erhe-quest-validation

Testing & Quality

Enable VK_LAYER_KHRONOS_validation on the erhe Quest APK so silent GPU hangs become loud aborts. Covers the bundle (default on), the runtime config knob, the on-device SPIR-V cache wipe via uninstall, and the device-error abort hook in editor.cpp. Use when a Quest build runs but renders nothing in VR, hangs at the Horizon launch panel, or otherwise misbehaves silently.

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Quest Vulkan validation layer

Quest's Vulkan loader has no validation layer of its own. Without it, GPU-side errors (descriptor mismatches, image-layout violations, multiview misuse, sync hazards, command-buffer lifecycle bugs) silently hang the editor on the first bad frame. With validation on, the same errors hit the device-error callback registered in editor.cpp (the device_message lambda; search for Message_severity::error -> ERHE_FATAL), so the process aborts with the offending VUID copied to the clipboard and dumped to logcat.

Bundling (build-time)

The Khronos validation layer .so is bundled in every Quest / Android APK by default. Gradle task fetchVulkanValidationLayer downloads libVkLayer_khronos_validation.so for arm64-v8a from the SDK release pinned in android-project/app/build.gradle (validationLayerVersion) and stages it under app/libs/arm64-v8a/. The .so adds ~10 MB to the APK; opt out with -Pvulkan_validation_skip (bare; bat-arg parser strips =).

Verify the .so is in the APK:

$env:JAVA_HOME = "C:\Program Files\Android\Android Studio\jbr"
& "$env:JAVA_HOME\bin\jar.exe" tf <apk-path> | Select-String "VkLayer|libVk"

Enabling at runtime

Edit config/editor/erhe_graphics.json so the vulkan block reads:
```
"vulkan": { "vulkan_validation_layers": true, ... }
```
Wipe the on-device SPIR-V cache so all shaders re-compile through the validator on next launch (otherwise stale cached SPIR-V from earlier runs is loaded straight to vkCreateShaderModule and validation never sees the source). Easiest: uninstall + install.
```
$LOCALAPPDATA/Android/Sdk/platform-tools/adb.exe uninstall org.libsdl.app.quest
scripts\install_android.bat quest
```

Launch via the standard headset-prompt protocol (see erhe-quest-launch). Validation messages route through:

debug_utils_messenger_callback (vulkan_device_debug.cpp)
  -> Device::device_message
  -> editor.cpp device_message lambda
  -> ERHE_FATAL on Message_severity::error

Confirming the layer actually loaded

In logcat, expect:

D vulkan: added global layer 'VK_LAYER_KHRONOS_validation' from library '...libVkLayer_khronos_validation.so'
I erhe: Vulkan Instance Layer: VK_LAYER_KHRONOS_validation spec_version 0x00404148 implementation_version 0x00000001 LunarG validation Layer
I erhe: Enabling VK_LAYER_KHRONOS_validation
I vulkan: Loaded layer VK_LAYER_KHRONOS_validation

spec_version decodes as VK_VERSION: 0x00404148 = 1.4.328 -- compare against validationLayerVersion in android-project/app/build.gradle.

The linked glslang version is also logged once per process (used by the SPIR-V cache-key salt; cache entries auto-invalidate when glslang is bumped):

I erhe: glslang version: 16.3.0

Disabling

Flip vulkan_validation_layers back to false in config/editor/erhe_graphics.json. The .so stays in the APK but the loader does not load it -- no per-frame overhead. The runtime cost only kicks in when both the bundle and the config knob are on.

Common VUIDs encountered + status

VUID	Cause	Status
`VUID-VkDeviceCreateInfo-pNext-02829`	`VkPhysicalDeviceVulkan11Features` chained alongside `VkPhysicalDevice16BitStorageFeatures` / `VkPhysicalDeviceMultiviewFeatures` (subsumed by 1.1 features struct)	Fixed in commit `524888f8`
`VUID-VkShaderModuleCreateInfo-pCode-08737` (`DebugGlobalVariable: expected operand Variable must be ...`)	glslang emits `DebugGlobalVariable` with `Variable` operand referencing `OpConstantComposite` for global const composite arrays + the synthesised `gl_WorkGroupSize`	Fixed in the `tksuoran/glslang` fork pinned by the root `CMakeLists.txt` `CPMAddPackage` (CPM PATCHES is banned repo-wide). See `doc/glslang_bug_report_debugglobalvariable.md` and the `erhe-quest-shader-failure` skill
`SYNC-HAZARD-READ-AFTER-WRITE` (vertex stage reads SSBO after compute dispatch)	`Memory_barrier_mask::vertex_attrib_array_barrier_bit` alone is insufficient when the consuming vertex shader reads via SSBO instead of the input assembler	Use `vertex_attrib_array_barrier_bit \| shader_storage_barrier_bit` between the compute encoder and the render encoder
`VUID-vkFreeCommandBuffers-pCommandBuffers-00047` (cb in pending state when freed)	Editor frees a command buffer the GPU has not finished with -- a frame-fence/lifecycle bug surfaced now that validation is on	Open as of 2026-05-02

When NOT to enable

Performance work (validation adds noticeable per-frame CPU overhead).
Any user-facing test (some VUIDs above abort the editor and a user-built APK should not).