add parent field to sexp_node for O(1) parent lookups

code/missioneditor/sexp_tree_model.cpp

@@ -694,6 +694,7 @@ int SexpTreeModel::save_branch(int cur, int at_root) const
 			start = node;
 		} else if (last >= 0) {
 			Sexp_nodes[last].rest = node;
+			Sexp_nodes[node].parent = Sexp_nodes[last].parent;
 		}
 
 		last = node;
@@ -767,8 +768,9 @@ int SexpTreeModel::find_ancestral_argument_number(int parent_op, int child_node)
 // which makes the special <argument> string a valid value at this position.
 bool SexpTreeModel::is_node_eligible_for_special_argument(int parent_node) const
 {
-	Assertion(parent_node != -1,
-		"Attempt to access invalid parent node for special arg eligibility check. Please report!");
+	// if there's no parent, it's certainly not eligible
+	if (parent_node < 0)
+		return false;
 
 	const int w_arg = find_ancestral_argument_number(OP_WHEN_ARGUMENT, parent_node);
 	const int e_arg = find_ancestral_argument_number(OP_EVERY_TIME_ARGUMENT, parent_node);

code/missioneditor/sexp_tree_opf.cpp

@@ -361,7 +361,9 @@ sexp_list_item *SexpTreeOPF::get_listing_opf_ai_goal(int parent_node) const
 {
 	sexp_list_item head;
 
-	Assertion(parent_node >= 0, "Invalid parent node");
+	// no parent context, nothing to list
+	if (parent_node < 0)
+		return nullptr;
 	int child = _model.tree_nodes[parent_node].child;
 	if (child < 0)
 		return nullptr;
@@ -414,7 +416,9 @@ sexp_list_item *SexpTreeOPF::get_listing_opf_docker_point(int parent_node, int a
 {
 	sexp_list_item head;
 
-	Assertion(parent_node >= 0, "Invalid parent node");
+	// no parent context, nothing to list
+	if (parent_node < 0)
+		return nullptr;
 	Assertion(!stricmp(_model.tree_nodes[parent_node].text, "ai-dock") || !stricmp(_model.tree_nodes[parent_node].text, "set-docked") ||
 		   get_operator_const(_model.tree_nodes[parent_node].text) >= static_cast<int>(First_available_operator_id), "Invalid node type");
 
@@ -479,7 +483,9 @@ sexp_list_item *SexpTreeOPF::get_listing_opf_dockee_point(int parent_node) const
 {
 	sexp_list_item head;
 
-	Assertion(parent_node >= 0, "Invalid parent node");
+	// no parent context, nothing to list
+	if (parent_node < 0)
+		return nullptr;
 	Assertion(!stricmp(_model.tree_nodes[parent_node].text, "ai-dock") || !stricmp(_model.tree_nodes[parent_node].text, "set-docked"), "Invalid node type");
 
 	int sh = -1;
@@ -765,7 +771,9 @@ sexp_list_item *SexpTreeOPF::get_listing_opf_goal_name(int parent_node) const
 {
 	sexp_list_item head;
 
-	Assertion(parent_node >= 0, "Invalid parent node");
+	// no parent context, nothing to list
+	if (parent_node < 0)
+		return nullptr;
 	int child = _model.tree_nodes[parent_node].child;
 
 	// reference_name is used by campaign editor to filter goals for a specific mission
@@ -843,7 +851,9 @@ sexp_list_item *SexpTreeOPF::get_listing_opf_event_name(int parent_node) const
 {
 	sexp_list_item head;
 
-	Assertion(parent_node >= 0, "Invalid parent node");
+	// no parent context, nothing to list
+	if (parent_node < 0)
+		return nullptr;
 	int child = _model.tree_nodes[parent_node].child;
 
 	// reference_name is used by campaign editor to filter events for a specific mission
@@ -1396,7 +1406,9 @@ sexp_list_item *SexpTreeOPF::get_listing_opf_animation_name(int parent_node) con
 {
 	sexp_list_item head;
 
-	Assertion(parent_node >= 0, "Invalid parent node");
+	// no parent context, nothing to list
+	if (parent_node < 0)
+		return nullptr;
 
 	// get the operator type of the node
 	const int op = get_operator_const(_model.tree_nodes[parent_node].text);
@@ -1593,11 +1605,13 @@ enum : int {
 sexp_list_item *SexpTreeOPF::get_listing_opf_subsystem(int parent_node, int arg_index) const
 {
 	sexp_list_item head;
-
+
+	// no parent context, nothing to list
+	if (parent_node < 0)
+		return nullptr;
 
 	// determine if the parent is one of the set subsystem strength items.  If so,
 	// we want to append the "Hull" name onto the end of the menu
-	Assertion(parent_node >= 0, "Invalid parent node");
 
 	// get the operator type of the node
 	int op = get_operator_const(_model.tree_nodes[parent_node].text);