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VkImageCreateInfo info = {};
info.sType = VK_STRUCTURE_TYPE_IMAGE_CREATE_INFO;
info.imageType = VK_IMAGE_TYPE_2D;
info.format = VK_FORMAT_R8G8B8A8_UNORM;
info.extent.width = width;
info.extent.height = height;
info.extent.depth = 1;
info.mipLevels = 1;
info.arrayLayers = 1;
info.samples = VK_SAMPLE_COUNT_1_BIT;
// 说想要直接访问图像Texel就需要设置为OPTIMAL
info.tiling = VK_IMAGE_TILING_OPTIMAL;
info.usage = VK_IMAGE_USAGE_SAMPLED_BIT | VK_IMAGE_USAGE_TRANSFER_DST_BIT;
info.sharingMode = VK_SHARING_MODE_EXCLUSIVE;
info.initialLayout = VK_IMAGE_LAYOUT_UNDEFINED;
err = vkCreateImage(v->Device, &info, v->Allocator, &bd->FontImage);
check_vk_result(err);
VkMemoryRequirements req;
vkGetImageMemoryRequirements(v->Device, bd->FontImage, &req);
VkMemoryAllocateInfo alloc_info = {};
alloc_info.sType = VK_STRUCTURE_TYPE_MEMORY_ALLOCATE_INFO;
alloc_info.allocationSize = req.size;
alloc_info.memoryTypeIndex = ImGui_ImplVulkan_MemoryType(VK_MEMORY_PROPERTY_DEVICE_LOCAL_BIT, req.memoryTypeBits);
err = vkAllocateMemory(v->Device, &alloc_info, v->Allocator, &bd->FontMemory);
check_vk_result(err);
// 在分配内存之后还要和Image进行绑定
err = vkBindImageMemory(v->Device, bd->FontImage, bd->FontMemory, 0);
check_vk_result(err);

VkImageViewCreateInfo info = {};
info.sType = VK_STRUCTURE_TYPE_IMAGE_VIEW_CREATE_INFO;
info.image = bd->FontImage;
info.viewType = VK_IMAGE_VIEW_TYPE_2D;
info.format = VK_FORMAT_R8G8B8A8_UNORM;
info.subresourceRange.aspectMask = VK_IMAGE_ASPECT_COLOR_BIT;
info.subresourceRange.levelCount = 1;
info.subresourceRange.layerCount = 1;
err = vkCreateImageView(v->Device, &info, v->Allocator, &bd->FontView);
check_vk_result(err);

// Bilinear sampling is required by default. Set 'io.Fonts->Flags |= ImFontAtlasFlags_NoBakedLines' or 'style.AntiAliasedLinesUseTex = false' to allow point/nearest sampling.
VkSamplerCreateInfo info = {};
info.sType = VK_STRUCTURE_TYPE_SAMPLER_CREATE_INFO;
info.magFilter = VK_FILTER_LINEAR;
info.minFilter = VK_FILTER_LINEAR;
info.mipmapMode = VK_SAMPLER_MIPMAP_MODE_LINEAR;
info.addressModeU = VK_SAMPLER_ADDRESS_MODE_REPEAT;
info.addressModeV = VK_SAMPLER_ADDRESS_MODE_REPEAT;
info.addressModeW = VK_SAMPLER_ADDRESS_MODE_REPEAT;
info.minLod = -1000;
info.maxLod = 1000;
info.maxAnisotropy = 1.0f;
VkResult err = vkCreateSampler(device, &info, allocator, &bd->FontSampler);

VkSampler sampler[1] = { bd->FontSampler };
VkDescriptorSetLayoutBinding binding[1] = {};
binding[0].descriptorType = VK_DESCRIPTOR_TYPE_COMBINED_IMAGE_SAMPLER;
binding[0].descriptorCount = 1;
binding[0].stageFlags = VK_SHADER_STAGE_FRAGMENT_BIT;
binding[0].pImmutableSamplers = sampler;
VkDescriptorSetLayoutCreateInfo info = {};
info.sType = VK_STRUCTURE_TYPE_DESCRIPTOR_SET_LAYOUT_CREATE_INFO;
info.bindingCount = 1;
info.pBindings = binding;
VkResult err = vkCreateDescriptorSetLayout(device, &info, allocator, &bd->DescriptorSetLayout);

bd->FontDescriptorSet = (VkDescriptorSet)ImGui_ImplVulkan_AddTexture(bd->FontSampler, bd->FontView, VK_IMAGE_LAYOUT_SHADER_READ_ONLY_OPTIMAL);

