revised readme and starting on basic OpenXR stuff

Maekfile.js

@@ -21,6 +21,7 @@ const maek = init_maek();
 //======================================================================
 
 const NEST_LIBS = `../nest-libs/${maek.OS}`;
+const OPENXR_SDK = `../openxr-sdk-source`;
 
 //set compile flags (these can also be overridden per-task using the "options" parameter):
 if (maek.OS === "windows") {
@@ -49,7 +50,9 @@ if (maek.OS === "windows") {
  //include paths for nest libraries:
  `-I${NEST_LIBS}/SDL2/include/SDL2`, `-D_THREAD_SAFE`, //the output of sdl-config --cflags
  `-I${NEST_LIBS}/glm/include`,
- `-I${NEST_LIBS}/libpng/include`
+ `-I${NEST_LIBS}/libpng/include`,
+ //OpenXR:
+ `-I${OPENXR_SDK}/include`
  );
  maek.options.LINKLibs.push(
  //linker flags for nest libraries:

README.md

@@ -1,15 +1,80 @@
-# (TODO: your game's title)
+# 15-466 Demonstration Code - NDK + OpenXR
 
-Author: (TODO: your name)
+This demonstration code shows how to use a `Maekfile.js` to build with the NDK for Android devices, and how to use OpenXR on such devices.
 
-Design: (TODO: In two sentences or fewer, describe what is new and interesting about your game.)
+Particularly, this code is designed to build for Meta Quest 3.
 
-Screen Shot:
+Based on [15-466-f23-base2](https://github.com/15-466/15-466-f23-base2) with modifications inspired by both the [Oculus OpenXR Mobile SDK](https://developer.oculus.com/downloads/package/oculus-openxr-mobile-sdk/) samples and the [OpenXR Source SDK](https://github.com/KhronosGroup/OpenXR-SDK-Source) samples.
 
-![Screen Shot](screenshot.png)
+## Setup
 
-How To Play:
+You will need to jump through some hoops to get your development environment set up, and to get your hardware ready for development.
 
-(TODO: describe the controls and (if needed) goals/strategy.)
+### Software
 
-This game was built with [NEST](NEST.md).
+Get the android sdk set up in a directory which is a sibling of this one using the `sdkmanager` utility. (Note, these instructions are based on https://developer.android.com/tools/sdkmanager .)
+
+
+Start with a "command line tools only" package from https://developer.android.com/studio (scroll to the bottom). Now extract it and get it working:
+
+```
+$ mkdir android-sdk
+$ cd android-sdk
+$ unzip ../downloads/commandlinetools-linux-10406996_latest.zip
+$ cd cmdline-tools
+$ mkdir latest
+#will complain about moving latest into itself, which is fine:
+$ mv * latest
+
+```
+
+Now get the things that the ovr SDK says we need (as per https://developer.oculus.com/documentation/native/android/mobile-studio-setup-android/ ):
+```
+#from android-sdk:
+$ ./cmdline-tools/latest/bin/sdkmanager --install 'platforms;android-26'
+# "version 28.0.3 or later"; latest as of --list is build-tools;34.0.0-rc3 but:
+$ ./cmdline-tools/latest/bin/sdkmanager --install 'build-tools;28.0.3'
+# android NDK (no version given, this is latest as of this writing):
+$ ./cmdline-tools/latest/bin/sdkmanager --install 'ndk;26.1.10909125'
+```
+
+Also download Meta's OpenXR SDK (from https://developer.oculus.com/downloads/package/oculus-openxr-mobile-sdk/) and extract into a sibling of this directory:
+```
+$ mkdir ovr-openxr-sdk
+$ cd ovr-openxr-sdk
+$ unzip ../downloads/ovr_openxr_mobile_sdk_57.0.zip #current version as of this writing
+```
+
+Once all of that is done you should have these three as siblings:
+```
+15466-f23-ndk-openxr #this folder
+android-sdk #android sdk, tools, etc
+ovr-openxr-sdk #Meta's OpenXR SDK stuff
+```
+
+### Hardware
+
+Set up your Quest 3 for development, as per https://developer.oculus.com/documentation/native/android/mobile-device-setup/ .
+- create a developer acct: https://developer.oculus.com/manage/organizations/create/
+ - might require setting up 2FA at: https://developer.oculus.com/manage/verify/
+- from oculus phone app: headset -> settings -> developer mode [set to: on]
+- connect via USB C (the included white cable works, though is annoyingly short) and allow data (notification will pop up in headset)
+
+
+You can now connect to the headset via the `adb` tool:
+```
+#from android-sdk:
+$ ./platform-tools/adb devices
+# shows "unauthorized" and causes the "allow debugging" dialog to pop on the headset
+# if dialog accepted, says "device" next to the device (maybe that's the device name?)
+$ ./platform-tools/adb devices
+# if you like to explore a bit, get a shell on your device:
+$ ./platform-tools/adb shell
+# interesting things include `top` (see what's running), `cat /proc/cpuinfo` (learn more about the cpu)
+#(ctrl-d to exit)
+```
+
+## Building
+
+
+...

