InfiniTime/doc/code/Apps.md

Apps

This page will teach you:

• what screens and apps are in InfiniTime
• how to implement your own app

Theory

The user interface of InfiniTime is made up of screens. Screens that are opened from the app launcher are considered apps. Every app in InfiniTime is its own class. An instance of the class is created when the app is launched, and destroyed when the user exits the app. Apps run inside the DisplayApp task (briefly discussed here). Apps are responsible for everything drawn on the screen when they are running. Apps can be refreshed periodically and reacts to external events (touch or button).

Interface

Every app class is declared inside the namespace Pinetime::Applications::Screens and inherits from Pinetime::Applications::Screens::Screen.

Each app defines its own constructor. The constructors mostly take references to InfiniTime Controllers (ex: Alarm, DateTime, BLE services, Settings,...) the app needs for its operations. The constructor is responsible for initializing the UI of the app.

The destructor cleans up LVGL and restores any changes (for example re-enable sleeping).

App classes can override bool OnButtonPushed(), bool OnTouchEvent(TouchEvents event) and bool OnTouchEvent(uint16_t x, uint16_t y) to implement their own functionality for those events.

Apps that need to be refreshed periodically create an lv_task (using lv_task_create()) that will call the method Refresh() periodically.

App types

There are basically 2 types of applications : system apps and user apps.

System applications are always built into InfiniTime, and InfiniTime cannot work properly without those apps. The watchfaces, settings, notifications and the application launcher are examples of such system applications.

User applications are optionally built into the firmware. They extend the functionalities of the system.

The distinction between system and user applications allows for more flexibility and customization. This allows to easily select which user applications must be built into the firmware without overflowing the system memory.

Apps initialization

Apps are created by DisplayApp in DisplayApp::LoadScreen(). This method simply call the creates an instance of the class that corresponds to the app specified in parameters.

The constructor of system apps is called directly. If the application is a user app, the corresponding AppDescription is first retrieved from userApps and then the function create is called to create an instance of the app.

User application selection at build time

The list of user applications is generated at build time by the consteval function CreateAppDescriptions() in UserApps.h. This method takes the list of applications that must be built into the firmware image. This list of applications is defined as a list Apps enum values named UserAppTypes in Apps.h. For each application listed in UserAppTypes, an entry of type AppDescription is added to the array userApps. This entry is created by using the information provided by a template AppTraits that is customized for every user application.

Here is an example of an AppTraits customized for the Alarm application. It defines the type of application, its icon and a function that returns an instance of the application.

template <>
struct AppTraits<Apps::Alarm> {
  static constexpr Apps app = Apps::Alarm;
  static constexpr const char* icon = Screens::Symbols::clock;

  static Screens::Screen* Create(AppControllers& controllers) {
    return new Screens::Alarm(controllers.alarmController,
                              controllers.settingsController.GetClockType(),
                              *controllers.systemTask,
                              controllers.motorController);
  };
};

This array userApps is used by DisplayApp to create the applications and the AppLauncher to list all available applications.

Creating your own app

A minimal user app could look like this:

MyApp.h:

#pragma once

#include "displayapp/Apps.h"
#include "displayapp/screens/Screen.h"
#include "displayapp/Controllers.h"
#include "Symbols.h"

namespace Pinetime {
  namespace Applications {
    namespace Screens {
      class MyApp : public Screen {
      public:
        MyApp();
        ~MyApp() override;
      };
    }
    
    template <>
    struct AppTraits<Apps:MyApp> {
      static constexpr Apps app = Apps::MyApp;
      static constexpr const char* icon = Screens::Symbol::myApp;
      static Screens::Screens* Create(AppController& controllers) {
        return new Screens::MyApp();
      }
    };
  }
}

MyApp.cpp:

#include "displayapp/screens/MyApp.h"

using namespace Pinetime::Applications::Screens;

MyApp::MyApp() {
  lv_obj_t* title = lv_label_create(lv_scr_act(), nullptr);
  lv_label_set_text_static(title, "My test application");
  lv_label_set_align(title, LV_LABEL_ALIGN_CENTER);
  lv_obj_align(title, lv_scr_act(), LV_ALIGN_CENTER, 0, 0);
}

MyApp::~MyApp() {
  lv_obj_clean(lv_scr_act());
}

Both of these files should be in displayapp/screens/.

Now we have our very own app, but InfiniTime does not know about it yet. The first step is to include your MyApp.cpp (or any new cpp files for that matter) in the compilation by adding it to CMakeLists.txt. The next step to making it launch-able is to give your app an id. To do this, add an entry in the enum class Pinetime::Applications::Apps (displayapp/Apps.h). Name this entry after your app. Add #include "displayapp/screens/MyApp.h" to the file displayapp/DisplayApp.cpp.

If your application is a system application, go to the function DisplayApp::LoadScreen and add another case to the switch statement. The case will be the id you gave your app earlier. If your app needs any additional arguments, this is the place to pass them.

If your application is a user application, you don't need to add anything in DisplayApp, everything will be automatically generated for you. The user application will also be automatically be added to the app launcher menu.

Since the list of user application is generated by CMake, you need to add the variable ENABLE_USERAPPS to the command line of CMake. This variable must be set with a string composed of an ordered list of the user applications that must be built into the firmware. The items of the list are fields from the enumeration Apps. Ex : build the firmware with 3 user application : Alarm, Timer and MyApp (the application will be listed in this specific order in the application menu).

$ cmake ... -DENABLE_USERAPPS="Apps::Alarm, Apps::Timer, Apps::MyApp" ... 

You should now be able to build the firmware and flash it to your PineTime. Yay!

Please remember to pay attention to the UI guidelines when designing an app that you want to be included in InfiniTime.