ImGui中Vulkan的窗口渲染

VkSurfaceKHR surface;
glfwCreateWindowSurface(g_Instance, window, g_Allocator, &surface);

const VkFormat requestSurfaceImageFormat[] = { VK_FORMAT_B8G8R8A8_UNORM, VK_FORMAT_R8G8B8A8_UNORM, VK_FORMAT_B8G8R8_UNORM, VK_FORMAT_R8G8B8_UNORM };
const VkColorSpaceKHR requestSurfaceColorSpace = VK_COLORSPACE_SRGB_NONLINEAR_KHR;
wd->SurfaceFormat = ImGui_ImplVulkanH_SelectSurfaceFormat(g_PhysicalDevice, wd->Surface, requestSurfaceImageFormat, (size_t)IM_ARRAYSIZE(requestSurfaceImageFormat), requestSurfaceColorSpace);

#ifdef IMGUI_UNLIMITED_FRAME_RATE
    VkPresentModeKHR present_modes[] = { VK_PRESENT_MODE_MAILBOX_KHR, VK_PRESENT_MODE_IMMEDIATE_KHR, VK_PRESENT_MODE_FIFO_KHR };
#else
    VkPresentModeKHR present_modes[] = { VK_PRESENT_MODE_FIFO_KHR };
#endif
    wd->PresentMode = ImGui_ImplVulkanH_SelectPresentMode(g_PhysicalDevice, wd->Surface, &present_modes[0], IM_ARRAYSIZE(present_modes));

// attachment
VkAttachmentDescription attachment = {};
attachment.format = wd->SurfaceFormat.format;
attachment.samples = VK_SAMPLE_COUNT_1_BIT;
attachment.loadOp = wd->ClearEnable ? VK_ATTACHMENT_LOAD_OP_CLEAR : VK_ATTACHMENT_LOAD_OP_DONT_CARE;
attachment.storeOp = VK_ATTACHMENT_STORE_OP_STORE;
attachment.stencilLoadOp = VK_ATTACHMENT_LOAD_OP_DONT_CARE;
attachment.stencilStoreOp = VK_ATTACHMENT_STORE_OP_DONT_CARE;
attachment.initialLayout = VK_IMAGE_LAYOUT_UNDEFINED;
attachment.finalLayout = VK_IMAGE_LAYOUT_PRESENT_SRC_KHR;
// attachment reference
VkAttachmentReference color_attachment = {};
color_attachment.attachment = 0;
color_attachment.layout = VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL;
// 一个Render Pass由若干Subpass组成
VkSubpassDescription subpass = {};
// bind point有compute和graphics两种，compute是计算管线，graphics是图形渲染管线
subpass.pipelineBindPoint = VK_PIPELINE_BIND_POINT_GRAPHICS;
subpass.colorAttachmentCount = 1;
subpass.pColorAttachments = &color_attachment;
// subpass依赖
VkSubpassDependency dependency = {};
// VK_SUBPASS_EXTERNAL表示了该subpass之前的subpass
dependency.srcSubpass = VK_SUBPASS_EXTERNAL;
// 0表示当前subpass吧大概
dependency.dstSubpass = 0;
dependency.srcStageMask = VK_PIPELINE_STAGE_COLOR_ATTACHMENT_OUTPUT_BIT;
dependency.dstStageMask = VK_PIPELINE_STAGE_COLOR_ATTACHMENT_OUTPUT_BIT;
dependency.srcAccessMask = 0;
dependency.dstAccessMask = VK_ACCESS_COLOR_ATTACHMENT_WRITE_BIT;
// Render Pass Create Info
VkRenderPassCreateInfo info = {};
info.sType = VK_STRUCTURE_TYPE_RENDER_PASS_CREATE_INFO;
info.attachmentCount = 1;
info.pAttachments = &attachment;
info.subpassCount = 1;
info.pSubpasses = &subpass;
info.dependencyCount = 1;
info.pDependencies = &dependency;
err = vkCreateRenderPass(device, &info, allocator, &wd->RenderPass);
check_vk_result(err);

