simplex-chat/apps/multiplatform/spec/client/navigation.md

Navigation Specification

Source: common/src/commonMain/kotlin/chat/simplex/common/App.kt (470 lines)

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Table of Contents

1. Overview
2. AppScreen Composable
3. MainScreen
4. Android Layout
5. Desktop Layout
6. ModalManager
7. Authentication Gate
8. Onboarding Flow
9. Source Files

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Executive Summary

SimpleX Chat navigation is a platform-adaptive system implemented in App.kt. The root AppScreen composable applies theming and safe-area insets, delegating to MainScreen which acts as a state machine routing between onboarding, authentication, database error, and the main chat interface. Android uses a 2-column sliding layout (AndroidScreen), while desktop uses a fixed 3-column layout (DesktopScreen). Modal presentation is managed by ModalManager, which provides named zones (start, center, end, fullscreen) for layered content. Authentication is gated by AppLock, and onboarding follows a linear OnboardingStage enum.

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1. Overview

AppScreen (line 46)
+-- SimpleXTheme
    +-- Surface
        +-- MainScreen (line 82)
            |-- [Migration in progress]     -> DefaultProgressView
            |-- [Database opening]          -> DefaultProgressView
            |-- [Database error]            -> DatabaseErrorView
            |-- [Encryption check pending]  -> SplashView
            |-- [Onboarding incomplete]     -> AnimatedContent { OnboardingStage views }
            |-- [Onboarding complete]
            |   |-- [Android]
            |   |   +-- AndroidWrapInCallLayout
            |   |       +-- AndroidScreen (line 293)
            |   |           |-- StartPartOfScreen (ChatListView)
            |   |           +-- ChatView (slide-in panel)
            |   +-- [Desktop]
            |       +-- DesktopScreen (line 406)
            |           |-- StartPartOfScreen + UserPicker (left column)
            |           |-- ModalManager.start (overlay on left)
            |           |-- CenterPartOfScreen / ChatView (center column)
            |           +-- ModalManager.end (right column)
            |-- [Unauthorized] -> AuthView / SplashView / PasscodeView
            |-- [Active call] -> ActiveCallView (desktop) / startCallActivity (Android)
            +-- [Incoming call] -> IncomingCallAlertView

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2. AppScreen Composable

Location: App.kt#L47

@Composable
fun AppScreen()

Responsibilities

1. Theme application: Wraps content in SimpleXTheme with Surface using MaterialTheme.colors.background.
2. Window insets: Computes safe padding for landscape mode, accounting for display cutouts on both sides. Uses WindowInsets.safeDrawing and WindowInsets.displayCutout to calculate symmetric padding.
3. Fullscreen gallery overlay: When chatModel.fullscreenGalleryVisible is true, draws a black rectangle behind content extending into the cutout areas to provide an immersive gallery background.
4. Delegates to MainScreen().

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3. MainScreen

Location: App.kt#L84

@Composable
fun MainScreen()

State Machine

MainScreen evaluates a series of conditions in priority order:

Priority	Condition	View
1	onboarding == Step1_SimpleXInfo && migrationState != null	SimpleXInfo (migration in progress)
2	dbMigrationInProgress	DefaultProgressView("Database migration...")
3	chatDbStatus == null && showInitializationView	DefaultProgressView("Opening database...")
4	showChatDatabaseError	DatabaseErrorView
5	chatDbEncrypted == null || localUserCreated == null	SplashView
6	onboarding == OnboardingComplete	Platform-specific main screen
7	Other onboarding stages	AnimatedContent with stage-specific views

Onboarding Complete Branch (line ~156)

When onboarding is complete:

1. Shows "advertise lock" alert if conditions met (not shown before, LA not enabled, >3 chats, no active call).
2. Routes to AndroidScreen or DesktopScreen based on platform.

Overlay Layers (bottom of MainScreen)

Layer	Condition	Content
ModalManager.fullscreen	Android + migration/onboarding	Fullscreen modals
SwitchingUsersView	User switch in progress	Loading overlay
Auth gate	userAuthorized != true	AuthView or SplashView + passcode
Active call	showCallView == true	ActiveCallView (desktop) or call activity (Android)
One-time passcode	Always	ModalManager.fullscreen.showOneTimePasscodeInView
Privacy alerts	Always	AlertManager.privacySensitive
Incoming call	activeCallInvitation != null	IncomingCallAlertView
Shared alerts	Always	AlertManager.shared

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4. Android Layout

Location: App.kt#L296

@Composable
fun AndroidScreen(userPickerState: MutableStateFlow<AnimatedViewState>)

2-Column Slide Animation

Uses BoxWithConstraints to get maxWidth, then two Box containers:

1. Left panel (StartPartOfScreen): Chat list, positioned at translationX = -offset.
2. Right panel (ChatView): Chat view, positioned at translationX = maxWidth - offset.

