Mesa

Mesa is an open source implementation of several graphics APIs including OpenGL and Vulkan.

Enabling Vulkan Layers

This article or section is out of date.

Reason: Vulkan layers are enabled by default since we merged #196310. However, this is a good example on how to properly override mesa's package attributes. (Discuss in Talk:Mesa)
Once the page has been updated this notice can be removed.

Vulkan Layers are not enabled by default in Nixpkgs. You can override the existing Mesa packages and specify them in config.hardware.opengl.

hardware = {
  opengl =
    let
      fn = oa: {
        nativeBuildInputs = oa.nativeBuildInputs ++ [ pkgs.glslang ];
        mesonFlags = oa.mesonFlags ++ [ "-Dvulkan-layers=device-select,overlay" ];
#       patches = oa.patches ++ [ ./mesa-vulkan-layer-nvidia.patch ]; See below 
        postInstall = oa.postInstall + ''
            mv $out/lib/libVkLayer* $drivers/lib

            #Device Select layer
            layer=VkLayer_MESA_device_select
            substituteInPlace $drivers/share/vulkan/implicit_layer.d/''${layer}.json \
              --replace "lib''${layer}" "$drivers/lib/lib''${layer}"

            #Overlay layer
            layer=VkLayer_MESA_overlay
            substituteInPlace $drivers/share/vulkan/explicit_layer.d/''${layer}.json \
              --replace "lib''${layer}" "$drivers/lib/lib''${layer}"
          '';
      };
    in
    with pkgs; {
      enable = true;
      driSupport32Bit = true;
      package = (mesa.overrideAttrs fn).drivers;
      package32 = (pkgsi686Linux.mesa.overrideAttrs fn).drivers;
    };

Nvidia users may need to apply this patch for the Device Select layer to work.

diff b/src/vulkan/device-select-layer/device_select_layer.c a/src/vulkan/device-select-layer/device_select_layer.c
--- b/src/vulkan/device-select-layer/device_select_layer.c
+++ a/src/vulkan/device-select-layer/device_select_layer.c
@@ -454,12 +454,8 @@
       exit(0);
    } else {
       unsigned selected_index = get_default_device(info, selection, physical_device_count, physical_devices);
-      selected_physical_device_count = physical_device_count;
+      selected_physical_device_count = 1;
       selected_physical_devices[0] = physical_devices[selected_index];
-      for (unsigned i = 0; i < physical_device_count - 1; ++i) {
-         unsigned  this_idx = i < selected_index ? i : i + 1;
-         selected_physical_devices[i + 1] = physical_devices[this_idx];
-      }
    }

    if (selected_physical_device_count == 0) {

Default drivers

In case you wonder where does ["auto"] in mesa's attributes lead you, this might be another way to see them (for 22.1.3[1]):

, galliumDrivers ?
  # Search for `gallium_drivers.contains('auto')` in meson.build
  if stdenv.isLinux then
    if stdenv.isi686 || stdenv.isx86_64  then ["r300" "r600" "radeonsi" "nouveau" "virgl" "svga" "swrast" "iris" "crocus" "i915"]
    else if stdenv.isAarch64 then ["v3d" "vc4" "freedreno" "etnaviv" "nouveau" "tegra" "virgl" "lima" "panfrost" "swrast"]
    else throw "Unsupported platform: this derivation only supports i686/x86_64/aarch64"
  else if stdenv.isDarwin then ["swrast"]
  else throw "Unsupported platform: this derivation only supports Linux/Darwin"
, vulkanDrivers ?
  # Search for `_vulkan_drivers.contains('auto')` in meson.build
  if stdenv.isLinux then
    if stdenv.isi686 || stdenv.isx86_64   then ["amd" "intel" "swrast"]
    else if stdenv.isAarch64 || stdenv.isArch32 then ["swrast"]
    else throw "Unsupported platform: this derivation only supports i686/x86_64/aarch64"
  else if stdenv.isDarwin then  []
  else throw "Unsupported platform: this derivation only supports Linux/Darwin"