VkImageViewCreateInfo info = {};
info.sType = VK_STRUCTURE_TYPE_IMAGE_VIEW_CREATE_INFO;
info.viewType = VK_IMAGE_VIEW_TYPE_2D;
info.format = wd->SurfaceFormat.format;
info.components.r = VK_COMPONENT_SWIZZLE_R;
info.components.g = VK_COMPONENT_SWIZZLE_G;
info.components.b = VK_COMPONENT_SWIZZLE_B;
info.components.a = VK_COMPONENT_SWIZZLE_A;
VkImageSubresourceRange image_range = { VK_IMAGE_ASPECT_COLOR_BIT, 0, 1, 0, 1 };
info.subresourceRange = image_range;
for (uint32_t i = 0; i < wd->ImageCount; i++)
{
    ImGui_ImplVulkanH_Frame* fd = &wd->Frames[i];
    info.image = fd->Backbuffer;
    err = vkCreateImageView(device, &info, allocator, &fd->BackbufferView);
    check_vk_result(err);
}

VkImageView attachment[1];
VkFramebufferCreateInfo info = {};
info.sType = VK_STRUCTURE_TYPE_FRAMEBUFFER_CREATE_INFO;
info.renderPass = wd->RenderPass;
info.attachmentCount = 1;
info.pAttachments = attachment;
info.width = wd->Width;
info.height = wd->Height;
info.layers = 1;
// 每个ImageView需要一个FrameBuffer
for (uint32_t i = 0; i < wd->ImageCount; i++)
{
    ImGui_ImplVulkanH_Frame* fd = &wd->Frames[i];
    attachment[0] = fd->BackbufferView;
    err = vkCreateFramebuffer(device, &info, allocator, &fd->Framebuffer);
    check_vk_result(err);
}

VkShaderModuleCreateInfo vert_info = {};
vert_info.sType = VK_STRUCTURE_TYPE_SHADER_MODULE_CREATE_INFO;
vert_info.codeSize = sizeof(__glsl_shader_vert_spv);
vert_info.pCode = (uint32_t*)__glsl_shader_vert_spv;
VkResult err = vkCreateShaderModule(device, &vert_info, allocator, &bd->ShaderModuleVert);
check_vk_result(err);

VkShaderModuleCreateInfo frag_info = {};
frag_info.sType = VK_STRUCTURE_TYPE_SHADER_MODULE_CREATE_INFO;
frag_info.codeSize = sizeof(__glsl_shader_frag_spv);
frag_info.pCode = (uint32_t*)__glsl_shader_frag_spv;
VkResult err = vkCreateShaderModule(device, &frag_info, allocator, &bd->ShaderModuleFrag);
check_vk_result(err);

#version 450 core
layout(location = 0) in vec2 aPos;
layout(location = 1) in vec2 aUV;
layout(location = 2) in vec4 aColor;
layout(push_constant) uniform uPushConstant { vec2 uScale; vec2 uTranslate; } pc;

out gl_PerVertex { vec4 gl_Position; };
layout(location = 0) out struct { vec4 Color; vec2 UV; } Out;

void main()
{
    Out.Color = aColor;
    Out.UV = aUV;
    gl_Position = vec4(aPos * pc.uScale + pc.uTranslate, 0, 1);
}

#version 450 core
layout(location = 0) out vec4 fColor;
layout(set=0, binding=0) uniform sampler2D sTexture;
layout(location = 0) in struct { vec4 Color; vec2 UV; } In;
void main()
{
    fColor = In.Color * texture(sTexture, In.UV.st);
}

VkPipelineShaderStageCreateInfo stage[2] = {};
stage[0].sType = VK_STRUCTURE_TYPE_PIPELINE_SHADER_STAGE_CREATE_INFO;
stage[0].stage = VK_SHADER_STAGE_VERTEX_BIT;
stage[0].module = bd->ShaderModuleVert;
stage[0].pName = "main";

stage[1].sType = VK_STRUCTURE_TYPE_PIPELINE_SHADER_STAGE_CREATE_INFO;
stage[1].stage = VK_SHADER_STAGE_FRAGMENT_BIT;
stage[1].module = bd->ShaderModuleFrag;
stage[1].pName = "main";

