robius-state-management

Robius State Management Skill

Best practices for state management and persistence in Makepad applications based on Robrix and Moly codebases.

Source codebases:

• Robrix: Matrix chat client - AppState, SelectedRoom, persistence via serde
• Moly: AI chat application - Central Store pattern, async initialization, Preferences

Triggers

Use this skill when:

• Designing application state structure
• Implementing state persistence
• Passing state through widget tree
• Managing UI state across sessions
• Keywords: app state, makepad state, persistence, Scope::with_data, save state, load state

Production Patterns

For production-ready state management patterns, see the _base/ directory:

AppState Structure

Core State Definition

use serde::{Serialize, Deserialize};
use std::collections::HashMap;
use matrix_sdk::ruma::OwnedRoomId;

/// App-wide state that is stored persistently across multiple app runs
/// and shared/​updated across various parts of the app.
#[derive(Clone, Default, Debug, Serialize, Deserialize)]
pub struct AppState {
    /// The currently-selected room
    pub selected_room: Option<SelectedRoom>,

    /// Saved UI layout state for main view
    pub saved_layout_state: SavedLayoutState,

    /// Per-item saved states (e.g., per-space dock layouts)
    pub saved_state_per_item: HashMap<OwnedRoomId, SavedLayoutState>,

    /// Whether a user is currently logged in
    #[serde(skip)]  // Don't persist login state
    pub logged_in: bool,
}

/// Represents a currently selected item
#[derive(Clone, Debug, Serialize, Deserialize)]
pub enum SelectedRoom {
    JoinedRoom { room_name_id: RoomNameId },
    InvitedRoom { room_name_id: RoomNameId },
    Space { space_name_id: RoomNameId },
}

impl SelectedRoom {
    pub fn room_id(&self) -> &OwnedRoomId {
        match self {
            Self::JoinedRoom { room_name_id } => room_name_id.room_id(),
            Self::InvitedRoom { room_name_id } => room_name_id.room_id(),
            Self::Space { space_name_id } => space_name_id.room_id(),
        }
    }

    /// Upgrade from invited to joined state
    pub fn upgrade_invite_to_joined(&mut self, room_id: &RoomId) -> bool {
        match self {
            Self::InvitedRoom { room_name_id } if room_name_id.room_id() == room_id => {
                let name = room_name_id.clone();
                *self = Self::JoinedRoom { room_name_id: name };
                true
            }
            _ => false,
        }
    }
}

// Equality based on room_id only
impl PartialEq for SelectedRoom {
    fn eq(&self, other: &Self) -> bool {
        self.room_id() == other.room_id()
    }
}
impl Eq for SelectedRoom {}

Layout/​Dock State Persistence

/// A snapshot of UI layout state for restoration
#[derive(Clone, Default, Debug, Serialize, Deserialize)]
pub struct SavedLayoutState {
    /// All items contained in the layout, keyed by ID
    pub layout_items: HashMap<LiveIdSerde, LayoutItemSerde>,

    /// Items currently open, keyed by ID
    pub open_items: HashMap<LiveIdSerde, SelectedRoom>,

    /// Order items were opened (chronological)
    pub item_order: Vec<SelectedRoom>,

    /// Currently selected item when state was saved
    pub selected_item: Option<SelectedRoom>,
}

/// Serializable wrapper for LiveId
#[derive(Clone, Debug, Hash, Eq, PartialEq, Serialize, Deserialize)]
pub struct LiveIdSerde(pub u64);

impl From<LiveId> for LiveIdSerde {
    fn from(id: LiveId) -> Self {
        Self(id.0)
    }
}

impl From<LiveIdSerde> for LiveId {
    fn from(s: LiveIdSerde) -> Self {
        LiveId(s.0)
    }
}

State Propagation via Scope

Passing State Through Widget Tree

impl AppMain for App {
    fn handle_event(&mut self, cx: &mut Cx, event: &Event) {
        // Forward to MatchEvent
        self.match_event(cx, event);

        // Create Scope with AppState data
        let scope = &mut Scope::with_data(&mut self.app_state);

        // Pass to widget tree - all children can access AppState
        self.ui.handle_event(cx, event, scope);
    }
}

Accessing State in Child Widgets

impl Widget for RoomScreen {
    fn handle_event(&mut self, cx: &mut Cx, event: &Event, scope: &mut Scope) {
        // Access AppState from scope
        if let Some(app_state) = scope.data.get::<AppState>() {
            if let Some(selected) = &app_state.selected_room {
                self.update_for_room(cx, selected);
            }
        }

        self.view.handle_event(cx, event, scope);
    }
}

Modifying State

impl Widget for RoomsList {
    fn handle_event(&mut self, cx: