Method FindBlockingModal

include/imgui/imgui.cpp:12250–12271

When a modal popup is open, newly created windows that want focus (i.e. are not popups and do not specify ImGuiWindowFlags_NoFocusOnAppearing) should be positioned behind that modal window, unless the window was created inside the modal begin-stack. In case of multiple stacked modals newly created window honors begin stack order and does not go below its own modal parent. - WindowA // F

// - FindBlockingModal(NULL) == NULL is generally equivalent to GetTopMostPopupModal() == NULL.
//   Only difference is here we check for ->Active/WasActive but it may be unnecessary.
ImGuiWindow* ImGui::FindBlockingModal(ImGuiWindow* window)
{
    ImGuiContext& g = *GImGui;
    if (g.OpenPopupStack.Size <= 0)
        return NULL;

    // Find a modal that has common parent with specified window. Specified window should be positioned behind that modal.
    for (ImGuiPopupData& popup_data : g.OpenPopupStack)
    {
        ImGuiWindow* popup_window = popup_data.Window;
        if (popup_window == NULL || !(popup_window->Flags & ImGuiWindowFlags_Modal))
            continue;
        if (!popup_window->Active && !popup_window->WasActive)  // Check WasActive, because this code may run before popup renders on current frame, also check Active to handle newly created windows.
            continue;
        if (window == NULL)                                     // FindBlockingModal(NULL) test for if FocusWindow(NULL) is naturally possible via a mouse click.
            return popup_window;
        if (IsWindowWithinBeginStackOf(window, popup_window))   // Window may be over modal
            continue;
        return popup_window;                                    // Place window right below first block modal
    }
    return NULL;
}

void ImGui::OpenPopup(const char* str_id, ImGuiPopupFlags popup_flags)
{