VkPipelineShaderStageCreateInfo stage[2] = {};
stage[0].sType = VK_STRUCTURE_TYPE_PIPELINE_SHADER_STAGE_CREATE_INFO;
stage[0].stage = VK_SHADER_STAGE_VERTEX_BIT;
stage[0].module = bd->ShaderModuleVert;
stage[0].pName = "main";
stage[1].sType = VK_STRUCTURE_TYPE_PIPELINE_SHADER_STAGE_CREATE_INFO;
stage[1].stage = VK_SHADER_STAGE_FRAGMENT_BIT;
stage[1].module = bd->ShaderModuleFrag;
stage[1].pName = "main";

VkPipelineVertexInputStateCreateInfo vertex_info = {};
vertex_info.sType = VK_STRUCTURE_TYPE_PIPELINE_VERTEX_INPUT_STATE_CREATE_INFO;
vertex_info.vertexBindingDescriptionCount = 1;
vertex_info.pVertexBindingDescriptions = binding_desc;
vertex_info.vertexAttributeDescriptionCount = 3;
// 用到了上文的Vertex Input Description
vertex_info.pVertexAttributeDescriptions = attribute_desc;

VkPipelineInputAssemblyStateCreateInfo ia_info = {};
ia_info.sType = VK_STRUCTURE_TYPE_PIPELINE_INPUT_ASSEMBLY_STATE_CREATE_INFO;
ia_info.topology = VK_PRIMITIVE_TOPOLOGY_TRIANGLE_LIST;

VkPipelineViewportStateCreateInfo viewport_info = {};
viewport_info.sType = VK_STRUCTURE_TYPE_PIPELINE_VIEWPORT_STATE_CREATE_INFO;
viewport_info.viewportCount = 1;
// scissor是对视口进行裁剪
viewport_info.scissorCount = 1;

VkPipelineRasterizationStateCreateInfo raster_info = {};
raster_info.sType = VK_STRUCTURE_TYPE_PIPELINE_RASTERIZATION_STATE_CREATE_INFO;
raster_info.polygonMode = VK_POLYGON_MODE_FILL;
// 可以进行正面或背面剔除(由此可见 剔除是在rasterization进行的，shaderlab只是进行了一些配置)
raster_info.cullMode = VK_CULL_MODE_NONE;
// frontFace表示 识别为正面的三角形的点的顺序 这里表示当组成三角面的三个点顺序是顺时针时为正面
raster_info.frontFace = VK_FRONT_FACE_COUNTER_CLOCKWISE;
raster_info.lineWidth = 1.0f;

VkPipelineMultisampleStateCreateInfo ms_info = {};
ms_info.sType = VK_STRUCTURE_TYPE_PIPELINE_MULTISAMPLE_STATE_CREATE_INFO;
ms_info.rasterizationSamples = (MSAASamples != 0) ? MSAASamples : VK_SAMPLE_COUNT_1_BIT;

VkPipelineColorBlendAttachmentState color_attachment[1] = {};
color_attachment[0].blendEnable = VK_TRUE;
color_attachment[0].srcColorBlendFactor = VK_BLEND_FACTOR_SRC_ALPHA;
color_attachment[0].dstColorBlendFactor = VK_BLEND_FACTOR_ONE_MINUS_SRC_ALPHA;
color_attachment[0].colorBlendOp = VK_BLEND_OP_ADD;
color_attachment[0].srcAlphaBlendFactor = VK_BLEND_FACTOR_ONE;
color_attachment[0].dstAlphaBlendFactor = VK_BLEND_FACTOR_ONE_MINUS_SRC_ALPHA;
color_attachment[0].alphaBlendOp = VK_BLEND_OP_ADD;
// writemask指明要输出哪些通道
color_attachment[0].colorWriteMask = VK_COLOR_COMPONENT_R_BIT | VK_COLOR_COMPONENT_G_BIT | VK_COLOR_COMPONENT_B_BIT | VK_COLOR_COMPONENT_A_BIT;

