Improve UX around max linked devices.

app/src/main/java/org/thoughtcrime/securesms/linkdevice/EditDeviceNameFragment.kt

@@ -72,6 +72,7 @@ class EditDeviceNameFragment : ComposeFragment() {
         LinkDeviceSettingsState.OneTimeEvent.ToastNetworkFailed,
         is LinkDeviceSettingsState.OneTimeEvent.ToastUnlinked,
         LinkDeviceSettingsState.OneTimeEvent.LaunchEmail,
+        LinkDeviceSettingsState.OneTimeEvent.SnackbarDeviceLimitReached,
         LinkDeviceSettingsState.OneTimeEvent.SnackbarLinkCancelled -> Unit
       }
     }

app/src/main/java/org/thoughtcrime/securesms/linkdevice/LinkDeviceFragment.kt

@@ -26,6 +26,7 @@ import androidx.compose.foundation.text.ClickableText
 import androidx.compose.foundation.text.InlineTextContent
 import androidx.compose.foundation.text.appendInlineContent
 import androidx.compose.foundation.verticalScroll
+import androidx.compose.material3.ButtonDefaults
 import androidx.compose.material3.CircularProgressIndicator
 import androidx.compose.material3.Icon
 import androidx.compose.material3.LocalTextStyle
@@ -74,6 +75,7 @@ import org.thoughtcrime.securesms.R
 import org.thoughtcrime.securesms.linkdevice.LinkDeviceSettingsState.DialogState
 import org.thoughtcrime.securesms.util.CommunicationActions
 import org.thoughtcrime.securesms.util.DateUtils
+import org.thoughtcrime.securesms.util.RemoteConfig
 import org.thoughtcrime.securesms.util.SupportEmailUtil
 import org.thoughtcrime.securesms.util.navigation.safeNavigate
 import org.signal.core.ui.R as CoreUiR
@@ -129,6 +131,7 @@ class LinkDeviceFragment : ComposeFragment() {
     val state by viewModel.state.collectAsStateWithLifecycle()
     val navController: NavController by remember { mutableStateOf(findNavController()) }
     val context = LocalContext.current
+    val atDeviceLimit = state.devices.size >= RemoteConfig.maxLinkedDevices
 
     LaunchedEffect(state.dialogState) {
       when (state.dialogState) {
@@ -158,6 +161,9 @@ class LinkDeviceFragment : ComposeFragment() {
         LinkDeviceSettingsState.OneTimeEvent.SnackbarLinkCancelled -> {
           Snackbar.make(requireView(), getString(R.string.LinkDeviceFragment__linking_cancelled), Snackbar.LENGTH_LONG).show()
         }
+        LinkDeviceSettingsState.OneTimeEvent.SnackbarDeviceLimitReached -> {
+          Snackbar.make(requireView(), getString(R.string.LinkDeviceFragment__you_can_only_have_d_linked_devices, RemoteConfig.maxLinkedDevices), Snackbar.LENGTH_LONG).show()
+        }
         LinkDeviceSettingsState.OneTimeEvent.ToastNetworkFailed -> {
           Toast.makeText(requireContext(), getString(R.string.DeviceListActivity_network_failed), Toast.LENGTH_LONG).show()
         }
@@ -195,10 +201,15 @@ class LinkDeviceFragment : ComposeFragment() {
       DeviceListScreen(
         state = state,
         modifier = Modifier.padding(contentPadding),
+        atDeviceLimit = atDeviceLimit,
         onLearnMoreClicked = { navController.safeNavigate(R.id.action_linkDeviceFragment_to_linkDeviceLearnMoreBottomSheet) },
         onLinkNewDeviceClicked = {
-          viewModel.stopExistingPolling()
-          navController.navigateToQrScannerIfAuthed()
+          if (atDeviceLimit) {
+            viewModel.onDeviceLimitReached()
+          } else {
+            viewModel.stopExistingPolling()
+            navController.navigateToQrScannerIfAuthed()
+          }
         },
         onDeviceSelectedForRemoval = { device -> viewModel.setDeviceToRemove(device) },
         onDeviceRemovalConfirmed = { device -> viewModel.removeDevice(device) },
@@ -272,6 +283,7 @@ class LinkDeviceFragment : ComposeFragment() {
 fun DeviceListScreen(
   state: LinkDeviceSettingsState,
   modifier: Modifier = Modifier,
+  atDeviceLimit: Boolean = false,
   onLearnMoreClicked: () -> Unit = {},
   onLinkNewDeviceClicked: () -> Unit = {},
   onDeviceSelectedForRemoval: (Device?) -> Unit = {},
@@ -411,8 +423,17 @@ fun DeviceListScreen(
 