The offset is an Animatable<Float>:

• 0f when no chat is selected (chat list visible).
• maxWidth.value when a chat is open (chat view visible).

Animation Flow

1. snapshotFlow { chatModel.chatId.value } detects chat ID changes.
2. When chatId becomes null, onComposed(null) animates offset to 0.
3. When ChatView finishes composing (calls onComposed(chatId)), offset animates to maxWidth.
4. Animation uses chatListAnimationSpec() (standard spring or tween).

Display Cutout Handling

If the device has a display cutout on horizontal sides (detected via WindowInsets.displayCutout), the panels are clipped with RectangleShape to prevent the chat list from showing through during transition.

Call Layout Wrapper

AndroidWrapInCallLayout (line ~279) adds a 40dp top padding when an active call is in progress (not in WaitCapabilities or InvitationAccepted state), with an ActiveCallInteractiveArea banner above.

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5. Desktop Layout

Location: App.kt#L410

@Composable
fun DesktopScreen(userPickerState: MutableStateFlow<AnimatedViewState>)

3-Column Layout

Column	Width	Content
Left	DEFAULT_START_MODAL_WIDTH * fontSizeSqrtMultiplier (fixed)	StartPartOfScreen (ChatListView) + UserPicker overlay
Left overlay	Same as left column	ModalManager.start modals + SwitchingUsersView
Center	min = DEFAULT_MIN_CENTER_MODAL_WIDTH, weight = 1f (flexible)	CenterPartOfScreen (ChatView or "no selected chat" placeholder, or ModalManager.center)
Right	max = DEFAULT_END_MODAL_WIDTH * fontSizeSqrtMultiplier (flexible, 0 when empty)	ModalManager.end (ChatInfoView, GroupChatInfoView, ChatItemInfoView, etc.)

Column Separators

• VerticalDivider between left and center columns (always visible).
• VerticalDivider between center and right columns (visible when ModalManager.end.hasModalsOpen()).

Click-to-Dismiss Overlay

When the UserPicker is visible or a start modal is open (but no center modal), a full-size clickable overlay covers the center+right area (line ~428). Clicking it closes start modals and hides the UserPicker.

CenterPartOfScreen

Location: App.kt#L373

• When chatId is null and no center modals: shows "No selected chat" placeholder.
• When chatId is null and center modals open: shows ModalManager.center.
• When chatId is set: shows ChatView.
• Automatically closes center modals when a chat is selected.

StartPartOfScreen

Location: App.kt#L352

Routes between:

• SetDeliveryReceiptsView (if chatModel.setDeliveryReceipts is true)
• ChatListView (normal operation)
• ShareListView (when chatModel.sharedContent is non-null, i.e., forwarding)

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6. ModalManager

Location: common/src/commonMain/kotlin/chat/simplex/common/views/helpers/ModalView.kt (line 92)

class ModalManager(private val placement: ModalPlacement?)

Zones

Zone	Android Behavior	Desktop Behavior
start	Shared (same as all others)	Left column overlay, slides from start
center	Shared	Center column overlay, replaces ChatView
end	Shared	Right column, slides from end
fullscreen	Shared	Fullscreen overlay

On Android, all four zones point to the same shared instance, meaning modals stack in a single overlay. On desktop, each zone is independent with its own ModalPlacement.

companion object {
  val start = if (appPlatform.isAndroid) shared else ModalManager(ModalPlacement.START)
  val center = if (appPlatform.isAndroid) shared else ModalManager(ModalPlacement.CENTER)
  val end = if (appPlatform.isAndroid) shared else ModalManager(ModalPlacement.END)
  val fullscreen = if (appPlatform.isAndroid) shared else ModalManager(ModalPlacement.FULLSCREEN)
}

Modal Stack

Each ModalManager maintains a stack of ModalViewHolder objects with:

• id: ModalViewId? -- optional identifier for deduplication
• animated: Boolean -- whether to use enter/exit transitions
• data: ModalData -- scoped data for the modal
• modal: @Composable ModalData.(close: () -> Unit) -> Unit -- the modal content

Key Methods

Method	Description
showModal	Push a simple modal onto the stack
showModalCloseable	Push a modal with a close callback
showCustomModal	Push a modal with full control over ModalView wrapper
closeModals	Pop all modals from the stack
closeModalsExceptFirst	Pop all but the bottom modal
hasModalsOpen()	Check if any modals are on the stack
showInView	Render the current modal stack into the composable tree

Usage Pattern

Action	Zone Used
Settings, New Chat, User Address	ModalManager.start
Onboarding conditions, What's New	ModalManager.center
ChatInfoView, GroupChatInfoView, ChatItemInfoView, GroupMemberInfoView	ModalManager.end
Passcode entry, Call view, Migration	ModalManager.fullscreen