VkPipelineDepthStencilStateCreateInfo depth_info = {};
depth_info.sType = VK_STRUCTURE_TYPE_PIPELINE_DEPTH_STENCIL_STATE_CREATE_INFO;

VkPipelineColorBlendStateCreateInfo blend_info = {};
blend_info.sType = VK_STRUCTURE_TYPE_PIPELINE_COLOR_BLEND_STATE_CREATE_INFO;
blend_info.attachmentCount = 1;
blend_info.pAttachments = color_attachment;

typedef enum VkDynamicState {
    VK_DYNAMIC_STATE_VIEWPORT = 0,
    VK_DYNAMIC_STATE_SCISSOR = 1,
    VK_DYNAMIC_STATE_LINE_WIDTH = 2,
    VK_DYNAMIC_STATE_DEPTH_BIAS = 3,
    VK_DYNAMIC_STATE_BLEND_CONSTANTS = 4,
    VK_DYNAMIC_STATE_DEPTH_BOUNDS = 5,
    VK_DYNAMIC_STATE_STENCIL_COMPARE_MASK = 6,
    VK_DYNAMIC_STATE_STENCIL_WRITE_MASK = 7,
    VK_DYNAMIC_STATE_STENCIL_REFERENCE = 8,
    VK_DYNAMIC_STATE_VIEWPORT_W_SCALING_NV = 1000087000,
    VK_DYNAMIC_STATE_DISCARD_RECTANGLE_EXT = 1000099000,
    VK_DYNAMIC_STATE_SAMPLE_LOCATIONS_EXT = 1000143000,
    VK_DYNAMIC_STATE_RAY_TRACING_PIPELINE_STACK_SIZE_KHR = 1000347000,
    VK_DYNAMIC_STATE_VIEWPORT_SHADING_RATE_PALETTE_NV = 1000164004,
    VK_DYNAMIC_STATE_VIEWPORT_COARSE_SAMPLE_ORDER_NV = 1000164006,
    VK_DYNAMIC_STATE_EXCLUSIVE_SCISSOR_NV = 1000205001,
    VK_DYNAMIC_STATE_FRAGMENT_SHADING_RATE_KHR = 1000226000,
    VK_DYNAMIC_STATE_LINE_STIPPLE_EXT = 1000259000,
    VK_DYNAMIC_STATE_CULL_MODE_EXT = 1000267000,
    VK_DYNAMIC_STATE_FRONT_FACE_EXT = 1000267001,
    VK_DYNAMIC_STATE_PRIMITIVE_TOPOLOGY_EXT = 1000267002,
    VK_DYNAMIC_STATE_VIEWPORT_WITH_COUNT_EXT = 1000267003,
    VK_DYNAMIC_STATE_SCISSOR_WITH_COUNT_EXT = 1000267004,
    VK_DYNAMIC_STATE_VERTEX_INPUT_BINDING_STRIDE_EXT = 1000267005,
    VK_DYNAMIC_STATE_DEPTH_TEST_ENABLE_EXT = 1000267006,
    VK_DYNAMIC_STATE_DEPTH_WRITE_ENABLE_EXT = 1000267007,
    VK_DYNAMIC_STATE_DEPTH_COMPARE_OP_EXT = 1000267008,
    VK_DYNAMIC_STATE_DEPTH_BOUNDS_TEST_ENABLE_EXT = 1000267009,
    VK_DYNAMIC_STATE_STENCIL_TEST_ENABLE_EXT = 1000267010,
    VK_DYNAMIC_STATE_STENCIL_OP_EXT = 1000267011,
    VK_DYNAMIC_STATE_VERTEX_INPUT_EXT = 1000352000,
    VK_DYNAMIC_STATE_PATCH_CONTROL_POINTS_EXT = 1000377000,
    VK_DYNAMIC_STATE_RASTERIZER_DISCARD_ENABLE_EXT = 1000377001,
    VK_DYNAMIC_STATE_DEPTH_BIAS_ENABLE_EXT = 1000377002,
    VK_DYNAMIC_STATE_LOGIC_OP_EXT = 1000377003,
    VK_DYNAMIC_STATE_PRIMITIVE_RESTART_ENABLE_EXT = 1000377004,
    VK_DYNAMIC_STATE_COLOR_WRITE_ENABLE_EXT = 1000381000,
    VK_DYNAMIC_STATE_MAX_ENUM = 0x7FFFFFFF
} VkDynamicState;

