Merge pull request #722 from clemensvonmolo/code-structure-doc

Add docs for app creation and code structure

README.md

@@ -72,7 +72,8 @@ As of now, here is the list of achievements of this project:
 ## Documentation
 
 ### Develop
-
+ - [Rough structure of the code](doc/code/Intro.md)
+ - [How to implement an application](doc/code/Apps.md)
  - [Generate the fonts and symbols](src/displayapp/fonts/README.md)
  - [Creating a stopwatch in Pinetime(article)](https://pankajraghav.com/2021/04/03/PINETIME-STOPCLOCK.html)
 

doc/code/Apps.md

@@ -0,0 +1,106 @@
+# Apps
+This page will teach you:
+- what apps in InfiniTime are
+- how to implement your own app
+
+## Theory
+Apps are the things you can launch from the app selection you get by swiping up.
+At the moment, settings and even the app launcher itself or the clock are implemented very similarly, this might change in the future though.
+Every app in InfiniTime is it's own class.
+An instance of the class is created when the app is launched and destroyed when the user exits the app.
+They run inside the "displayapp" task (briefly discussed [here](./Intro.md)).
+Apps are responsible for everything drawn on the screen when they are running.
+By default, apps only do something (as in a function is executed) when they are created or when a touch event is detected.
+
+## Interface
+Every app class has to be inside the namespace `Pinetime::Applications::Screens` and inherit from `Screen`.
+The constructor should have at least one parameter `DisplayApp* app`, which it needs for the constructor of its parent class Screen.
+Other parameters should be references to controllers that the app needs.
+A destructor is needed to clean up LVGL and restore 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.
+If an app only needs to display some text and do something upon a touch screen button press,
+it does not need to override any of these functions, as LVGL can also handle touch events for you.
+If you have any doubts, you can always look at how the other apps are doing things.
+
+### Continuous updating
+If your app needs to be updated continuously, yo can do so by overriding the `Refresh()` function in your class
+and calling `lv_task_create` inside the constructor.
+An example call could look like this: <br>
+`taskRefresh = lv_task_create(RefreshTaskCallback, LV_DISP_DEF_REFR_PERIOD, LV_TASK_PRIO_MID, this);` <br>
+With `taskRefresh` being a member variable of your class and of type `lv_task_t*`.
+Remember to delete the task again using `lv_task_del`.
+The function `RefreshTaskCallback` is inherited from screen and just calls your `Refresh` function.
+
+### Apps with multiple screens
+InfiniTime provides a mini-library in [displayapp/screens/ScreenList.h](/src/displayapp/screens/ScreenList.h)
+which makes it relatively  easy to add multiple screens to your app.
+To use it, #include it in the header file of your app and add a ScreenList member to your class.
+The template argument should be the number of screens you need.
+You will also need to add `CreateScreen` functions that return `std::unique_ptr<Screen>`
+to your class, one for every screen you have.
+There are still some things left to to that I won't cover here.
+To figure them out, have a look at the "apps" ApplicationList, Settings and SystemInfo.
+
+
+## Creating your own app
+A minimal app could look like this: <br>
+MyApp.h:
+```cpp
+#pragma once
+
+#include "displayapp/screens/Screen.h"
+#include <lvgl/lvgl.h>
+
+namespace PineTime {
+  namespace Applications {
+    namespace Screens {
+      class MyApp : public Screen {
+      public:
+        MyApp(DisplayApp* app);
+        ~MyApp() override;
+      }
+    }
+  }
+}
+```
+
+MyApp.cpp:
+```cpp
+#include "MyApp.h"
+#include "displayapp/DisplayApp.h"
+
+using namespace Pinetime::Applications::Screens;
+
+MyApp::MyApp(DisplayApp* app) : Screen(app) {
+  lv_obj_t* title = lv_label_create(lv_scr_act(), NULL);  
+  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/](/src/displayapp/screens/)
+or [displayapp/screens/settings/](/src/displayapp/screens/settings/) if it's a setting app.
+
+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](/CMakeLists.txt).
+The next step to making it launchable is to give your app an id.
+To do this, add an entry in the enum class `Pinetime::Applications::Apps` ([displayapp/Apps.h](/src/displayapp/Apps.h)).
+Name this entry after your app. Add `#include "displayapp/screens/MyApp.h"` to the file [displayapp/DisplayApp.cpp](/src/displayapp/DisplayApp.cpp).
+Now, go to the function `DisplayApp::LoadApp` 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 you want your app to be launched from the regular app launcher, go to [displayapp/screens/ApplicationList.cpp](/src/displayapp/screens/ApplicationList.cpp).
+Add your app to one of the `CreateScreen` functions, or add another `CreateScreen` function if there are no empty spaces for your app. <br>
+If your app is a setting, do the same procedure in [displayapp/screens/settings/Settings.cpp](/src/displayapp/screens/settings/Settings.cpp).
+
+You should now be able to [build](../buildAndProgram.md) the firmware
+and flash it to your PineTime. Yay!
+
+Please remember to pay attention to the [UI guidelines](../ui_guidelines.md)
+when designing an app that you want to include in mainstream InfiniTime.

