Method BeginMenuBar

include/imgui/imgui_widgets.cpp:9152–9180

FIXME: Provided a rectangle perhaps e.g. a BeginMenuBarEx() could be used anywhere.. Currently the main responsibility of this function being to setup clip-rect + horizontal layout + menu navigation layer. Ideally we also want this to be responsible for claiming space out of the main window scrolling rectangle, in which case ImGuiWindowFlags_MenuBar will become unnecessary. Then later the same sys

// Ideally we also want this to be responsible for claiming space out of the main window scrolling rectangle, in which case ImGuiWindowFlags_MenuBar will become unnecessary.
// Then later the same system could be used for multiple menu-bars, scrollbars, side-bars.
bool ImGui::BeginMenuBar()
{
    ImGuiWindow* window = GetCurrentWindow();
    if (window->SkipItems)
        return false;
    if (!(window->Flags & ImGuiWindowFlags_MenuBar))
        return false;

    IM_ASSERT(!window->DC.MenuBarAppending);
    BeginGroup(); // Backup position on layer 0 // FIXME: Misleading to use a group for that backup/restore
    PushID("##MenuBar");

    // We don't clip with current window clipping rectangle as it is already set to the area below. However we clip with window full rect.
    // We remove 1 worth of rounding to Max.x to that text in long menus and small windows don't tend to display over the lower-right rounded area, which looks particularly glitchy.
    const float border_top = ImMax(window->WindowBorderSize * 0.5f - window->TitleBarHeight, 0.0f);
    ImRect bar_rect = window->MenuBarRect();
    ImRect clip_rect(IM_ROUND(bar_rect.Min.x + window->WindowBorderSize * 0.5f), IM_ROUND(bar_rect.Min.y + border_top), IM_ROUND(ImMax(bar_rect.Min.x, bar_rect.Max.x - ImMax(window->WindowRounding, window->WindowBorderSize * 0.5f))), IM_ROUND(bar_rect.Max.y));
    clip_rect.ClipWith(window->OuterRectClipped);
    PushClipRect(clip_rect.Min, clip_rect.Max, false);

    // We overwrite CursorMaxPos because BeginGroup sets it to CursorPos (essentially the .EmitItem hack in EndMenuBar() would need something analogous here, maybe a BeginGroupEx() with flags).
    window->DC.CursorPos = window->DC.CursorMaxPos = ImVec2(bar_rect.Min.x + window->DC.MenuBarOffset.x, bar_rect.Min.y + window->DC.MenuBarOffset.y);
    window->DC.LayoutType = ImGuiLayoutType_Horizontal;
    window->DC.IsSameLine = false;
    window->DC.NavLayerCurrent = ImGuiNavLayer_Menu;
    window->DC.MenuBarAppending = true;
    AlignTextToFramePadding();
    return true;
}

void ImGui::EndMenuBar()
{