VkDynamicState dynamic_states[2] = { VK_DYNAMIC_STATE_VIEWPORT, VK_DYNAMIC_STATE_SCISSOR };
VkPipelineDynamicStateCreateInfo dynamic_state = {};
dynamic_state.sType = VK_STRUCTURE_TYPE_PIPELINE_DYNAMIC_STATE_CREATE_INFO;
dynamic_state.dynamicStateCount = (uint32_t)IM_ARRAYSIZE(dynamic_states);
dynamic_state.pDynamicStates = dynamic_states;

VkGraphicsPipelineCreateInfo info = {};
info.sType = VK_STRUCTURE_TYPE_GRAPHICS_PIPELINE_CREATE_INFO;
info.flags = bd->PipelineCreateFlags;
info.stageCount = 2;
info.pStages = stage;
info.pVertexInputState = &vertex_info;
info.pInputAssemblyState = &ia_info;
info.pViewportState = &viewport_info;
info.pRasterizationState = &raster_info;
info.pMultisampleState = &ms_info;
info.pDepthStencilState = &depth_info;
info.pColorBlendState = &blend_info;
info.pDynamicState = &dynamic_state;
info.layout = bd->PipelineLayout;
info.renderPass = renderPass;
info.subpass = subpass;
VkResult err = vkCreateGraphicsPipelines(device, pipelineCache, 1, &info, allocator, pipeline);

vkAcquireNextImageKHR(g_Device, wd->Swapchain, UINT64_MAX, image_acquired_semaphore, VK_NULL_HANDLE, &wd->FrameIndex);

ImGui_ImplVulkanH_Frame* fd = &wd->Frames[wd->FrameIndex];
{
    err = vkWaitForFences(g_Device, 1, &fd->Fence, VK_TRUE, UINT64_MAX);    // wait indefinitely instead of periodically checking
    check_vk_result(err);

    err = vkResetFences(g_Device, 1, &fd->Fence);
    check_vk_result(err);
}

err = vkResetCommandPool(g_Device, fd->CommandPool, 0);
check_vk_result(err);
VkCommandBufferBeginInfo info = {};
info.sType = VK_STRUCTURE_TYPE_COMMAND_BUFFER_BEGIN_INFO;
info.flags |= VK_COMMAND_BUFFER_USAGE_ONE_TIME_SUBMIT_BIT;
err = vkBeginCommandBuffer(fd->CommandBuffer, &info);
check_vk_result(err);

 // Create or resize the vertex/index buffers
 size_t vertex_size = draw_data->TotalVtxCount * sizeof(ImDrawVert);
 size_t index_size = draw_data->TotalIdxCount * sizeof(ImDrawIdx);
 if (rb->VertexBuffer == VK_NULL_HANDLE || rb->VertexBufferSize < vertex_size)
     CreateOrResizeBuffer(rb->VertexBuffer, rb->VertexBufferMemory, rb->VertexBufferSize, vertex_size, VK_BUFFER_USAGE_VERTEX_BUFFER_BIT);
 if (rb->IndexBuffer == VK_NULL_HANDLE || rb->IndexBufferSize < index_size)
     CreateOrResizeBuffer(rb->IndexBuffer, rb->IndexBufferMemory, rb->IndexBufferSize, index_size, VK_BUFFER_USAGE_INDEX_BUFFER_BIT);

 static void CreateOrResizeBuffer(VkBuffer& buffer, VkDeviceMemory& buffer_memory, VkDeviceSize& p_buffer_size, size_t new_size, VkBufferUsageFlagBits usage)
 {
     ImGui_ImplVulkan_Data* bd = ImGui_ImplVulkan_GetBackendData();
     ImGui_ImplVulkan_InitInfo* v = &bd->VulkanInitInfo;
     VkResult err;
     if (buffer != VK_NULL_HANDLE)
         vkDestroyBuffer(v->Device, buffer, v->Allocator);
     if (buffer_memory != VK_NULL_HANDLE)
         vkFreeMemory(v->Device, buffer_memory, v->Allocator);
 
