From 573bf91c9325008a9e4b29df901c9cc12fa300e8 Mon Sep 17 00:00:00 2001
From: Daniel McNab <36049421+DJMcNab@users.noreply.github.com>
Date: Fri, 23 Aug 2024 14:32:21 +0100
Subject: [PATCH 01/16] Expose the raw swapchain from a vulkan `Surface`

---
 wgpu-hal/src/vulkan/mod.rs | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/wgpu-hal/src/vulkan/mod.rs b/wgpu-hal/src/vulkan/mod.rs
index 26186d5fa8..3197eea5a9 100644
--- a/wgpu-hal/src/vulkan/mod.rs
+++ b/wgpu-hal/src/vulkan/mod.rs
@@ -375,6 +375,16 @@ pub struct Surface {
     swapchain: RwLock<Option<Swapchain>>,
 }
 
+impl Surface {
+    /// Get the raw Vulkan swapchain associated with this surface.
+    ///
+    /// Returns `None` if the surface is not configured.
+    pub fn raw_swapchain(&self) -> Option<vk::SwapchainKHR> {
+        let read = self.swapchain.read();
+        read.as_ref().map(|it| it.raw)
+    }
+}
+
 #[derive(Debug)]
 pub struct SurfaceTexture {
     index: u32,

From 0189345078b1afd1fea8f439314108c2b145e0b1 Mon Sep 17 00:00:00 2001
From: Daniel McNab <36049421+DJMcNab@users.noreply.github.com>
Date: Fri, 23 Aug 2024 19:41:01 +0100
Subject: [PATCH 02/16] Allow setting the present timing information on hal
 Vulkan

---
 wgpu-hal/Cargo.toml            |  9 ++++--
 wgpu-hal/src/vulkan/adapter.rs | 13 +++++++-
 wgpu-hal/src/vulkan/device.rs  |  1 +
 wgpu-hal/src/vulkan/mod.rs     | 56 ++++++++++++++++++++++++++++++++--
 4 files changed, 74 insertions(+), 5 deletions(-)

diff --git a/wgpu-hal/Cargo.toml b/wgpu-hal/Cargo.toml
index ee2808b19d..74b32f0b3f 100644
--- a/wgpu-hal/Cargo.toml
+++ b/wgpu-hal/Cargo.toml
@@ -105,6 +105,11 @@ device_lost_panic = []
 # Only affects the d3d12 and vulkan backends.
 internal_error_panic = []
 
+# Enable the VK_GOOGLE_display_timing Vulkan extension if supported.
+# This API has no stability guarantees.
+# https://registry.khronos.org/vulkan/specs/1.3-extensions/man/html/VK_GOOGLE_display_timing.html
+unstable_vulkan_google_display_timing = []
+
 [[example]]
 name = "halmark"
 
@@ -204,8 +209,8 @@ features = ["wgsl-in"]
 [dev-dependencies]
 cfg-if.workspace = true
 env_logger.workspace = true
-glam.workspace = true # for ray-traced-triangle example
-winit.workspace = true # for "halmark" example
+glam.workspace = true       # for ray-traced-triangle example
+winit.workspace = true      # for "halmark" example
 
 [target.'cfg(not(target_arch = "wasm32"))'.dev-dependencies]
 glutin.workspace = true # for "gles" example
diff --git a/wgpu-hal/src/vulkan/adapter.rs b/wgpu-hal/src/vulkan/adapter.rs
index f323456eaa..7059eaeec1 100644
--- a/wgpu-hal/src/vulkan/adapter.rs
+++ b/wgpu-hal/src/vulkan/adapter.rs
@@ -1,6 +1,6 @@
 use super::conv;
 
-use ash::{amd, ext, khr, vk};
+use ash::{amd, ext, google, khr, vk};
 use parking_lot::Mutex;
 
 use std::{collections::BTreeMap, ffi::CStr, sync::Arc};
@@ -1004,6 +1004,12 @@ impl PhysicalDeviceProperties {
             extensions.push(khr::shader_atomic_int64::NAME);
         }
 
+        #[cfg(feature = "unstable_vulkan_google_display_timing")]
+        // Support VK_GOOGLE_display_timing if it is requested *and* available.
+        if self.supports_extension(google::display_timing::NAME) {
+            extensions.push(google::display_timing::NAME);
+        }
+
         extensions
     }
 
@@ -1812,6 +1818,9 @@ impl super::Adapter {
             0, 0, 0, 0,
         ];
 
+        #[cfg(feature = "unstable_vulkan_google_display_timing")]
+        let has_display_timing = enabled_extensions.contains(&google::display_timing::NAME);
+
         let shared = Arc::new(super::DeviceShared {
             raw: raw_device,
             family_index,
@@ -1821,6 +1830,8 @@ impl super::Adapter {
             instance: Arc::clone(&self.instance),
             physical_device: self.raw,
             enabled_extensions: enabled_extensions.into(),
+            #[cfg(feature = "unstable_vulkan_google_display_timing")]
+            has_google_display_timing_extension: has_display_timing,
             extension_fns: super::DeviceExtensionFunctions {
                 debug_utils: debug_utils_fn,
                 draw_indirect_count: indirect_count_fn,
diff --git a/wgpu-hal/src/vulkan/device.rs b/wgpu-hal/src/vulkan/device.rs
index 70136bdfb5..9ba50fc46b 100644
--- a/wgpu-hal/src/vulkan/device.rs
+++ b/wgpu-hal/src/vulkan/device.rs
@@ -642,6 +642,7 @@ impl super::Device {
             view_formats: wgt_view_formats,
             surface_semaphores,
             next_semaphore_index: 0,
+            next_present_times: None,
         })
     }
 
diff --git a/wgpu-hal/src/vulkan/mod.rs b/wgpu-hal/src/vulkan/mod.rs
index 3197eea5a9..58c1483e12 100644
--- a/wgpu-hal/src/vulkan/mod.rs
+++ b/wgpu-hal/src/vulkan/mod.rs
@@ -40,7 +40,10 @@ use std::{
 };
 
 use arrayvec::ArrayVec;
-use ash::{ext, khr, vk};
+use ash::{
+    ext, khr,
+    vk::{self, PresentTimeGOOGLE},
+};
 use parking_lot::{Mutex, RwLock};
 use wgt::InternalCounter;
 
