astrum wiki

Subscriptions are the only way to update your state and view logic after an external event occurs.
Subscriptions will trigger every window's view and signal logic (might change in the future, depending on libcosmic)

To use a subscription, you must subscribe to a specific service.
Here is a hyprland workspace changed subscription example:

local state = {
    -- most services have types
    ---@type HyprlandWorkspaces
    workspaces = {}
}

App:window("workspace_example", {
    view = function()
        local row = Widgets:row({})

        for _, workspace in pairs(state.workspaces) do
            row:push(Widgets:text(tostring(workspace.id)))
        end

        return row
    end,
    -- Tells the application to subscribe to the `Hyprland` service
    subscriptions = {
        hyprland = {
            ---Specifies that whenever there is a workspace change, send the following signal that goes by the name of `on_workspace`
            workspaces = "on_workspace"
        }
    }
    signals = {
        on_workspace = function(signal_data)
            -- Signal data is of type `HyprlandWorkspaces`
            state.workspaces = signal_data
        end
    }
})