doc: add build notes to README

README.md

@@ -14,17 +14,36 @@ If you'd like to build from source, check below.
 
 ## Development Environment Prerequisites
 
-- Godot 4.1.1 [Download Page](https://godotengine.org/download)
+- Godot 4.2.1 [Download Page](https://godotengine.org/download)
 
-Currently only scripted in GDScript, but we could use the .NET version of Godot
-which brings C# support.
+```bash
+# macOS
+$ brew install godot
 
-Once you've gotten your development environment set up:
+# Ubuntu/Debian
+$ snap install godot-4 # note: this gets installed as godot-4, not godot
 
-- Clone repo
-- Open the project and run
+# Windows
+$ choco install godot
+```
 
-### Important
+## Getting started
+
+Ensure that `godot` is installed such that is in on your `$PATH`.
+
+For building releases, so-called "export templates" has to be downloaded. These
+are available from the official
+[website](https://github.com/godotengine/godot/releases/download/4.2.1-stable/Godot_v4.2.1-stable_export_templates.tpz).
+Note that these are unique per version of Godot, but _not_ unique per platform
+we're exporting for.
+
+From the GUI, these templates can be downloaded like this:
+
+1. "Project" menu in the toolbar
+2. "Export" item within the "Project" menu
+3. "Download and install"
+
+## Important
 
 The app relies on external binaries to be downloaded from a specific GitHub
 release. This is a bit cumbersome, but was the best we could come up with for
@@ -45,7 +64,77 @@ now.
   keychain. More info here:
   https://developer.apple.com/help/account/create-certificates/create-developer-id-certificates
 
-### LICENSE
+## Export preset notes
+
+The file `export_presets.cfg` controls the export (i.e. build) process for the
+Launcher. It is controlled through the Godot GUI. If you write comments in the
+file, they will get **erased** once the file is saved. Furthermore, enums are
+represented as numbers, not strings...
+
+`export_presets.cfg` is kept in Git. This file does not contain anything
+sensitive. It is _merged_ with `.godot/export_credentials.cfg`, which _does_
+contain sensitive information. This file is also merged with certain environment
+variables, such that this can be done on CI without fiddling around with files.
+
+### macOS
+
+Signing (and therefore also notarizing) the application requires having the
+correct set of certificates + private keys on the machine doing the export.
+Certificates can be viewed using `Keychain Access.app`. Seeing certificates
+capable of signing (i.e. certificates with private keys):
+
+```bash
+$ security find-identity -v -p codesigning | grep LayerTwo`
+```
+
+Notarizing the app requires an App Store Connect API key. Docs for generating
+this can be found
+[here](https://developer.apple.com/documentation/appstoreconnectapi/creating_api_keys_for_app_store_connect_api).
+There's three components to this key, which should go into
+`.godot/export_credentials.cfg` before exporting:
+
+1. Issuer ID (`notarization/api_uuid`). This is an UUID indicating which
+   organization the key belongs to. This is available over the
+   [list of active keys](https://appstoreconnect.apple.com/access/integrations/api).
+2. The key itself (`notarization/api_key`). This is a path to a `.p8` file, and
+   can only be obtained when creating the key.
+3. Key ID (`notarization/api_key_id`). This is available in the
+   [list of active keys](https://appstoreconnect.apple.com/access/integrations/api).
+
+Explanation of export config file options:
+
+```
+export/distribution_type
+0=testing ?
+1=distribution
+2=app store
+
+codesign/codesign
+0=disabled
+1=built-in ad-hoc
+2=rcodesign ruby tool for exporting from Linux
+3=Xcode codesign
+
+notarization/notarization
+0=disabled
+2=xcrun notarytool
+```
+
+Generate App Store Connect API keys:
+
+Download the key somewhere
+
+Docs on macOS:
+https://docs.godotengine.org/en/stable/tutorials/export/exporting_for_macos.html
+
+### Windows
+
+Signing (is that the correct Windows nomenclature?) of the build artifacts does
+not happen in our pipeline. This leads to a scary pop-up warning the user when
+they try and launch the app. This could probably be set up, somehow. Left as an
+exercise to the reader!
+
+## LICENSE
 
 MIT License