feat(host): HDR Vulkan layer so Vulkan games get HDR on the virtual display

NVIDIA/AMD Vulkan ICDs refuse to *advertise* an HDR color space for a surface on an
IddCx indirect/virtual display, so Vulkan games (Doom: The Dark Ages, id Tech, Indiana
Jones, …) report "device does not support HDR" — even though Windows HDR, DWM compose,
and the client PQ stream all work, and the ICD happily *accepts + presents* a forced HDR
swapchain there. The whole gap is enumeration; the community (Apollo/Sunshine/VDD) wrote
this off as kernel-side / unfixable.

Add VK_LAYER_PUNKTFUNK_hdr_inject (packaging/windows/pf-vkhdr-layer/): a standalone
cdylib Vulkan implicit layer that appends {A2B10G10R10, HDR10_ST2084} + {RGBA16F, scRGB}
to vkGetPhysicalDeviceSurfaceFormats[2]KHR (no need to hook vkCreateSwapchainKHR — the
ICD doesn't validate the color space there). Self-gated on the surface monitor's actual
advanced-color state (DisplayConfig GET_ADVANCED_COLOR_INFO), so it is a complete no-op
on SDR sessions and real monitors (dedup). Always-on (registry-discovered) so it works
regardless of how a game is launched — env-scoping silently fails for already-running
Steam. Escape hatches: DISABLE_PF_VKHDR, PF_VKHDR_EXCLUDE, and a built-in kernel-anti-
cheat denylist.

The installer builds/signs/stages it and registers it under
HKLM64\SOFTWARE\Khronos\Vulkan\ImplicitLayers (opt-out "Install the HDR Vulkan layer"
task); windows-host CI fmt+clippy-gates it (msvc-only FFI).

Live-validated on the RTX box: Doom: The Dark Ages enables HDR over the pf-vdisplay
virtual display.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.gitea/workflows/windows-host.yml

@@ -96,6 +96,18 @@ jobs:
         # First-ever Windows lint coverage for the host (Linux CI never lints the windows-cfg code).
         run: cargo clippy -p punktfunk-host --features nvenc,amf-qsv -- -D warnings
 
+      - name: Build + lint the HDR Vulkan layer (pf-vkhdr-layer)
+        shell: pwsh
+        # Standalone cdylib (own [workspace]) the installer bundles + registers (it lets Vulkan games
+        # like Doom use HDR on the virtual display). Lint here so a regression fails CI instead of
+        # silently shipping the host without the layer (pack-host-installer.ps1 builds it non-fatally).
+        # Windows-only FFI (user32 + the vk_layer loader glue) → can't be linted on the Linux CI.
+        run: |
+          Push-Location packaging/windows/pf-vkhdr-layer
+          cargo fmt --check; if ($LASTEXITCODE) { throw "pf-vkhdr-layer rustfmt" }
+          cargo clippy --release -- -D warnings; if ($LASTEXITCODE) { throw "pf-vkhdr-layer clippy" }
+          Pop-Location
+
       - name: Ensure Inno Setup
         shell: pwsh
         run: |

packaging/windows/pack-host-installer.ps1

@@ -211,6 +211,38 @@ if ($WebDir -and (Test-Path $WebDir) -and $BunExe -and (Test-Path $BunExe)) {
 }
 else { Write-Host "no -WebDir/-BunExe -> installer built WITHOUT the web console" }
 
+# --- build + stage the HDR Vulkan layer (pf-vkhdr-layer) --------------------------------------
+# A tiny always-on Vulkan implicit layer (cdylib) that advertises HDR10/scRGB surface formats on the
+# virtual display so Vulkan games (Doom: The Dark Ages, etc.) can enable HDR while streaming — the
+# NVIDIA/AMD ICDs hide HDR formats on an indirect display even though they accept+present a forced HDR
+# swapchain there. Self-gated on the display's actual advanced-color state, so it's a no-op on SDR.
+# Standalone crate (own [workspace]); built here and registered by the installer. Skipped if cargo
+# is unavailable or the build fails -> installer is produced WITHOUT the layer (non-fatal).
+$layerSrc = Join-Path $here 'pf-vkhdr-layer'
+if (Test-Path (Join-Path $layerSrc 'Cargo.toml')) {
+    $layerTarget = Join-Path $OutDir 'vklayer-target'
+    Write-Host "==> building pf-vkhdr-layer (cdylib)"
+    $prevTarget = $env:CARGO_TARGET_DIR
+    $env:CARGO_TARGET_DIR = $layerTarget
+    Push-Location $layerSrc
+    & cargo build --release
+    $layerExit = $LASTEXITCODE
+    Pop-Location
+    if ($prevTarget) { $env:CARGO_TARGET_DIR = $prevTarget } else { Remove-Item Env:\CARGO_TARGET_DIR -ErrorAction SilentlyContinue }
+    $layerDll = Join-Path $layerTarget 'release\pf_vkhdr_layer.dll'
+    if ($layerExit -eq 0 -and (Test-Path $layerDll)) {
+        $layerStage = Join-Path $OutDir 'vklayer'
+        New-Item -ItemType Directory -Force -Path $layerStage | Out-Null
+        Copy-Item $layerDll (Join-Path $layerStage 'pf_vkhdr_layer.dll') -Force
+        Copy-Item (Join-Path $layerSrc 'pf_vkhdr_layer.json') (Join-Path $layerStage 'pf_vkhdr_layer.json') -Force
+        Sign-File (Join-Path $layerStage 'pf_vkhdr_layer.dll')
+        $defines += "/DVkLayerDir=$layerStage"
+        Write-Host "==> staged pf-vkhdr-layer -> $layerStage"
+    }
+    else { Write-Warning "pf-vkhdr-layer build failed ($layerExit) — installer built WITHOUT the HDR Vulkan layer" }
+}
+else { Write-Host "no pf-vkhdr-layer crate -> installer built WITHOUT the HDR Vulkan layer" }
+
 # --- build the installer (from the non-redirected copy under C:\t) -----------------------------
 Write-Host "==> ISCC $($defines -join ' ') $issLocal"
 & $iscc @defines $issLocal

