Oculus Go font loading SEGV

[avaer]

Loading <canvas> 2D bootstraps the font system in Skia, which tries to load default system fonts. This fails on Oculus Go, resulting in a segfault:

0x0000007f74d46fb4 in SkFontMgr_Android::SkFontMgr_Android(SkFontMgr_Android_CustomFonts const*) () from /home/a/exokit/android/app/src/main/arm64-v8a/libnative-main.so

We need to make sure the requisite font location is correct/the default font loads successfully to unlock <canvas> 2D on Android.

[avaer]

Found the culprit. The reason for this error is that we are literally using the magic leap build of skia in the android build, and that build has an OS-specific hack to load fonts.xml from the package instead of the operating system: https://github.com/modulesio/skia/pull/6/files

We'll need to rebuild skia and somehow make this hack contingent on the ANDROID/LUMIN difference. Ideally it's detected at runtime so we can continue to share the lib across both platforms...

[chrislatorres]

That is the change from here? avaer/skia@534a3a0

[avaer]

Yeah, probably.

For runtime detection I think the presence of ANDROID_HOME might work: https://github.com/modulesio/skia/pull/6/files#diff-17ccc70e187937a2f38ca4845a74ef75R784

[chrislatorres]

found a reference for android env variables:

ANDROID_ASSETS: /system/app
ANDROID_DATA: /data
ANDROID_ROOT: /system
ASEC_MOUNTPOINT: /mnt/asec
BOOTCLASSPATH: /system/framework/core.jar:/system/framework/core-...
EXTERNAL_STORAGE: /storage/sdcard
LOOP_MOUNTPOINT: /mnt/obb
PATH: /sbin:/vendor/bin:/system/sbin:/system/bin:/system/xbin

source

[avaer]

Yes but the real question is does LUMIN define these, so can we rely on it to differentiate?