Method BeginChildEx

extern/imgui/imgui.cpp:5822–5871

}

bool ImGui::BeginChildEx(const char* name, ImGuiID id, const ImVec2& size_arg, bool border, ImGuiWindowFlags flags)
{
    ImGuiContext& g = *GImGui;
    ImGuiWindow* parent_window = g.CurrentWindow;

    flags |= ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoSavedSettings | ImGuiWindowFlags_ChildWindow | ImGuiWindowFlags_NoDocking;
    flags |= (parent_window->Flags & ImGuiWindowFlags_NoMove);  // Inherit the NoMove flag

    // Size
    const ImVec2 content_avail = GetContentRegionAvail();
    ImVec2 size = ImFloor(size_arg);
    const int auto_fit_axises = ((size.x == 0.0f) ? (1 << ImGuiAxis_X) : 0x00) | ((size.y == 0.0f) ? (1 << ImGuiAxis_Y) : 0x00);
    if (size.x <= 0.0f)
        size.x = ImMax(content_avail.x + size.x, 4.0f); // Arbitrary minimum child size (0.0f causing too many issues)
    if (size.y <= 0.0f)
        size.y = ImMax(content_avail.y + size.y, 4.0f);
    SetNextWindowSize(size);

    // Build up name. If you need to append to a same child from multiple location in the ID stack, use BeginChild(ImGuiID id) with a stable value.
    const char* temp_window_name;
    if (name)
        ImFormatStringToTempBuffer(&temp_window_name, NULL, "%s/%s_%08X", parent_window->Name, name, id);
    else
        ImFormatStringToTempBuffer(&temp_window_name, NULL, "%s/%08X", parent_window->Name, id);

    const float backup_border_size = g.Style.ChildBorderSize;
    if (!border)
        g.Style.ChildBorderSize = 0.0f;
    bool ret = Begin(temp_window_name, NULL, flags);
    g.Style.ChildBorderSize = backup_border_size;

    ImGuiWindow* child_window = g.CurrentWindow;
    child_window->ChildId = id;
    child_window->AutoFitChildAxises = (ImS8)auto_fit_axises;

    // Set the cursor to handle case where the user called SetNextWindowPos()+BeginChild() manually.
    // While this is not really documented/defined, it seems that the expected thing to do.
    if (child_window->BeginCount == 1)
        parent_window->DC.CursorPos = child_window->Pos;

    // Process navigation-in immediately so NavInit can run on first frame
    if (g.NavActivateId == id && !(flags & ImGuiWindowFlags_NavFlattened) && (child_window->DC.NavLayersActiveMask != 0 || child_window->DC.NavHasScroll))
    {
        FocusWindow(child_window);
        NavInitWindow(child_window, false);
        SetActiveID(id + 1, child_window); // Steal ActiveId with another arbitrary id so that key-press won't activate child item
        g.ActiveIdSource = ImGuiInputSource_Nav;
    }
    return ret;
}

bool ImGui::BeginChild(const char* str_id, const ImVec2& size_arg, bool border, ImGuiWindowFlags extra_flags)
{