main.cpp

@@ -13,15 +13,25 @@
 //for screenshots:
 #include "load_save_png.hpp"
 
+#ifdef __ANDROID__
+//libSDL not used on android(!)
+#else
 //Includes for libSDL:
 #include <SDL.h>
+#endif
+
+//for OpenXR:
+#include <openxr/openxr.h>
+#define XR_USE_GRAPHICS_API_OPENGL
+#include <openxr/openxr_platform.h>
 
 //...and for c++ standard library functions:
 #include <chrono>
 #include <iostream>
 #include <stdexcept>
 #include <memory>
 #include <algorithm>
+#include <cstring>
 
 #ifdef _WIN32
 extern "C" { uint32_t GetACP(); }
@@ -42,7 +52,52 @@ int main(int argc, char **argv) {
  try {
 #endif
 
- //------------ initialization ------------
+ //------------ OpenXR init ------------
+
+ {
+ //OpenXR needs an "instance" to store global state:
+ XrInstance instance{XR_NULL_HANDLE};
+ XrInstanceCreateInfo create_info{XR_TYPE_INSTANCE_CREATE_INFO};
+
+ //with reference to openxr_program.cpp from openxr-sdk-source + the openxr specification
+
+ std::strcpy(create_info.applicationInfo.applicationName, "gp23 openxr demo");
+ create_info.applicationInfo.apiVersion = XR_CURRENT_API_VERSION;
+
+ //TODO: ON ANROID --> set create_info->next to point to an XrInstanceCreateInfoAndroidKHR structure
+ // filled in as per openxr-sdk-source's platformplugin_android.cpp
+
+ std::vector< const char * > extensions{
+ XR_KHR_OPENGL_ENABLE_EXTENSION_NAME,
+ //TOOD: ON ANROID --> XR_KHR_ANDROID_CREATE_INSTANCE_EXTENSION_NAME
+ };
+
+ create_info.enabledExtensionCount = uint32_t(extensions.size());
+ create_info.enabledExtensionNames = extensions.data();
+
+ if (XrResult res = xrCreateInstance( &create_info, &instance);
+ res != XR_SUCCESS) {
+ std::cerr << "Failed to create OpenXR instance: " << res << std::endl;
+ return 1;
+ }
+
+ //Query the instance to learn what runtime this is using:
+ XrInstanceProperties properties{XR_TYPE_INSTANCE_PROPERTIES};
+ if (XrResult res = xrGetInstanceProperties(instance, &properties);
+ res != XR_SUCCESS) {
+ std::cerr << "Failed to get OpenXR instance properties: " << res << std::endl;
+ return 1;
+ }
+ std::cout << "OpenXR Runtime is '" << properties.runtimeName << "', version "
+ << (properties.runtimeVersion >> 48)
+ << "." << ((properties.runtimeVersion >> 32) & 0xffff)
+ << "." << (properties.runtimeVersion & 0xffffffff)
+ << std::endl;
+
+ //TODO, later: xrDestroyInstance !
+ }
+
+ //------------ initialization ------------
 
  //Initialize SDL library:
  SDL_Init(SDL_INIT_VIDEO);
@@ -63,7 +118,7 @@ int main(int argc, char **argv) {
 
  //create window:
  SDL_Window *window = SDL_CreateWindow(
- "gp23 game2: enter the matr... virtual world", //TODO: remember to set a title for your game!
+ "gp23: openxr demo code", //TODO: remember to set a title for your game!
  SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED,
  1280, 720, //TODO: modify window size if you'd like
  SDL_WINDOW_OPENGL