Method BeginMenuEx

src/imgui/imgui_widgets.cpp:9127–9337

}

bool ImGui::BeginMenuEx(const char* label, const char* icon, bool enabled)
{
    ImGuiWindow* window = GetCurrentWindow();
    if (window->SkipItems)
        return false;

    ImGuiContext& g = *GImGui;
    const ImGuiStyle& style = g.Style;
    const ImGuiID id = window->GetID(label);
    bool menu_is_open = IsPopupOpen(id, ImGuiPopupFlags_None);

    // Sub-menus are ChildWindow so that mouse can be hovering across them (otherwise top-most popup menu would steal focus and not allow hovering on parent menu)
    // The first menu in a hierarchy isn't so hovering doesn't get across (otherwise e.g. resizing borders with ImGuiButtonFlags_FlattenChildren would react), but top-most BeginMenu() will bypass that limitation.
    ImGuiWindowFlags window_flags = ImGuiWindowFlags_ChildMenu | ImGuiWindowFlags_AlwaysAutoResize | ImGuiWindowFlags_NoMove | ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoSavedSettings | ImGuiWindowFlags_NoNavFocus;
    if (window->Flags & ImGuiWindowFlags_ChildMenu)
        window_flags |= ImGuiWindowFlags_ChildWindow;

    // If a menu with same the ID was already submitted, we will append to it, matching the behavior of Begin().
    // We are relying on a O(N) search - so O(N log N) over the frame - which seems like the most efficient for the expected small amount of BeginMenu() calls per frame.
    // If somehow this is ever becoming a problem we can switch to use e.g. ImGuiStorage mapping key to last frame used.
    if (g.MenusIdSubmittedThisFrame.contains(id))
    {
        if (menu_is_open)
            menu_is_open = BeginPopupMenuEx(id, label, window_flags); // menu_is_open can be 'false' when the popup is completely clipped (e.g. zero size display)
        else
            g.NextWindowData.ClearFlags();          // we behave like Begin() and need to consume those values
        return menu_is_open;
    }

    // Tag menu as used. Next time BeginMenu() with same ID is called it will append to existing menu
    g.MenusIdSubmittedThisFrame.push_back(id);

    ImVec2 label_size = CalcTextSize(label, NULL, true);

    // Odd hack to allow hovering across menus of a same menu-set (otherwise we wouldn't be able to hover parent without always being a Child window)
    // This is only done for items for the menu set and not the full parent window.
    const bool menuset_is_open = IsRootOfOpenMenuSet();
    if (menuset_is_open)
        PushItemFlag(ImGuiItemFlags_NoWindowHoverableCheck, true);

    // The reference position stored in popup_pos will be used by Begin() to find a suitable position for the child menu,
    // However the final position is going to be different! It is chosen by FindBestWindowPosForPopup().
    // e.g. Menus tend to overlap each other horizontally to amplify relative Z-ordering.
    ImVec2 popup_pos, pos = window->DC.CursorPos;
    PushID(label);
    if (!enabled)
        BeginDisabled();
    const ImGuiMenuColumns* offsets = &window->DC.MenuColumns;
    bool pressed;

    // We use ImGuiSelectableFlags_NoSetKeyOwner to allow down on one menu item, move, up on another.
    const ImGuiSelectableFlags selectable_flags = ImGuiSelectableFlags_NoHoldingActiveID | ImGuiSelectableFlags_NoSetKeyOwner | ImGuiSelectableFlags_SelectOnClick | ImGuiSelectableFlags_NoAutoClosePopups;
    if (window->DC.LayoutType == ImGuiLayoutType_Horizontal)
    {
        // Menu inside a horizontal menu bar
        // Selectable extend their highlight by half ItemSpacing in each direction.
        // For ChildMenu, the popup position will be overwritten by the call to FindBestWindowPosForPopup() in Begin()
        popup_pos = ImVec2(pos.x - 1.0f - IM_TRUNC(style.ItemSpacing.x * 0.5f), pos.y - style.FramePadding.y + window->MenuBarHeight);