Mob 0.9.28 released!

Mob 0.9.28 has been released.

Changed

• A component callback repaints its screen only when the component’s
  rendered props change. Before, every Mob.Component handle_event/3 and
  handle_info/2 repainted the screen, whatever it returned. What an app
  upgrading from 0.9.27 should know:

  • A component’s render/1 is treated as a function of its assigns, as in
    LiveView. Anything else it reads (a clock, ETS) is picked up on the next
    screen paint, not by a callback that changed no assign.
  • A component event that leaves the component’s props alone no longer
    re-renders the parent screen. A screen whose render/1 reads state a
    component writes outside messages (ETS, an Agent) and relied on component
    events to refresh it should be sent a message instead.
  • A native view is no longer re-committed with identical props. A view
    whose update block reset rejected input from props on every commit now
    keeps the typed text; to force a commit, have the component bump an assign
    its render/1 returns (a revision counter) when it rejects input.

  Decision: decisions/2026-11-12-component-events-repaint-only-on-changed-props.md.

Fixed

• A native view event that changes nothing no longer commits the whole
  tree. Every component callback used to send {:component_changed, ...},
  and the screen repainted and called set_root without checking anything. A
  native view that sends an event per key press or knob move therefore
  committed twice per press: on a Moto G Power 2021, 5-15 ms of BEAM work plus
  10-20 ms of Compose recomposition per commit. Now a component notifies its
  screen only when render/1 returns props that differ from the ones the
  screen last fetched, and does not render to check if its assigns are
  unchanged (!==). The screen repaints through the same unchanged-tree skip
  its own messages use, so several notices queued behind one paint commit
  once. Verified on a Moto G Power 2021 and an iPhone SE (3rd gen). The last
  rendered props a component keeps for this are redacted in its crash report
  and :sys.get_status/1, as its assigns are (MOB-310).

Mob Info

Classification: Hybrid Mobile Framework
Description: BEAM-on-device mobile framework for Elixir. OTP runs inside your iOS and Android apps — embedded directly in the app bundle, no server required. Screens are GenServers; the UI is rendered by Compose and SwiftUI via a thin NIF.
Forum/tag: mob

Click here to view Mob’s main announcement thread.