Cannot reload fonts on DX12

[nr-jpg]

Howdy, I'm trying to do some basic DPI awareness on a DX12 app by reloading the fonts as starters. My code logic in a nutshell is to wait for the GPU to be idle if there is a pending DPI awareness change (from WM_DPICHANGED message) and then clear the fonts and reload them with the new scale

WaitForGPU();

const float dpiScale = std::max(GameWindow::GetInstance().GetDPI() / 96.0f, 1.0f);
const float fontScale = dpiScale * GlobalFontScale;

ImGui::GetIO().Fonts->ClearFonts();
ImGui::GetIO().Fonts->AddFontFromFileTTF(
    "C:\\Windows\\Fonts\\Arial.ttf",
    14.0f * fontScale,
    NULL,
    ImGui::GetIO().Fonts->GetGlyphRangesDefault());

I call the above code after the present, I use the same logic for resizing, fullscreen, etc, no issues there.

I call the same code during initialization for the initial font load and for the starting window imgui works just fine. However, attempting to move to a monitor with different DPI causes the following assert:

Assertion failed!

Program: ...\Binaries\Debug\playground.exe
File: ...\imgui-1...\imgui.cpp
Line: 10344

Expression: g.IO.Fonts->IsBuilt() && "Font Atlas not built! Make sure you called ImGui_ImplXXXX_NewFrame() function for renderer backend, which should call io.Fonts->GetTexDataAsRGBA32() / GetTexDataAsAlpha8()"

Looking at the code the assert message is misleading/wrong, new frame for DX12 does nothing if the device objects exist, so I tried adding a "ImGui_ImplDX12_InvalidateDeviceObjects()" call as well when reloading fonts. This results in another assert during the "ImGui_ImplDX12_NewFrame()" or "create device objects" call:

Assertion failed!

Program: ...\Debug\playground.exe
File: ...\im...\imgui_draw.cpp
Line: 2827

Expression: cfg.DstFont && (!cfg.DstFont->IsLoaded() || cfg.DstFont->ContainerAtlas == atlas)

Any ideas what I'm missing here?

I was looking at this post + FAQ, but did not see anything about the issues I'm having.
#3925

Using imgui-1.91.5.

[ocornut]

(I’ll try to look but FYI i am in parallel rewriting the system to facilitate more dynamic use of fonts and incremental texture updates, so hopefully there will be a much better version of this in a month or two)

[ocornut]

But FYI it should already be possible to do what you are doing, perhaps providing code would help narrowing your issue.

[nr-jpg]

Thanks for your reply, I'm still using the demo view to get it working properly, so there is not much code to provide really.

The init:

        IMGUI_CHECKVERSION();

        ImGui::CreateContext();
        Bool status = ImGui_ImplWin32_Init(GameWindow::GetInstance().GetHandle());
        Assert(status);

        D3D12_DESCRIPTOR_HEAP_TYPE heapType = D3D12_DESCRIPTOR_HEAP_TYPE_CBV_SRV_UAV;
        D3D12_CPU_DESCRIPTOR_HANDLE imGuiFontCPUHandle = GetGPUDescriptorAllocator()->AllocPersistent(heapType, 1);
        D3D12_GPU_DESCRIPTOR_HANDLE imGuiFontGPUHandle = GetGPUDescriptorAllocator()->GetGPUHandle(imGuiFontCPUHandle, heapType);

        ImGui_ImplDX12_Init(
            GetDevice(),
            Config::Graphic::MaxFramesInProgress,
            Config::Graphic::SwapChainFormat,
            GetGPUDescriptorAllocator()->GetHeap(heapType),
            imGuiFontCPUHandle,
            imGuiFontGPUHandle);

        UpdateImGuiFonts(); // contains the code from above with font reload

The update + rendering part (I've copy-pasted them together for now)

    ImGui_ImplDX12_NewFrame();
    ImGui_ImplWin32_NewFrame();
    ImGui::NewFrame();
    ImGui::ShowDemoWindow(); // Show demo window! :)

    RenderTarget* backBuffer = GetSwapChain()->GetCurrentFrameBuffer();
    context.Transition(backBuffer, D3D12_RESOURCE_STATE_RENDER_TARGET);

    auto cpuHandle = backBuffer->GetRTV().GetCPUHandle();
    context->OMSetRenderTargets(1, &cpuHandle, false, nullptr);

    ImGui::Render();
    ImGui_ImplDX12_RenderDrawData(ImGui::GetDrawData(), context.GetD3DCommandList());

[nr-jpg]

Seems like it's easily reproductible in the example_win32_directx12 project.

Inserting the following code before the NewFrame calls produces same error:

    WaitForLastSubmittedFrame();

    ImGui_ImplDX12_InvalidateDeviceObjects();

    ImGui::GetIO().Fonts->ClearFonts();
    ImGui::GetIO().Fonts->AddFontFromFileTTF(
        "C:\\Windows\\Fonts\\Arial.ttf",
        14.0f,
        NULL,
        ImGui::GetIO().Fonts->GetGlyphRangesDefault());