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tactility/.claude/rules/app-framework.md
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Ken Van Hoeylandt ab75d2022d Refactored events (#621)
Event handling:

- Added unified event handling for application, system, and Wi‑Fi events.
- Updated all apps to reflect event handling changes

Wi-Fi:

- Refactored event handling from listener interface to task & event group.
- Added direct Wi‑Fi radio controls and improved event subscriptions.
- Wi‑Fi screens now refresh asynchronously and handle unavailable devices more gracefully.
- Enabled Wi‑Fi by default on in dts files, but radio on/off is still done by code. The main reason was reliable event subscription and consistent devicetree states.
- Improved Wi‑Fi shutdown cleanup and radio-state handling.

Other:
- Renamed the Kernel Display app to Display.
2026-08-25 17:44:20 +02:00

1.8 KiB

Architecture: App Framework

Apps are event-driven, C API (app-module, <app/*.h>), not a C++ class. Each app has an AppManifest (id, name, category, location, flags) and a main(argc, argv) entry point (AppMainFn), modelled on a C program's main(). Every app instance gets its own dedicated task for its whole lifetime, and blocks in that task until it returns. Use app_scheduler_current_app_id() (app/scheduler.h) to identify the running instance - it's not passed as a parameter.

Lifecycle and inter-app communication go through app_manager_*() (app/manager.h) and app_event_*() (app/event.h):

  • app_manager_start()/app_manager_start_with_parameters() launch a plain instance; app_manager_start_for_result() launches a modal child that reports back to a parent instance.
  • An app subscribes with app_event_subscribe() (registers for its own instance's events, no id argument needed), blocks via task_event_group_wait()/task_event_group_wait_any(), and drains with app_event_poll(), reacting to APP_EVENT_CLOSE (terminate now) and APP_EVENT_RESULT (a child it started reported back).
  • An app closes itself by calling app_manager_finish() right before returning from main(); another instance is closed via app_manager_stop().

Apps are registered at startup via app_manager_add(). External apps can be loaded from SD card via manifest.properties files, or side-loaded as ELF binaries on ESP32 (see app/loader.h's AppLoaderApi).

Apps can be loaded from:

  • memory (APP_LOCATION_MEMORY)
  • a path pointing to an install folder where an .app file was installed (APP_LOCATION_PATH)
  • a path pointing to an .elf file (APP_LOCATION_PATH)

An app can build an optional UI via the LVGL window-manager module (see lvgl.md).