packaging/windows/pf-vkhdr-layer/Cargo.toml

@@ -0,0 +1,23 @@
+[package]
+name = "pf-vkhdr-layer"
+version = "0.1.0"
+edition = "2021"
+description = "punktfunk Vulkan implicit layer: inject HDR10/scRGB surface formats on the virtual display so Vulkan games (id Tech, etc.) detect HDR over an IddCx virtual display"
+license = "MIT OR Apache-2.0"
+publish = false
+
+[lib]
+name = "pf_vkhdr_layer"
+crate-type = ["cdylib"]
+
+[dependencies]
+ash = "=0.38.0+1.3.281"
+
+[profile.release]
+opt-level = 2
+panic = "abort"
+strip = true
+
+# Standalone package (not a member of the main punktfunk cargo workspace) — it's a Windows-only
+# cdylib built on its own by pack-host-installer.ps1, like the UMDF driver crates next to it.
+[workspace]

packaging/windows/pf-vkhdr-layer/README.md

@@ -0,0 +1,70 @@
+# pf-vkhdr-layer — HDR Vulkan layer for the virtual display
+
+A tiny Vulkan **implicit layer** (`VK_LAYER_PUNKTFUNK_hdr_inject`) that lets **Vulkan games enable
+HDR while streaming over the punktfunk virtual display**.
+
+## The problem it solves
+
+On Windows, NVIDIA/AMD Vulkan ICDs do **not** advertise any HDR color space
+(`VK_COLOR_SPACE_HDR10_ST2084_EXT`, `VK_COLOR_SPACE_EXTENDED_SRGB_LINEAR_EXT`) for a surface that
+lives on an **IddCx indirect / virtual display** — even when Windows "Use HDR" is on and the desktop
+is composited at 10-bit. So Vulkan games (Doom: The Dark Ages and the rest of id Tech, Indiana Jones
+and the Great Circle, …) query `vkGetPhysicalDeviceSurfaceFormatsKHR`, find no HDR color space, and
+refuse HDR ("This device does not support HDR"). D3D11/D3D12 HDR works on the very same display
+because the OS compositor drives it — only the **Vulkan WSI enumeration** is gated.
+
+This was long believed unfixable from outside the GPU driver (the Apollo/Sunshine/Virtual-Display-
+Driver communities all concluded "it's in Windows's kernel"). It isn't: an on-box experiment proved
+the ICD happily **accepts and presents a *forced* HDR swapchain** on that exact virtual-display
+surface (`vkCreateSwapchainKHR` + `vkSetHdrMetadataEXT` + present all succeed) — it simply won't
+*advertise* the format. So the whole fix is to add the HDR surface formats to the enumeration the
+game queries; once the game requests that swapchain, the ICD honors it. **Validated live: Doom: The
+Dark Ages enables HDR over the virtual display with this layer.**
+
+## What it does
+
+- Intercepts `vkGetPhysicalDeviceSurfaceFormatsKHR` / `...2KHR`, calls down to the ICD, and appends
+  `{A2B10G10R10_UNORM_PACK32, HDR10_ST2084_EXT}` + `{R16G16B16A16_SFLOAT, EXTENDED_SRGB_LINEAR_EXT}`
+  (deduped — a no-op on real HDR monitors that already list them).
+- **Self-gates**: it only injects when the surface's monitor actually has Windows advanced-color
+  (HDR) *enabled* right now (checked via `DisplayConfigGetDeviceInfo` / `GET_ADVANCED_COLOR_INFO`).
+  So it does **nothing** on SDR sessions/displays — no washed-out "SDR-in-HDR". It tracks
+  `VkSurfaceKHR → HWND` by intercepting `vkCreateWin32SurfaceKHR`.
+- Everything else is pass-through dispatch chaining (instance + device).
+
+It is shipped as an **always-on** implicit layer (loads via the registry, so it works regardless of
+how a game is launched — including via an already-running Steam, which env-based scoping can't
+guarantee). Because of the self-gate it is inert outside HDR streaming.
+
+## Controls
+
+| Variable | Effect |
+|---|---|
+| `DISABLE_PF_VKHDR=1` | Loader-standard off-switch — disables the whole layer for that process. |
+| `PF_VKHDR_EXCLUDE=foo.exe,bar.exe` | Extra exe basenames to skip (in addition to a small built-in kernel-anti-cheat default list: `cs2.exe`, `rainbowsix.exe`, …). |
+| `PF_VKHDR_LOG=1` | Write a debug log to `%TEMP%\pf_vkhdr_layer.log`. |
+
+## Build / install
+
+Standalone crate (own `[workspace]`), Windows-only `cdylib`:
+
+```sh
+cargo build --release           # -> target/release/pf_vkhdr_layer.dll
+```
+
+The host installer (`packaging/windows/pack-host-installer.ps1` → `punktfunk-host.iss`) builds it,
+lays `pf_vkhdr_layer.dll` + `pf_vkhdr_layer.json` into `{app}\vklayer`, and registers it under
+`HKLM64\SOFTWARE\Khronos\Vulkan\ImplicitLayers` (opt-out task "Install the HDR Vulkan layer").
+
+Manual dev install: drop the DLL + JSON in one directory and add a `REG_DWORD` value named after the
+JSON's full path (data `0`) under `HKLM\SOFTWARE\Khronos\Vulkan\ImplicitLayers` (or `HKCU\...`).
+Confirm with `vulkaninfo` (Surface section) — `HDR10_ST2084_EXT` should appear when the display has
+HDR enabled.
+
+## Notes
+
+- x64 only (the Windows host is x64 only).
+- Anti-cheat: the layer is benign (it only *adds* surface formats; it never touches rendering,
+  memory, or input) and is signed, but because it's always-on it is *present* in every Vulkan
+  process. The built-in exclude list + `PF_VKHDR_EXCLUDE` + `DISABLE_PF_VKHDR` cover kernel-anti-
+  cheat titles you'd rather it stay out of.

