Dynamic loading of OpenXR Loader on Android

This change implements dynamic loading of the OpenXR Loader library
on Android. If an OpenXR Loader library is not found,
Godot will still function with OpenXR disabled.

Also, on every platform, the OpenXR symbols are resolved at runtime
using xrGetInstanceProcAddr.

On Windows and Linux the OpenXR loader is included in the main
engine binary.

On Android, the OpenXR Loader is not built with the engine. Separately
distributed Android plugins will be provided with the correct loader
library for each device.

Co-authored-by: Gábor Pál Korom <gabor.p.korom@migeran.com>
Co-authored-by: Gábor Koncz <gabor.koncz@migeran.com>

1 files changed, 33 insertions, 28 deletions

diff --git a/modules/openxr/SCsub b/modules/openxr/SCsub
index 593d1ff3c1..298977f96d 100644
--- a/modules/openxr/SCsub
+++ b/modules/openxr/SCsub
@@ -18,38 +18,36 @@ env_openxr.Prepend(
         thirdparty_dir + "/src",
         thirdparty_dir + "/src/common",
         thirdparty_dir + "/src/external/jsoncpp/include",
-        thirdparty_dir + "/src/loader",
     ]
 )
 
-# may need to check and set:
-# - XR_USE_TIMESPEC
-
-env_thirdparty = env_openxr.Clone()
-env_thirdparty.disable_warnings()
-env_thirdparty.AppendUnique(CPPDEFINES=["DISABLE_STD_FILESYSTEM"])
-
 if env["platform"] == "android":
     # may need to set OPENXR_ANDROID_VERSION_SUFFIX
-    env_thirdparty.AppendUnique(CPPDEFINES=["XR_OS_ANDROID", "XR_USE_PLATFORM_ANDROID"])
+    env_openxr.AppendUnique(CPPDEFINES=["XR_OS_ANDROID", "XR_USE_PLATFORM_ANDROID"])
+    env_openxr.AppendUnique(CPPDEFINES=["JSON_USE_EXCEPTION=0"])
 
     # may need to include java parts of the openxr loader
 elif env["platform"] == "linuxbsd":
-    env_thirdparty.AppendUnique(CPPDEFINES=["XR_OS_LINUX"])
+    env_openxr.AppendUnique(CPPDEFINES=["XR_OS_LINUX"])
 
     if env["x11"]:
-        env_thirdparty.AppendUnique(CPPDEFINES=["XR_USE_PLATFORM_XLIB"])
+        env_openxr.AppendUnique(CPPDEFINES=["XR_USE_PLATFORM_XLIB"])
 
     # FIXME: Review what needs to be set for Android and macOS.
-    env_thirdparty.AppendUnique(CPPDEFINES=["HAVE_SECURE_GETENV"])
+    env_openxr.AppendUnique(CPPDEFINES=["HAVE_SECURE_GETENV"])
 elif env["platform"] == "windows":
-    env_thirdparty.AppendUnique(CPPDEFINES=["XR_OS_WINDOWS", "NOMINMAX", "XR_USE_PLATFORM_WIN32"])
+    env_openxr.AppendUnique(CPPDEFINES=["XR_OS_WINDOWS", "NOMINMAX", "XR_USE_PLATFORM_WIN32"])
 
-env_thirdparty.add_source_files(thirdparty_obj, thirdparty_dir + "/src/xr_generated_dispatch_table.c")
+# may need to check and set:
+# - XR_USE_TIMESPEC
 
-# add in common files (hope these don't clash with us)
-env_thirdparty.add_source_files(thirdparty_obj, thirdparty_dir + "/src/common/filesystem_utils.cpp")
-env_thirdparty.add_source_files(thirdparty_obj, thirdparty_dir + "/src/common/object_info.cpp")
+env_thirdparty = env_openxr.Clone()
+env_thirdparty.disable_warnings()
+env_thirdparty.AppendUnique(CPPDEFINES=["DISABLE_STD_FILESYSTEM"])
+
+if "-fno-exceptions" in env_thirdparty["CXXFLAGS"]:
+    env_thirdparty["CXXFLAGS"].remove("-fno-exceptions")
+env_thirdparty.Append(CPPPATH=[thirdparty_dir + "/src/loader"])
 
 # add in external jsoncpp dependency
 env_thirdparty.add_source_files(thirdparty_obj, thirdparty_dir + "/src/external/jsoncpp/src/lib_json/json_reader.cpp")
@@ -57,17 +55,24 @@ env_thirdparty.add_source_files(thirdparty_obj, thirdparty_dir + "/src/external/
 env_thirdparty.add_source_files(thirdparty_obj, thirdparty_dir + "/src/external/jsoncpp/src/lib_json/json_writer.cpp")
 
 # add in load
-if env["platform"] == "android":
-    env_thirdparty.add_source_files(thirdparty_obj, thirdparty_dir + "/src/loader/android_utilities.cpp")
-
-env_thirdparty.add_source_files(thirdparty_obj, thirdparty_dir + "/src/loader/api_layer_interface.cpp")
-env_thirdparty.add_source_files(thirdparty_obj, thirdparty_dir + "/src/loader/loader_core.cpp")
-env_thirdparty.add_source_files(thirdparty_obj, thirdparty_dir + "/src/loader/loader_instance.cpp")
-env_thirdparty.add_source_files(thirdparty_obj, thirdparty_dir + "/src/loader/loader_logger_recorders.cpp")
-env_thirdparty.add_source_files(thirdparty_obj, thirdparty_dir + "/src/loader/loader_logger.cpp")
-env_thirdparty.add_source_files(thirdparty_obj, thirdparty_dir + "/src/loader/manifest_file.cpp")
-env_thirdparty.add_source_files(thirdparty_obj, thirdparty_dir + "/src/loader/runtime_interface.cpp")
-env_thirdparty.add_source_files(thirdparty_obj, thirdparty_dir + "/src/loader/xr_generated_loader.cpp")
+if env["platform"] != "android":
+    # On Android the openxr_loader is provided by separate plugins for each device
+    # Build the engine using object files
+    khrloader_obj = []
+    env_thirdparty.add_source_files(khrloader_obj, thirdparty_dir + "/src/xr_generated_dispatch_table.c")
+
+    env_thirdparty.add_source_files(khrloader_obj, thirdparty_dir + "/src/common/filesystem_utils.cpp")
+    env_thirdparty.add_source_files(khrloader_obj, thirdparty_dir + "/src/common/object_info.cpp")
+
+    env_thirdparty.add_source_files(khrloader_obj, thirdparty_dir + "/src/loader/api_layer_interface.cpp")
+    env_thirdparty.add_source_files(khrloader_obj, thirdparty_dir + "/src/loader/loader_core.cpp")
+    env_thirdparty.add_source_files(khrloader_obj, thirdparty_dir + "/src/loader/loader_instance.cpp")
+    env_thirdparty.add_source_files(khrloader_obj, thirdparty_dir + "/src/loader/loader_logger_recorders.cpp")
+    env_thirdparty.add_source_files(khrloader_obj, thirdparty_dir + "/src/loader/loader_logger.cpp")
+    env_thirdparty.add_source_files(khrloader_obj, thirdparty_dir + "/src/loader/manifest_file.cpp")
+    env_thirdparty.add_source_files(khrloader_obj, thirdparty_dir + "/src/loader/runtime_interface.cpp")
+    env_thirdparty.add_source_files(khrloader_obj, thirdparty_dir + "/src/loader/xr_generated_loader.cpp")
+    env.modules_sources += khrloader_obj
 
 env.modules_sources += thirdparty_obj