C++ conversion (#80)

Converted project to C++

Documentation/app-lifecycle.md

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+# Application Lifecycle
+
+The app goes through these states:
+
+![app lifecycle state diagram](pics/app-lifecycle.png)
+
+Let's look at a scenario where an app launches another app:
+
+1. `first` app starts: `first.on_create()` -> `first.on_show()`
+2. `second` app starts: `first.on_hide()` -> `second.on_create()` -> `second.on_show()`
+3. `second` app stops: `second.on_hide()` -> `second.on_destroy()` -> `first.on_show()`
+4. `first` app stops: `first.on_hide()` -> `first.on_destroy()`

Documentation/app-lifecycle.puml

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+@startuml
+[*] --> on_create : app is started
+on_create --> on_show : app becomes visible
+on_show --> on_hide : app is no longer visible
+on_hide --> on_destroy : app is being closed
+on_destroy --> [*]
+skinparam ranksep 25
+skinparam padding 2
+@enduml

Documentation/ideas.md

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+# TODOs
+- Update `view_port` to use `ViewPort` as handle externally and `ViewPortData` internally
+- Create more unit tests for `tactility-core` and `tactility` (PC-only for now)
+- Have a way to deinit LVGL drivers that are created from `HardwareConfig`
+- Show a warning screen if firmware encryption or secure boot are off when saving WiFi credentials.
+- Show a warning screen when a user plugs in the SD card on a device that only supports mounting at boot.
+- Try out Waveshare S3 120MHz mode for PSRAM (see "enabling 120M PSRAM is necessary" in [docs](https://www.waveshare.com/wiki/ESP32-S3-Touch-LCD-4.3#Other_Notes))
+- T-Deck has random sdcard SPI crashes due to sharing bus with screen SPI: make it use the LVGL lock for sdcard operations?
+- Wi-Fi connect app should show info about connection result
+- Check service/app id on registration to see if it is a duplicate id
+- Fix screenshot app on ESP32: it currently blocks when allocating memory
+- Localisation of texts
+- Portrait support for GPIO app
+- App lifecycle docs mention on_create/on_destroy but app lifecycle is on_start/on_stop
+- Explore LVGL9's FreeRTOS functionality
+- Explore LVGL9's ILI93414 driver for 2.4" Yellow Board
+- Bug: in LVGL9 with M5Core2, crash when bottom item is clicked without scrolling first
+- Publish firmwares with upload tool
+- De-duplicate WiFi SSIDs.
+- Move libs/M5 projects to boards/M5Shared
+
+# Core Ideas
+- Make a HAL? It would mainly be there to support PC development. It's a lot of effort for supporting what's effectively a dev-only feature.
+- Support for displays with different DPI. Consider the layer-based system like on Android.
+- If present, use LED to show boot status
+- 2 wire speaker support
+- tt_app_start() and similar functions as proxies for Loader app start/stop/etc.
+- tt_app_set_result() for apps that need to return data to other apps (e.g. file selection)
+- Wi-Fi using dispatcher to dispatch its main functionality to the dedicated Wi-Fi CPU core (to avoid main loop hack)
+
+# App Improvement Ideas
+- Sort desktop apps by name.
+- Light/dark mode selection in Display settings app.
+
+# App Ideas
+- File viewer (images, text... binary?)
+- BlueTooth keyboard app
+- Chip 8 emulator
+- BadUSB
+- Discord bot
+- IR transceiver app
+- GPS app
+- Investigate CSI https://stevenmhernandez.github.io/ESP32-CSI-Tool/

Documentation/project-structure.puml

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+@startuml
+skinparam componentStyle uml1
+
+[Tactility] as t
+note right of t : to build and use graphical apps
+[TactilityHeadless] as theadless
+note right of theadless : to build and use background services
+[TactilityCore] as tcore
+note right of tcore : defines, data types, logging, async, etc.
+
+package "Applications" {
+  [AppSim] as appsim
+  [AppEsp32] as appesp
+}
+
+note right of appesp : AppEsp depends on the board \n projects for configuration
+
+[t] ..> [theadless]
+[theadless] ..> [tcore]
+[appsim] ..> [t]
+[appesp] ..> [t]
+
+@enduml