     Spacer(modifier = Modifier.size(20.dp))
 
+    val linkButtonColors = ButtonDefaults.filledTonalButtonColors()
     Buttons.LargeTonal(
       onClick = onLinkNewDeviceClicked,
+      colors = if (atDeviceLimit) {
+        linkButtonColors.copy(
+          containerColor = linkButtonColors.disabledContainerColor,
+          contentColor = linkButtonColors.disabledContentColor
+        )
+      } else {
+        linkButtonColors
+      },
       modifier = Modifier
         .defaultMinSize(300.dp)
         .padding(bottom = 8.dp)

app/src/main/java/org/thoughtcrime/securesms/linkdevice/LinkDeviceSettingsState.kt

@@ -41,6 +41,7 @@ data class LinkDeviceSettingsState(
     data class ToastUnlinked(val name: String) : OneTimeEvent
     data class ToastLinked(val name: String) : OneTimeEvent
     data object SnackbarLinkCancelled : OneTimeEvent
+    data object SnackbarDeviceLimitReached : OneTimeEvent
     data object SnackbarNameChangeSuccess : OneTimeEvent
     data object SnackbarNameChangeFailure : OneTimeEvent
     data object ShowFinishedSheet : OneTimeEvent

app/src/main/java/org/thoughtcrime/securesms/linkdevice/LinkDeviceViewModel.kt

@@ -152,6 +152,10 @@ class LinkDeviceViewModel : ViewModel() {
     pollJob?.cancel()
   }
 
+  fun onDeviceLimitReached() {
+    _state.update { it.copy(oneTimeEvent = OneTimeEvent.SnackbarDeviceLimitReached) }
+  }
+
   fun markQrEducationSheetSeen() {
     SignalStore.uiHints.markHasSeenLinkDeviceQrEducationSheet()
     _state.update {

app/src/main/java/org/thoughtcrime/securesms/util/RemoteConfig.kt

@@ -605,6 +605,15 @@ object RemoteConfig {
     hotSwappable = true
   )
 
+  /** The maximum number of linked devices a user can have. */
+  @JvmStatic
+  @get:JvmName("maxLinkedDevices")
+  val maxLinkedDevices: Int by remoteInt(
+    key = "global.maxLinkedDevices",
+    defaultValue = 5,
+    hotSwappable = true
+  )
+
   /** The maximum number of grapheme  */
   @JvmStatic
   val maxGroupNameGraphemeLength: Int by remoteValue(

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

@@ -1122,6 +1122,8 @@
     <string name="LinkDeviceFragment__edit_name">Edit name</string>
     <!-- Toast shown when the process of linking a device has been cancelled -->
     <string name="LinkDeviceFragment__linking_cancelled">Linking cancelled</string>
+    <!-- Snackbar shown when the user tries to link a new device but has already reached the maximum number of linked devices. Placeholder is the maximum count. -->
+    <string name="LinkDeviceFragment__you_can_only_have_d_linked_devices">You can only have %1$d linked devices.</string>
     <!-- Message shown in progress dialog telling users to avoid closing the app while messages are being synced -->
     <string name="LinkDeviceFragment__do_not_close">Do not close app</string>
     <!-- Dialog title shown when a device is unlinked -->