Fix key press event bubbling for nested layouts.

src/musikcube/cursespp/LayoutBase.cpp

@@ -493,6 +493,19 @@ bool LayoutBase::KeyPress(const std::string& key) {
         this->FocusNext();
         return true;
     }
+    /* we find the focus recursively, then let the child deepest in the
+    hierarchy process the key event. if that fails we move up to its parent,
+    and so on until we reach ourself. */
+    auto focus = this->GetFocus().get();
+    while (focus != this) {
+        auto asKeyHandler = dynamic_cast<IKeyHandler*>(focus);
+        if (asKeyHandler) {
+            if (asKeyHandler->KeyPress(key)) {
+                return true;
+            }
+        }
+        focus = focus->GetParent();
+    }
 
     return false;
 }