnsupportedProtocol(message: String) : ErrorType(message)
+
+    /**
+     * Secrets backup not set up properly.
+     */
+    class MissingSecretsBackup(message: String) : ErrorType(message)
+
+    /**
+     * The rendezvous session was not found and might have expired.
+     */
+    class NotFound(message: String) : ErrorType(message)
+
+    /**
+     * The device could not be created.
+     */
+    class UnableToCreateDevice(message: String) : ErrorType(message)
+
+    /**
+     * An unknown error has happened.
+     */
+    class Unknown(message: String) : ErrorType(message)
+}

libraries/matrix/api/src/main/kotlin/io/element/android/libraries/matrix/api/linknewdevice/LinkDesktopHandler.kt

@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.matrix.api.linknewdevice
+
+import io.element.android.libraries.matrix.api.auth.qrlogin.QrCodeDecodeException
+import kotlinx.coroutines.flow.StateFlow
+
+interface LinkDesktopHandler {
+    val linkDesktopStep: StateFlow<LinkDesktopStep>
+    suspend fun handleScannedQrCode(data: ByteArray)
+}
+
+sealed interface LinkDesktopStep {
+    data object Uninitialized : LinkDesktopStep
+    data object Starting : LinkDesktopStep
+    data class WaitingForAuth(
+        val verificationUri: String,
+    ) : LinkDesktopStep
+
+    data class EstablishingSecureChannel(
+        val checkCode: UByte,
+        val checkCodeString: String,
+    ) : LinkDesktopStep
+
+    data class InvalidQrCode(
+        val error: QrCodeDecodeException,
+    ) : LinkDesktopStep
+
+    data class Error(
+        val errorType: ErrorType,
+    ) : LinkDesktopStep
+
+    data object SyncingSecrets : LinkDesktopStep
+
+    data object Done : LinkDesktopStep
+}

libraries/matrix/api/src/main/kotlin/io/element/android/libraries/matrix/api/linknewdevice/LinkMobileHandler.kt

@@ -0,0 +1,26 @@
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.matrix.api.linknewdevice
+
+import kotlinx.coroutines.flow.Flow
+
+interface LinkMobileHandler {
+    val linkMobileStep: Flow<LinkMobileStep>
+    suspend fun start()
+}
+
+sealed interface LinkMobileStep {
+    data object Uninitialized : LinkMobileStep
+    data object Starting : LinkMobileStep
+    data class QrReady(val data: String) : LinkMobileStep
+    data class WaitingForAuth(val verificationUri: String) : LinkMobileStep
+    data class QrScanned(val checkCodeSender: CheckCodeSender) : LinkMobileStep
+    data class Error(val errorType: ErrorType) : LinkMobileStep
+    data object SyncingSecrets : LinkMobileStep
+    data object Done : LinkMobileStep
+}

libraries/matrix/api/src/main/kotlin/io/element/android/libraries/matrix/api/logs/LoggerTags.kt

@@ -0,0 +1,14 @@
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.matrix.api.logs
+
+import io.element.android.libraries.core.log.logger.LoggerTag
+
+object LoggerTags {
+    val linkNewDevice = LoggerTag("LinkNewDevice")
+}

libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/RustMatrixClient.kt

@@ -25,6 +25,8 @@ import io.element.android.libraries.matrix.api.core.RoomIdOrAlias
 import io.element.android.libraries.matrix.api.core.UserId
 import io.element.android.libraries.matrix.api.createroom.CreateRoomParameters
 import io.element.android.libraries.matrix.api.createroom.RoomPreset
+import io.element.android.libraries.matrix.api.linknewdevice.LinkDesktopHandler
+import io.element.android.libraries.matrix.api.linknewdevice.LinkMobileHandler
 import io.element.android.libraries.matrix.api.media.MatrixMediaLoader
 import io.element.android.libraries.matrix.api.oidc.AccountManagementAction
 import io.element.android.libraries.matrix.api.room.BaseRoom
@@ -45,6 +47,8 @@ import io.element.android.libraries.matrix.api.user.MatrixSearchUserResults
 import io.element.android.libraries.matrix.api.user.MatrixUser
 import io.element.android.libraries.matrix.impl.encryption.RustEncryptionService
 import io.element.android.libraries.matrix.impl.exception.mapClientException
+import io.element.android.libraries.matrix.impl.linknewdevice.RustLinkDesktopHandler
+import io.element.android.libraries.matrix.impl.linknewdevice.RustLinkMobileHandler
 import io.element.android.libraries.matrix.impl.mapper.map
 import io.element.android.libraries.matrix.impl.media.RustMediaLoader
 import io.element.android.libraries.matrix.impl.media.RustMediaPreviewService
@@ -726,6 +730,34 @@ class RustMatrixClient(
         }
     }
 
