[Impeller] MacOS+SwiftShader doesn't render. #134852
Description
In order to get some Vulkan validation checking on CI, we'll need to use Swift Shader (Software Rendering). However, as of HEAD (flutter/engine@d0ff708 at time of writing), there are two problems with Vulkan+Swift Shader on MacOS hosts (which I can also reproduce locally):
- Asynchronous presentation causes a timeout
- Even with synchronous presentation, the image is blank
There is a some more information here:
- [Impeller] Validation errors when running playgrounds with Vulkan validation enabled. #133506 (comment)
- [Impeller] Wire up a SwiftShader backend for Impeller unit-tests. #126022 (comment)
It's likely the issues are same (nothing is being drawn).
To reproduce (remember, MacOS host - and I only tried ARM64):
# Assuming you're in $ENGINE/src/flutter
# GN
./tools/gn \
--unopt \
--mac-cpu arm64 \
--enable-vulkan-validation-layers \
--enable-impeller-vulkan \
--target-dir=host_debug_impeller_vulkan \
--no-stripped
# Ninja
ninja -j1000 -C ../out/host_debug_impeller_vulkan impeller_unittests
# Make sure this path is right, if not you'll silently use MoltenVK, which works fine.
ls ../out/host_debug_impeller_vulkan/vk_swiftshader_icd.json
# Run, providing Swift Shader, and enabling validation.
VK_ICD_FILENAMES=../out/host_debug_impeller_vulkan/vk_swiftshader_icd.json \
../out/host_debug_impeller_vulkan/impeller_unittests \
--gtest_filter="Play/AiksTest.*/Vulkan" \
--playground_timeout_ms=1000 \
--enable_vulkan_validationI'm filing this issue so we can at least get validation coverage (flutter/engine#45918).