packaging/windows/pf-vkhdr-layer/pf_vkhdr_layer.json

@@ -0,0 +1,17 @@
+{
+    "file_format_version": "1.2.0",
+    "layer": {
+        "name": "VK_LAYER_PUNKTFUNK_hdr_inject",
+        "type": "GLOBAL",
+        "library_path": ".\\pf_vkhdr_layer.dll",
+        "api_version": "1.4.280",
+        "implementation_version": "1",
+        "description": "punktfunk: advertise HDR10/scRGB Vulkan surface formats on the virtual display (NVIDIA/AMD ICDs hide them on indirect displays even though the ICD accepts + presents a forced HDR swapchain).",
+        "functions": {
+            "vkNegotiateLoaderLayerInterfaceVersion": "vkNegotiateLoaderLayerInterfaceVersion"
+        },
+        "disable_environment": {
+            "DISABLE_PF_VKHDR": "1"
+        }
+    }
+}

packaging/windows/pf-vkhdr-layer/src/lib.rs

@@ -0,0 +1,841 @@
+//! punktfunk Vulkan implicit layer — `VK_LAYER_PUNKTFUNK_hdr_inject`.
+//!
+//! ## Why
+//! On Windows, NVIDIA/AMD Vulkan ICDs do **not** advertise any HDR color space
+//! (`HDR10_ST2084_EXT`, `EXTENDED_SRGB_LINEAR_EXT`) for a surface on an IddCx *indirect / virtual*
+//! display — even when Windows "Use HDR" is enabled and the desktop is composited at 10-bit. So
+//! Vulkan games (Doom: The Dark Ages and the rest of id Tech, Indiana Jones, …) query
+//! `vkGetPhysicalDeviceSurfaceFormatsKHR`, find no HDR color space, and refuse HDR
+//! ("This device does not support HDR"). DX11/DX12 HDR works on the same display because the OS
+//! compositor drives it; only the Vulkan WSI *enumeration* is gated. An on-box spike proved the ICD
+//! *accepts and presents* a forced HDR swapchain on that exact surface — it just won't *advertise*
+//! the format. So the entire fix is to append the HDR surface formats to the enumeration the game
+//! queries; once the game asks for that swapchain, the ICD honors it.
+//!
+//! ## What this layer does
+//! Intercepts `vkGetPhysicalDeviceSurfaceFormatsKHR` / `...2KHR`, calls down to the ICD, and appends
+//! `{A2B10G10R10_UNORM_PACK32, HDR10_ST2084_EXT}` and `{R16G16B16A16_SFLOAT, EXTENDED_SRGB_LINEAR_EXT}`
+//! (deduped). **Self-gating:** it only injects when the surface's monitor actually has Windows
+//! advanced-color (HDR) *enabled* — so it is a complete no-op on SDR sessions and on real monitors
+//! (which already advertise HDR, and dedup drops the duplicate). It tracks `VkSurfaceKHR -> HWND` by
+//! intercepting `vkCreateWin32SurfaceKHR`. Everything else is pass-through dispatch chaining.
+//!
+//! Off-switches: the loader-standard `DISABLE_PF_VKHDR=1` (disables the whole layer), and
+//! `PF_VKHDR_EXCLUDE` (comma/semicolon list of exe basenames to skip — defaults include known
+//! kernel-anti-cheat titles). `PF_VKHDR_LOG=1` enables a debug log in `%TEMP%\pf_vkhdr_layer.log`.
+
+#![allow(non_snake_case)]
+#![allow(clippy::missing_safety_doc)]
+#![allow(clippy::too_many_arguments)]
+// HWND / HMONITOR etc. deliberately mirror the Win32 names.
+#![allow(clippy::upper_case_acronyms)]
+
+use ash::vk;
+use ash::vk::Handle;
+use std::collections::HashMap;
+use std::ffi::{c_char, c_void, CStr};
+use std::ptr;
+use std::sync::{Mutex, OnceLock};
+
+// ---- Vulkan loader<->layer glue (vk_layer.h; not in the core registry / ash) ----
+// The loader's private create-info sTypes squat on 47/48 (NOT the 1000211xxx range).
+const LOADER_INSTANCE_CREATE_INFO: i32 = 47;
+const LOADER_DEVICE_CREATE_INFO: i32 = 48;
+const VK_LAYER_LINK_INFO: i32 = 0;
+const LAYER_NEGOTIATE_INTERFACE_STRUCT: i32 = 1;
+
+type PfnGipa = vk::PFN_vkGetInstanceProcAddr;
+type PfnGdpa = vk::PFN_vkGetDeviceProcAddr;
+type PfnGpdpa = unsafe extern "system" fn(vk::Instance, *const c_char) -> vk::PFN_vkVoidFunction;
+
+#[repr(C)]
+struct BaseIn {
+    s_type: vk::StructureType,
+    p_next: *const c_void,
+}
+#[repr(C)]
+struct LayerInstanceLink {
+    p_next: *mut LayerInstanceLink,
+    next_gipa: PfnGipa,
+    next_gpdpa: Option<PfnGpdpa>,
+}
+#[repr(C)]
+struct LayerInstanceCreateInfo {
+    s_type: vk::StructureType,
+    p_next: *const c_void,
+    function: i32,
+    u: *mut LayerInstanceLink,
+}
+#[repr(C)]
+struct LayerDeviceLink {
+    p_next: *mut LayerDeviceLink,
+    next_gipa: PfnGipa,
+    next_gdpa: PfnGdpa,
+}
+#[repr(C)]
+struct LayerDeviceCreateInfo {
+    s_type: vk::StructureType,
+    p_next: *const c_void,
+    function: i32,
+    u: *mut LayerDeviceLink,
+}
+#[repr(C)]
+pub struct NegotiateLayerInterface {
+    s_type: i32,
+    p_next: *mut c_void,
+    loader_layer_interface_version: u32,
+    pfn_gipa: Option<PfnGipa>,
+    pfn_gdpa: Option<PfnGdpa>,
+    pfn_gpdpa: Option<PfnGpdpa>,
+}
+
+// raw mirror of VkSurfaceFormat2KHR (avoid ash lifetime generics in fn-pointer types)
+#[repr(C)]
+#[derive(Clone, Copy)]
+struct SurfaceFormat2Raw {
+    s_type: vk::StructureType,
+    p_next: *mut c_void,
+    surface_format: vk::SurfaceFormatKHR,
+}
+
+// ---- ICD function-pointer typedefs we call down to (raw pointers, no lifetimes) ----
+type FnCreateInstance =
+    unsafe extern "system" fn(*const c_void, *const c_void, *mut vk::Instance) -> vk::Result;
+type FnDestroyInstance = unsafe extern "system" fn(vk::Instance, *const c_void);
+type FnCreateDevice = unsafe extern "system" fn(
+    vk::PhysicalDevice,
+    *const c_void,
+    *const c_void,
+    *mut vk::Device,
+) -> vk::Result;
+type FnGetSurfFmts = unsafe extern "system" fn(
+    vk::PhysicalDevice,
+    vk::SurfaceKHR,
+    *mut u32,
+    *mut vk::SurfaceFormatKHR,
+) -> vk::Result;
+type FnGetSurfFmts2 = unsafe extern "system" fn(
+    vk::PhysicalDevice,
+    *const c_void,
+    *mut u32,
+    *mut c_void,
+) -> vk::Result;
+type FnCreateWin32Surface = unsafe extern "system" fn(
+    vk::Instance,
+    *const c_void,