+    override suspend fun canLinkNewDevice(): Result<Boolean> = withContext(sessionDispatcher) {
+        runCatchingExceptions {
+            innerClient.isLoginWithQrCodeSupported()
+        }
+    }
+
+    override fun createLinkMobileHandler(): Result<LinkMobileHandler> {
+        return runCatchingExceptions {
+            val handler = innerClient.newGrantLoginWithQrCodeHandler()
+            RustLinkMobileHandler(
+                inner = handler,
+                sessionCoroutineScope = sessionCoroutineScope,
+                sessionDispatcher = sessionDispatcher,
+            )
+        }
+    }
+
+    override fun createLinkDesktopHandler(): Result<LinkDesktopHandler> {
+        return runCatchingExceptions {
+            val handler = innerClient.newGrantLoginWithQrCodeHandler()
+            RustLinkDesktopHandler(
+                inner = handler,
+                sessionCoroutineScope = sessionCoroutineScope,
+                sessionDispatcher = sessionDispatcher,
+            )
+        }
+    }
+
     override suspend fun markRoomAsFullyRead(roomId: RoomId, eventId: EventId): Result<Unit> = withContext(sessionDispatcher) {
         runCatchingExceptions {
             val room = innerClient.getRoom(roomId.value) ?: error("Could not fetch associated room")

libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/linknewdevice/HumanQrGrantLoginExceptionExtension.kt

@@ -0,0 +1,21 @@
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.matrix.impl.linknewdevice
+
+import io.element.android.libraries.matrix.api.linknewdevice.ErrorType
+import org.matrix.rustcomponents.sdk.HumanQrGrantLoginException
+
+internal fun HumanQrGrantLoginException.map() = when (this) {
+    is HumanQrGrantLoginException.DeviceIdAlreadyInUse -> ErrorType.DeviceIdAlreadyInUse(message.orEmpty())
+    is HumanQrGrantLoginException.InvalidCheckCode -> ErrorType.InvalidCheckCode(message.orEmpty())
+    is HumanQrGrantLoginException.MissingSecretsBackup -> ErrorType.MissingSecretsBackup(message.orEmpty())
+    is HumanQrGrantLoginException.NotFound -> ErrorType.NotFound(message.orEmpty())
+    is HumanQrGrantLoginException.UnableToCreateDevice -> ErrorType.UnableToCreateDevice(message.orEmpty())
+    is HumanQrGrantLoginException.Unknown -> ErrorType.Unknown(message.orEmpty())
+    is HumanQrGrantLoginException.UnsupportedProtocol -> ErrorType.UnsupportedProtocol(message.orEmpty())
+}

libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/linknewdevice/RustCheckCodeSender.kt

@@ -0,0 +1,33 @@
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.matrix.impl.linknewdevice
+
+import io.element.android.libraries.core.extensions.runCatchingExceptions
+import io.element.android.libraries.matrix.api.linknewdevice.CheckCodeSender
+import kotlinx.coroutines.CoroutineDispatcher
+import kotlinx.coroutines.withContext
+import org.matrix.rustcomponents.sdk.CheckCodeSender as FfiCheckCodeSender
+
+class RustCheckCodeSender(
+    private val inner: FfiCheckCodeSender,
+    private val sessionDispatcher: CoroutineDispatcher,
+) : CheckCodeSender {
+    override suspend fun validate(code: UByte): Boolean = withContext(sessionDispatcher) {
+        runCatchingExceptions {
+            // TODO https://github.com/matrix-org/matrix-rust-sdk/pull/5957
+            // inner.validate(code)
+            true
+        }.getOrNull() ?: true
+    }
+
+    override suspend fun send(code: UByte): Result<Unit> = withContext(sessionDispatcher) {
+        runCatchingExceptions {
+            inner.send(code)
+        }
+    }
+}

libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/linknewdevice/RustLinkDesktopHandler.kt