     // ceil，奇怪的是，明明在创建字体Atlas的贴图时并没有考虑对齐的问题
     // 试了一下，其实不对齐也没有问题
     VkDeviceSize vertex_buffer_size_aligned = ((new_size - 1) / bd->BufferMemoryAlignment + 1) * bd->BufferMemoryAlignment;
     VkBufferCreateInfo buffer_info = {};
     buffer_info.sType = VK_STRUCTURE_TYPE_BUFFER_CREATE_INFO;
     buffer_info.size = vertex_buffer_size_aligned;
     // usage用来表明是Vertex还是Index之类
     buffer_info.usage = usage;
     buffer_info.sharingMode = VK_SHARING_MODE_EXCLUSIVE;
     // 创建Buffer
     err = vkCreateBuffer(v->Device, &buffer_info, v->Allocator, &buffer);
     check_vk_result(err);
 
     VkMemoryRequirements req;
     vkGetBufferMemoryRequirements(v->Device, buffer, &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);
     // 为Buffer分配内存
     err = vkAllocateMemory(v->Device, &alloc_info, v->Allocator, &buffer_memory);
     check_vk_result(err);
     // 将Buffer和内存绑定
     err = vkBindBufferMemory(v->Device, buffer, buffer_memory, 0);
     check_vk_result(err);
     p_buffer_size = req.size;
 }

 // Upload vertex/index data into a single contiguous GPU buffer
 ImDrawVert* vtx_dst = nullptr;
 ImDrawIdx* idx_dst = nullptr;
 VkResult err = vkMapMemory(v->Device, rb->VertexBufferMemory, 0, rb->VertexBufferSize, 0, (void**)(&vtx_dst));
 check_vk_result(err);
 err = vkMapMemory(v->Device, rb->IndexBufferMemory, 0, rb->IndexBufferSize, 0, (void**)(&idx_dst));
 check_vk_result(err);
 // 将主机内存中的相关数据拷贝到Buffer
 for (int n = 0; n < draw_data->CmdListsCount; n++)
 {
     const ImDrawList* cmd_list = draw_data->CmdLists[n];
     memcpy(vtx_dst, cmd_list->VtxBuffer.Data, cmd_list->VtxBuffer.Size * sizeof(ImDrawVert));
     memcpy(idx_dst, cmd_list->IdxBuffer.Data, cmd_list->IdxBuffer.Size * sizeof(ImDrawIdx));
     vtx_dst += cmd_list->VtxBuffer.Size;
     idx_dst += cmd_list->IdxBuffer.Size;
 }
 // 将Memory刷到GPU(大概) 有一个疑问，就是这个刷入的过程并不是cmd的，不知道会不会有同步问题
 VkMappedMemoryRange range[2] = {};
 range[0].sType = VK_STRUCTURE_TYPE_MAPPED_MEMORY_RANGE;
 range[0].memory = rb->VertexBufferMemory;
 range[0].size = VK_WHOLE_SIZE;
 range[1].sType = VK_STRUCTURE_TYPE_MAPPED_MEMORY_RANGE;
 range[1].memory = rb->IndexBufferMemory;
 range[1].size = VK_WHOLE_SIZE;
 err = vkFlushMappedMemoryRanges(v->Device, 2, range);
 check_vk_result(err);
 vkUnmapMemory(v->Device, rb->VertexBufferMemory);
 vkUnmapMemory(v->Device, rb->IndexBufferMemory);

ImGui_ImplVulkan_RenderDrawData(draw_data, fd->CommandBuffer);