@@ -355,6 +358,8 @@ struct Swapchain {
     /// index as the image index, but we need to specify the semaphore as an argument
     /// to the acquire_next_image function which is what tells us which image to use.
     next_semaphore_index: usize,
+    #[cfg(feature = "unstable_vulkan_google_display_timing")]
+    next_present_times: Option<PresentTimeGOOGLE>,
 }
 
 impl Swapchain {
@@ -383,6 +388,27 @@ impl Surface {
         let read = self.swapchain.read();
         read.as_ref().map(|it| it.raw)
     }
+
+    /// Set the present timing information which will be used for the next presentation.
+    ///
+    /// Warns if the device doesn't [support present timing](Device::supports_google_display_timing).
+    ///
+    /// # Panics
+    ///
+    /// If the surface hasn't been configured.
+    #[cfg(feature = "unstable_vulkan_google_display_timing")]
+    #[track_caller]
+    pub fn set_next_present_times(&self, present_timing: PresentTimeGOOGLE) {
+        let mut swapchain = self.swapchain.write();
+        let swapchain = swapchain
+            .as_mut()
+            .expect("Surface should have been configured");
+        if swapchain.device.has_google_display_timing_extension {
+            swapchain.next_present_times = Some(present_timing);
+        } else {
+            log::warn!("Tried to call set_next_present_times on a device which doesn't support.");
+        }
+    }
 }
 
 #[derive(Debug)]
@@ -561,6 +587,8 @@ struct DeviceShared {
     instance: Arc<InstanceShared>,
     physical_device: vk::PhysicalDevice,
     enabled_extensions: Vec<&'static CStr>,
+    #[cfg(feature = "unstable_vulkan_google_display_timing")]
+    has_google_display_timing_extension: bool,
     extension_fns: DeviceExtensionFunctions,
     vendor_id: u32,
     pipeline_cache_validation_key: [u8; 16],
@@ -585,6 +613,16 @@ pub struct Device {
     counters: wgt::HalCounters,
 }
 
+impl Device {
+    /// Returns true if this device supports [VK_GOOGLE_display_timing].
+    ///
+    /// [VK_GOOGLE_display_timing]: https://registry.khronos.org/vulkan/specs/1.3-extensions/man/html/VK_GOOGLE_display_timing.html
+    #[cfg(feature = "unstable_vulkan_google_display_timing")]
+    pub fn supports_google_display_timing(&self) -> bool {
+        self.shared.has_google_display_timing_extension
+    }
+}
+
 /// Semaphores for forcing queue submissions to run in order.
 ///
 /// The [`wgpu_hal::Queue`] trait promises that if two calls to [`submit`] are
@@ -1167,7 +1205,21 @@ impl crate::Queue for Queue {
             .swapchains(&swapchains)
             .image_indices(&image_indices)
             .wait_semaphores(swapchain_semaphores.get_present_wait_semaphores());
-
+        #[cfg(feature = "unstable_vulkan_google_display_timing")]
+        let mut display_timing;
+        #[cfg(feature = "unstable_vulkan_google_display_timing")]
+        let present_times;
+        #[cfg(feature = "unstable_vulkan_google_display_timing")]
+        let vk_info = if let Some(present_time) = ssc.next_present_times.take() {
+            assert!(ssc.device.has_google_display_timing_extension);
+            display_timing = vk::PresentTimesInfoGOOGLE::default();
+            present_times = [present_time];
+            display_timing = display_timing.times(&present_times);
+            // Safety: We know that the display_timing extension is present.
+            vk_info.push_next(&mut display_timing)
+        } else {
+            vk_info
+        };
         let suboptimal = {
             profiling::scope!("vkQueuePresentKHR");
             unsafe { self.swapchain_fn.queue_present(self.raw, &vk_info) }.map_err(|error| {

From 8e975d62692284015d48150a96dd0e4088b88b5d Mon Sep 17 00:00:00 2001
From: Daniel McNab <36049421+DJMcNab@users.noreply.github.com>
Date: Fri, 23 Aug 2024 20:02:30 +0100
Subject: [PATCH 03/16] Fix clippy without the feature enabled

---
 wgpu-hal/src/vulkan/adapter.rs | 8 ++++----
 wgpu-hal/src/vulkan/device.rs  | 1 +
 wgpu-hal/src/vulkan/mod.rs     | 9 +++------
 3 files changed, 8 insertions(+), 10 deletions(-)

diff --git a/wgpu-hal/src/vulkan/adapter.rs b/wgpu-hal/src/vulkan/adapter.rs
index 7059eaeec1..23039786a8 100644
--- a/wgpu-hal/src/vulkan/adapter.rs
+++ b/wgpu-hal/src/vulkan/adapter.rs
@@ -1,6 +1,6 @@
 use super::conv;
 
-use ash::{amd, ext, google, khr, vk};
+use ash::{amd, ext, khr, vk};
 use parking_lot::Mutex;
 
 use std::{collections::BTreeMap, ffi::CStr, sync::Arc};
@@ -1006,8 +1006,8 @@ impl PhysicalDeviceProperties {
 
         #[cfg(feature = "unstable_vulkan_google_display_timing")]
         // Support VK_GOOGLE_display_timing if it is requested *and* available.
-        if self.supports_extension(google::display_timing::NAME) {
-            extensions.push(google::display_timing::NAME);
+        if self.supports_extension(ash::google::display_timing::NAME) {
+            extensions.push(ash::google::display_timing::NAME);
         }
 
         extensions
@@ -1819,7 +1819,7 @@ impl super::Adapter {
         ];
 