@@ -0,0 +1,82 @@
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.matrix.impl.linknewdevice
+
+import io.element.android.libraries.core.log.logger.LoggerTag
+import io.element.android.libraries.matrix.api.linknewdevice.LinkDesktopHandler
+import io.element.android.libraries.matrix.api.linknewdevice.LinkDesktopStep
+import io.element.android.libraries.matrix.api.logs.LoggerTags
+import io.element.android.libraries.matrix.impl.auth.qrlogin.QrErrorMapper
+import kotlinx.coroutines.CoroutineDispatcher
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.asStateFlow
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.withContext
+import org.matrix.rustcomponents.sdk.GrantLoginWithQrCodeHandler
+import org.matrix.rustcomponents.sdk.GrantQrLoginProgress
+import org.matrix.rustcomponents.sdk.GrantQrLoginProgressListener
+import org.matrix.rustcomponents.sdk.HumanQrGrantLoginException
+import org.matrix.rustcomponents.sdk.QrCodeData
+import org.matrix.rustcomponents.sdk.QrCodeDecodeException
+import timber.log.Timber
+
+private val tag = LoggerTag("RustLinkDesktopHandler", LoggerTags.linkNewDevice)
+
+class RustLinkDesktopHandler(
+    private val inner: GrantLoginWithQrCodeHandler,
+    private val sessionCoroutineScope: CoroutineScope,
+    private val sessionDispatcher: CoroutineDispatcher,
+) : LinkDesktopHandler {
+    private val _linkDesktopStep = MutableStateFlow<LinkDesktopStep>(LinkDesktopStep.Uninitialized)
+    override val linkDesktopStep: StateFlow<LinkDesktopStep> = _linkDesktopStep.asStateFlow()
+
+    override suspend fun handleScannedQrCode(data: ByteArray) = withContext(sessionDispatcher) {
+        Timber.tag(tag.value).d("Emit Uninitialized")
+        _linkDesktopStep.emit(LinkDesktopStep.Uninitialized)
+        try {
+            val qrCodeData = QrCodeData.fromBytes(data)
+            inner.scan(
+                qrCodeData = qrCodeData,
+                progressListener = object : GrantQrLoginProgressListener {
+                    override fun onUpdate(state: GrantQrLoginProgress) {
+                        sessionCoroutineScope.launch {
+                            val mappedState = state.map()
+                            Timber.tag(tag.value).d("Emit ${mappedState::class.java.simpleName}")
+                            _linkDesktopStep.emit(mappedState)
+                        }
+                    }
+                }
+            )
+        } catch (e: QrCodeDecodeException) {
+            Timber.tag(tag.value).w(e, "Invalid QR code scanned")
+            _linkDesktopStep.emit(
+                LinkDesktopStep.InvalidQrCode(
+                    error = QrErrorMapper.map(e)
+                )
+            )
+        } catch (e: HumanQrGrantLoginException) {
+            Timber.tag(tag.value).w(e, "Error during QR login grant")
+            _linkDesktopStep.emit(LinkDesktopStep.Error(e.map()))
+        }
+    }
+
+    private fun GrantQrLoginProgress.map() = when (this) {
+        GrantQrLoginProgress.Done -> LinkDesktopStep.Done
+        GrantQrLoginProgress.Starting -> LinkDesktopStep.Starting
+        GrantQrLoginProgress.SyncingSecrets -> LinkDesktopStep.SyncingSecrets
+        is GrantQrLoginProgress.WaitingForAuth -> LinkDesktopStep.WaitingForAuth(
+            verificationUri = verificationUri,
+        )
+        is GrantQrLoginProgress.EstablishingSecureChannel -> LinkDesktopStep.EstablishingSecureChannel(
+            checkCode = checkCode,
+            checkCodeString = checkCodeString,
+        )
+    }
+}

libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/linknewdevice/RustLinkMobileHandler.kt

