Function IsRootOfOpenMenuSet

imgui_tiny_app/imgui/imgui_widgets.cpp:9212–9234

}

static bool IsRootOfOpenMenuSet()
{
    ImGuiContext& g = *GImGui;
    ImGuiWindow* window = g.CurrentWindow;
    if ((g.OpenPopupStack.Size <= g.BeginPopupStack.Size) || (window->Flags & ImGuiWindowFlags_ChildMenu))
        return false;

    // Initially we used 'upper_popup->OpenParentId == window->IDStack.back()' to differentiate multiple menu sets from each others
    // (e.g. inside menu bar vs loose menu items) based on parent ID.
    // This would however prevent the use of e.g. PushID() user code submitting menus.
    // Previously this worked between popup and a first child menu because the first child menu always had the _ChildWindow flag,
    // making hovering on parent popup possible while first child menu was focused - but this was generally a bug with other side effects.
    // Instead we don't treat Popup specifically (in order to consistently support menu features in them), maybe the first child menu of a Popup
    // doesn't have the _ChildWindow flag, and we rely on this IsRootOfOpenMenuSet() check to allow hovering between root window/popup and first child menu.
    // In the end, lack of ID check made it so we could no longer differentiate between separate menu sets. To compensate for that, we at least check parent window nav layer.
    // This fixes the most common case of menu opening on hover when moving between window content and menu bar. Multiple different menu sets in same nav layer would still
    // open on hover, but that should be a lesser problem, because if such menus are close in proximity in window content then it won't feel weird and if they are far apart
    // it likely won't be a problem anyone runs into.
    const ImGuiPopupData* upper_popup = &g.OpenPopupStack[g.BeginPopupStack.Size];
    if (window->DC.NavLayerCurrent != upper_popup->ParentNavLayer)
        return false;
    return upper_popup->Window && (upper_popup->Window->Flags & ImGuiWindowFlags_ChildMenu) && ImGui::IsWindowChildOf(upper_popup->Window, window, true, false);
}

bool ImGui::BeginMenuEx(const char* label, const char* icon, bool enabled)
{