// Typically, 1 command = 1 GPU draw call (unless command is a callback)
// - VtxOffset: When 'io.BackendFlags & ImGuiBackendFlags_RendererHasVtxOffset' is enabled,
//   this fields allow us to render meshes larger than 64K vertices while keeping 16-bit indices.
//   Backends made for <1.71. will typically ignore the VtxOffset fields.
// - The ClipRect/TextureId/VtxOffset fields must be contiguous as we memcmp() them together (this is asserted for).
struct ImDrawCmd
{
    ImVec4          ClipRect;           // 4*4  // Clipping rectangle (x1, y1, x2, y2). Subtract ImDrawData->DisplayPos to get clipping rectangle in "viewport" coordinates
    ImTextureID     TextureId;          // 4-8  // User-provided texture ID. Set by user in ImfontAtlas::SetTexID() for fonts or passed to Image*() functions. Ignore if never using images or multiple fonts atlas.
    unsigned int    VtxOffset;          // 4    // Start offset in vertex buffer. ImGuiBackendFlags_RendererHasVtxOffset: always 0, otherwise may be >0 to support meshes larger than 64K vertices with 16-bit indices.
    unsigned int    IdxOffset;          // 4    // Start offset in index buffer.
    unsigned int    ElemCount;          // 4    // Number of indices (multiple of 3) to be rendered as triangles. Vertices are stored in the callee ImDrawList's vtx_buffer[] array, indices in idx_buffer[].
    ImDrawCallback  UserCallback;       // 4-8  // If != NULL, call the function instead of rendering the vertices. clip_rect and texture_id will be set normally.
    void*           UserCallbackData;   // 4-8  // The draw callback code can access this.

    ImDrawCmd() { memset(this, 0, sizeof(*this)); } // Also ensure our padding fields are zeroed

    // Since 1.83: returns ImTextureID associated with this draw call. Warning: DO NOT assume this is always same as 'TextureId' (we will change this function for an upcoming feature)
    inline ImTextureID GetTexID() const { return TextureId; }
};

// Project scissor/clipping rectangles into framebuffer space
ImVec2 clip_min((pcmd->ClipRect.x - clip_off.x) * clip_scale.x, (pcmd->ClipRect.y - clip_off.y) * clip_scale.y);
ImVec2 clip_max((pcmd->ClipRect.z - clip_off.x) * clip_scale.x, (pcmd->ClipRect.w - clip_off.y) * clip_scale.y);

// Clamp to viewport as vkCmdSetScissor() won't accept values that are off bounds
if (clip_min.x < 0.0f) { clip_min.x = 0.0f; }
if (clip_min.y < 0.0f) { clip_min.y = 0.0f; }
if (clip_max.x > fb_width) { clip_max.x = (float)fb_width; }
if (clip_max.y > fb_height) { clip_max.y = (float)fb_height; }
if (clip_max.x <= clip_min.x || clip_max.y <= clip_min.y)
    continue;

// Bind DescriptorSet with font or user texture
VkDescriptorSet desc_set[1] = { (VkDescriptorSet)pcmd->TextureId };
if (sizeof(ImTextureID) < sizeof(ImU64))
{
    // We don't support texture switches if ImTextureID hasn't been redefined to be 64-bit. Do a flaky check that other textures haven't been used.
    IM_ASSERT(pcmd->TextureId == (ImTextureID)bd->FontDescriptorSet);
    desc_set[0] = bd->FontDescriptorSet;
}
vkCmdBindDescriptorSets(command_buffer, VK_PIPELINE_BIND_POINT_GRAPHICS, bd->PipelineLayout, 0, 1, desc_set, 0, nullptr);

vkCmdDrawIndexed(command_buffer, pcmd->ElemCount, 1, pcmd->IdxOffset + global_idx_offset, pcmd->VtxOffset + global_vtx_offset, 0);

