Function MakeWindowNWidgetTree

src/widget.cpp:3429–3459

* Make a nested widget tree for a window from a parts array. Besides loading, it inserts a shading selection widget * between the title bar and the window body if the first widget in the parts array looks like a title bar (it is a horizontal * container with a caption widget) and has a shade box widget. * @param nwid_parts Span of nested widget parts. * @param[out] shade_select Pointer to the

 * @ingroup NestedWidgetParts
 */
std::unique_ptr<NWidgetBase> MakeWindowNWidgetTree(std::span<const NWidgetPart> nwid_parts, NWidgetStacked **shade_select)
{
	auto nwid_begin = std::begin(nwid_parts);
	auto nwid_end = std::end(nwid_parts);

	*shade_select = nullptr;

	/* Read the first widget recursively from the array. */
	std::unique_ptr<NWidgetBase> nwid = nullptr;
	nwid_begin = MakeWidgetTree(nwid_begin, nwid_end, nwid);
	assert(nwid != nullptr);

	NWidgetHorizontal *hor_cont = dynamic_cast<NWidgetHorizontal *>(nwid.get());

	auto root = std::make_unique<NWidgetVertical>();
	root->Add(std::move(nwid));
	if (nwid_begin == nwid_end) return root; // There is no body at all.

	if (hor_cont != nullptr && hor_cont->GetWidgetOfType(WWT_CAPTION) != nullptr && hor_cont->GetWidgetOfType(WWT_SHADEBOX) != nullptr) {
		/* If the first widget has a title bar and a shade box, silently add a shade selection widget in the tree. */
		auto shade_stack = std::make_unique<NWidgetStacked>(INVALID_WIDGET);
		*shade_select = shade_stack.get();
		/* Load the remaining parts into the shade stack. */
		shade_stack->Add(MakeNWidgets({nwid_begin, nwid_end}, std::make_unique<NWidgetVertical>()));
		root->Add(std::move(shade_stack));
		return root;
	}

	/* Load the remaining parts into 'root'. */
	return MakeNWidgets({nwid_begin, nwid_end}, std::move(root));
}

/**
 * Make a number of rows with button-like graphics, for enabling/disabling each company.