+    *const c_void,
+    *mut vk::SurfaceKHR,
+) -> vk::Result;
+type FnDestroySurface = unsafe extern "system" fn(vk::Instance, vk::SurfaceKHR, *const c_void);
+
+struct InstanceData {
+    instance: vk::Instance,
+    next_gipa: PfnGipa,
+    next_gpdpa: Option<PfnGpdpa>,
+    destroy_instance: Option<FnDestroyInstance>,
+    get_surface_formats: Option<FnGetSurfFmts>,
+    get_surface_formats2: Option<FnGetSurfFmts2>,
+    create_win32_surface: Option<FnCreateWin32Surface>,
+    destroy_surface: Option<FnDestroySurface>,
+}
+unsafe impl Send for InstanceData {}
+
+struct DeviceData {
+    next_gdpa: PfnGdpa,
+}
+unsafe impl Send for DeviceData {}
+
+fn instances() -> &'static Mutex<HashMap<usize, InstanceData>> {
+    static M: OnceLock<Mutex<HashMap<usize, InstanceData>>> = OnceLock::new();
+    M.get_or_init(|| Mutex::new(HashMap::new()))
+}
+fn devices() -> &'static Mutex<HashMap<usize, DeviceData>> {
+    static M: OnceLock<Mutex<HashMap<usize, DeviceData>>> = OnceLock::new();
+    M.get_or_init(|| Mutex::new(HashMap::new()))
+}
+/// VkSurfaceKHR handle -> the HWND it was created from (so we can resolve its monitor's HDR state).
+fn surface_hwnds() -> &'static Mutex<HashMap<u64, isize>> {
+    static M: OnceLock<Mutex<HashMap<u64, isize>>> = OnceLock::new();
+    M.get_or_init(|| Mutex::new(HashMap::new()))
+}
+
+// dispatch key = first pointer word of a dispatchable handle (loader dispatch table ptr).
+#[inline]
+unsafe fn key(raw: u64) -> usize {
+    *(raw as usize as *const usize)
+}
+#[inline]
+unsafe fn as_pfn(p: *const c_void) -> vk::PFN_vkVoidFunction {
+    Some(std::mem::transmute::<
+        *const c_void,
+        unsafe extern "system" fn(),
+    >(p))
+}
+#[inline]
+unsafe fn resolve<T: Copy>(gipa: PfnGipa, inst: vk::Instance, name: &CStr) -> Option<T> {
+    gipa(inst, name.as_ptr()).map(|f| std::mem::transmute_copy::<_, T>(&f))
+}
+
+fn log(msg: &str) {
+    if std::env::var_os("PF_VKHDR_LOG").is_none() {
+        return;
+    }
+    use std::io::Write;
+    let mut path = std::env::temp_dir();
+    path.push("pf_vkhdr_layer.log");
+    if let Ok(mut f) = std::fs::OpenOptions::new()
+        .create(true)
+        .append(true)
+        .open(path)
+    {
+        let _ = writeln!(f, "{msg}");
+    }
+}
+
+fn hdr_extra() -> [vk::SurfaceFormatKHR; 2] {
+    [
+        vk::SurfaceFormatKHR {
+            format: vk::Format::A2B10G10R10_UNORM_PACK32,
+            color_space: vk::ColorSpaceKHR::HDR10_ST2084_EXT,
+        },
+        vk::SurfaceFormatKHR {
+            format: vk::Format::R16G16B16A16_SFLOAT,
+            color_space: vk::ColorSpaceKHR::EXTENDED_SRGB_LINEAR_EXT,
+        },
+    ]
+}
+
+/// `false` if this process is on the anti-cheat exclude list (built-in + `PF_VKHDR_EXCLUDE`).
+/// Computed once per process.
+fn injection_allowed_for_process() -> bool {
+    static C: OnceLock<bool> = OnceLock::new();
+    *C.get_or_init(|| {
+        let exe = std::env::current_exe()
+            .ok()
+            .and_then(|p| p.file_name().map(|s| s.to_string_lossy().to_lowercase()))
+            .unwrap_or_default();
+        if exe.is_empty() {
+            return true;
+        }
+        // Conservative default skip-list for kernel-level anti-cheat titles. Users can extend or
+        // clear via PF_VKHDR_EXCLUDE. (HDR injection is benign, but we err toward not being present
+        // in these process' WSI path at all.)
+        const DENY: &[&str] = &[
+            "cs2.exe",
+            "rainbowsix.exe",
+            "rainbowsixgame.exe",
+            "r5apex.exe",
+        ];
+        let mut denied = false;
+        for d in DENY {
+            if *d == exe {
+                denied = true;
+            }
+        }
+        if let Ok(extra) = std::env::var("PF_VKHDR_EXCLUDE") {
+            for e in extra.split([',', ';']) {
+                if e.trim().to_lowercase() == exe {
+                    denied = true;
+                }
+            }
+        }
+        if denied {
+            log(&format!("injection disabled for excluded process: {exe}"));
+        }
+        !denied
+    })
+}
+
+// ---- Win32 / DisplayConfig: is the surface's monitor HDR-enabled right now? ----
+mod hdr {
+    use std::ffi::c_void;
+    pub type HWND = isize;
+    pub type HMONITOR = isize;
+
+    #[repr(C)]
+    #[derive(Clone, Copy)]
+    pub struct Rect {
+        pub l: i32,
+        pub t: i32,
+        pub r: i32,
+        pub b: i32,
+    }
+    #[repr(C)]
+    #[derive(Clone, Copy)]
+    pub struct MonitorInfoExW {
+        pub cb: u32,
+        pub rc_monitor: Rect,
+        pub rc_work: Rect,
+        pub flags: u32,
+        pub sz_device: [u16; 32],
+    }
+    #[repr(C)]
+    #[derive(Clone, Copy)]
+    pub struct Luid {
+        pub low: u32,
+        pub high: i32,
+    }
+    #[repr(C)]
+    #[derive(Clone, Copy)]
+    pub struct Rational {
+        pub num: u32,
+        pub den: u32,
+    }
+    #[repr(C)]
+    #[derive(Clone, Copy)]
+    pub struct Source {
+        pub adapter: Luid,
+        pub id: u32,
+        pub mode_idx: u32,
+        pub status: u32,
+    }
+    #[repr(C)]
+    #[derive(Clone, Copy)]
+    pub struct Target {
+        pub adapter: Luid,
+        pub id: u32,
+        pub mode_idx: u32,
+        pub tech: i32,
+        pub rotation: i32,
+        pub scaling: i32,
+        pub refresh: Rational,
+        pub scanline: i32,
+        pub available: i32,
+        pub status: u32,
+    }
+    #[repr(C)]
+    #[derive(Clone, Copy)]
+    pub struct PathInfo {
+        pub src: Source,
+        pub tgt: Target,
+        pub flags: u32,
+    }
+    #[repr(C)]
+    #[derive(Clone, Copy)]
+    pub struct ModeInfo {
+        pub _b: [u8; 64],