@@ -0,0 +1,75 @@
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.matrix.impl.linknewdevice
+
+import io.element.android.libraries.core.log.logger.LoggerTag
+import io.element.android.libraries.matrix.api.linknewdevice.LinkMobileHandler
+import io.element.android.libraries.matrix.api.linknewdevice.LinkMobileStep
+import io.element.android.libraries.matrix.api.logs.LoggerTags
+import kotlinx.coroutines.CoroutineDispatcher
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.asStateFlow
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.withContext
+import org.matrix.rustcomponents.sdk.GrantGeneratedQrLoginProgress
+import org.matrix.rustcomponents.sdk.GrantGeneratedQrLoginProgressListener
+import org.matrix.rustcomponents.sdk.GrantLoginWithQrCodeHandler
+import org.matrix.rustcomponents.sdk.HumanQrGrantLoginException
+import timber.log.Timber
+
+private val tag = LoggerTag("RustLinkMobileHandler", LoggerTags.linkNewDevice)
+
+class RustLinkMobileHandler(
+    private val inner: GrantLoginWithQrCodeHandler,
+    private val sessionCoroutineScope: CoroutineScope,
+    private val sessionDispatcher: CoroutineDispatcher,
+) : LinkMobileHandler {
+    private val _linkMobileStep = MutableStateFlow<LinkMobileStep>(LinkMobileStep.Uninitialized)
+    override val linkMobileStep: Flow<LinkMobileStep> = _linkMobileStep.asStateFlow()
+
+    override suspend fun start() = withContext(sessionDispatcher) {
+        Timber.tag(tag.value).d("Emit Uninitialized")
+        _linkMobileStep.emit(LinkMobileStep.Uninitialized)
+        try {
+            inner.generate(
+                progressListener = object : GrantGeneratedQrLoginProgressListener {
+                    override fun onUpdate(state: GrantGeneratedQrLoginProgress) {
+                        sessionCoroutineScope.launch {
+                            val mappedState = state.map()
+                            Timber.tag(tag.value).d("Emit ${mappedState::class.java.simpleName}")
+                            _linkMobileStep.emit(mappedState)
+                        }
+                    }
+                }
+            )
+        } catch (e: HumanQrGrantLoginException) {
+            Timber.tag(tag.value).w(e, "Error during QR login grant")
+            _linkMobileStep.emit(LinkMobileStep.Error(e.map()))
+        }
+    }
+
+    private fun GrantGeneratedQrLoginProgress.map(): LinkMobileStep {
+        return when (this) {
+            GrantGeneratedQrLoginProgress.Done -> LinkMobileStep.Done
+            is GrantGeneratedQrLoginProgress.QrReady -> {
+                LinkMobileStep.QrReady(String(qrCode.toBytes(), Charsets.ISO_8859_1))
+            }
+            is GrantGeneratedQrLoginProgress.QrScanned -> LinkMobileStep.QrScanned(
+                RustCheckCodeSender(
+                    inner = checkCodeSender,
+                    sessionDispatcher = sessionDispatcher,
+                )
+            )
+            GrantGeneratedQrLoginProgress.Starting -> LinkMobileStep.Starting
+            GrantGeneratedQrLoginProgress.SyncingSecrets -> LinkMobileStep.SyncingSecrets
+            is GrantGeneratedQrLoginProgress.WaitingForAuth -> LinkMobileStep.WaitingForAuth(verificationUri)
+        }
+    }
+}

libraries/matrix/test/src/main/kotlin/io/element/android/libraries/matrix/test/FakeMatrixClient.kt