VkDescriptorSet ImGui_ImplVulkan_AddTexture(VkSampler sampler, VkImageView image_view, VkImageLayout image_layout)
{
    ImGui_ImplVulkan_Data* bd = ImGui_ImplVulkan_GetBackendData();
    ImGui_ImplVulkan_InitInfo* v = &bd->VulkanInitInfo;

    // Create Descriptor Set:
    // 先给Descriptor Set申请内存大概
    VkDescriptorSet descriptor_set;
    {
        VkDescriptorSetAllocateInfo alloc_info = {};
        alloc_info.sType = VK_STRUCTURE_TYPE_DESCRIPTOR_SET_ALLOCATE_INFO;
        alloc_info.descriptorPool = v->DescriptorPool;
        alloc_info.descriptorSetCount = 1;
        alloc_info.pSetLayouts = &bd->DescriptorSetLayout;
        VkResult err = vkAllocateDescriptorSets(v->Device, &alloc_info, &descriptor_set);
        check_vk_result(err);
    }

    // Update the Descriptor Set:
    // 然后更新Image的Descriptor Set
    // 要创建多少纹理就需要创建多少个Descriptor Set
    {
        VkDescriptorImageInfo desc_image[1] = {};
        desc_image[0].sampler = sampler;
        desc_image[0].imageView = image_view;
        desc_image[0].imageLayout = image_layout;
        VkWriteDescriptorSet write_desc[1] = {};
        write_desc[0].sType = VK_STRUCTURE_TYPE_WRITE_DESCRIPTOR_SET;
        write_desc[0].dstSet = descriptor_set;
        write_desc[0].descriptorCount = 1;
        write_desc[0].descriptorType = VK_DESCRIPTOR_TYPE_COMBINED_IMAGE_SAMPLER;
        write_desc[0].pImageInfo = desc_image;
        vkUpdateDescriptorSets(v->Device, 1, write_desc, 0, nullptr);
    }
    return descriptor_set;
}

VkBufferCreateInfo buffer_info = {};
buffer_info.sType = VK_STRUCTURE_TYPE_BUFFER_CREATE_INFO;
// buffer info里的size属性用的是直接用图像大小深度计算的大小，看起来这里的size并不需要考虑内存对齐问题
buffer_info.size = upload_size;
buffer_info.usage = VK_BUFFER_USAGE_TRANSFER_SRC_BIT;
buffer_info.sharingMode = VK_SHARING_MODE_EXCLUSIVE;
err = vkCreateBuffer(v->Device, &buffer_info, v->Allocator, &bd->UploadBuffer);
check_vk_result(err);
VkMemoryRequirements req;
vkGetBufferMemoryRequirements(v->Device, bd->UploadBuffer, &req);
bd->BufferMemoryAlignment = (bd->BufferMemoryAlignment > req.alignment) ? bd->BufferMemoryAlignment : req.alignment;
VkMemoryAllocateInfo alloc_info = {};
alloc_info.sType = VK_STRUCTURE_TYPE_MEMORY_ALLOCATE_INFO;
alloc_info.allocationSize = req.size;
alloc_info.memoryTypeIndex = ImGui_ImplVulkan_MemoryType(VK_MEMORY_PROPERTY_HOST_VISIBLE_BIT, req.memoryTypeBits);
// 实际分配内存
err = vkAllocateMemory(v->Device, &alloc_info, v->Allocator, &bd->UploadBufferMemory);
check_vk_result(err);
// 将buffer和内存绑定
err = vkBindBufferMemory(v->Device, bd->UploadBuffer, bd->UploadBufferMemory, 0);
check_vk_result(err);

char* map = nullptr;
err = vkMapMemory(v->Device, bd->UploadBufferMemory, 0, upload_size, 0, (void**)(&map));
check_vk_result(err);
memcpy(map, pixels, upload_size);
VkMappedMemoryRange range[1] = {};
range[0].sType = VK_STRUCTURE_TYPE_MAPPED_MEMORY_RANGE;
range[0].memory = bd->UploadBufferMemory;
range[0].size = upload_size;
err = vkFlushMappedMemoryRanges(v->Device, 1, range);
check_vk_result(err);
// 之后不需要对这个内存进行修改，因此unmap
vkUnmapMemory(v->Device, bd->UploadBufferMemory);