+    }
+    #[repr(C)]
+    #[derive(Clone, Copy)]
+    pub struct Header {
+        pub typ: i32,
+        pub size: u32,
+        pub adapter: Luid,
+        pub id: u32,
+    }
+    #[repr(C)]
+    pub struct AdvInfo {
+        pub header: Header,
+        pub value: u32,
+        pub enc: i32,
+        pub bpc: i32,
+    }
+    #[repr(C)]
+    pub struct SourceName {
+        pub header: Header,
+        pub gdi: [u16; 32],
+    }
+
+    #[link(name = "user32")]
+    extern "system" {
+        fn MonitorFromWindow(h: HWND, flags: u32) -> HMONITOR;
+        fn GetMonitorInfoW(h: HMONITOR, mi: *mut MonitorInfoExW) -> i32;
+        fn GetDisplayConfigBufferSizes(flags: u32, np: *mut u32, nm: *mut u32) -> i32;
+        fn QueryDisplayConfig(
+            flags: u32,
+            np: *mut u32,
+            pa: *mut PathInfo,
+            nm: *mut u32,
+            ma: *mut ModeInfo,
+            topo: *mut c_void,
+        ) -> i32;
+        fn DisplayConfigGetDeviceInfo(p: *mut c_void) -> i32;
+    }
+    const QDC_ONLY_ACTIVE_PATHS: u32 = 2;
+    const GET_SOURCE_NAME: i32 = 1;
+    const GET_ADVANCED_COLOR_INFO: i32 = 9;
+    const MONITOR_DEFAULTTONEAREST: u32 = 2;
+
+    unsafe fn active_paths() -> Vec<PathInfo> {
+        let (mut np, mut nm) = (0u32, 0u32);
+        if GetDisplayConfigBufferSizes(QDC_ONLY_ACTIVE_PATHS, &mut np, &mut nm) != 0 || np == 0 {
+            return Vec::new();
+        }
+        let mut pa: Vec<PathInfo> = vec![std::mem::zeroed(); np as usize];
+        let mut ma: Vec<ModeInfo> = vec![std::mem::zeroed(); nm as usize];
+        if QueryDisplayConfig(
+            QDC_ONLY_ACTIVE_PATHS,
+            &mut np,
+            pa.as_mut_ptr(),
+            &mut nm,
+            ma.as_mut_ptr(),
+            std::ptr::null_mut(),
+        ) != 0
+        {
+            return Vec::new();
+        }
+        pa.truncate(np as usize);
+        pa
+    }
+
+    unsafe fn target_hdr_enabled(p: &PathInfo) -> bool {
+        let mut ai: AdvInfo = std::mem::zeroed();
+        ai.header.typ = GET_ADVANCED_COLOR_INFO;
+        ai.header.size = std::mem::size_of::<AdvInfo>() as u32;
+        ai.header.adapter = p.tgt.adapter;
+        ai.header.id = p.tgt.id;
+        if DisplayConfigGetDeviceInfo(&mut ai as *mut _ as *mut c_void) != 0 {
+            return false;
+        }
+        // value bitfield: bit0 advancedColorSupported, bit1 advancedColorEnabled.
+        (ai.value & 0b10) != 0
+    }
+
+    unsafe fn source_gdi(p: &PathInfo) -> [u16; 32] {
+        let mut sn: SourceName = std::mem::zeroed();
+        sn.header.typ = GET_SOURCE_NAME;
+        sn.header.size = std::mem::size_of::<SourceName>() as u32;
+        sn.header.adapter = p.src.adapter;
+        sn.header.id = p.src.id;
+        let _ = DisplayConfigGetDeviceInfo(&mut sn as *mut _ as *mut c_void);
+        sn.gdi
+    }
+
+    /// Is HDR (Windows advanced color) currently enabled on the display this surface lives on?
+    /// `hwnd == 0`/unknown falls back to "any active display has HDR enabled".
+    pub unsafe fn enabled_for(hwnd: HWND) -> bool {
+        let paths = active_paths();
+        if hwnd != 0 {
+            let mon = MonitorFromWindow(hwnd, MONITOR_DEFAULTTONEAREST);
+            let mut mi: MonitorInfoExW = std::mem::zeroed();
+            mi.cb = std::mem::size_of::<MonitorInfoExW>() as u32;
+            if GetMonitorInfoW(mon, &mut mi) != 0 {
+                for p in &paths {
+                    if source_gdi(p) == mi.sz_device {
+                        return target_hdr_enabled(p);
+                    }
+                }
+            }
+        }
+        paths.iter().any(|p| target_hdr_enabled(p))
+    }
+}
+
+/// Should we inject HDR formats for this surface right now?
+unsafe fn should_inject(surface: vk::SurfaceKHR) -> bool {
+    if !injection_allowed_for_process() {
+        return false;
+    }
+    let hwnd = surface_hwnds()
+        .lock()
+        .ok()
+        .and_then(|m| m.get(&surface.as_raw()).copied())
+        .unwrap_or(0);
+    hdr::enabled_for(hwnd)
+}
+
+// ---- entry point ----
+
+#[no_mangle]
+pub unsafe extern "system" fn vkNegotiateLoaderLayerInterfaceVersion(
+    p: *mut NegotiateLayerInterface,
+) -> vk::Result {
+    if p.is_null() {
+        return vk::Result::ERROR_INITIALIZATION_FAILED;
+    }
+    let s = &mut *p;
+    if s.s_type != LAYER_NEGOTIATE_INTERFACE_STRUCT {
+        return vk::Result::ERROR_INITIALIZATION_FAILED;
+    }
+    if s.loader_layer_interface_version > 2 {
+        s.loader_layer_interface_version = 2;
+    }
+    s.pfn_gipa = Some(layer_gipa);
+    s.pfn_gdpa = Some(layer_gdpa);
+    s.pfn_gpdpa = Some(layer_gpdpa);
+    log("negotiate: VK_LAYER_PUNKTFUNK_hdr_inject active (v2)");
+    vk::Result::SUCCESS
+}
+
+// ---- proc-addr dispatch ----
+
+unsafe extern "system" fn layer_gipa(
+    instance: vk::Instance,
+    p_name: *const c_char,
+) -> vk::PFN_vkVoidFunction {
+    if p_name.is_null() {
+        return None;
+    }
+    match CStr::from_ptr(p_name).to_bytes() {
+        b"vkGetInstanceProcAddr" => as_pfn(layer_gipa as *const c_void),
+        b"vkGetDeviceProcAddr" => as_pfn(layer_gdpa as *const c_void),
+        b"vkCreateInstance" => as_pfn(create_instance as *const c_void),
+        b"vkDestroyInstance" => as_pfn(destroy_instance as *const c_void),
+        b"vkCreateDevice" => as_pfn(create_device as *const c_void),
+        b"vkGetPhysicalDeviceSurfaceFormatsKHR" => as_pfn(get_surface_formats as *const c_void),
+        b"vkGetPhysicalDeviceSurfaceFormats2KHR" => as_pfn(get_surface_formats2 as *const c_void),
+        b"vkCreateWin32SurfaceKHR" => as_pfn(create_win32_surface as *const c_void),
