Issue with ImGui_ImplMetal_Shutdown - Crashes inside ImGui_ImplMetal_DestroyFontsTexture

[werewolf2188]

Version/Branch of Dear ImGui:

docking

Back-ends:

imgui_impl_metal.mm

Compiler, OS:

Xcode

Full config/build information:

No response

Details:

Crash inside ImGui_ImplMetal_DestroyFontsTexture:

While using ImGui with metal, I noticed that it was crashing during the shutdown. That's because, inside ImGui_ImplMetal_Shutdown, line 160, the code io.BackendRendererUserData = nullptr; is making the function ImGui_ImplMetal_GetBackendData to return nullptr, and thus, all subsequent functions (to destroy objects and fonts) are going to crash.

THERE IS already a function to clean the io.BackendRendererUserData and it's called ImGui_ImplMetal_DestroyBackendData

I can make a PR if needed, but this is going to crash for whoever uses it.

Screenshots/Video:

No response

Minimal, Complete and Verifiable Example code:

void ImGui_ImplMetal_Shutdown()
{
    ImGui_ImplMetal_Data* bd = ImGui_ImplMetal_GetBackendData();
    IM_ASSERT(bd != nullptr && "No renderer backend to shutdown, or already shutdown?");
    ImGui_ImplMetal_ShutdownPlatformInterface();

    ImGuiIO& io = ImGui::GetIO();
    io.BackendRendererName = nullptr;
//    io.BackendRendererUserData = nullptr; // <-- this is going to crash whatever function calls ImGui_ImplMetal_GetBackendData later.
    io.BackendFlags &= ~(ImGuiBackendFlags_RendererHasVtxOffset | ImGuiBackendFlags_RendererHasViewports);
    ImGui_ImplMetal_DestroyDeviceObjects();
    ImGui_ImplMetal_DestroyBackendData();
}

[ocornut]

Hello,
This is not how the function looks on latest:

void ImGui_ImplMetal_Shutdown()
{
    ImGui_ImplMetal_Data* bd = ImGui_ImplMetal_GetBackendData();
    IM_ASSERT(bd != nullptr && "No renderer backend to shutdown, or already shutdown?");
    ImGui_ImplMetal_ShutdownPlatformInterface();
    ImGui_ImplMetal_DestroyDeviceObjects();
    ImGui_ImplMetal_DestroyBackendData();

    ImGuiIO& io = ImGui::GetIO();
    io.BackendRendererName = nullptr;
    io.BackendRendererUserData = nullptr;
    io.BackendFlags &= ~(ImGuiBackendFlags_RendererHasVtxOffset | ImGuiBackendFlags_RendererHasViewports);
}

This was fixed by 70cca1e in April 2023 so I assume you are using an old version?

[werewolf2188]

@ocornut Yeah, I haven't updated for a while, and I'm also using a fork. Thank you for letting me know.