         #[cfg(feature = "unstable_vulkan_google_display_timing")]
-        let has_display_timing = enabled_extensions.contains(&google::display_timing::NAME);
+        let has_display_timing = enabled_extensions.contains(&ash::google::display_timing::NAME);
 
         let shared = Arc::new(super::DeviceShared {
             raw: raw_device,
diff --git a/wgpu-hal/src/vulkan/device.rs b/wgpu-hal/src/vulkan/device.rs
index 9ba50fc46b..28735ff771 100644
--- a/wgpu-hal/src/vulkan/device.rs
+++ b/wgpu-hal/src/vulkan/device.rs
@@ -642,6 +642,7 @@ impl super::Device {
             view_formats: wgt_view_formats,
             surface_semaphores,
             next_semaphore_index: 0,
+            #[cfg(feature = "unstable_vulkan_google_display_timing")]
             next_present_times: None,
         })
     }
diff --git a/wgpu-hal/src/vulkan/mod.rs b/wgpu-hal/src/vulkan/mod.rs
index 58c1483e12..984ea02f71 100644
--- a/wgpu-hal/src/vulkan/mod.rs
+++ b/wgpu-hal/src/vulkan/mod.rs
@@ -40,10 +40,7 @@ use std::{
 };
 
 use arrayvec::ArrayVec;
-use ash::{
-    ext, khr,
-    vk::{self, PresentTimeGOOGLE},
-};
+use ash::{ext, khr, vk};
 use parking_lot::{Mutex, RwLock};
 use wgt::InternalCounter;
 
@@ -359,7 +356,7 @@ struct Swapchain {
     /// to the acquire_next_image function which is what tells us which image to use.
     next_semaphore_index: usize,
     #[cfg(feature = "unstable_vulkan_google_display_timing")]
-    next_present_times: Option<PresentTimeGOOGLE>,
+    next_present_times: Option<vk::PresentTimeGOOGLE>,
 }
 
 impl Swapchain {
@@ -398,7 +395,7 @@ impl Surface {
     /// If the surface hasn't been configured.
     #[cfg(feature = "unstable_vulkan_google_display_timing")]
     #[track_caller]
-    pub fn set_next_present_times(&self, present_timing: PresentTimeGOOGLE) {
+    pub fn set_next_present_times(&self, present_timing: vk::PresentTimeGOOGLE) {
         let mut swapchain = self.swapchain.write();
         let swapchain = swapchain
             .as_mut()

From 5a7a205e58787bc47bae2bea6e29e9d70fb0ed20 Mon Sep 17 00:00:00 2001
From: Daniel McNab <36049421+DJMcNab@users.noreply.github.com>
Date: Fri, 23 Aug 2024 20:09:38 +0100
Subject: [PATCH 04/16] CHANGELOG

---
 CHANGELOG.md | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 21ec6bde0c..90117f1056 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -61,6 +61,10 @@ By @wumpf in [#6069](https://github.com/gfx-rs/wgpu/pull/6069), [#6099](https://
 
 * Support constant evaluation for `firstLeadingBit` and `firstTrailingBit` numeric built-ins in WGSL. Front-ends that translate to these built-ins also benefit from constant evaluation. By @ErichDonGubler in [#5101](https://github.com/gfx-rs/wgpu/pull/5101).
 
+#### Vulkan
+
+- Allow using [VK_GOOGLE_display_timing](https://registry.khronos.org/vulkan/specs/1.3-extensions/man/html/VK_GOOGLE_display_timing.html) unsafely. By @DJMcNab in [#6149](https://github.com/gfx-rs/wgpu/pull/6149)
+
 ### Bug Fixes
 
 - Fix incorrect hlsl image output type conversion. By @atlv24 in [#6123](https://github.com/gfx-rs/wgpu/pull/6123)

From 62cef44a1fa04f9ef811362d2b3fd8f80ee306b6 Mon Sep 17 00:00:00 2001
From: Daniel McNab <36049421+DJMcNab@users.noreply.github.com>
Date: Sat, 24 Aug 2024 09:07:00 +0100
Subject: [PATCH 05/16] Revert inadvertently formatted Cargo.toml

---
 wgpu-hal/Cargo.toml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/wgpu-hal/Cargo.toml b/wgpu-hal/Cargo.toml
index 74b32f0b3f..6a3508d4d1 100644
--- a/wgpu-hal/Cargo.toml
+++ b/wgpu-hal/Cargo.toml
@@ -209,8 +209,8 @@ features = ["wgsl-in"]
 [dev-dependencies]
 cfg-if.workspace = true
 env_logger.workspace = true
-glam.workspace = true       # for ray-traced-triangle example
-winit.workspace = true      # for "halmark" example
+glam.workspace = true # for ray-traced-triangle example
+winit.workspace = true # for "halmark" example
 
 [target.'cfg(not(target_arch = "wasm32"))'.dev-dependencies]
 glutin.workspace = true # for "gles" example

From 064c5f6b301f9d5acf8c04146f2de3d1ac5a6a6d Mon Sep 17 00:00:00 2001
From: Daniel McNab <36049421+DJMcNab@users.noreply.github.com>
Date: Tue, 27 Aug 2024 10:30:23 +0100
Subject: [PATCH 06/16] Move display timing to a feature

---
 wgpu-hal/Cargo.toml            |  4 ----
 wgpu-hal/src/vulkan/adapter.rs | 17 +++++++-------
 wgpu-hal/src/vulkan/device.rs  |  1 -
 wgpu-hal/src/vulkan/mod.rs     | 43 ++++++++++++++--------------------
 wgpu-types/src/lib.rs          | 13 ++++++++++
 5 files changed, 39 insertions(+), 39 deletions(-)

diff --git a/wgpu-hal/Cargo.toml b/wgpu-hal/Cargo.toml
index 6a3508d4d1..654ce8a6da 100644
--- a/wgpu-hal/Cargo.toml
+++ b/wgpu-hal/Cargo.toml
@@ -105,10 +105,6 @@ device_lost_panic = []
 # Only affects the d3d12 and vulkan backends.
 internal_error_panic = []
 
-# Enable the VK_GOOGLE_display_timing Vulkan extension if supported.
-# This API has no stability guarantees.
-# https://registry.khronos.org/vulkan/specs/1.3-extensions/man/html/VK_GOOGLE_display_timing.html
-unstable_vulkan_google_display_timing = []
 
