Add a transfer queue to VulkanoContext (#2573)

* Add a transfer queue to `VulkanoContext`

* Might as well

vulkano-util/src/context.rs

@@ -93,8 +93,7 @@ pub struct VulkanoContext {
     instance: Arc<Instance>,
     _debug_utils_messenger: Option<DebugUtilsMessenger>,
     device: Arc<Device>,
-    graphics_queue: Arc<Queue>,
+    queues: Queues,
-    compute_queue: Arc<Queue>,
     memory_allocator: Arc<StandardMemoryAllocator>,
 }
 
@@ -166,20 +165,18 @@ impl VulkanoContext {
         }
 
         // Create device
-        let (device, graphics_queue, compute_queue) = Self::create_device(
+        let (device, queues) = Self::create_device(
             physical_device,
             config.device_extensions,
             config.device_features,
         );
-
         let memory_allocator = Arc::new(StandardMemoryAllocator::new_default(device.clone()));
 
         Self {
             instance,
             _debug_utils_messenger,
             device,
-            graphics_queue,
+            queues,
-            compute_queue,
             memory_allocator,
         }
     }
@@ -190,7 +187,7 @@ impl VulkanoContext {
         physical_device: Arc<PhysicalDevice>,
         device_extensions: DeviceExtensions,
         device_features: DeviceFeatures,
-    ) -> (Arc<Device>, Arc<Queue>, Arc<Queue>) {
+    ) -> (Arc<Device>, Queues) {
         let queue_family_graphics = physical_device
             .queue_family_properties()
             .iter()
@@ -209,25 +206,37 @@ impl VulkanoContext {
                 q.queue_flags.intersects(QueueFlags::COMPUTE) && *i != queue_family_graphics
             })
             .map(|(i, _)| i);
-        let is_separate_compute_queue = queue_family_compute.is_some();
+        // Try finding a separate queue for transfer
+        let queue_family_transfer = physical_device
+            .queue_family_properties()
+            .iter()
+            .enumerate()
+            .map(|(i, q)| (i as u32, q))
+            .find(|(_i, q)| {
+                q.queue_flags.intersects(QueueFlags::TRANSFER)
+                    && !q
+                        .queue_flags
+                        .intersects(QueueFlags::GRAPHICS | QueueFlags::COMPUTE)
+            })
+            .map(|(i, _)| i);
 
-        let queue_create_infos = if let Some(queue_family_compute) = queue_family_compute {
+        let queue_create_infos: Vec<_> = [
-            vec![
+            Some(QueueCreateInfo {
-                QueueCreateInfo {
-                    queue_family_index: queue_family_graphics,
-                    ..Default::default()
-                },
-                QueueCreateInfo {
-                    queue_family_index: queue_family_compute,
-                    ..Default::default()
-                },
-            ]
-        } else {
-            vec![QueueCreateInfo {
                 queue_family_index: queue_family_graphics,
                 ..Default::default()
-            }]
+            }),
-        };
+            queue_family_compute.map(|queue_family_index| QueueCreateInfo {
+                queue_family_index,
+                ..Default::default()
+            }),
+            queue_family_transfer.map(|queue_family_index| QueueCreateInfo {
+                queue_family_index,
+                ..Default::default()
+            }),
+        ]
+        .into_iter()
+        .flatten()
+        .collect();
 
         let (device, mut queues) = {
             Device::new(
@@ -241,13 +250,24 @@ impl VulkanoContext {
             )
             .expect("failed to create device")
         };
-        let gfx_queue = queues.next().unwrap();
+
-        let compute_queue = if is_separate_compute_queue {
+        let graphics_queue = queues.next().unwrap();
-            queues.next().unwrap()
+        let compute_queue = queue_family_compute
-        } else {
+            .is_some()
-            gfx_queue.clone()
+            .then(|| queues.next().unwrap())
-        };
+            .unwrap_or(graphics_queue.clone());
-        (device, gfx_queue, compute_queue)
+        let transfer_queue = queue_family_transfer
+            .is_some()
+            .then(|| queues.next().unwrap());
+
+        (
+            device,
+            Queues {
+                graphics_queue,
+                compute_queue,
+                transfer_queue,
+            },
+        )
     }
 
     /// Returns the name of the device.
@@ -286,15 +306,22 @@ impl VulkanoContext {
     /// Returns the graphics queue.
     #[inline]
     pub fn graphics_queue(&self) -> &Arc<Queue> {
-        &self.graphics_queue
+        &self.queues.graphics_queue
     }
 
     /// Returns the compute queue.
     ///
-    /// Depending on your device, this might be the same as graphics queue.
+    /// Depending on your device, this might be the same as the graphics queue.
     #[inline]
     pub fn compute_queue(&self) -> &Arc<Queue> {
-        &self.compute_queue
+        &self.queues.compute_queue
+    }
+
+    /// Returns the transfer queue, if the device has a queue family that is dedicated for
+    /// transfers (does not support graphics or compute).
+    #[inline]
+    pub fn transfer_queue(&self) -> Option<&Arc<Queue>> {
+        self.queues.transfer_queue.as_ref()
     }
 
     /// Returns the memory allocator.
@@ -303,3 +330,9 @@ impl VulkanoContext {
         &self.memory_allocator
     }
 }
+
+struct Queues {
+    graphics_queue: Arc<Queue>,
+    compute_queue: Arc<Queue>,
+    transfer_queue: Option<Arc<Queue>>,
+}