Function MakeWidgetTree

src/widget.cpp:3366–3401

* Build a nested widget tree by recursively filling containers with nested widgets read from their parts. * @param nwid_begin Iterator to beginning of nested widget parts. * @param nwid_end Iterator to ending of nested widget parts. * @param parent Pointer or container to use for storing the child widgets (*parent == nullptr or *parent == container or background widget). * @return Iterator to

 * @return Iterator to remaining nested widget parts.
 */
static std::span<const NWidgetPart>::iterator MakeWidgetTree(std::span<const NWidgetPart>::iterator nwid_begin, std::span<const NWidgetPart>::iterator nwid_end, std::unique_ptr<NWidgetBase> &parent)
{
	/* If *parent == nullptr, only the first widget is read and returned. Otherwise, *parent must point to either
	 * a #NWidgetContainer or a #NWidgetBackground object, and parts are added as much as possible. */
	NWidgetContainer *nwid_cont = dynamic_cast<NWidgetContainer *>(parent.get());
	NWidgetBackground *nwid_parent = dynamic_cast<NWidgetBackground *>(parent.get());
	assert(parent == nullptr || (nwid_cont != nullptr && nwid_parent == nullptr) || (nwid_cont == nullptr && nwid_parent != nullptr));

	while (nwid_begin != nwid_end) {
		std::unique_ptr<NWidgetBase> sub_widget = nullptr;
		bool fill_sub = false;
		nwid_begin = MakeNWidget(nwid_begin, nwid_end, sub_widget, fill_sub);

		/* Break out of loop when end reached */
		if (sub_widget == nullptr) break;

		/* If sub-widget is a container, recursively fill that container. */
		if (fill_sub && IsContainerWidgetType(sub_widget->type)) {
			nwid_begin = MakeWidgetTree(nwid_begin, nwid_end, sub_widget);
		}

		/* Add sub_widget to parent container if available, otherwise return the widget to the caller. */
		if (nwid_cont != nullptr) nwid_cont->Add(std::move(sub_widget));
		if (nwid_parent != nullptr) nwid_parent->Add(std::move(sub_widget));
		if (nwid_cont == nullptr && nwid_parent == nullptr) {
			parent = std::move(sub_widget);
			return nwid_begin;
		}
	}

	if (nwid_begin == nwid_end) return nwid_begin; // Reached the end of the array of parts?

	assert(nwid_begin < nwid_end);
	assert(nwid_begin->type == WPT_ENDCONTAINER);
	return std::next(nwid_begin); // *nwid_begin is also 'used'
}

/**
 * Construct a nested widget tree from an array of parts.