 [[example]]
 name = "halmark"
diff --git a/wgpu-hal/src/vulkan/adapter.rs b/wgpu-hal/src/vulkan/adapter.rs
index 23039786a8..7b8f3d37c6 100644
--- a/wgpu-hal/src/vulkan/adapter.rs
+++ b/wgpu-hal/src/vulkan/adapter.rs
@@ -1,6 +1,6 @@
 use super::conv;
 
-use ash::{amd, ext, khr, vk};
+use ash::{amd, ext, google, khr, vk};
 use parking_lot::Mutex;
 
 use std::{collections::BTreeMap, ffi::CStr, sync::Arc};
@@ -771,6 +771,11 @@ impl PhysicalDeviceFeatures {
             );
         }
 
+        features.set(
+            F::VULKAN_GOOGLE_DISPLAY_TIMING,
+            caps.supports_extension(google::display_timing::NAME),
+        );
+
         (features, dl_flags)
     }
 
@@ -1004,9 +1009,8 @@ impl PhysicalDeviceProperties {
             extensions.push(khr::shader_atomic_int64::NAME);
         }
 
-        #[cfg(feature = "unstable_vulkan_google_display_timing")]
-        // Support VK_GOOGLE_display_timing if it is requested *and* available.
-        if self.supports_extension(ash::google::display_timing::NAME) {
+        // Require `VK_GOOGLE_display_timing` if the associated feature was requested
+        if requested_features.contains(wgt::Features::VULKAN_GOOGLE_DISPLAY_TIMING) {
             extensions.push(ash::google::display_timing::NAME);
         }
 
@@ -1818,9 +1822,6 @@ impl super::Adapter {
             0, 0, 0, 0,
         ];
 
-        #[cfg(feature = "unstable_vulkan_google_display_timing")]
-        let has_display_timing = enabled_extensions.contains(&ash::google::display_timing::NAME);
-
         let shared = Arc::new(super::DeviceShared {
             raw: raw_device,
             family_index,
@@ -1830,8 +1831,6 @@ impl super::Adapter {
             instance: Arc::clone(&self.instance),
             physical_device: self.raw,
             enabled_extensions: enabled_extensions.into(),
-            #[cfg(feature = "unstable_vulkan_google_display_timing")]
-            has_google_display_timing_extension: has_display_timing,
             extension_fns: super::DeviceExtensionFunctions {
                 debug_utils: debug_utils_fn,
                 draw_indirect_count: indirect_count_fn,
diff --git a/wgpu-hal/src/vulkan/device.rs b/wgpu-hal/src/vulkan/device.rs
index 28735ff771..9ba50fc46b 100644
--- a/wgpu-hal/src/vulkan/device.rs
+++ b/wgpu-hal/src/vulkan/device.rs
@@ -642,7 +642,6 @@ impl super::Device {
             view_formats: wgt_view_formats,
             surface_semaphores,
             next_semaphore_index: 0,
-            #[cfg(feature = "unstable_vulkan_google_display_timing")]
             next_present_times: None,
         })
     }
diff --git a/wgpu-hal/src/vulkan/mod.rs b/wgpu-hal/src/vulkan/mod.rs
index 984ea02f71..7c866d190c 100644
--- a/wgpu-hal/src/vulkan/mod.rs
+++ b/wgpu-hal/src/vulkan/mod.rs
@@ -355,7 +355,10 @@ struct Swapchain {
     /// index as the image index, but we need to specify the semaphore as an argument
     /// to the acquire_next_image function which is what tells us which image to use.
     next_semaphore_index: usize,
-    #[cfg(feature = "unstable_vulkan_google_display_timing")]
+    /// The times which will be set in the next present times.
+    ///
+    /// SAFETY: This is only set if [wgt::Features::VULKAN_GOOGLE_DISPLAY_TIMING] is enabled, and
+    /// so `VK_GOOGLE_display_timing` is set.
     next_present_times: Option<vk::PresentTimeGOOGLE>,
 }
 
@@ -386,24 +389,24 @@ impl Surface {
         read.as_ref().map(|it| it.raw)
     }
 
-    /// Set the present timing information which will be used for the next presentation.
-    ///
-    /// Warns if the device doesn't [support present timing](Device::supports_google_display_timing).
+    /// Set the present timing information which will be used for the next presentation using `VK_GOOGLE_display_timing`.
     ///
     /// # Panics
     ///
-    /// If the surface hasn't been configured.
-    #[cfg(feature = "unstable_vulkan_google_display_timing")]
+    /// - If the surface hasn't been configured.
+    /// - If the device doesn't [support present timing](wgt::Features::VULKAN_GOOGLE_DISPLAY_TIMING).
     #[track_caller]
     pub fn set_next_present_times(&self, present_timing: vk::PresentTimeGOOGLE) {
         let mut swapchain = self.swapchain.write();
         let swapchain = swapchain
             .as_mut()
             .expect("Surface should have been configured");
-        if swapchain.device.has_google_display_timing_extension {
+        let features = wgt::Features::VULKAN_GOOGLE_DISPLAY_TIMING;
+        if swapchain.device.features.contains(features) {
             swapchain.next_present_times = Some(present_timing);
         } else {
-            log::warn!("Tried to call set_next_present_times on a device which doesn't support.");
+            // Ideally we'd use something like `device.required_features` here, but that's in `wgpu-core`, which we are a dependency of
+            panic!("Tried to set display timing properties without the corresponding feature ({features:?}) enabled.");
         }
     }
 }
@@ -584,8 +587,6 @@ struct DeviceShared {
     instance: Arc<InstanceShared>,
     physical_device: vk::PhysicalDevice,
     enabled_extensions: Vec<&'static CStr>,
-    #[cfg(feature = "unstable_vulkan_google_display_timing")]
-    has_google_display_timing_extension: bool,
     extension_fns: DeviceExtensionFunctions,
     vendor_id: u32,
     pipeline_cache_validation_key: [u8; 16],
@@ -610,16 +611,6 @@ pub struct Device {
     counters: wgt::HalCounters,
 }
 
