IM_ASSERT(viewport->RendererUserData == NULL && viewport->PlatformUserData == NULL) in ImGui_ImplWin32_Shutdown()

[SimpsonGSD]

Version/Branch of Dear ImGui:

Version: f1a0731
Branch: docking

Back-end/Renderer/Compiler/OS

Back-ends: imgui_impl_win32.cpp + imgui_impl_vulkan.cpp
Compiler: msvc
Operating System: Windows 10

My Issue/Question:

Hi, I am getting the assert IM_ASSERT(viewport->RendererUserData == NULL && viewport->PlatformUserData == NULL); when calling ImGui_ImplWin32_Shutdown() .

I have ImGuiConfigFlags_DockingEnable but not ImGuiConfigFlags_ViewportsEnable.

Should the call to ImGui_ImplWin32_ShutdownPlatformInterface(); be wrapped in if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable) like ImGui_ImplWin32_InitPlatformInterface()?
Doing this fixes my issue but it could also be user error on my part.

Thanks.

[ocornut]

ImGui_ImplDX12_Shutdown
imgui_impl_vulkan.cpp

Please clarify the inconsistency above.

Also please test and see if it happens with stock examples.
Thank you :)

[SimpsonGSD]

Apologies! Updated - it should say Win32 not DX12..
I will test the examples.

[ocornut]

Basically the assert imply you should shutdown the renderer backend before the platform backend.
But as per #4656 and bac748f we supposedly lifted that, so it is strange.
If I swap the calls in example_win32_directx11/main.cpp it still works.
So you will need to investigate what else you may be doing wrong....

Normally either backend would end up calling ImGui::DestroyPlatformWindows() which will call through the g.PlatformIO.Renderer_DestroyWindow() and g.PlatformIO.Platform_DestroyWindow() handler for all viewports.

[SimpsonGSD]

I tested the examples and could not reproduce - though there is no combination of win32+vulkan I still couldn't repro in examples that used one of these.
I am indeed shutting down the platform before the renderer. I will try reversing them.

[SimpsonGSD]

I called ImGui_ImplVulkan_Shutdown() before ImGui_ImplWin32_Shutdown() but then I get a different assert:
IM_ASSERT(bd != NULL && "No platform backend to shutdown, or already shutdown?");

[SimpsonGSD]

Found the issue.
Originally I was calling
ImGui_ImplWin32_Shutdown() then
ImGui_ImplVulkan_Shutdown()

I swapped them around and got a different assert but what I actually found was this order
ImGui_ImplVulkan_Shutdown()
ImGui::DestroyContext()
ImGui_ImplWin32_Shutdown()

Changing it to the expected order is fine:
ImGui_ImplVulkan_Shutdown()
ImGui_ImplWin32_Shutdown()
ImGui::DestroyContext()