Add app development stuff

Author: ThomasFarstrike

docs/apps/appstore.md

@@ -1,12 +1,15 @@
 # App Store
 
-The MicroPythonOS App Store allows users to download and install new apps to extend system functionality. Visit [apps.micropythonos.com](https://apps.micropythonos.com) for available apps.
+The MicroPythonOS App Store allows users to download and install new apps to extend system functionality.
+
+App discovery is currently done by downloading the app list from [apps.micropythonos.com](https://apps.micropythonos.com).
 
 ## Example Apps
 
 - **Hello World**: A sample app demonstrating basic functionality.
 - **Camera**: Captures images and scans QR codes.
 - **Image Viewer**: Displays images stored in `/data/images/`.
+- **IMU**: Visualize data from the Intertial Measurement Unit, also known as the accellerometer.
 
 ## Screenshots
 

docs/apps/developing.md

@@ -0,0 +1,125 @@
+# Developing Apps
+
+Apps are written in MicroPython and installed in `/apps/`. See [Filesystem Layout](../architecture/filesystem.md) for the app directory structure.
+
+Here we'll go over how to create and install a simple HelloWorld app.
+
+More advanced app examples are available in the [source code repository](https://github.com/MicroPythonOS/MicroPythonOS/tree/main/internal_filesystem/apps).
+
+## Structure
+
+Create the following file and folder structure:
+
+```
+com.micropythonos.helloworld/
+├── assets/
+│   └── hello.py
+├── META-INF/
+│   └── MANIFEST.JSON
+└── res/
+    └── mipmap-mdpi/
+        └── icon_64x64.png
+```
+
+## App code
+
+In `hello.py`, put:
+
+```
+from mpos.apps import Activity
+
+class Hello(Activity):
+
+    def onCreate(self):
+        screen = lv.obj()
+        label = lv.label(screen)
+        label.set_text('Hello World!')
+        label.center()
+        self.setContentView(screen)
+```
+
+The code above creates a new screen, adds a label, sets the label text, centers the label and activates the screen.
+
+## Manifest
+
+In `MANIFEST.JSON`, put:
+
+```
+{
+"name": "HelloWorld",
+"publisher": "MicroPythonOS",
+"short_description": "Minimal app",
+"long_description": "Demonstrates the simplest app.",
+"fullname": "com.micropythonos.helloworld",
+"version": "0.0.2",
+"category": "development",
+"activities": [
+    {
+      "entrypoint": "assets/hello.py",
+      "classname": "Hello",
+      "intent_filters": [
+        {
+          "action": "main",
+          "category": "launcher"
+        }
+      ]
+    }
+  ]
+}
+```
+
+## Icon
+
+The icon is a simple 64x64 pixel PNG image, which you can create with any tool, such as GIMP.
+
+It's recommended to keep it as small as possible by setting compression level to 9 and not storing any metadata such as background color, resolution, creation time, comments, Exif data, XMP data, thumbnail or color profile.
+
+The size will be somewhere between 3 and 7KB.
+
+## Installing the App
+
+The app can be installed by copying the top-level folder `com.micropythonos.helloworld/` (and its contents) to the `/apps/` folder.
+
+### On desktop
+
+You probably already have a clone of the [internal_filesystem](https://github.com/MicroPythonOS/MicroPythonOS/tree/main/internal_filesystem) that you're using to run MicroPythonOS on desktop.
+
+Just copy or move your the top-level folder `com.micropythonos.helloworld/` (and its contents) to `internal_filesystem/apps/` and you're good to go!
+
+### On ESP32
+
+On the ESP32, you can use MicroPython tools such as [mpremote.py](https://github.com/micropython/micropython/tree/master/tools/mpremote) to copy files and folders from-to your device using the MicroPython REPL.
+
+You may need to change this one line:
+
+```
+diff --git a/tools/mpremote/mpremote/main.py b/tools/mpremote/mpremote/main.py
+index e6e3970..7f5d934 100644
+--- a/tools/mpremote/mpremote/main.py
++++ b/tools/mpremote/mpremote/main.py
+@@ -477,7 +477,7 @@ class State:
+         self.ensure_connected()
+         soft_reset = self._auto_soft_reset if soft_reset is None else soft_reset
+         if soft_reset or not self.transport.in_raw_repl:
+-            self.transport.enter_raw_repl(soft_reset=soft_reset)
++            self.transport.enter_raw_repl(soft_reset=False)
+             self._auto_soft_reset = False
+ 
+     def ensure_friendly_repl(self):
+```
+
+Then copy your app using:
+
+```
+/path/to/mpremote.py fs cp -r com.micropythonos.helloworld/ :/apps/
+```
+
+## Starting the App
+
+If the app is installed into the /apps/ folder, it should show up in the launcher after refreshing it.
+
+You can also launch it manually by typing this in the MicroPython REPL:
+
+```
+import mpos.apps; mpos.apps.start_app('apps/com.micropythonos.helloworld/')
+```

mkdocs.yml

@@ -41,6 +41,7 @@ nav:
       - Overview: apps/index.md
       - Built-in Apps: apps/built-in-apps.md
       - App Store: apps/appstore.md
+      - Developing Apps: apps/developing.md
   - Architecture:
       - Overview: architecture/overview.md
       - System Components: architecture/system-components.md