-impl Device {
-    /// Returns true if this device supports [VK_GOOGLE_display_timing].
-    ///
-    /// [VK_GOOGLE_display_timing]: https://registry.khronos.org/vulkan/specs/1.3-extensions/man/html/VK_GOOGLE_display_timing.html
-    #[cfg(feature = "unstable_vulkan_google_display_timing")]
-    pub fn supports_google_display_timing(&self) -> bool {
-        self.shared.has_google_display_timing_extension
-    }
-}
-
 /// Semaphores for forcing queue submissions to run in order.
 ///
 /// The [`wgpu_hal::Queue`] trait promises that if two calls to [`submit`] are
@@ -1202,17 +1193,19 @@ impl crate::Queue for Queue {
             .swapchains(&swapchains)
             .image_indices(&image_indices)
             .wait_semaphores(swapchain_semaphores.get_present_wait_semaphores());
-        #[cfg(feature = "unstable_vulkan_google_display_timing")]
         let mut display_timing;
-        #[cfg(feature = "unstable_vulkan_google_display_timing")]
         let present_times;
-        #[cfg(feature = "unstable_vulkan_google_display_timing")]
         let vk_info = if let Some(present_time) = ssc.next_present_times.take() {
-            assert!(ssc.device.has_google_display_timing_extension);
+            debug_assert!(
+                ssc.device
+                    .features
+                    .contains(wgt::Features::VULKAN_GOOGLE_DISPLAY_TIMING),
+                "`next_present_times` should only be set if `VULKAN_GOOGLE_DISPLAY_TIMING` is enabled"
+            );
             display_timing = vk::PresentTimesInfoGOOGLE::default();
             present_times = [present_time];
             display_timing = display_timing.times(&present_times);
-            // Safety: We know that the display_timing extension is present.
+            // Safety: We know that VK_GOOGLE_display_timing is present because of the safety contract on `next_present_times`.
             vk_info.push_next(&mut display_timing)
         } else {
             vk_info
diff --git a/wgpu-types/src/lib.rs b/wgpu-types/src/lib.rs
index 4f15e68a17..6fa54bbfc6 100644
--- a/wgpu-types/src/lib.rs
+++ b/wgpu-types/src/lib.rs
@@ -952,6 +952,19 @@ bitflags::bitflags! {
         ///
         /// This is a native only feature.
         const SHADER_INT64_ATOMIC_ALL_OPS = 1 << 61;
+        /// Allows using the [VK_GOOGLE_display_timing] Vulkan extension.
+        /// This is used for frame pacing to reduce latency, and is generally only available on Android.
+        ///
+        /// This feature does not have a `wgpu`-level API, and must be accessed via `wgpu-hal`,
+        /// through various `as_hal` functions.
+        ///
+        /// Supported platforms:
+        /// - Vulkan (with [VK_GOOGLE_display_timing])
+        ///
+        /// This is a native only feature.
+        ///
+        /// [VK_GOOGLE_display_timing]: https://registry.khronos.org/vulkan/specs/1.3-extensions/man/html/VK_GOOGLE_display_timing.html
+        const VULKAN_GOOGLE_DISPLAY_TIMING = 1 << 62;
     }
 }
 

From 91afed829d79ffc982f909cc5c531b71f725d851 Mon Sep 17 00:00:00 2001
From: Daniel McNab <36049421+DJMcNab@users.noreply.github.com>
Date: Tue, 27 Aug 2024 10:32:26 +0100
Subject: [PATCH 07/16] Update the changelog

---
 CHANGELOG.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 90117f1056..48f652969e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -63,7 +63,7 @@ By @wumpf in [#6069](https://github.com/gfx-rs/wgpu/pull/6069), [#6099](https://
 
 #### Vulkan
 
-- Allow using [VK_GOOGLE_display_timing](https://registry.khronos.org/vulkan/specs/1.3-extensions/man/html/VK_GOOGLE_display_timing.html) unsafely. By @DJMcNab in [#6149](https://github.com/gfx-rs/wgpu/pull/6149)
+- Allow using [VK_GOOGLE_display_timing](https://registry.khronos.org/vulkan/specs/1.3-extensions/man/html/VK_GOOGLE_display_timing.html) unsafely with the `VULKAN_GOOGLE_DISPLAY_TIMING` feature. By @DJMcNab in [#6149](https://github.com/gfx-rs/wgpu/pull/6149)
 
 ### Bug Fixes
 

From 911178b9e8010dd5cd82271e01900acdda3f2c63 Mon Sep 17 00:00:00 2001
From: Daniel McNab <36049421+DJMcNab@users.noreply.github.com>
Date: Tue, 27 Aug 2024 10:41:19 +0100
Subject: [PATCH 08/16] Whitespace and doc wording tweaks

---
 wgpu-hal/Cargo.toml        | 5 ++---
 wgpu-hal/src/vulkan/mod.rs | 4 +++-
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/wgpu-hal/Cargo.toml b/wgpu-hal/Cargo.toml
index 654ce8a6da..060d7a0c31 100644
--- a/wgpu-hal/Cargo.toml
+++ b/wgpu-hal/Cargo.toml
@@ -105,7 +105,6 @@ device_lost_panic = []
 # Only affects the d3d12 and vulkan backends.
 internal_error_panic = []
 
-
 [[example]]
 name = "halmark"
 
@@ -205,8 +204,8 @@ features = ["wgsl-in"]
 [dev-dependencies]
 cfg-if.workspace = true
 env_logger.workspace = true
-glam.workspace = true # for ray-traced-triangle example
-winit.workspace = true # for "halmark" example
+glam.workspace = true       # for ray-traced-triangle example
+winit.workspace = true      # for "halmark" example
 
 [target.'cfg(not(target_arch = "wasm32"))'.dev-dependencies]
 glutin.workspace = true # for "gles" example
diff --git a/wgpu-hal/src/vulkan/mod.rs b/wgpu-hal/src/vulkan/mod.rs
index 7c866d190c..3e01a01047 100644
--- a/wgpu-hal/src/vulkan/mod.rs
+++ b/wgpu-hal/src/vulkan/mod.rs
@@ -358,7 +358,7 @@ struct Swapchain {
     /// The times which will be set in the next present times.
     ///
     /// SAFETY: This is only set if [wgt::Features::VULKAN_GOOGLE_DISPLAY_TIMING] is enabled, and
-    /// so `VK_GOOGLE_display_timing` is set.
+    /// so the `VK_GOOGLE_display_timing` extension is present.
     next_present_times: Option<vk::PresentTimeGOOGLE>,
 }
 
