Draft Vulkan DescriptorHeap

A utility class from a personal project for managing a heap of
descriptors of a particular layout.

Allows the display graphics pipeline to be successfully created,
satisfying its descriptor layout issues.

src/core/renderer_vk/renderer_vk.cpp

@@ -1093,6 +1093,17 @@ void RendererVK::initGraphicsContext(SDL_Window* window) {
 		}
 	}
 
+	static vk::DescriptorSetLayoutBinding displayShaderLayout[] = {
+		{// Just a singular texture slot
+		 0, vk::DescriptorType::eCombinedImageSampler, 1, vk::ShaderStageFlagBits::eFragment},
+	};
+
+	if (auto createResult = Vulkan::DescriptorHeap::create(device.get(), displayShaderLayout); createResult.has_value()) {
+		displayDescriptorHeap = std::make_unique<Vulkan::DescriptorHeap>(std::move(createResult.value()));
+	} else {
+		Helpers::panic("Error creating descriptor heap\n");
+	}
+
 	auto vk_resources = cmrc::RendererVK::get_filesystem();
 	auto displayVertexShader = vk_resources.open("vulkan_display.vert.spv");
 	auto displayFragmentShader = vk_resources.open("vulkan_display.frag.spv");
@@ -1103,7 +1114,8 @@ void RendererVK::initGraphicsContext(SDL_Window* window) {
 	vk::RenderPass screenTextureRenderPass = getRenderPass(screenTextureInfo.format, {});
 
 	std::tie(displayPipeline, displayPipelineLayout) = createGraphicsPipeline(
-		device.get(), {}, {}, displayVertexShaderModule.get(), displayFragmentShaderModule.get(), {}, {}, screenTextureRenderPass
+		device.get(), {}, {{displayDescriptorHeap.get()->getDescriptorSetLayout()}}, displayVertexShaderModule.get(),
+		displayFragmentShaderModule.get(), {}, {}, screenTextureRenderPass
 	);
 }
 

src/core/renderer_vk/vk_descriptor_heap.cpp

@@ -0,0 +1,119 @@
+#include "renderer_vk/vk_descriptor_heap.hpp"
+
+#include <algorithm>
+#include <optional>
+#include <unordered_map>
+
+namespace Vulkan {
+
+	DescriptorHeap::DescriptorHeap(vk::Device device) : device(device) {}
+
+	std::optional<vk::DescriptorSet> DescriptorHeap::allocateDescriptorSet() {
+		// Find a free slot
+		const auto freeSlot = std::find(allocationMap.begin(), allocationMap.end(), false);
+
+		// If there is no free slot, return
+		if (freeSlot == allocationMap.end()) {
+			return std::nullopt;
+		}
+
+		// Mark the slot as allocated
+		*freeSlot = true;
+
+		const u16 index = static_cast<u16>(std::distance(allocationMap.begin(), freeSlot));
+
+		vk::UniqueDescriptorSet& newDescriptorSet = descriptorSets[index];
+
+		if (!newDescriptorSet) {
+			// Descriptor set doesn't exist yet. Allocate a new one
+			vk::DescriptorSetAllocateInfo allocateInfo = {};
+
+			allocateInfo.descriptorPool = descriptorPool.get();
+			allocateInfo.pSetLayouts = &descriptorSetLayout.get();
+			allocateInfo.descriptorSetCount = 1;
+
+			if (auto AllocateResult = device.allocateDescriptorSetsUnique(allocateInfo); AllocateResult.result == vk::Result::eSuccess) {
+				newDescriptorSet = std::move(AllocateResult.value[0]);
+			} else {
+				// Error allocating descriptor set
+				return std::nullopt;
+			}
+		}
+
+		return newDescriptorSet.get();
+	}
+
+	bool DescriptorHeap::freeDescriptorSet(vk::DescriptorSet Set) {
+		// Find the descriptor set
+		const auto found =
+			std::find_if(descriptorSets.begin(), descriptorSets.end(), [&Set](const auto& CurSet) -> bool { return CurSet.get() == Set; });
+
+		// If the descriptor set is not found, return
+		if (found == descriptorSets.end()) {
+			return false;
+		}
+
+		// Mark the slot as free
+		const u16 index = static_cast<u16>(std::distance(descriptorSets.begin(), found));
+
+		allocationMap[index] = false;
+
+		return true;
+	}
+
+	std::optional<DescriptorHeap> DescriptorHeap::create(
+		vk::Device device, std::span<const vk::DescriptorSetLayoutBinding> bindings, u16 descriptorHeapCount
+	) {
+		DescriptorHeap newDescriptorHeap(device);
+
+		// Create a histogram of each of the descriptor types and how many of each
+		// the pool should have
+		// Todo: maybe keep this around as a hash table to do more dynamic
+		// allocations of descriptor sets rather than allocating them all up-front
+		std::vector<vk::DescriptorPoolSize> poolSizes;
+		{
+			std::unordered_map<vk::DescriptorType, u16> descriptorTypeCounts;
+
+			for (const auto& binding : bindings) {
+				descriptorTypeCounts[binding.descriptorType] += binding.descriptorCount;
+			}
+			for (const auto& descriptorTypeCount : descriptorTypeCounts) {
+				poolSizes.push_back(vk::DescriptorPoolSize(descriptorTypeCount.first, descriptorTypeCount.second * descriptorHeapCount));
+			}
+		}
+
+		// Create descriptor pool
+		{
+			vk::DescriptorPoolCreateInfo poolInfo;
+			poolInfo.flags = vk::DescriptorPoolCreateFlagBits::eFreeDescriptorSet;
+			poolInfo.maxSets = descriptorHeapCount;
+			poolInfo.pPoolSizes = poolSizes.data();
+			poolInfo.poolSizeCount = poolSizes.size();
+			if (auto createResult = device.createDescriptorPoolUnique(poolInfo); createResult.result == vk::Result::eSuccess) {
+				newDescriptorHeap.descriptorPool = std::move(createResult.value);
+			} else {
+				return std::nullopt;
+			}
+		}
+
+		// Create descriptor set layout
+		{
+			vk::DescriptorSetLayoutCreateInfo layoutInfo;
+			layoutInfo.pBindings = bindings.data();
+			layoutInfo.bindingCount = bindings.size();
+
+			if (auto createResult = device.createDescriptorSetLayoutUnique(layoutInfo); createResult.result == vk::Result::eSuccess) {
+				newDescriptorHeap.descriptorSetLayout = std::move(createResult.value);
+			} else {
+				return std::nullopt;
+			}
+		}
+
+		newDescriptorHeap.descriptorSets.resize(descriptorHeapCount);
+		newDescriptorHeap.allocationMap.resize(descriptorHeapCount);
+
+		newDescriptorHeap.bindings.assign(bindings.begin(), bindings.end());
+
+		return {std::move(newDescriptorHeap)};
+	}
+}  // namespace Vulkan