Windows DX12: imgui assert: Backend does not support ImGuiBackendFlags_RendererHasTextures

[footballhead]

Running dx12_sample_04_cube produces an Imgui assert.

Building and run

cmake . -Bbuild -GNinja -DCMAKE_BUILD_TYPE=Debug -DCMAKE_POLICY_VERSION_MINIMUM=3.5
cmake --build build --target dx12_sample_04_cube
build\bin\dx12_sample_04_cube.exe

assert

Logging started
KNOB: extra-assets-path : ()
KNOB: config-json-path : ()
KNOB: deterministic : (false)
KNOB: enable-metrics : (false)
KNOB: frame-count : (0)
KNOB: gpu : (0)
KNOB: headless : (false)
KNOB: list-gpus : (false)
KNOB: metrics-filename : (report_@.json)
KNOB: overwrite-metrics-file : (false)
KNOB: resolution : (0, 0)
KNOB: run-time-ms : (0)
KNOB: screenshot-frame-number : (-1)
KNOB: screenshot-path : (screenshot_frame_#.ppm)
KNOB: stats-frame-window : (-1)
KNOB: use-software-renderer : (false)
KNOB: shading-rate-mode : ()
CPU info for 13th Gen Intel(R) Core(TM) i7-13800H
   vendor             : GenuineIntel
   microarchitecture  : Unknown X86 Architecture
   L1 cache size      : 0
   L2 cache size      : 0
   L3 cache size      : 0
   L1 cache line size : 0
   L2 cache line size : 0
   L3 cache line size : 0
   SSE                : 1
   SSE2               : 1
   SSE3               : 1
   SSSE3              : 1
   SSE4_1             : 1
   SSE4_2             : 1
   SSE4A              : 1
   AVX                : 1
   AVX2               : 1
Creating application graphics device using Intel(R) Iris(R) Xe Graphics
   requested graphics queue count : 1
   requested compute  queue count : 0
   requested transfer queue count : 0
Created device: Intel(R) Iris(R) Xe Graphics
Creating application swapchain
   resolution  : 1280x720
   image count : 2
Swapchain created
   resolution  : 1280x720
   image count : 2
Loaded shader from "C:\\Users\\hitchens\\Desktop\\git\\bigwheels\\build\\bin\\..\\assets\\basic/shaders\\dxil\\VertexColors.vs.dxil"
Loaded shader from "C:\\Users\\hitchens\\Desktop\\git\\bigwheels\\build\\bin\\..\\assets\\basic/shaders\\dxil\\VertexColors.ps.dxil"
Setup() finished: 0.005297 seconds.
[00001] [imgui-error] (current settings: Assert=1, Log=1, Tooltip=1)
[00001] [imgui-error] In window 'NULL': Backend does not support ImGuiBackendFlags_RendererHasTextures, and font atlas is not built! Update backend OR make sure you called ImGui_ImplXXXX_NewFrame() function for renderer backend, which should call io.Fonts->GetTexDataAsRGBA32() / GetTexDataAsAlpha8().
Assertion failed: (atlas->TexIsBuilt) && "Backend does not support ImGuiBackendFlags_RendererHasTextures, and font atlas is not built! Update backend OR make sure you called ImGui_ImplXXXX_NewFrame() function for renderer backend, which should call io.Fonts->GetTexDataAsRGBA32() / GetTexDataAsAlpha8().", file C:\Users\hitchens\Desktop\git\bigwheels\third_party\imgui\imgui_draw.cpp, line 2751

NOTE That Imgui was recently updated

[footballhead]

bisected to baac9c5 (as suspected). We could always revert if this is blocking someone. Otherwise, I'll just try to fix it

[footballhead]

As far as I can tell, 1.92.0 changed how fonts are rendered, which requires the backend to actually implement. https://github.com/ocornut/imgui/releases/tag/v1.92.0 Trying to figure out what's up with the DX12 backend, or if we can try to use the old behavior

[footballhead]

We use the "Legacy initialization API" ImGui_ImplDX12_Init() that was "Obsoleted in 1.91.5".

 #ifndef IMGUI_DISABLE_OBSOLETE_FUNCTIONS
// Legacy initialization API Obsoleted in 1.91.5
// font_srv_cpu_desc_handle and font_srv_gpu_desc_handle are handles to a single SRV descriptor to use for the internal font texture, they must be in 'srv_descriptor_heap'
bool ImGui_ImplDX12_Init(ID3D12Device* device, int num_frames_in_flight, DXGI_FORMAT rtv_format, ID3D12DescriptorHeap* srv_descriptor_heap, D3D12_CPU_DESCRIPTOR_HANDLE font_srv_cpu_desc_handle, D3D12_GPU_DESCRIPTOR_HANDLE font_srv_gpu_desc_handle)

The new API added in 1.91.6 https://github.com/ocornut/imgui/releases/tag/v1.91.6

bool ImGui_ImplDX12_Init(ImGui_ImplDX12_InitInfo* init_info)

[footballhead]

IMGUI_DISABLE_OBSOLETE_FUNCTIONS is part of imconfig.h. When defined, it fails to compile (as expected).