@@ -18,6 +18,8 @@ import io.element.android.libraries.matrix.api.core.SessionId
 import io.element.android.libraries.matrix.api.core.UserId
 import io.element.android.libraries.matrix.api.createroom.CreateRoomParameters
 import io.element.android.libraries.matrix.api.encryption.EncryptionService
+import io.element.android.libraries.matrix.api.linknewdevice.LinkDesktopHandler
+import io.element.android.libraries.matrix.api.linknewdevice.LinkMobileHandler
 import io.element.android.libraries.matrix.api.media.MatrixMediaLoader
 import io.element.android.libraries.matrix.api.media.MediaPreviewService
 import io.element.android.libraries.matrix.api.notification.NotificationService
@@ -95,6 +97,9 @@ class FakeMatrixClient(
     private val deactivateAccountResult: (String, Boolean) -> Result<Unit> = { _, _ -> lambdaError() },
     private val currentSlidingSyncVersionLambda: () -> Result<SlidingSyncVersion> = { lambdaError() },
     private val ignoreUserResult: (UserId) -> Result<Unit> = { lambdaError() },
+    private val canLinkNewDeviceResult: () -> Result<Boolean> = { lambdaError() },
+    private val createLinkMobileHandlerResult: () -> Result<LinkMobileHandler> = { lambdaError() },
+    private val createLinkDesktopHandlerResult: () -> Result<LinkDesktopHandler> = { lambdaError() },
     private var unIgnoreUserResult: (UserId) -> Result<Unit> = { Result.success(Unit) },
     private val canReportRoomLambda: () -> Boolean = { false },
     private val isLivekitRtcSupportedLambda: () -> Boolean = { false },
@@ -356,4 +361,16 @@ class FakeMatrixClient(
     override suspend fun performDatabaseVacuum(): Result<Unit> {
         return performDatabaseVacuumLambda()
     }
+
+    override suspend fun canLinkNewDevice(): Result<Boolean> = simulateLongTask {
+        return canLinkNewDeviceResult()
+    }
+
+    override fun createLinkDesktopHandler(): Result<LinkDesktopHandler> {
+        return createLinkDesktopHandlerResult()
+    }
+
+    override fun createLinkMobileHandler(): Result<LinkMobileHandler> {
+        return createLinkMobileHandlerResult()
+    }
 }

libraries/matrix/test/src/main/kotlin/io/element/android/libraries/matrix/test/TestData.kt

@@ -100,3 +100,31 @@ const val A_LOGIN_HINT = "mxid:@alice:example.org"
 
 @ColorInt
 const val A_COLOR_INT: Int = 0xFFFF0000.toInt()
+
+// From https://github.com/matrix-org/matrix-rust-sdk/blob/3a63838cdb50cde3d74da920186fbae0a2e6db37/crates/matrix-sdk-crypto/src/types/qr_login.rs#L275
+// Test vector for the QR code data, copied from the MSC.
+@Suppress("ktlint:standard:argument-list-wrapping")
+val QR_CODE_DATA = listOf(
+    0x4D, 0x41, 0x54, 0x52, 0x49, 0x58, 0x02, 0x03, 0xd8, 0x86, 0x68, 0x6a, 0xb2, 0x19, 0x7b,
+    0x78, 0x0e, 0x30, 0x0a, 0x9d, 0x4a, 0x21, 0x47, 0x48, 0x07, 0x00, 0xd7, 0x92, 0x9f, 0x39,
+    0xab, 0x31, 0xb9, 0xe5, 0x14, 0x37, 0x02, 0x48, 0xed, 0x6b, 0x00, 0x47, 0x68, 0x74, 0x74,
+    0x70, 0x73, 0x3a, 0x2f, 0x2f, 0x72, 0x65, 0x6e, 0x64, 0x65, 0x7a, 0x76, 0x6f, 0x75, 0x73,
+    0x2e, 0x6c, 0x61, 0x62, 0x2e, 0x65, 0x6c, 0x65, 0x6d, 0x65, 0x6e, 0x74, 0x2e, 0x64, 0x65,
+    0x76, 0x2f, 0x65, 0x38, 0x64, 0x61, 0x36, 0x33, 0x35, 0x35, 0x2d, 0x35, 0x35, 0x30, 0x62,
+    0x2d, 0x34, 0x61, 0x33, 0x32, 0x2d, 0x61, 0x31, 0x39, 0x33, 0x2d, 0x31, 0x36, 0x31, 0x39,
+    0x64, 0x39, 0x38, 0x33, 0x30, 0x36, 0x36, 0x38,
+).map { it.toByte() }.toByteArray()
+
+// Test vector for the QR code data, copied from the MSC, with the mode set to reciprocate.
+@Suppress("ktlint:standard:argument-list-wrapping")
+val QR_CODE_DATA_RECIPROCATE = listOf(
+    0x4D, 0x41, 0x54, 0x52, 0x49, 0x58, 0x02, 0x04, 0xd8, 0x86, 0x68, 0x6a, 0xb2, 0x19, 0x7b,
+    0x78, 0x0e, 0x30, 0x0a, 0x9d, 0x4a, 0x21, 0x47, 0x48, 0x07, 0x00, 0xd7, 0x92, 0x9f, 0x39,
+    0xab, 0x31, 0xb9, 0xe5, 0x14, 0x37, 0x02, 0x48, 0xed, 0x6b, 0x00, 0x47, 0x68, 0x74, 0x74,
+    0x70, 0x73, 0x3a, 0x2f, 0x2f, 0x72, 0x65, 0x6e, 0x64, 0x65, 0x7a, 0x76, 0x6f, 0x75, 0x73,
+    0x2e, 0x6c, 0x61, 0x62, 0x2e, 0x65, 0x6c, 0x65, 0x6d, 0x65, 0x6e, 0x74, 0x2e, 0x64, 0x65,
+    0x76, 0x2f, 0x65, 0x38, 0x64, 0x61, 0x36, 0x33, 0x35, 0x35, 0x2d, 0x35, 0x35, 0x30, 0x62,
+    0x2d, 0x34, 0x61, 0x33, 0x32, 0x2d, 0x61, 0x31, 0x39, 0x33, 0x2d, 0x31, 0x36, 0x31, 0x39,
+    0x64, 0x39, 0x38, 0x33, 0x30, 0x36, 0x36, 0x38, 0x00, 0x0A, 0x6d, 0x61, 0x74, 0x72, 0x69,
+    0x78, 0x2e, 0x6f, 0x72, 0x67,
+).map { it.toByte() }.toByteArray()