@@ -1193,6 +1193,7 @@ impl crate::Queue for Queue {
             .swapchains(&swapchains)
             .image_indices(&image_indices)
             .wait_semaphores(swapchain_semaphores.get_present_wait_semaphores());
+
         let mut display_timing;
         let present_times;
         let vk_info = if let Some(present_time) = ssc.next_present_times.take() {
@@ -1210,6 +1211,7 @@ impl crate::Queue for Queue {
         } else {
             vk_info
         };
+
         let suboptimal = {
             profiling::scope!("vkQueuePresentKHR");
             unsafe { self.swapchain_fn.queue_present(self.raw, &vk_info) }.map_err(|error| {

From 1c04a515b318fa8ce50692f75f352422084d25b5 Mon Sep 17 00:00:00 2001
From: Daniel McNab <36049421+DJMcNab@users.noreply.github.com>
Date: Tue, 27 Aug 2024 10:52:27 +0100
Subject: [PATCH 09/16] Apply suggestions from code review

Co-authored-by: Marijn Suijten <marijns95@gmail.com>
---
 wgpu-hal/src/vulkan/mod.rs | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/wgpu-hal/src/vulkan/mod.rs b/wgpu-hal/src/vulkan/mod.rs
index 3e01a01047..e4f3b1b3d0 100644
--- a/wgpu-hal/src/vulkan/mod.rs
+++ b/wgpu-hal/src/vulkan/mod.rs
@@ -357,7 +357,7 @@ struct Swapchain {
     next_semaphore_index: usize,
     /// The times which will be set in the next present times.
     ///
-    /// SAFETY: This is only set if [wgt::Features::VULKAN_GOOGLE_DISPLAY_TIMING] is enabled, and
+    /// SAFETY: This is only set if [`wgt::Features::VULKAN_GOOGLE_DISPLAY_TIMING`] is enabled, and
     /// so the `VK_GOOGLE_display_timing` extension is present.
     next_present_times: Option<vk::PresentTimeGOOGLE>,
 }
@@ -383,7 +383,7 @@ pub struct Surface {
 impl Surface {
     /// Get the raw Vulkan swapchain associated with this surface.
     ///
-    /// Returns `None` if the surface is not configured.
+    /// Returns [`None`] if the surface is not configured.
     pub fn raw_swapchain(&self) -> Option<vk::SwapchainKHR> {
         let read = self.swapchain.read();
         read.as_ref().map(|it| it.raw)
@@ -1206,7 +1206,7 @@ impl crate::Queue for Queue {
             display_timing = vk::PresentTimesInfoGOOGLE::default();
             present_times = [present_time];
             display_timing = display_timing.times(&present_times);
-            // Safety: We know that VK_GOOGLE_display_timing is present because of the safety contract on `next_present_times`.
+            // SAFETY: We know that VK_GOOGLE_display_timing is present because of the safety contract on `next_present_times`.
             vk_info.push_next(&mut display_timing)
         } else {
             vk_info

From 50ab5d56235ce84128adecbbe614ef48bcfa475f Mon Sep 17 00:00:00 2001
From: Daniel McNab <36049421+DJMcNab@users.noreply.github.com>
Date: Tue, 27 Aug 2024 10:53:08 +0100
Subject: [PATCH 10/16] Revert inadvertent formatting changes again

---
 wgpu-hal/Cargo.toml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/wgpu-hal/Cargo.toml b/wgpu-hal/Cargo.toml
index 060d7a0c31..ee2808b19d 100644
--- a/wgpu-hal/Cargo.toml
+++ b/wgpu-hal/Cargo.toml
@@ -204,8 +204,8 @@ features = ["wgsl-in"]
 [dev-dependencies]
 cfg-if.workspace = true
 env_logger.workspace = true
-glam.workspace = true       # for ray-traced-triangle example
-winit.workspace = true      # for "halmark" example
+glam.workspace = true # for ray-traced-triangle example
+winit.workspace = true # for "halmark" example
 
 [target.'cfg(not(target_arch = "wasm32"))'.dev-dependencies]
 glutin.workspace = true # for "gles" example

From 4c5f56b05f887e04ab5f8080d40c193e1729a7fd Mon Sep 17 00:00:00 2001
From: Daniel McNab <36049421+DJMcNab@users.noreply.github.com>
Date: Tue, 27 Aug 2024 10:54:10 +0100
Subject: [PATCH 11/16] Remove unused qualification

Co-authored-by: Marijn Suijten <marijns95@gmail.com>
---
 wgpu-hal/src/vulkan/adapter.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/wgpu-hal/src/vulkan/adapter.rs b/wgpu-hal/src/vulkan/adapter.rs
index 7b8f3d37c6..d7db62364f 100644
--- a/wgpu-hal/src/vulkan/adapter.rs
+++ b/wgpu-hal/src/vulkan/adapter.rs
@@ -1011,7 +1011,7 @@ impl PhysicalDeviceProperties {
 
         // Require `VK_GOOGLE_display_timing` if the associated feature was requested
         if requested_features.contains(wgt::Features::VULKAN_GOOGLE_DISPLAY_TIMING) {
-            extensions.push(ash::google::display_timing::NAME);
+            extensions.push(google::display_timing::NAME);
         }
 
         extensions

From 354e9a998117d2e144765abdf50ea8a28125aa9e Mon Sep 17 00:00:00 2001
From: Daniel McNab <36049421+DJMcNab@users.noreply.github.com>
Date: Tue, 27 Aug 2024 11:00:55 +0100
Subject: [PATCH 12/16] Address review feedback