// Install GLFW callbacks for secondary viewports
glfwSetWindowFocusCallback(vd->Window, ImGui_ImplGlfw_WindowFocusCallback);
glfwSetCursorEnterCallback(vd->Window, ImGui_ImplGlfw_CursorEnterCallback);
glfwSetCursorPosCallback(vd->Window, ImGui_ImplGlfw_CursorPosCallback);
glfwSetMouseButtonCallback(vd->Window, ImGui_ImplGlfw_MouseButtonCallback);
glfwSetScrollCallback(vd->Window, ImGui_ImplGlfw_ScrollCallback);
glfwSetKeyCallback(vd->Window, ImGui_ImplGlfw_KeyCallback);
glfwSetCharCallback(vd->Window, ImGui_ImplGlfw_CharCallback);
glfwSetWindowCloseCallback(vd->Window, ImGui_ImplGlfw_WindowCloseCallback);
glfwSetWindowPosCallback(vd->Window, ImGui_ImplGlfw_WindowPosCallback);
glfwSetWindowSizeCallback(vd->Window, ImGui_ImplGlfw_WindowSizeCallback);

if (is_new_platform_window)
{
// On startup ensure new platform window don't steal focus (give it a few frames, as nested contents may lead to viewport being created a few frames late)
if (g.FrameCount < 3)
viewport->Flags |= ImGuiViewportFlags_NoFocusOnAppearing;

// Show window
g.PlatformIO.Platform_ShowWindow(viewport);

// Even without focus, we assume the window becomes front-most.
// This is useful for our platform z-order heuristic when io.MouseHoveredViewport is not available.
if (viewport->LastFrontMostStampCount != g.ViewportFrontMostStampCount)
viewport->LastFrontMostStampCount = ++g.ViewportFrontMostStampCount;
}

// Update our implicit z-order knowledge of platform windows, which is used when the backend cannot provide io.MouseHoveredViewport.
// When setting Platform_GetWindowFocus, it is expected that the platform backend can handle calls without crashing if it doesn't have data stored.
// FIXME-VIEWPORT: We should use this information to also set dear imgui-side focus, allowing us to handle os-level alt+tab.
if (g.PlatformIO.Platform_GetWindowFocus != NULL)
{
    ImGuiViewportP* focused_viewport = NULL;
    for (int n = 0; n < g.Viewports.Size && focused_viewport == NULL; n++)
    {
        ImGuiViewportP* viewport = g.Viewports[n];
        if (viewport->PlatformWindowCreated)
            if (g.PlatformIO.Platform_GetWindowFocus(viewport))
                focused_viewport = viewport;
    }

    // Store a tag so we can infer z-order easily from all our windows
    // We compare PlatformLastFocusedViewportId so newly created viewports with _NoFocusOnAppearing flag
    // will keep the front most stamp instead of losing it back to their parent viewport.
    if (focused_viewport && g.PlatformLastFocusedViewportId != focused_viewport->ID)
    {
        if (focused_viewport->LastFrontMostStampCount != g.ViewportFrontMostStampCount)
            focused_viewport->LastFrontMostStampCount = ++g.ViewportFrontMostStampCount;
        g.PlatformLastFocusedViewportId = focused_viewport->ID;
    }
}

err = vkAcquireNextImageKHR(v->Device, wd->Swapchain, UINT64_MAX, fsd->ImageAcquiredSemaphore, VK_NULL_HANDLE, &wd->FrameIndex);
check_vk_result(err);
fd = &wd->Frames[wd->FrameIndex];

err = vkWaitForFences(v->Device, 1, &fd->Fence, VK_TRUE, 100);
if (err == VK_SUCCESS) break;
if (err == VK_TIMEOUT) continue;
check_vk_result(err);

err = vkResetCommandPool(v->Device, fd->CommandPool, 0);
check_vk_result(err);
VkCommandBufferBeginInfo info = {};
info.sType = VK_STRUCTURE_TYPE_COMMAND_BUFFER_BEGIN_INFO;
info.flags |= VK_COMMAND_BUFFER_USAGE_ONE_TIME_SUBMIT_BIT;
err = vkBeginCommandBuffer(fd->CommandBuffer, &info);
check_vk_result(err);