libraries/matrix/test/src/main/kotlin/io/element/android/libraries/matrix/test/linknewdevice/FakeCheckCodeSender.kt

@@ -0,0 +1,25 @@
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.matrix.test.linknewdevice
+
+import io.element.android.libraries.matrix.api.linknewdevice.CheckCodeSender
+import io.element.android.tests.testutils.lambda.lambdaError
+import io.element.android.tests.testutils.simulateLongTask
+
+class FakeCheckCodeSender(
+    private val validateResult: (UByte) -> Boolean = { lambdaError() },
+    private val sendResult: (UByte) -> Result<Unit> = { lambdaError() },
+) : CheckCodeSender {
+    override suspend fun validate(code: UByte): Boolean = simulateLongTask {
+        validateResult(code)
+    }
+
+    override suspend fun send(code: UByte): Result<Unit> = simulateLongTask {
+        sendResult(code)
+    }
+}

libraries/matrix/test/src/main/kotlin/io/element/android/libraries/matrix/test/linknewdevice/FakeLinkDesktopHandler.kt

@@ -0,0 +1,31 @@
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.matrix.test.linknewdevice
+
+import io.element.android.libraries.matrix.api.linknewdevice.LinkDesktopHandler
+import io.element.android.libraries.matrix.api.linknewdevice.LinkDesktopStep
+import io.element.android.tests.testutils.lambda.lambdaError
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.asStateFlow
+
+class FakeLinkDesktopHandler(
+    private val handleScannedQrCodeResult: (ByteArray) -> Unit = { lambdaError() },
+) : LinkDesktopHandler {
+    private val mutableLinkDesktopStep: MutableStateFlow<LinkDesktopStep> = MutableStateFlow(LinkDesktopStep.Uninitialized)
+    override val linkDesktopStep: StateFlow<LinkDesktopStep>
+        get() = mutableLinkDesktopStep.asStateFlow()
+
+    override suspend fun handleScannedQrCode(data: ByteArray) {
+        handleScannedQrCodeResult(data)
+    }
+
+    suspend fun emitStep(step: LinkDesktopStep) {
+        mutableLinkDesktopStep.emit(step)
+    }
+}

libraries/matrix/test/src/main/kotlin/io/element/android/libraries/matrix/test/linknewdevice/FakeLinkMobileHandler.kt