+        b"vkDestroySurfaceKHR" => as_pfn(destroy_surface as *const c_void),
+        _ => {
+            if instance == vk::Instance::null() {
+                return None;
+            }
+            let next = {
+                let g = instances().lock().ok()?;
+                g.get(&key(instance.as_raw())).map(|d| d.next_gipa)
+            };
+            next.and_then(|gipa| gipa(instance, p_name))
+        }
+    }
+}
+
+unsafe extern "system" fn layer_gpdpa(
+    instance: vk::Instance,
+    p_name: *const c_char,
+) -> vk::PFN_vkVoidFunction {
+    if p_name.is_null() {
+        return None;
+    }
+    match CStr::from_ptr(p_name).to_bytes() {
+        b"vkGetPhysicalDeviceSurfaceFormatsKHR" => as_pfn(get_surface_formats as *const c_void),
+        b"vkGetPhysicalDeviceSurfaceFormats2KHR" => as_pfn(get_surface_formats2 as *const c_void),
+        _ => {
+            if instance == vk::Instance::null() {
+                return None;
+            }
+            let next = {
+                let g = instances().lock().ok()?;
+                g.get(&key(instance.as_raw())).and_then(|d| d.next_gpdpa)
+            };
+            next.and_then(|gpdpa| gpdpa(instance, p_name))
+        }
+    }
+}
+
+unsafe extern "system" fn layer_gdpa(
+    device: vk::Device,
+    p_name: *const c_char,
+) -> vk::PFN_vkVoidFunction {
+    if p_name.is_null() {
+        return None;
+    }
+    if CStr::from_ptr(p_name).to_bytes() == b"vkGetDeviceProcAddr" {
+        return as_pfn(layer_gdpa as *const c_void);
+    }
+    if device == vk::Device::null() {
+        return None;
+    }
+    let next = {
+        let g = match devices().lock() {
+            Ok(g) => g,
+            Err(_) => return None,
+        };
+        g.get(&key(device.as_raw())).map(|d| d.next_gdpa)
+    };
+    next.and_then(|gdpa| gdpa(device, p_name))
+}
+
+// ---- instance chain ----
+
+unsafe fn find_instance_link(p_ci: *const c_void) -> *mut LayerInstanceCreateInfo {
+    let mut node = (*(p_ci as *const BaseIn)).p_next as *const BaseIn;
+    while !node.is_null() {
+        if (*node).s_type.as_raw() == LOADER_INSTANCE_CREATE_INFO {
+            let lci = node as *mut LayerInstanceCreateInfo;
+            if (*lci).function == VK_LAYER_LINK_INFO {
+                return lci;
+            }
+        }
+        node = (*node).p_next as *const BaseIn;
+    }
+    ptr::null_mut()
+}
+
+unsafe extern "system" fn create_instance(
+    p_ci: *const c_void,
+    p_alloc: *const c_void,
+    p_inst: *mut vk::Instance,
+) -> vk::Result {
+    let lci = find_instance_link(p_ci);
+    if lci.is_null() {
+        return vk::Result::ERROR_INITIALIZATION_FAILED;
+    }
+    let link = (*lci).u;
+    if link.is_null() {
+        return vk::Result::ERROR_INITIALIZATION_FAILED;
+    }
+    let next_gipa = (*link).next_gipa;
+    let next_gpdpa = (*link).next_gpdpa;
+    (*lci).u = (*link).p_next;
+
+    let create: FnCreateInstance =
+        match resolve(next_gipa, vk::Instance::null(), c"vkCreateInstance") {
+            Some(f) => f,
+            None => return vk::Result::ERROR_INITIALIZATION_FAILED,
+        };
+    let res = create(p_ci, p_alloc, p_inst);
+    if res != vk::Result::SUCCESS {
+        return res;
+    }
+    let inst = *p_inst;
+    let data = InstanceData {
+        instance: inst,
+        next_gipa,
+        next_gpdpa,
+        destroy_instance: resolve(next_gipa, inst, c"vkDestroyInstance"),
+        get_surface_formats: resolve(next_gipa, inst, c"vkGetPhysicalDeviceSurfaceFormatsKHR"),
+        get_surface_formats2: resolve(next_gipa, inst, c"vkGetPhysicalDeviceSurfaceFormats2KHR"),
+        create_win32_surface: resolve(next_gipa, inst, c"vkCreateWin32SurfaceKHR"),
+        destroy_surface: resolve(next_gipa, inst, c"vkDestroySurfaceKHR"),
+    };
+    if let Ok(mut g) = instances().lock() {
+        g.insert(key(inst.as_raw()), data);
+    }
+    log("create_instance: hooked");
+    vk::Result::SUCCESS
+}
+
+unsafe extern "system" fn destroy_instance(inst: vk::Instance, p_alloc: *const c_void) {
+    if inst == vk::Instance::null() {
+        return;
+    }
+    let data = instances()
+        .lock()
+        .ok()
+        .and_then(|mut g| g.remove(&key(inst.as_raw())));
+    if let Some(d) = data {
+        if let Some(f) = d.destroy_instance {
+            f(inst, p_alloc);
+        }
+    }
+}
+
+// ---- device chain (pass-through; keeps device-level dispatch working) ----
+
+unsafe fn find_device_link(p_ci: *const c_void) -> *mut LayerDeviceCreateInfo {
+    let mut node = (*(p_ci as *const BaseIn)).p_next as *const BaseIn;
+    while !node.is_null() {
+        if (*node).s_type.as_raw() == LOADER_DEVICE_CREATE_INFO {
+            let lci = node as *mut LayerDeviceCreateInfo;
+            if (*lci).function == VK_LAYER_LINK_INFO {
+                return lci;
+            }
+        }
+        node = (*node).p_next as *const BaseIn;
+    }
+    ptr::null_mut()
+}
+
+unsafe extern "system" fn create_device(
+    pdev: vk::PhysicalDevice,
+    p_ci: *const c_void,
+    p_alloc: *const c_void,
+    p_dev: *mut vk::Device,
+) -> vk::Result {
+    let lci = find_device_link(p_ci);
+    if lci.is_null() {
+        return vk::Result::ERROR_INITIALIZATION_FAILED;
+    }
+    let link = (*lci).u;
+    if link.is_null() {
+        return vk::Result::ERROR_INITIALIZATION_FAILED;
+    }
+    let next_gipa = (*link).next_gipa;
+    let next_gdpa = (*link).next_gdpa;
+    (*lci).u = (*link).p_next;
+
+    let inst = instances()
+        .lock()
+        .ok()
+        .and_then(|g| g.get(&key(pdev.as_raw())).map(|d| d.instance))
+        .unwrap_or(vk::Instance::null());
+
+    let create: FnCreateDevice = match resolve(next_gipa, inst, c"vkCreateDevice") {
