From 506ab93dadd5f8a410ddbad9ab7970fe1bd7b2a3 Mon Sep 17 00:00:00 2001
From: Dominik Thalhammer <dominik@thalhammer.it>
Date: Wed, 5 Jan 2022 23:44:33 +0100
Subject: [PATCH] Backend Vulkan: Make descriptor set optional

---
 backends/imgui_impl_vulkan.cpp | 33 +++++++++++++++++++++++++++++++--
 1 file changed, 31 insertions(+), 2 deletions(-)

diff --git a/backends/imgui_impl_vulkan.cpp b/backends/imgui_impl_vulkan.cpp
index c9de32567a06..d251a8b064b5 100644
--- a/backends/imgui_impl_vulkan.cpp
+++ b/backends/imgui_impl_vulkan.cpp
@@ -106,6 +106,7 @@ struct ImGui_ImplVulkan_Data
     uint32_t                    Subpass;
     VkShaderModule              ShaderModuleVert;
     VkShaderModule              ShaderModuleFrag;
+    VkDescriptorPool            DescriptorPool;
 
     // Font data
     VkSampler                   FontSampler;
@@ -969,11 +970,39 @@ bool ImGui_ImplVulkan_CreateDeviceObjects()
         check_vk_result(err);
     }
 
+    if (v->DescriptorPool == VK_NULL_HANDLE)
+    {
+        // This is taken from the examples, but probably way oversized.
+        // We should try to size them based on what we actually need.
+        VkDescriptorPoolSize pool_sizes[] = {
+			{VK_DESCRIPTOR_TYPE_SAMPLER, 1000},
+			{VK_DESCRIPTOR_TYPE_COMBINED_IMAGE_SAMPLER, 1000},
+			{VK_DESCRIPTOR_TYPE_SAMPLED_IMAGE, 1000},
+			{VK_DESCRIPTOR_TYPE_STORAGE_IMAGE, 1000},
+			{VK_DESCRIPTOR_TYPE_UNIFORM_TEXEL_BUFFER, 1000},
+			{VK_DESCRIPTOR_TYPE_STORAGE_TEXEL_BUFFER, 1000},
+			{VK_DESCRIPTOR_TYPE_UNIFORM_BUFFER, 1000},
+			{VK_DESCRIPTOR_TYPE_STORAGE_BUFFER, 1000},
+			{VK_DESCRIPTOR_TYPE_UNIFORM_BUFFER_DYNAMIC, 1000},
+			{VK_DESCRIPTOR_TYPE_STORAGE_BUFFER_DYNAMIC, 1000},
+			{VK_DESCRIPTOR_TYPE_INPUT_ATTACHMENT, 1000}};
+
+		VkDescriptorPoolCreateInfo pool_info = {};
+		pool_info.sType = VK_STRUCTURE_TYPE_DESCRIPTOR_POOL_CREATE_INFO;
+		pool_info.flags = VK_DESCRIPTOR_POOL_CREATE_FREE_DESCRIPTOR_SET_BIT;
+		pool_info.maxSets = 1000 * IM_ARRAYSIZE(pool_sizes);
+		pool_info.poolSizeCount = IM_ARRAYSIZE(pool_sizes);
+		pool_info.pPoolSizes = pool_sizes;
+
+		err = vkCreateDescriptorPool(v->Device, &pool_info, v->Allocator, &bd->DescriptorPool);
+        check_vk_result(err);
+    }
+
     // Create Descriptor Set:
     {
         VkDescriptorSetAllocateInfo alloc_info = {};
         alloc_info.sType = VK_STRUCTURE_TYPE_DESCRIPTOR_SET_ALLOCATE_INFO;
-        alloc_info.descriptorPool = v->DescriptorPool;
+        alloc_info.descriptorPool = v->DescriptorPool ? v->DescriptorPool : bd->DescriptorPool;
         alloc_info.descriptorSetCount = 1;
         alloc_info.pSetLayouts = &bd->DescriptorSetLayout;
         err = vkAllocateDescriptorSets(v->Device, &alloc_info, &bd->DescriptorSet);
@@ -1035,6 +1064,7 @@ void    ImGui_ImplVulkan_DestroyDeviceObjects()
     if (bd->DescriptorSetLayout)  { vkDestroyDescriptorSetLayout(v->Device, bd->DescriptorSetLayout, v->Allocator); bd->DescriptorSetLayout = VK_NULL_HANDLE; }
     if (bd->PipelineLayout)       { vkDestroyPipelineLayout(v->Device, bd->PipelineLayout, v->Allocator); bd->PipelineLayout = VK_NULL_HANDLE; }
     if (bd->Pipeline)             { vkDestroyPipeline(v->Device, bd->Pipeline, v->Allocator); bd->Pipeline = VK_NULL_HANDLE; }
+    if (bd->DescriptorPool)       { vkDestroyDescriptorPool(v->Device, bd->DescriptorPool, v->Allocator); bd->DescriptorPool = VK_NULL_HANDLE; }
 }
 
 bool    ImGui_ImplVulkan_LoadFunctions(PFN_vkVoidFunction(*loader_func)(const char* function_name, void* user_data), void* user_data)
@@ -1076,7 +1106,6 @@ bool    ImGui_ImplVulkan_Init(ImGui_ImplVulkan_InitInfo* info, VkRenderPass rend
     IM_ASSERT(info->PhysicalDevice != VK_NULL_HANDLE);
     IM_ASSERT(info->Device != VK_NULL_HANDLE);
     IM_ASSERT(info->Queue != VK_NULL_HANDLE);
-    IM_ASSERT(info->DescriptorPool != VK_NULL_HANDLE);
     IM_ASSERT(info->MinImageCount >= 2);
     IM_ASSERT(info->ImageCount >= info->MinImageCount);
     IM_ASSERT(render_pass != VK_NULL_HANDLE);