@@ -0,0 +1,32 @@
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.matrix.test.linknewdevice
+
+import io.element.android.libraries.matrix.api.linknewdevice.LinkMobileHandler
+import io.element.android.libraries.matrix.api.linknewdevice.LinkMobileStep
+import io.element.android.tests.testutils.lambda.lambdaError
+import io.element.android.tests.testutils.simulateLongTask
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.asStateFlow
+
+class FakeLinkMobileHandler(
+    private val startResult: () -> Unit = { lambdaError() },
+) : LinkMobileHandler {
+    private val mutableLinkMobileStep: MutableStateFlow<LinkMobileStep> = MutableStateFlow(LinkMobileStep.Uninitialized)
+    override val linkMobileStep: StateFlow<LinkMobileStep>
+        get() = mutableLinkMobileStep.asStateFlow()
+
+    override suspend fun start() = simulateLongTask {
+        startResult()
+    }
+
+    suspend fun emitStep(step: LinkMobileStep) {
+        mutableLinkMobileStep.emit(step)
+    }
+}

libraries/qrcode/build.gradle.kts

@@ -19,4 +19,5 @@ dependencies {
     implementation(libs.androidx.camera.view)
     implementation(libs.androidx.camera.camera2)
     implementation(libs.zxing.cpp)
+    implementation(libs.google.zxing)
 }

libraries/qrcode/src/main/kotlin/io/element/android/libraries/qrcode/QrCodeCameraView.kt

@@ -31,6 +31,7 @@ import androidx.compose.ui.draw.clipToBounds
 import androidx.compose.ui.graphics.asImageBitmap
 import androidx.compose.ui.platform.LocalContext
 import androidx.compose.ui.platform.LocalInspectionMode
+import androidx.compose.ui.text.style.TextAlign
 import androidx.compose.ui.viewinterop.AndroidView
 import androidx.core.content.ContextCompat
 import androidx.lifecycle.compose.LocalLifecycleOwner
@@ -117,7 +118,13 @@ fun QrCodeCameraView(
                     .background(color = ElementTheme.colors.bgSubtlePrimary),
                 contentAlignment = Alignment.Center,
             ) {
-                Text("CameraView")
+                Text(
+                    text = buildString {
+                        append("CameraView\n")
+                        append(if (isScanning) "scanning" else "frozen")
+                    },
+                    textAlign = TextAlign.Center,
+                )
             }
         } else {
             AndroidView(

libraries/qrcode/src/main/kotlin/io/element/android/libraries/qrcode/QrCodeImage.kt

@@ -0,0 +1,92 @@
+/*
+ * Copyright (c) 2025 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.qrcode
+
+import android.graphics.Bitmap
+import android.graphics.Color
+import androidx.annotation.ColorInt
+import androidx.compose.foundation.Image
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.fillMaxHeight
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.graphics.asImageBitmap
+import androidx.compose.ui.layout.onSizeChanged
+import androidx.compose.ui.tooling.preview.Preview
+import androidx.compose.ui.unit.IntSize
+import com.google.zxing.BarcodeFormat
+import com.google.zxing.common.BitMatrix
+import com.google.zxing.qrcode.QRCodeWriter
+import io.element.android.libraries.designsystem.modifiers.squareSize
+import io.element.android.libraries.designsystem.utils.ForceMaxBrightness
+
+private fun String.toBitMatrix(size: Int): BitMatrix {
+    return QRCodeWriter().encode(
+        this,
+        BarcodeFormat.QR_CODE,
+        size,
+        size,
+    )
+}
+
+private fun BitMatrix.toBitmap(
+    @ColorInt backgroundColor: Int = Color.WHITE,
+    @ColorInt foregroundColor: Int = Color.BLACK,
+): Bitmap {
+    val colorBuffer = IntArray(width * height)
+    var rowOffset = 0
+    for (y in 0 until height) {
+        for (x in 0 until width) {
+            val arrayIndex = x + rowOffset
+            colorBuffer[arrayIndex] = if (get(x, y)) foregroundColor else backgroundColor
+        }
+        rowOffset += width
+    }
+    return Bitmap.createBitmap(colorBuffer, width, height, Bitmap.Config.ARGB_8888)
+}
+
+@Composable
+fun QrCodeImage(
+    data: String,
+    forceMaxBrightness: Boolean = true,
+    modifier: Modifier = Modifier,
+) {
+    if (forceMaxBrightness) {
+        ForceMaxBrightness()
+    }
+    var size by remember { mutableStateOf(IntSize.Zero) }
+    Box(
+        modifier = modifier
+            .squareSize()
+            .onSizeChanged {
+                size = it
+            },
+    ) {
+        val image = remember(data, size) {
+            val sideSide = maxOf(size.width, size.height).coerceAtLeast(128)
+            data.toBitMatrix(sideSide).toBitmap().asImageBitmap()
+        }
+        Image(
+            contentDescription = null,
+            bitmap = image,
+        )
+    }
+}
+
+@Composable
+@Preview
+internal fun QrCodeViewPreview() {
+    QrCodeImage(
+        modifier = Modifier.fillMaxHeight(),
+        data = "RANDOM_QRCODE_DATA",
+    )
+}