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7. Authentication Gate

Location: AppLock.kt#L17

object AppLock {
  val userAuthorized = mutableStateOf<Boolean?>(null)
  val enteredBackground = mutableStateOf<Long?>(null)
  val laFailed = mutableStateOf(false)
}

State

Field	Type	Description
userAuthorized	MutableState<Boolean?>	null = not yet determined, true = authenticated, false = locked
enteredBackground	MutableState<Long?>	Timestamp when app entered background (for lock delay)
laFailed	MutableState<Boolean>	True if last authentication attempt failed

Authentication Flow

1. MainScreen checks unauthorized (derived: userAuthorized.value != true) at line ~135.
2. If unauthorized and not in an active call:
   • Launches AppLock.runAuthenticate() which triggers platform-specific biometric/passcode prompt.
   • On Android with system auth finishing during activity destruction, authentication is skipped.
3. If performLA preference is set and laFailed is true: shows AuthView with "Unlock" button.
4. If performLA is set and laFailed is false: shows SplashView with passcode overlay.

Lock Delay

The laLockDelay preference controls how long after backgrounding the app requires re-authentication. When laLockDelay == 0, screen rotation triggers a 3-second grace period (line ~270) to prevent unnecessary re-auth.

Lock Modes

• LAMode.SYSTEM: Uses Android biometric/system lock screen.
• LAMode.PASSCODE: Uses in-app passcode (SetAppPasscodeView).

First-Time Lock Notice

showLANotice (line ~33 in AppLock.kt) prompts users to enable SimpleX Lock when they have more than 3 chats, have not yet been shown the notice, and have not enabled lock. On Android, it offers a choice between system auth and passcode.

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8. Onboarding Flow

Location: common/src/commonMain/kotlin/chat/simplex/common/views/onboarding/OnboardingView.kt (line 3)

enum class OnboardingStage {
  Step1_SimpleXInfo,
  Step2_CreateProfile,
  LinkAMobile,
  Step2_5_SetupDatabasePassphrase,
  Step3_ChooseServerOperators,
  Step3_CreateSimpleXAddress,
  Step4_SetNotificationsMode,
  OnboardingComplete
}

Stage Progression

Stage	View	Next Stage
Step1_SimpleXInfo	SimpleXInfo -- app introduction, privacy features	Step2_CreateProfile or LinkAMobile (desktop)
Step2_CreateProfile	CreateFirstProfile -- display name, optional image	Step2_5_SetupDatabasePassphrase or Step3_ChooseServerOperators
LinkAMobile	LinkAMobile -- desktop linking to mobile device	Step2_CreateProfile
Step2_5_SetupDatabasePassphrase	SetupDatabasePassphrase -- optional DB encryption	Step3_ChooseServerOperators
Step3_ChooseServerOperators	OnboardingConditionsView -- server operator selection, T&C	Step3_CreateSimpleXAddress or Step4_SetNotificationsMode
Step3_CreateSimpleXAddress	SetNotificationsMode (legacy backcompat)	Step4_SetNotificationsMode
Step4_SetNotificationsMode	SetNotificationsMode -- notification permission setup	OnboardingComplete
OnboardingComplete	Main app screen	--

Animated Transitions

Onboarding uses AnimatedContent with directional transitions:

• Forward: fromEndToStartTransition (slide left).
• Backward: fromStartToEndTransition (slide right).

The stage value is stored in appPrefs.onboardingStage and persisted across app restarts.

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9. Source Files

File	Description
App.kt	AppScreen, MainScreen, AndroidScreen, DesktopScreen, StartPartOfScreen, CenterPartOfScreen, EndPartOfScreen
AppLock.kt	AppLock object, authentication state, lock notice, LA mode selection
views/helpers/ModalView.kt	ModalManager class, ModalPlacement enum, modal stack management
views/onboarding/OnboardingView.kt	OnboardingStage enum
views/onboarding/SimpleXInfo.kt	Step 1: App introduction
views/WelcomeView.kt	Step 2: Profile creation (CreateFirstProfile)
views/onboarding/LinkAMobileView.kt	Desktop: Link a mobile device
views/onboarding/SetupDatabasePassphrase.kt	Step 2.5: Database passphrase
views/onboarding/ChooseServerOperators.kt	Step 3: Server operators and conditions
views/onboarding/SetNotificationsMode.kt	Step 4: Notification setup
views/chatlist/ChatListView.kt	Chat list (StartPartOfScreen content)
views/chatlist/UserPicker.kt	User switching panel
views/chat/ChatView.kt	Chat view (CenterPartOfScreen content)
views/database/DatabaseErrorView.kt	Database error recovery
views/SplashView.kt	Splash / loading screen
views/call/CallView.kt	In-call fullscreen view (ActiveCallView)
views/localauth/PasswordEntry.kt	Column divider utility (contains VerticalDivider)