Function AddRootWindowToDrawData

extern/imgui/imgui.cpp:5240–5243

Layer is locked for the root window, however child windows may use a different viewport (e.g. extruding menu)

// Layer is locked for the root window, however child windows may use a different viewport (e.g. extruding menu)
static inline void AddRootWindowToDrawData(ImGuiWindow* window)
{
    AddWindowToDrawData(window, GetWindowDisplayLayer(window));
}

void ImDrawDataBuilder::FlattenIntoSingleLayer()
{