Opening a modal causues incorrect TotalVtx/IdxCount

[ZingBallyhoo]

Version/Branch of Dear ImGui:

Version: 1.89.9 WIP (18982)
Branch: docking (unable to reproduce on master)

Back-end/Renderer/Compiler/OS

Back-ends: Multiple (tested on custom, imgui_impl_dx11.cpp & imgui_impl_opengl3.cpp)
Compiler: MSVC
Operating System: Windows 10

My Issue/Question:

When opening a modal on recent docking branch (upgrading from 1.89.4), the sum of vertex/index buffer counts across all draw lists becomes greater than TotalVtx/IdxCount. A backend that uses these values directly for buffer copying will have graphical corruption (I noticed this due to missing modal backgrounds)

Standalone, minimal, complete and verifiable example:

Add the following code to any ImGui_ImplXXX_RenderDrawData

int actualVertexCount = 0;
int actualIndexCount = 0;
for (int n = 0; n < draw_data->CmdListsCount; n++)
{
    const ImDrawList* cmd_list = draw_data->CmdLists[n];
    actualVertexCount += cmd_list->VtxBuffer.Size;
    actualIndexCount += cmd_list->IdxBuffer.Size;
}
printf("%d %d - %d %d\n", draw_data->TotalVtxCount, actualVertexCount, draw_data->TotalIdxCount, actualIndexCount);

Open any modal (e.g Demo -> Popups & Modal Windows -> Modals -> Delete)
Observe that the reported total (left part of pair) becomes less than the actual sum (right part of pair)

[ocornut]

Thank you. Confirmed as a bug. This is due to
#6406 (comment) and precisely this commit dbeeeae
Where we call AddDrawListToDrawDataEx() earlier than then afterward append a ImDrawCmd in RenderDimmedBackgrounds().

[ocornut]

I have pushed a fix f422e78
Thank you for reporting !