VK_LAYER_PATH equivalent for implicit layers about vulkan-loader HOT 2 OPEN

I am unsure of the historical decision as to why VK_LAYER_PATH only modifies explicit layer paths, but I am not keen to change it due to potential side effects across the ecosystem.

Still, a VK_IMPLICIT_LAYER_PATH and VK_ADD_IMPLICIT_LAYER_PATH would make sense and I do not think it is impossible to add. I'm no fan of adding more environment variables (there already are too many in my opinion) but they at least close an existing hole.

As a side note, it would be helpful to have some extra debug text in VK_LOADER_DEBUG=all to indicate which types of manifests

Looking at the log, we do print "looking for layer|driver manifests" but I always 'knew' what was being searched for because the paths involved said "explicit_layer.d/Vk_layer_foo.json". Still, that is a useful thing to print.

As for why it works the way it does, it may have to do with the loader's inability to distinguish implicit from explicit layers directly, instead expecting the different layer types to be in separate paths/registries. But I have no solid evidence of that fact.

from vulkan-loader.

PR #1400 Is a quick addition to add "explicit" or "implicit" to the 'searching for layer manifests' log message.
I think it would be better to open a separate issue to track more detailed logging suggestions, in order to prevent this issue from getting cluttered up.

EDIT: I went ahead and did that - let me know if that summarizes the intent of your suggestion. Cause I believe the root problem was not knowing where the search paths came from, rather than only knowing if any given env-var was the source.

from vulkan-loader.