Odin Quest

This is a small experiment to build an Odin codebase from scratch to run a meaningful application on the Quest 2. See the original repo for information about building Quest .apk without build systems.

This repo extends that example, replacing the C++ application code with Odin. The only major difference in the build process is that we build a quest.o file using the Odin compiler, then link that into the existing build process. Compared to the rest of the process, the part involving Odin is mercifully simple, just:

odin build quest -target:linux_arm64 -build-mode:obj -reloc-mode:pic

Bindings

I had to write some bindings to get this to work

• EGL: The OpenGL ES loader, in quest/egl
• OpenXR: I reused my existing OpenXR bindings and made some edits to support the OpenGLES structures
• Android Native App Glue: I wrote a very barebones version of android_native_app_glue.h and the minimal subset of the Android headers needed to support it.

The OpenGLES bindings are fudged. I just attempt to load desktop OpenGL functions using Odin's vendored OpenGL loader (and EGL), then only use the shared subset.

How to Build

First, ensure you have the relevant Android SDK, NDK, and build tools installed, the official docs get this bit right, so just follow them. Make sure you actually open Android Studio, then open a blank project as well, because these actually seems to be required to complete the installation... alternatively, there are the plain command line tools (scroll down) but I haven't tested a fresh install with those yet.

The build process depends on the following executables:

• aapt the Android Asset Packaging Tool which ships with the Android SDK
• adb the Android Debug Bridge, used to install the apk
• clang the clang compiler that ships with the Android SDK (more specifically, the NDK)
• jarsigner in the Android JDK, used to sign our apk (instead of apksigner, since we're Android < 30)
• keytool in the Android JDK, used to generate a key store for signing
• zipalign which is a zip alignment tool optimises the archive so it can be mmaped, which ships with the Android SDK

Once that's all set up, and you preferably have some sort of example application built to validate your install, just take a peek at build.ps1 for the actual build incantations. Make sure you generate a debug key with the commented out command!