libraries/ui-strings/src/main/res/values/localazy.xml

@@ -434,32 +434,6 @@ Are you sure you want to continue?"</string>
   <string name="screen_create_poll_options_section_title">"Options"</string>
   <string name="screen_create_poll_remove_accessibility_label">"Remove %1$s"</string>
   <string name="screen_create_poll_settings_section_title">"Settings"</string>
-  <string name="screen_link_new_device_desktop_scanning_title">"Scan the QR code"</string>
-  <string name="screen_link_new_device_desktop_step1">"Open %1$s on a laptop or desktop computer"</string>
-  <string name="screen_link_new_device_desktop_step3">"Scan the QR code with this device"</string>
-  <string name="screen_link_new_device_desktop_submit">"Ready to scan"</string>
-  <string name="screen_link_new_device_desktop_title">"Open %1$s on a desktop computer to get the QR code"</string>
-  <string name="screen_link_new_device_enter_number_error_numbers_do_not_match">"The numbers don’t match"</string>
-  <string name="screen_link_new_device_enter_number_notice">"Enter 2-digit code"</string>
-  <string name="screen_link_new_device_enter_number_subtitle">"This will verify that the connection to your other device is secure."</string>
-  <string name="screen_link_new_device_enter_number_title">"Enter the number shown on your other device"</string>
-  <string name="screen_link_new_device_error_app_not_supported_subtitle">"Your account provider does not support %1$s."</string>
-  <string name="screen_link_new_device_error_app_not_supported_title">"%1$s not supported"</string>
-  <string name="screen_link_new_device_error_not_supported_subtitle">"Your account provider doesn’t support signing into a new device with a QR code."</string>
-  <string name="screen_link_new_device_error_not_supported_title">"QR code not supported"</string>
-  <string name="screen_link_new_device_error_request_cancelled_subtitle">"The sign in was cancelled on the other device."</string>
-  <string name="screen_link_new_device_error_request_cancelled_title">"Sign in request cancelled"</string>
-  <string name="screen_link_new_device_error_request_timeout_subtitle">"Sign in expired. Please try again."</string>
-  <string name="screen_link_new_device_error_request_timeout_title">"The sign in was not completed in time"</string>
-  <string name="screen_link_new_device_mobile_step1">"Open %1$s on the other device"</string>
-  <string name="screen_link_new_device_mobile_step2">"Select %1$s"</string>
-  <string name="screen_link_new_device_mobile_step2_action">"“Sign in with QR code”"</string>
-  <string name="screen_link_new_device_mobile_step3">"Scan the QR code shown here with the other device"</string>
-  <string name="screen_link_new_device_mobile_title">"Open %1$s on the other device"</string>
-  <string name="screen_link_new_device_root_desktop_computer">"Desktop computer"</string>
-  <string name="screen_link_new_device_root_loading_qr_code">"Loading QR code…"</string>
-  <string name="screen_link_new_device_root_mobile_device">"Mobile device"</string>
-  <string name="screen_link_new_device_root_title">"What type of device do you want to link?"</string>
   <string name="screen_manage_authorized_spaces_header">"Spaces where members can join the room without an invitation."</string>
   <string name="screen_manage_authorized_spaces_title">"Manage spaces"</string>
   <string name="screen_manage_authorized_spaces_unknown_space">"(Unknown space)"</string>