The comments for imconfig.h have some nuggets:

// A) You may edit imconfig.h (and not overwrite it when updating Dear ImGui, or maintain a patch/rebased branch with your modifications to it)
// B) or '#define IMGUI_USER_CONFIG "my_imgui_config.h"' in your project and then add directives in your own file without touching this template.

// ...

//---- Don't define obsolete functions/enums/behaviors. Consider enabling from time to time after updating to clean your code of obsolete function/names.
//#define IMGUI_DISABLE_OBSOLETE_FUNCTIONS

Since imgui is a submodule, we may want to define our own IMGUI_USER_CONFIG which has IMGUI_DISABLE_OBSOLETE_FUNCTIONS enabled

[footballhead]

The InitInfo struct:

// Initialization data, for ImGui_ImplDX12_Init()
struct ImGui_ImplDX12_InitInfo
{
    ID3D12Device*               Device;
    ID3D12CommandQueue*         CommandQueue;       // Command queue used for queuing texture uploads.
    int                         NumFramesInFlight;
    DXGI_FORMAT                 RTVFormat;          // RenderTarget format.
    DXGI_FORMAT                 DSVFormat;          // DepthStencilView format.
    void*                       UserData;

    // Allocating SRV descriptors for textures is up to the application, so we provide callbacks.
    // (current version of the backend will only allocate one descriptor, from 1.92 the backend will need to allocate more)
    ID3D12DescriptorHeap*       SrvDescriptorHeap;
    void                        (*SrvDescriptorAllocFn)(ImGui_ImplDX12_InitInfo* info, D3D12_CPU_DESCRIPTOR_HANDLE* out_cpu_desc_handle, D3D12_GPU_DESCRIPTOR_HANDLE* out_gpu_desc_handle);
    void                        (*SrvDescriptorFreeFn)(ImGui_ImplDX12_InitInfo* info, D3D12_CPU_DESCRIPTOR_HANDLE cpu_desc_handle, D3D12_GPU_DESCRIPTOR_HANDLE gpu_desc_handle);
#ifndef IMGUI_DISABLE_OBSOLETE_FUNCTIONS
    D3D12_CPU_DESCRIPTOR_HANDLE LegacySingleSrvCpuDescriptor; // To facilitate transition from single descriptor to allocator callback, you may use those.
    D3D12_GPU_DESCRIPTOR_HANDLE LegacySingleSrvGpuDescriptor;
#endif

    ImGui_ImplDX12_InitInfo()   { memset((void*)this, 0, sizeof(*this)); }
};

(NB. RTV is short for Render Target View, DSV is short for Depth Stencil View, and SRV is short for Shader Resource View. THese are types of DirectX12 descriptors.)

Compared to the old function signature:

bool ImGui_ImplDX12_Init(
  ID3D12Device* device,
  int num_frames_in_flight,
  DXGI_FORMAT rtv_format,
  ID3D12DescriptorHeap* srv_descriptor_heap,
  D3D12_CPU_DESCRIPTOR_HANDLE font_srv_cpu_desc_handle,
  D3D12_GPU_DESCRIPTOR_HANDLE font_srv_gpu_desc_handle
)

So missing

• CommandQueue
• DSVFormat
• SrvDescriptorAllocFn
• SrvDescriptorFreeFn

The example (example_win32_directx12/main.cpp) uses

    ImGui_ImplDX12_InitInfo init_info = {};
    init_info.Device = g_pd3dDevice;
    init_info.CommandQueue = g_pd3dCommandQueue;
    init_info.NumFramesInFlight = APP_NUM_FRAMES_IN_FLIGHT;
    init_info.RTVFormat = DXGI_FORMAT_R8G8B8A8_UNORM;
    init_info.DSVFormat = DXGI_FORMAT_UNKNOWN;
    // Allocating SRV descriptors (for textures) is up to the application, so we provide callbacks.
    // (current version of the backend will only allocate one descriptor, future versions will need to allocate more)
    init_info.SrvDescriptorHeap = g_pd3dSrvDescHeap;
    init_info.SrvDescriptorAllocFn = [](ImGui_ImplDX12_InitInfo*, D3D12_CPU_DESCRIPTOR_HANDLE* out_cpu_handle, D3D12_GPU_DESCRIPTOR_HANDLE* out_gpu_handle) { return g_pd3dSrvDescHeapAlloc.Alloc(out_cpu_handle, out_gpu_handle); };
    init_info.SrvDescriptorFreeFn = [](ImGui_ImplDX12_InitInfo*, D3D12_CPU_DESCRIPTOR_HANDLE cpu_handle, D3D12_GPU_DESCRIPTOR_HANDLE gpu_handle)            { return g_pd3dSrvDescHeapAlloc.Free(cpu_handle, gpu_handle); };
    ImGui_ImplDX12_Init(&init_info);