Android: Document the android-in-docker hackathon

Change-Id: Idb6ad65538ede75b687307d24d00a36b338f4c5e
Reviewed-by: hjk <hjk@qt.io>

tests/manual/docker/android/Makefile

@@ -1,5 +1,5 @@
-qt-android-sdk-31: Dockerfile
+qt-android-sdk-31: Dockerfile-qt-6.3.2-android-ubuntu-22.04
-	docker build --platform linux/x86_64 . -t qt-android-sdk:31 -t qt-android-sdk
+	docker build --platform linux/x86_64 . -f Dockerfile-qt-6.3.2-android-ubuntu-22.04 -t qt-android-sdk:31 -t qt-android-sdk
 
 qt-android-sdk-31-run: qt-android-sdk-31
 	docker run --platform linux/x86_64 -it --rm qt-android-sdk:31 /bin/bash

tests/manual/docker/android/README.md

@@ -1,2 +1,61 @@
+# Android Builder in a Docker
+
+## Introduction
+
+This was a one-day hackathon where we tried to put a Qt for Android build environment into a Docker container.
+
+## Prerequisites
+
+Things you need:
+* Docker
+
+## Building the Docker image
+
+The accompanying Makefile contains the target `qt-android-sdk-31` which will build the Docker image. It will take a while to download the neceesary packages.
+
+To build it simply run `make qt-android-sdk-31`.
+
+## Running the Docker image
+
+The Makefile also contains a target to run the docker image called `qt-android-sdk-31-run`.
+
+## Limitations
+
+* The Docker image is not optimized for size. It is currently 5.5 GB.
+* The Docker image is only available for x86_64, this makes it rather useless on macos M1 machines.
+* Qt Creator will not detect the Android SDK, Qt, compilers and other tools.
+
+## Future work
+
+
+### Integration with Qt Creator
+
+* Create a mechanism that allows Qt Creator to better find components inside the Docker image.
+  * Our current thinking is to create some sort of .json file in a known location that contains information on where components can be found.
+
+### Deployment
+
+We need to come up with a way to deploy either to a Hardware device or the Emulator.
+Current thinking is to run ADB inside the Docker container and forward the ports to the host.
+
+### Emulator
+
+We see two options for the emulator:
+
+1. Run the emulator on the host
+
+    This would mean that we still might have to take care of installing and maintaining the Emulator ourselves on the Host.
+
+2. Run the emulator inside the docker and pipe its UI to the Host
+
+    Simple on Linux via X11, but hard / impossible that way on macOS and Windows.
+    Android studio seems to have a way to pipe the output into their own app, further research is needed to find a way that would allow us to do the same.
+
+### Debugging
+
+Probably we can run the debugger inside the container, and tunnel trough the host to the device/emulator.
+
+### ADB Tunnel
+
+We would want a generic way to connect to the device/emulator. The current thinking is that this might be possible by using a tunnel from the docker to the host.
 
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