+        Some(f) => f,
+        None => return vk::Result::ERROR_INITIALIZATION_FAILED,
+    };
+    let res = create(pdev, p_ci, p_alloc, p_dev);
+    if res != vk::Result::SUCCESS {
+        return res;
+    }
+    let dev = *p_dev;
+    if let Ok(mut g) = devices().lock() {
+        g.insert(key(dev.as_raw()), DeviceData { next_gdpa });
+    }
+    vk::Result::SUCCESS
+}
+
+// ---- surface tracking (so we can resolve a surface's monitor) ----
+
+unsafe extern "system" fn create_win32_surface(
+    inst: vk::Instance,
+    p_ci: *const c_void,
+    p_alloc: *const c_void,
+    p_surface: *mut vk::SurfaceKHR,
+) -> vk::Result {
+    let down = instances().lock().ok().and_then(|g| {
+        g.get(&key(inst.as_raw()))
+            .and_then(|d| d.create_win32_surface)
+    });
+    let down = match down {
+        Some(f) => f,
+        None => return vk::Result::ERROR_EXTENSION_NOT_PRESENT,
+    };
+    let res = down(inst, p_ci, p_alloc, p_surface);
+    if res == vk::Result::SUCCESS {
+        // VkWin32SurfaceCreateInfoKHR: sType@0, pNext@8, flags@16, hinstance@24, hwnd@32
+        let hwnd = *((p_ci as *const u8).add(32) as *const isize);
+        if let Ok(mut m) = surface_hwnds().lock() {
+            m.insert((*p_surface).as_raw(), hwnd);
+        }
+    }
+    res
+}
+
+unsafe extern "system" fn destroy_surface(
+    inst: vk::Instance,
+    surface: vk::SurfaceKHR,
+    p_alloc: *const c_void,
+) {
+    if let Ok(mut m) = surface_hwnds().lock() {
+        m.remove(&surface.as_raw());
+    }
+    let down = instances()
+        .lock()
+        .ok()
+        .and_then(|g| g.get(&key(inst.as_raw())).and_then(|d| d.destroy_surface));
+    if let Some(f) = down {
+        f(inst, surface, p_alloc);
+    }
+}
+
+// ---- the actual fix: append HDR surface formats (self-gated on display HDR state) ----
+
+unsafe extern "system" fn get_surface_formats(
+    pdev: vk::PhysicalDevice,
+    surface: vk::SurfaceKHR,
+    p_count: *mut u32,
+    p_formats: *mut vk::SurfaceFormatKHR,
+) -> vk::Result {
+    let down = instances().lock().ok().and_then(|g| {
+        g.get(&key(pdev.as_raw()))
+            .and_then(|d| d.get_surface_formats)
+    });
+    let down = match down {
+        Some(f) => f,
+        None => return vk::Result::ERROR_INITIALIZATION_FAILED,
+    };
+
+    let mut n = 0u32;
+    let r = down(pdev, surface, &mut n, ptr::null_mut());
+    if r != vk::Result::SUCCESS {
+        return r;
+    }
+    let mut real = vec![vk::SurfaceFormatKHR::default(); n as usize];
+    if n > 0 {
+        let r = down(pdev, surface, &mut n, real.as_mut_ptr());
+        if r != vk::Result::SUCCESS {
+            return r;
+        }
+    }
+    real.truncate(n as usize);
+
+    let mut aug = real;
+    if !aug.is_empty() && should_inject(surface) {
+        for e in hdr_extra() {
+            if !aug
+                .iter()
+                .any(|x| x.format == e.format && x.color_space == e.color_space)
+            {
+                aug.push(e);
+            }
+        }
+    }
+
+    if p_formats.is_null() {
+        *p_count = aug.len() as u32;
+        return vk::Result::SUCCESS;
+    }
+    let m = (*p_count as usize).min(aug.len());
+    ptr::copy_nonoverlapping(aug.as_ptr(), p_formats, m);
+    *p_count = m as u32;
+    if m < aug.len() {
+        vk::Result::INCOMPLETE
+    } else {
+        vk::Result::SUCCESS
+    }
+}
+
+unsafe extern "system" fn get_surface_formats2(
+    pdev: vk::PhysicalDevice,
+    p_info: *const c_void,
+    p_count: *mut u32,
+    p_formats: *mut c_void,
+) -> vk::Result {
+    let down = instances().lock().ok().and_then(|g| {
+        g.get(&key(pdev.as_raw()))
+            .and_then(|d| d.get_surface_formats2)
+    });
+    let down = match down {
+        Some(f) => f,
+        None => return vk::Result::ERROR_INITIALIZATION_FAILED,
+    };
+
+    let mut n = 0u32;
+    let r = down(pdev, p_info, &mut n, ptr::null_mut());
+    if r != vk::Result::SUCCESS {
+        return r;
+    }
+    let mut real: Vec<SurfaceFormat2Raw> = (0..n)
+        .map(|_| SurfaceFormat2Raw {
+            s_type: vk::StructureType::SURFACE_FORMAT_2_KHR,
+            p_next: ptr::null_mut(),
+            surface_format: vk::SurfaceFormatKHR::default(),
+        })
+        .collect();
+    if n > 0 {
+        let r = down(pdev, p_info, &mut n, real.as_mut_ptr() as *mut c_void);
+        if r != vk::Result::SUCCESS {
+            return r;
+        }
+    }
+    real.truncate(n as usize);
+
+    // VkPhysicalDeviceSurfaceInfo2KHR: sType@0, pNext@8, surface@16
+    let surface = vk::SurfaceKHR::from_raw(*((p_info as *const u8).add(16) as *const u64));
+
+    let mut extras: Vec<vk::SurfaceFormatKHR> = Vec::new();
+    if !real.is_empty() && should_inject(surface) {
+        for e in hdr_extra() {
+            if !real.iter().any(|x| {
+                x.surface_format.format == e.format && x.surface_format.color_space == e.color_space
+            }) {
+                extras.push(e);
+            }
+        }
+    }
+    let total = real.len() + extras.len();
+
+    if p_formats.is_null() {
+        *p_count = total as u32;
+        return vk::Result::SUCCESS;
+    }
+    let m = (*p_count as usize).min(total);
+    let out = p_formats as *mut SurfaceFormat2Raw;
+    for i in 0..m {
+        let sf = if i < real.len() {
+            real[i].surface_format
+        } else {
+            extras[i - real.len()]
+        };
+        let dst = out.add(i);
+        (*dst).s_type = vk::StructureType::SURFACE_FORMAT_2_KHR;
+        (*dst).surface_format = sf;
+    }
+    *p_count = m as u32;
+    if m < total {
+        vk::Result::INCOMPLETE
+    } else {
+        vk::Result::SUCCESS
+    }
+}

