Add keyboard navigation and menu list support

ui/src/Scene.cpp

@@ -374,6 +374,46 @@ Visual *Scene::FindFocusableAt(const PointF &point)
     return root_ ? root_->FindFocusableAt(point) : nullptr;
 }
 
+Visual *Scene::FindNextFocusable(Visual *current, bool reverse)
+{
+    std::vector<Visual *> focusables;
+    if (!popups_.empty())
+    {
+        if (popups_.back().visual)
+        {
+            popups_.back().visual->AppendFocusableVisuals(focusables);
+        }
+    }
+    else if (root_)
+    {
+        root_->AppendFocusableVisuals(focusables);
+    }
+
+    if (focusables.empty())
+    {
+        return nullptr;
+    }
+
+    auto it = std::find(focusables.begin(), focusables.end(), current);
+    if (it == focusables.end())
+    {
+        return reverse ? focusables.back() : focusables.front();
+    }
+
+    const ptrdiff_t index = std::distance(focusables.begin(), it);
+    if (reverse)
+    {
+        return focusables[(index + static_cast<ptrdiff_t>(focusables.size()) - 1) % static_cast<ptrdiff_t>(focusables.size())];
+    }
+
+    return focusables[(index + 1) % focusables.size()];
+}
+
+bool Scene::HasPopups() const
+{
+    return !popups_.empty();
+}
+
 bool Scene::OnMouseWheel(const POINT &point, short delta, WPARAM keyState)
 {
     for (auto it = popups_.rbegin(); it != popups_.rend(); ++it)