perf(window): drop dead present-mode queries from swapchain recreate (#45)

CreateSwapchain unconditionally used VK_PRESENT_MODE_FIFO_KHR, but still
ran two vkGetPhysicalDeviceSurfacePresentModesKHR calls plus a heap-allocated
std::vector to enumerate present modes that were never consulted. Delete
them and assign the constant directly.

compositeAlpha is a surface property that does not change across swapchain
recreation, so select it once at construction instead of re-deriving it
(with another heap-allocated vector) on every resize configure. The
vkQueueWaitIdle before recreation is left intact as required.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

implementations/Crafter.Graphics-Window.cpp

@@ -405,6 +405,26 @@ Window::Window(std::uint32_t width, std::uint32_t height) : width(width), height
 	colorFormat = selectedFormat.format;
 	colorSpace = selectedFormat.colorSpace;
 
+	// Select a supported composite alpha format (not all devices support alpha
+	// opaque). This is a surface property, so pick it once here rather than on
+	// every CreateSwapchain. Simply select the first available.
+	{
+		VkSurfaceCapabilitiesKHR surfCaps;
+		Device::CheckVkResult(vkGetPhysicalDeviceSurfaceCapabilitiesKHR(Device::physDevice, vulkanSurface, &surfCaps));
+		const VkCompositeAlphaFlagBitsKHR compositeAlphaFlags[] = {
+			VK_COMPOSITE_ALPHA_OPAQUE_BIT_KHR,
+			VK_COMPOSITE_ALPHA_PRE_MULTIPLIED_BIT_KHR,
+			VK_COMPOSITE_ALPHA_POST_MULTIPLIED_BIT_KHR,
+			VK_COMPOSITE_ALPHA_INHERIT_BIT_KHR,
+		};
+		for (const VkCompositeAlphaFlagBitsKHR compositeAlphaFlag : compositeAlphaFlags) {
+			if (surfCaps.supportedCompositeAlpha & compositeAlphaFlag) {
+				compositeAlpha = compositeAlphaFlag;
+				break;
+			}
+		}
+	}
+
     CreateSwapchain();
 
     VkCommandBufferAllocateInfo cmdBufAllocateInfo {};
@@ -896,18 +916,6 @@ void Window::CreateSwapchain()
 	}
 
 
-	// Select a present mode for the swapchain
-	uint32_t presentModeCount;
-	Device::CheckVkResult(vkGetPhysicalDeviceSurfacePresentModesKHR(Device::physDevice, vulkanSurface, &presentModeCount, NULL));
-	assert(presentModeCount > 0);
-
-	std::vector<VkPresentModeKHR> presentModes(presentModeCount);
-	Device::CheckVkResult(vkGetPhysicalDeviceSurfacePresentModesKHR(Device::physDevice, vulkanSurface, &presentModeCount, presentModes.data()));
-
-	// The VK_PRESENT_MODE_FIFO_KHR mode must always be present as per spec
-	// This mode waits for the vertical blank ("v-sync")
-	VkPresentModeKHR swapchainPresentMode = VK_PRESENT_MODE_FIFO_KHR;
-
 	// Find the transformation of the surface
 	VkSurfaceTransformFlagsKHR preTransform;
 	if (surfCaps.supportedTransforms & VK_SURFACE_TRANSFORM_IDENTITY_BIT_KHR)
@@ -920,22 +928,6 @@ void Window::CreateSwapchain()
 		preTransform = surfCaps.currentTransform;
 	}
 
-	// Find a supported composite alpha format (not all devices support alpha opaque)
-	VkCompositeAlphaFlagBitsKHR compositeAlpha = VK_COMPOSITE_ALPHA_OPAQUE_BIT_KHR;
-	// Simply select the first composite alpha format available
-	std::vector<VkCompositeAlphaFlagBitsKHR> compositeAlphaFlags = {
-		VK_COMPOSITE_ALPHA_OPAQUE_BIT_KHR,
-		VK_COMPOSITE_ALPHA_PRE_MULTIPLIED_BIT_KHR,
-		VK_COMPOSITE_ALPHA_POST_MULTIPLIED_BIT_KHR,
-		VK_COMPOSITE_ALPHA_INHERIT_BIT_KHR,
-	};
-	for (auto& compositeAlphaFlag : compositeAlphaFlags) {
-		if (surfCaps.supportedCompositeAlpha & compositeAlphaFlag) {
-			compositeAlpha = compositeAlphaFlag;
-			break;
-		};
-	}
-
 	VkSwapchainCreateInfoKHR swapchainCI = {};
 	swapchainCI.sType = VK_STRUCTURE_TYPE_SWAPCHAIN_CREATE_INFO_KHR;
 	swapchainCI.surface = vulkanSurface;
@@ -948,7 +940,9 @@ void Window::CreateSwapchain()
 	swapchainCI.imageArrayLayers = 1;
 	swapchainCI.imageSharingMode = VK_SHARING_MODE_EXCLUSIVE;
 	swapchainCI.queueFamilyIndexCount = 0;
-	swapchainCI.presentMode = swapchainPresentMode;
+	// VK_PRESENT_MODE_FIFO_KHR ("v-sync") is guaranteed available per spec, so
+	// it is used unconditionally — no present-mode enumeration is needed.
+	swapchainCI.presentMode = VK_PRESENT_MODE_FIFO_KHR;
 	// Setting oldSwapChain to the saved handle of the previous swapchain aids in resource reuse and makes sure that we can still present already acquired images
 	swapchainCI.oldSwapchain = oldSwapchain;
 	// Setting clipped to VK_TRUE allows the implementation to discard rendering outside of the surface area

interfaces/Crafter.Graphics-Window.cppm

@@ -253,6 +253,11 @@ export namespace Crafter {
         VkSwapchainKHR swapChain = VK_NULL_HANDLE;
         VkFormat colorFormat;
         VkColorSpaceKHR colorSpace;
+        // Supported composite-alpha mode for vulkanSurface. A surface property
+        // that does not change across swapchain recreation, so it is selected
+        // once at construction rather than re-derived on every CreateSwapchain
+        // (i.e. on every resize configure).
+        VkCompositeAlphaFlagBitsKHR compositeAlpha = VK_COMPOSITE_ALPHA_OPAQUE_BIT_KHR;
         VkImage images[numFrames];
         VkImageViewCreateInfo imageViews[numFrames];
         // Tracks whether each swapchain image has been rendered (and thus