packaging/windows/punktfunk-host.iss

@@ -56,6 +56,13 @@
     #define WithWeb
   #endif
 #endif
+; VkLayerDir (the staged pf-vkhdr-layer: pf_vkhdr_layer.dll + .json) is optional — present when the
+; HDR Vulkan layer was built. It lets Vulkan games (Doom: The Dark Ages, etc.) enable HDR over the
+; virtual display (the ICD won't advertise HDR there; the layer injects the surface formats, self-
+; gated on the display's actual HDR state).
+#ifdef VkLayerDir
+  #define WithVkLayer
+#endif
 
 [Setup]
 AppId={{7C9E6A52-1F4B-4E8D-A3C7-2B5D8F1E0A93}
@@ -89,6 +96,9 @@ Name: "installdriver"; Description: "Install the pf-vdisplay virtual display dri
 #ifdef WithGamepad
 Name: "installgamepad"; Description: "Install the virtual gamepad drivers (DualSense / DualShock 4 / Xbox 360 — no ViGEmBus needed)"
 #endif
+#ifdef WithVkLayer
+Name: "installhdrlayer"; Description: "Install the HDR Vulkan layer (lets Vulkan games like Doom use HDR on the virtual display)"
+#endif
 Name: "startservice"; Description: "Start the punktfunk host service now (also starts on every boot)"
 
 [Files]
@@ -119,6 +129,22 @@ Source: "{#StageDir}\*"; DestDir: "{tmp}\pfvdisplay"; Flags: deleteafterinstall
 ; The vendored UMDF gamepad drivers + install-gamepad-drivers.ps1, extracted to {tmp}, removed after.
 Source: "{#GamepadStageDir}\*"; DestDir: "{tmp}\gamepad"; Flags: deleteafterinstall recursesubdirs createallsubdirs; Tasks: installgamepad
 #endif
+#ifdef WithVkLayer
+; The HDR Vulkan implicit layer (cdylib + its JSON manifest) laid into {app}\vklayer and registered
+; below. The manifest's library_path is ".\pf_vkhdr_layer.dll" (relative to the JSON), so the two
+; must live in the same directory.
+Source: "{#VkLayerDir}\pf_vkhdr_layer.dll"; DestDir: "{app}\vklayer"; Flags: ignoreversion; Tasks: installhdrlayer
+Source: "{#VkLayerDir}\pf_vkhdr_layer.json"; DestDir: "{app}\vklayer"; Flags: ignoreversion; Tasks: installhdrlayer
+#endif
+
+[Registry]
+#ifdef WithVkLayer
+; Register the HDR Vulkan implicit layer system-wide. The 64-bit Vulkan loader reads
+; HKLM64\SOFTWARE\Khronos\Vulkan\ImplicitLayers; the value NAME is the manifest path and the DWORD
+; DATA is 0 (= enabled). uninsdeletevalue removes just this value on uninstall. The layer is inert
+; unless the target display has HDR enabled, and honors DISABLE_PF_VKHDR=1 as a global off-switch.
+Root: HKLM64; Subkey: "SOFTWARE\Khronos\Vulkan\ImplicitLayers"; ValueType: dword; ValueName: "{app}\vklayer\pf_vkhdr_layer.json"; ValueData: 0; Flags: uninsdeletevalue; Tasks: installhdrlayer
+#endif
 
 [Run]
 #ifdef WithDriver