// 奇怪的是 居然没有设置srcAccessMask
VkImageMemoryBarrier copy_barrier[1] = {};
copy_barrier[0].sType = VK_STRUCTURE_TYPE_IMAGE_MEMORY_BARRIER;
copy_barrier[0].dstAccessMask = VK_ACCESS_TRANSFER_WRITE_BIT;
copy_barrier[0].oldLayout = VK_IMAGE_LAYOUT_UNDEFINED;
copy_barrier[0].newLayout = VK_IMAGE_LAYOUT_TRANSFER_DST_OPTIMAL;
// 当队列族不变时都设置为VK_QUEUE_FAMILY_IGNORED
copy_barrier[0].srcQueueFamilyIndex = VK_QUEUE_FAMILY_IGNORED;
copy_barrier[0].dstQueueFamilyIndex = VK_QUEUE_FAMILY_IGNORED;
copy_barrier[0].image = bd->FontImage;
copy_barrier[0].subresourceRange.aspectMask = VK_IMAGE_ASPECT_COLOR_BIT;
copy_barrier[0].subresourceRange.levelCount = 1;
copy_barrier[0].subresourceRange.layerCount = 1;
// 需要注意，置barrier是通过cmd进行的，说明这也是在command buffer里的一个命令
// 这里的srcStage是Host，dstStage是Transition，是从host拷贝到Image的过程大概
vkCmdPipelineBarrier(command_buffer, VK_PIPELINE_STAGE_HOST_BIT, VK_PIPELINE_STAGE_TRANSFER_BIT, 0, 0, nullptr, 0, nullptr, 1, copy_barrier);

// 看起来在GPU里 Buffer里的数据需要拷贝到Image里面
VkBufferImageCopy region = {};
region.imageSubresource.aspectMask = VK_IMAGE_ASPECT_COLOR_BIT;
region.imageSubresource.layerCount = 1;
region.imageExtent.width = width;
region.imageExtent.height = height;
region.imageExtent.depth = 1;
vkCmdCopyBufferToImage(command_buffer, bd->UploadBuffer, bd->FontImage, VK_IMAGE_LAYOUT_TRANSFER_DST_OPTIMAL, 1, &region);

// 在拷贝之后设置barrier，在执行完拷贝指令并将缓存刷到最新之后，再进行下一个Stage
VkImageMemoryBarrier use_barrier[1] = {};
use_barrier[0].sType = VK_STRUCTURE_TYPE_IMAGE_MEMORY_BARRIER;
use_barrier[0].srcAccessMask = VK_ACCESS_TRANSFER_WRITE_BIT;
use_barrier[0].dstAccessMask = VK_ACCESS_SHADER_READ_BIT;
use_barrier[0].oldLayout = VK_IMAGE_LAYOUT_TRANSFER_DST_OPTIMAL;
use_barrier[0].newLayout = VK_IMAGE_LAYOUT_SHADER_READ_ONLY_OPTIMAL;
use_barrier[0].srcQueueFamilyIndex = VK_QUEUE_FAMILY_IGNORED;
use_barrier[0].dstQueueFamilyIndex = VK_QUEUE_FAMILY_IGNORED;
use_barrier[0].image = bd->FontImage;
use_barrier[0].subresourceRange.aspectMask = VK_IMAGE_ASPECT_COLOR_BIT;
use_barrier[0].subresourceRange.levelCount = 1;
use_barrier[0].subresourceRange.layerCount = 1;
vkCmdPipelineBarrier(command_buffer, VK_PIPELINE_STAGE_TRANSFER_BIT, VK_PIPELINE_STAGE_FRAGMENT_SHADER_BIT, 0, 0, nullptr, 0, nullptr, 1, use_barrier);