---
 wgpu-hal/src/vulkan/adapter.rs |  2 +-
 wgpu-hal/src/vulkan/mod.rs     | 10 +++++++---
 wgpu-types/src/lib.rs          |  7 +++++--
 3 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/wgpu-hal/src/vulkan/adapter.rs b/wgpu-hal/src/vulkan/adapter.rs
index d7db62364f..edeeca5e91 100644
--- a/wgpu-hal/src/vulkan/adapter.rs
+++ b/wgpu-hal/src/vulkan/adapter.rs
@@ -1009,7 +1009,7 @@ impl PhysicalDeviceProperties {
             extensions.push(khr::shader_atomic_int64::NAME);
         }
 
-        // Require `VK_GOOGLE_display_timing` if the associated feature was requested
+        // Require VK_GOOGLE_display_timing if the associated feature was requested
         if requested_features.contains(wgt::Features::VULKAN_GOOGLE_DISPLAY_TIMING) {
             extensions.push(google::display_timing::NAME);
         }
diff --git a/wgpu-hal/src/vulkan/mod.rs b/wgpu-hal/src/vulkan/mod.rs
index e4f3b1b3d0..64979acb11 100644
--- a/wgpu-hal/src/vulkan/mod.rs
+++ b/wgpu-hal/src/vulkan/mod.rs
@@ -357,8 +357,10 @@ struct Swapchain {
     next_semaphore_index: usize,
     /// The times which will be set in the next present times.
     ///
-    /// SAFETY: This is only set if [`wgt::Features::VULKAN_GOOGLE_DISPLAY_TIMING`] is enabled, and
-    /// so the `VK_GOOGLE_display_timing` extension is present.
+    /// # SAFETY
+    ///
+    /// This must only be set if [`wgt::Features::VULKAN_GOOGLE_DISPLAY_TIMING`] is enabled, and
+    /// so the VK_GOOGLE_display_timing extension is present.
     next_present_times: Option<vk::PresentTimeGOOGLE>,
 }
 
@@ -389,12 +391,14 @@ impl Surface {
         read.as_ref().map(|it| it.raw)
     }
 
-    /// Set the present timing information which will be used for the next presentation using `VK_GOOGLE_display_timing`.
+    /// Set the present timing information which will be used for the next presentation using [VK_GOOGLE_display_timing].
     ///
     /// # Panics
     ///
     /// - If the surface hasn't been configured.
     /// - If the device doesn't [support present timing](wgt::Features::VULKAN_GOOGLE_DISPLAY_TIMING).
+    ///
+    /// [VK_GOOGLE_display_timing]: https://registry.khronos.org/vulkan/specs/1.3-extensions/man/html/VK_GOOGLE_display_timing.html
     #[track_caller]
     pub fn set_next_present_times(&self, present_timing: vk::PresentTimeGOOGLE) {
         let mut swapchain = self.swapchain.write();
diff --git a/wgpu-types/src/lib.rs b/wgpu-types/src/lib.rs
index 6fa54bbfc6..f34a32ea52 100644
--- a/wgpu-types/src/lib.rs
+++ b/wgpu-types/src/lib.rs
@@ -953,10 +953,12 @@ bitflags::bitflags! {
         /// This is a native only feature.
         const SHADER_INT64_ATOMIC_ALL_OPS = 1 << 61;
         /// Allows using the [VK_GOOGLE_display_timing] Vulkan extension.
+        ///
         /// This is used for frame pacing to reduce latency, and is generally only available on Android.
         ///
-        /// This feature does not have a `wgpu`-level API, and must be accessed via `wgpu-hal`,
-        /// through various `as_hal` functions.
+        /// This feature does not have a `wgpu`-level API, and so users of wgpu wishing
+        /// to use this functionality must access it using various `as_hal` functions,
+        /// primarily [`Surface::as_hal`], to then use.
         ///
         /// Supported platforms:
         /// - Vulkan (with [VK_GOOGLE_display_timing])
@@ -964,6 +966,7 @@ bitflags::bitflags! {
         /// This is a native only feature.
         ///
         /// [VK_GOOGLE_display_timing]: https://registry.khronos.org/vulkan/specs/1.3-extensions/man/html/VK_GOOGLE_display_timing.html
+        /// [`Surface::as_hal`]: https://docs.rs/wgpu/latest/wgpu/struct.Surface.html#method.as_hal
         const VULKAN_GOOGLE_DISPLAY_TIMING = 1 << 62;
     }
 }

From 374b2591b8c82324968377b6df55dd1c2dc417fd Mon Sep 17 00:00:00 2001
From: Daniel McNab <36049421+DJMcNab@users.noreply.github.com>
Date: Tue, 27 Aug 2024 11:03:31 +0100
Subject: [PATCH 13/16] Fix flow of sentence and follow intra-doc-link

---
 wgpu-hal/src/vulkan/mod.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/wgpu-hal/src/vulkan/mod.rs b/wgpu-hal/src/vulkan/mod.rs
index 64979acb11..7ce3b34ab4 100644
--- a/wgpu-hal/src/vulkan/mod.rs
+++ b/wgpu-hal/src/vulkan/mod.rs
@@ -355,7 +355,7 @@ struct Swapchain {
     /// index as the image index, but we need to specify the semaphore as an argument
     /// to the acquire_next_image function which is what tells us which image to use.
     next_semaphore_index: usize,
-    /// The times which will be set in the next present times.
+    /// The present timing information which will be set in the next call to [`present`](crate::Queue::present).
     ///
     /// # SAFETY
     ///

From 7a3d7597f5c54678003016a01238002710bc8d19 Mon Sep 17 00:00:00 2001
From: Daniel McNab <36049421+DJMcNab@users.noreply.github.com>
Date: Tue, 27 Aug 2024 11:08:18 +0100
Subject: [PATCH 14/16] Add more docs to `set_next_present_time`, and rename

---
 wgpu-hal/src/vulkan/mod.rs | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/wgpu-hal/src/vulkan/mod.rs b/wgpu-hal/src/vulkan/mod.rs
index 7ce3b34ab4..b2c95c9f23 100644
--- a/wgpu-hal/src/vulkan/mod.rs
+++ b/wgpu-hal/src/vulkan/mod.rs
@@ -391,7 +391,15 @@ impl Surface {
         read.as_ref().map(|it| it.raw)
     }
 
