GUI2/Tree View: added interface for moving nodes between parent nodes

src/gui/dialogs/multiplayer/mp_options_helper.cpp

@@ -129,7 +129,7 @@ int mp_options_helper::remove_nodes_for_type(const std::string& type)
 
 	// Remove each node in reverse, so that in the end we have the position of the first node removed
 	for(auto i = type_node_vector.rbegin(); i != type_node_vector.rend(); i++) {
-		position = options_tree_.remove_node(*i);
+		position = options_tree_.remove_node(*i).second;
 	}
 
 	type_node_vector.clear();

src/gui/widgets/tree_view.cpp

@@ -19,7 +19,6 @@
 #include "gui/core/log.hpp"
 #include "gui/core/window_builder/helper.hpp"
 #include "gui/core/register_widget.hpp"
-#include "gui/widgets/tree_view_node.hpp"
 #include "gui/widgets/window.hpp"
 #include "gettext.hpp"
 #include "wml_exception.hpp"
@@ -66,7 +65,7 @@ tree_view_node& tree_view::add_node(
 	return get_root_node().add_child(id, data, index);
 }
 
-int tree_view::remove_node(tree_view_node* node)
+std::pair<tree_view_node::ptr_t, int> tree_view::remove_node(tree_view_node* node)
 {
 	assert(node && node != root_node_.get() && node->parent_node_);
 	const point node_size = node->get_size();
@@ -79,6 +78,9 @@ int tree_view::remove_node(tree_view_node* node)
 
 	assert(node_itor != siblings.end());
 
+	auto old_node = std::move(*node_itor);
+	old_node->parent_node_ = nullptr;
+
 	const int position = std::distance(siblings.begin(), node_itor);
 
 	siblings.erase(node_itor);
@@ -88,7 +90,7 @@ int tree_view::remove_node(tree_view_node* node)
 		resize_content(0, -node_size.y);
 	}
 
-	return position;
+	return std::make_pair(std::move(old_node), position);
 }
 
 void tree_view::clear()

src/gui/widgets/tree_view.hpp

@@ -15,6 +15,7 @@
 #pragma once
 
 #include "gui/widgets/scrollbar_container.hpp"
+#include "gui/widgets/tree_view_node.hpp"
 
 namespace gui2
 {
@@ -59,7 +60,15 @@ public:
 			 const std::map<std::string /* widget id */, string_map>& data,
 			 const int index = -1);
 
-	int remove_node(tree_view_node* tree_view_node);
+	/**
+	 * Removes the given node as a child of its parent node.
+	 *
+	 * @param node      A pointer to the node to remove.
+	 *
+	 * @returns         A pair consisting of a smart pointer managing the removed
+	 *                  node, and its position before removal.
+	 */
+	std::pair<tree_view_node::ptr_t, int> remove_node(tree_view_node* node);
 
 	void clear();
 

src/gui/widgets/tree_view_node.cpp

@@ -127,10 +127,7 @@ void tree_view_node::clear_before_destruct()
 	}
 }
 
-tree_view_node& tree_view_node::add_child(
-		const std::string& id,
-		const std::map<std::string /* widget id */, string_map>& data,
-		const int index)
+tree_view_node& tree_view_node::add_child_impl(ptr_t&& new_node, const int index)
 {
 	auto itor = children_.end();
 
@@ -138,14 +135,22 @@ tree_view_node& tree_view_node::add_child(
 		itor = children_.begin() + index;
 	}
 
-	itor = children_.emplace(itor, new tree_view_node(id, this, get_tree_view(), data));
+	tree_view_node& node = **children_.insert(itor, std::move(new_node));
+
+	// NOTE: we currently don't support moving nodes between different trees, so this
+	// just ensures that wasn't tried. Remove this if we implement support for that.
+	assert(node.tree_view_ == tree_view_);
+
+	// Safety check. Might only fail if someone accidentally removed the parent_node_
+	// setter in add_child().
+	assert(node.parent_node_ == this);
 
 	if(is_folded() /*|| is_root_node()*/) {
-		return **itor;
+		return node;
 	}
 
 	if(get_tree_view().get_size() == point()) {
-		return **itor;
+		return node;
 	}
 
 	assert(get_tree_view().content_grid());
@@ -153,7 +158,7 @@ tree_view_node& tree_view_node::add_child(
 
 	// Calculate width modification.
 	// This increases tree width if the width of the new node is greater than the current width.
-	point best_size = (*itor)->get_best_size();
+	point best_size = node.get_best_size();
 	best_size.x += get_indentation_level() * get_tree_view().indentation_step_size_;
 
 	const int width_modification = best_size.x > current_size.x
@@ -165,7 +170,7 @@ tree_view_node& tree_view_node::add_child(
 	// is larger than its current size. This prevents the scrollbar being reserved even when there's obviously
 	// enough visual space.
 
-	// Throw away cached best size to force a recomputation.
+	// Throw away cached best size to force a recalculation.
 	get_tree_view().layout_initialize(false);
 
 	const point tree_best_size = get_tree_view().get_best_size();
@@ -177,9 +182,9 @@ tree_view_node& tree_view_node::add_child(
 	assert(height_modification >= 0);
 
 	// Request new size.
-	get_tree_view().resize_content(width_modification, height_modification, -1, (*itor)->calculate_ypos());
+	get_tree_view().resize_content(width_modification, height_modification, -1, node.calculate_ypos());
 
-	return **itor;
+	return node;
 }
 
 unsigned tree_view_node::get_indentation_level() const

src/gui/widgets/tree_view_node.hpp

@@ -52,7 +52,7 @@ public:
 	~tree_view_node();
 
 	/**
-	 * Adds a child item to the list of child nodes.
+	 * Constructs a new child node.
 	 *
 	 * @param id                  The id of the node definition to use for the
 	 *                            new node.
@@ -66,10 +66,26 @@ public:
 	 * @param index               The item before which to add the new item,
 	 *                            0 == begin, -1 == end.
 	 */
-	tree_view_node&
-	add_child(const std::string& id,
-			  const std::map<std::string /* widget id */, string_map>& data,
-			  const int index = -1);
+	tree_view_node& add_child(const std::string& id,
+			const std::map<std::string /* widget id */, string_map>& data,
+			const int index = -1)
+	{
+		ptr_t new_node(new tree_view_node(id, this, get_tree_view(), data));
+		return add_child_impl(std::move(new_node), index);
+	}
+
+	/**
+	 * Adds a previously-constructed node as a child of this node at the given position.
+	 *
+	 * @param new_node            A smart pointer to the node object to insert.
+	 * @param index               The item before which to add the new item,
+	 *                            0 == begin, -1 == end.
+	 */
+	tree_view_node& add_child(ptr_t new_node, const int index = -1)
+	{
+		new_node->parent_node_ = this;
+		return add_child_impl(std::move(new_node), index);
+	}
 
 	/**
 	 * Adds a sibbling for a node at the end of the list.
@@ -92,12 +108,20 @@ public:
 		return parent_node().add_child(id, data);
 	}
 
+private:
+	/** Implementation detail for @ref add_child. */
+	tree_view_node& add_child_impl(ptr_t&& new_node, const int index);
+
+public:
 	/**
 	 * Is this node the root node?
 	 *
 	 * When the parent tree view is created it adds one special node, the root
 	 * node. This node has no parent node and some other special features so
 	 * several code paths need to check whether they are the parent node.
+	 *
+	 * This also returns true for a detecthed node returned with @ref tree_view::
+	 * remove_node.
 	 */
 	bool is_root_node() const
 	{