vkBasalt: don't check if available by using a path

[SuperSamus]

Currently, Bottles checks whether vkBasalt is installed or not by checking some paths, and returning True if at least one of them exists. https://github.com/bottlesdevs/Bottles/blob/bfa8d25e8a336aecaf694722ea954d1f4142b8b0/bottles/backend/globals.py#L45-L54 However, just because vkBasalt is in one of these paths, it doesn't mean it is enabled. (The opposite might also apply: vkBasalt might be enabled without being in any of the paths.) These situations might happen for example in distros that don't respect FHS, like NixOS. I'm not a Vulkan expert, so I'm not really sure on what is the best alternative. An idea could be executing vulkaninfo and grepping VK_LAYER_VKBASALT_post_processing.

[TheEvilSkeleton]

Hmm... I tried on the Bottles flatpak on my AMD laptop, but there doesn't seem to be anything interesting in vulkaninfo:

VK_LAYER_VKBASALT_post_processing (a post processing layer) Vulkan version 1.3.223, layer version 1:
    Layer Extensions: count = 0
    Devices: count = 2
        GPU id = 0 (AMD Radeon Graphics (RADV RENOIR))
        Layer-Device Extensions: count = 0

        GPU id = 1 (llvmpipe (LLVM 14.0.6, 256 bits))
        Layer-Device Extensions: count = 0

I don't like the current approach, so I'm definitely open to suggestions.

[Kinsteen]

This extension is only there if vkBasalt is available, so grepping the result could be a good way to see if it's available or not

[TheEvilSkeleton]

Good point. I wonder how we could detect the location automatically.

[Kinsteen]

It seems that there is a vkBasalt.json in /usr/share/vulkan/implicit_layer.d, like MangoHud. Maybe this path is standard, or there's a way to get the path of this folder with a vulkan command?

[TheEvilSkeleton]

It seems that there is a vkBasalt.json in /usr/share/vulkan/implicit_layer.d, like MangoHud. Maybe this path is standard, or there's a way to get the path of this folder with a vulkan command?

After two days of researching, no. If we use the vulkan library, then the process is complicated.

What @SuperSamus suggested seems to be the easiest and most maintainable approach, thanks! I don't think we will need to find paths, as vulkaninfo provides necessary information for layers:

$ vulkaninfo
...
VK_LAYER_MANGOAPP_overlay (Mangoapp Layer) Vulkan version 1.3.0, layer version 1:
    Layer Extensions: count = 0
    Devices: count = 2
        GPU id = 0 (AMD Radeon Graphics (RADV RENOIR))
        Layer-Device Extensions: count = 0

        GPU id = 1 (llvmpipe (LLVM 15.0.7, 256 bits))
        Layer-Device Extensions: count = 0

VK_LAYER_MANGOHUD_overlay (Vulkan Hud Overlay) Vulkan version 1.3.0, layer version 1:
    Layer Extensions: count = 0
    Devices: count = 2
        GPU id = 0 (AMD Radeon Graphics (RADV RENOIR))
        Layer-Device Extensions: count = 0

        GPU id = 1 (llvmpipe (LLVM 15.0.7, 256 bits))
        Layer-Device Extensions: count = 0
...
VK_LAYER_VKBASALT_post_processing (a post processing layer) Vulkan version 1.3.223, layer version 1:
    Layer Extensions: count = 0
    Devices: count = 2
        GPU id = 0 (AMD Radeon Graphics (RADV RENOIR))
        Layer-Device Extensions: count = 0

        GPU id = 1 (llvmpipe (LLVM 15.0.7, 256 bits))
        Layer-Device Extensions: count = 0

The cool part about vulkaninfo is that we can use it to check if Vulkan exists too. If it fails, the error looks like this:

❯ vulkaninfo 
ERROR: [Loader Message] Code 0 : vkCreateInstance: Found no drivers!
Cannot create Vulkan instance.
This problem is often caused by a faulty installation of the Vulkan driver or attempting to use a GPU that does not support Vulkan.
ERROR at /build/vulkan-tools/src/Vulkan-Tools-1.3.235/vulkaninfo/vulkaninfo.h:674:vkCreateInstance failed with ERROR_INCOMPATIBLE_DRIVER

[TheEvilSkeleton]

Also, for the course I'm taking, I am developing overlay, which is a vkBasalt and MangoHud manager. Once I'm done with this, I'll use that as a library for Bottles.