-    /// Set the present timing information which will be used for the next presentation using [VK_GOOGLE_display_timing].
+    /// Set the present timing information which will be used for the next [presentation](crate::Queue::present) of this surface,
+    /// using [VK_GOOGLE_display_timing].
+    ///
+    /// This can be used to give an id to presentations, for future use of `VkPastPresentationTimingGOOGLE`.
+    /// Note that `wgpu-hal` does *not* provide a way to use that API - you should manually access this through `ash`.
+    ///
+    /// This can also be used to add a "not before" timestamp to the presentation.
+    ///
+    /// The exact semantics of the fields are also documented in the [specification](https://registry.khronos.org/vulkan/specs/1.3-extensions/man/html/VkPresentTimeGOOGLE.html) for the extension.
     ///
     /// # Panics
     ///
@@ -400,7 +408,7 @@ impl Surface {
     ///
     /// [VK_GOOGLE_display_timing]: https://registry.khronos.org/vulkan/specs/1.3-extensions/man/html/VK_GOOGLE_display_timing.html
     #[track_caller]
-    pub fn set_next_present_times(&self, present_timing: vk::PresentTimeGOOGLE) {
+    pub fn set_next_present_time(&self, present_timing: vk::PresentTimeGOOGLE) {
         let mut swapchain = self.swapchain.write();
         let swapchain = swapchain
             .as_mut()

From 53b6826163e4e4531b34adc28f7127d534cb444b Mon Sep 17 00:00:00 2001
From: Daniel McNab <36049421+DJMcNab@users.noreply.github.com>
Date: Tue, 27 Aug 2024 11:09:10 +0100
Subject: [PATCH 15/16] Also rename `next_present_times`

---
 wgpu-hal/src/vulkan/device.rs | 2 +-
 wgpu-hal/src/vulkan/mod.rs    | 6 +++---
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/wgpu-hal/src/vulkan/device.rs b/wgpu-hal/src/vulkan/device.rs
index 9ba50fc46b..6c9ddfe807 100644
--- a/wgpu-hal/src/vulkan/device.rs
+++ b/wgpu-hal/src/vulkan/device.rs
@@ -642,7 +642,7 @@ impl super::Device {
             view_formats: wgt_view_formats,
             surface_semaphores,
             next_semaphore_index: 0,
-            next_present_times: None,
+            next_present_time: None,
         })
     }
 
diff --git a/wgpu-hal/src/vulkan/mod.rs b/wgpu-hal/src/vulkan/mod.rs
index b2c95c9f23..1d287464f3 100644
--- a/wgpu-hal/src/vulkan/mod.rs
+++ b/wgpu-hal/src/vulkan/mod.rs
@@ -361,7 +361,7 @@ struct Swapchain {
     ///
     /// This must only be set if [`wgt::Features::VULKAN_GOOGLE_DISPLAY_TIMING`] is enabled, and
     /// so the VK_GOOGLE_display_timing extension is present.
-    next_present_times: Option<vk::PresentTimeGOOGLE>,
+    next_present_time: Option<vk::PresentTimeGOOGLE>,
 }
 
 impl Swapchain {
@@ -415,7 +415,7 @@ impl Surface {
             .expect("Surface should have been configured");
         let features = wgt::Features::VULKAN_GOOGLE_DISPLAY_TIMING;
         if swapchain.device.features.contains(features) {
-            swapchain.next_present_times = Some(present_timing);
+            swapchain.next_present_time = Some(present_timing);
         } else {
             // Ideally we'd use something like `device.required_features` here, but that's in `wgpu-core`, which we are a dependency of
             panic!("Tried to set display timing properties without the corresponding feature ({features:?}) enabled.");
@@ -1208,7 +1208,7 @@ impl crate::Queue for Queue {
 
         let mut display_timing;
         let present_times;
-        let vk_info = if let Some(present_time) = ssc.next_present_times.take() {
+        let vk_info = if let Some(present_time) = ssc.next_present_time.take() {
             debug_assert!(
                 ssc.device
                     .features

From e99a2167bfc1d6f6bb24908e04192e2dbcf1fff1 Mon Sep 17 00:00:00 2001
From: Daniel McNab <36049421+DJMcNab@users.noreply.github.com>
Date: Tue, 27 Aug 2024 11:11:23 +0100
Subject: [PATCH 16/16] Apply suggestions from code review

Co-authored-by: Marijn Suijten <marijns95@gmail.com>
---
 wgpu-hal/src/vulkan/mod.rs | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/wgpu-hal/src/vulkan/mod.rs b/wgpu-hal/src/vulkan/mod.rs
index 1d287464f3..9e57f77d03 100644
--- a/wgpu-hal/src/vulkan/mod.rs
+++ b/wgpu-hal/src/vulkan/mod.rs
@@ -355,9 +355,9 @@ struct Swapchain {
     /// index as the image index, but we need to specify the semaphore as an argument
     /// to the acquire_next_image function which is what tells us which image to use.
     next_semaphore_index: usize,
-    /// The present timing information which will be set in the next call to [`present`](crate::Queue::present).
+    /// The present timing information which will be set in the next call to [`present()`](crate::Queue::present()).
     ///
-    /// # SAFETY
+    /// # Safety
     ///
     /// This must only be set if [`wgt::Features::VULKAN_GOOGLE_DISPLAY_TIMING`] is enabled, and
     /// so the VK_GOOGLE_display_timing extension is present.
@@ -1215,9 +1215,8 @@ impl crate::Queue for Queue {
                     .contains(wgt::Features::VULKAN_GOOGLE_DISPLAY_TIMING),
                 "`next_present_times` should only be set if `VULKAN_GOOGLE_DISPLAY_TIMING` is enabled"
             );
-            display_timing = vk::PresentTimesInfoGOOGLE::default();
             present_times = [present_time];
-            display_timing = display_timing.times(&present_times);
+            display_timing = vk::PresentTimesInfoGOOGLE::default().times(&present_times);
             // SAFETY: We know that VK_GOOGLE_display_timing is present because of the safety contract on `next_present_times`.
             vk_info.push_next(&mut display_timing)
         } else {