doc/code/Intro.md

@@ -0,0 +1,42 @@
+# Introduction to the code
+This page is meant to guide you through the source code, so you can find the relevant files for what you're working on.
+
+## FreeRTOS
+Infinitime is based on FreeRTOS, a real-time operating system.
+FreeRTOS provides several quality of life abstractions (for example easy software timers)
+and most importantly supports multiple tasks.
+If you want to read up on real-time operating systems, you can look [here](https://www.freertos.org/implementation/a00002.html) and [here](https://www.freertos.org/features.html).
+The main "process" creates at least one task and then starts the FreeRTOS task scheduler.
+This main "process" is the standard main() function inside [main.cpp](/src/main.cpp).
+The task scheduler is responsible for giving every task enough cpu time.
+As there is only one core on the SoC of the PineTime, real concurrency is impossible and the scheduler has to swap tasks in and out to emulate it.
+
+### Tasks
+Tasks are created by calling `xTaskCreate` and passing a function with the signature `void functionName(void*)`.
+For more info on task creation see the [FreeRTOS Documentation](https://www.freertos.org/a00125.html).
+In our case, main calls `systemTask.Start()`, which creates the **"MAIN" task**.
+The function running inside that task is `SystemTask::Work()`.
+You may also see this task being referred to as the **work task**.
+Both functions are located inside [systemtask/SystemTask.cpp](/src/systemtask/SystemTask.cpp). `SystemTask::Work()` initializes all the driver and controller objects.
+It also starts the **task "displayapp"**, which is responsible for launching and running apps, controlling the screen and handling touch events (or forwarding them to the active app).
+You can find the "displayapp" task inside [displayapp/DisplayApp.cpp](/src/displayapp/DisplayApp.cpp).
+There are also other tasks that are responsible for Bluetooth ("ll" and "ble" inside [libs/mynewt-nimble/porting/npl/freertos/src/nimble_port_freertos.c](/src/libs/mynewt-nimble/porting/npl/freertos/src/nimble_port_freertos.c))
+and periodic tasks like heartrate measurements ([heartratetask/HeartRateTask.cpp](/src/heartratetask/HeartRateTask.cpp)). <br>
+While it is possible for you to create your own task when you need it, it is recommended to just add functionality to `SystemTask::Work()` if possible.
+If you absolutely need to create another task, try to guess how much [stack space](https://www.freertos.org/FAQMem.html#StackSize) (in words/4-byte packets)
+it will need instead of just typing in a large-ish number.
+You can use the define `configMINIMAL_STACK_SIZE` which is currently set to 120 words.
+
+## Controllers
+Controllers in InfiniTime are singleton objects that can provide access to certain resources to apps.
+Some of them interface with drivers, others are the driver for the resource.
+The resources provided don't have to be hardware-based.
+They are declared in main.cpp and initialized in [systemtask/SystemTask.cpp](/src/systemtask/SystemTask.cpp).
+Some controllers can be passed by reference to apps that need access to the resource (for example vibration motor).
+They reside in [components/](/src/components/) inside their own subfolder.
+
+## Apps
+For more detail see the [Apps page](./Apps.md)
+
+## Bluetooth
+Header files with short documentation for the functions are inside [libs/mynewt-nimble/nimble/host/include/host/](/src/libs/mynewt-nimble/nimble/host/include/host/).