Strings: Avoid unnecessary std::string allocation churn in sorters

Author: JGRennison

src/build_vehicle_gui.cpp

@@ -275,18 +275,20 @@ static EngineID _last_engine[2] = { INVALID_ENGINE, INVALID_ENGINE };
  */
 static bool EngineNameSorter(const GUIEngineListItem &a, const GUIEngineListItem &b, const GUIEngineListSortCache &cache)
 {
-	static std::string last_name[2] = { {}, {} };
+	static format_buffer last_name[2] = { {}, {} };
 
 	if (a.engine_id != _last_engine[0]) {
 		_last_engine[0] = a.engine_id;
 		SetDParam(0, PackEngineNameDParam(a.engine_id, EngineNameContext::PurchaseList));
-		last_name[0] = GetString(STR_ENGINE_NAME);
+		last_name[0].clear();
+		AppendStringInPlace(last_name[0], STR_ENGINE_NAME);
 	}
 
 	if (b.engine_id != _last_engine[1]) {
 		_last_engine[1] = b.engine_id;
 		SetDParam(0, PackEngineNameDParam(b.engine_id, EngineNameContext::PurchaseList));
-		last_name[1] = GetString(STR_ENGINE_NAME);
+		last_name[1].clear();
+		AppendStringInPlace(last_name[1], STR_ENGINE_NAME);
 	}
 
 	int r = StrNaturalCompare(last_name[0], last_name[1]); // Sort by name (natural sorting).

src/cargotype.cpp

@@ -9,6 +9,7 @@
 
 #include "stdafx.h"
 #include "cargotype.h"
+#include "core/format.hpp"
 #include "core/geometry_func.hpp"
 #include "gfx_func.h"
 #include "newgrf_cargo.h"
@@ -199,8 +200,10 @@ std::span<const CargoSpec *> _sorted_standard_cargo_specs; ///< Standard cargo s
 /** Sort cargo specifications by their name. */
 static bool CargoSpecNameSorter(const CargoSpec * const &a, const CargoSpec * const &b)
 {
-	std::string a_name = GetString(a->name);
-	std::string b_name = GetString(b->name);
+	format_buffer a_name;
+	format_buffer b_name;
+	AppendStringInPlace(a_name, a->name);
+	AppendStringInPlace(b_name, b->name);
 
 	int res = StrNaturalCompare(a_name, b_name); // Sort by name (natural sorting).
 

src/core/format.hpp

@@ -226,7 +226,9 @@ struct format_buffer_base : public format_to_buffer {
  * Includes convenience wrappers to access the buffer.
  * Can be used as a fmt argument.
  */
-struct format_buffer final : public format_buffer_base<fmt::inline_buffer_size> {};
+struct format_buffer final : public format_buffer_base<fmt::inline_buffer_size> {
+	format_buffer() {}
+};
 
 /**
  * format_to_buffer subtype where the fmt::memory_buffer is built-in.
@@ -236,7 +238,9 @@ struct format_buffer final : public format_buffer_base<fmt::inline_buffer_size>
  * Can be used as a fmt argument.
  */
 template <size_t SIZE>
-struct format_buffer_sized final : public format_buffer_base<SIZE> {};
+struct format_buffer_sized final : public format_buffer_base<SIZE> {
+	format_buffer_sized() {}
+};
 
 template <typename T>
 struct format_by_string_view_cast : public fmt::formatter<std::string_view> {

src/group_gui.cpp

@@ -172,18 +172,19 @@ void BuildGuiGroupList(GUIGroupList &dst, bool fold, Owner owner, VehicleType ve
 	list.ForceResort();
 
 	/* Sort the groups by their name */
-	std::array<std::pair<const Group *, std::string>, 2> last_group{};
+	std::array<std::pair<const Group *, format_buffer>, 2> last_group{};
 
 	list.Sort([&last_group](const GUIGroupListItem &a, const GUIGroupListItem &b) -> bool {
-		if (a.group != last_group[0].first) {
-			SetDParam(0, a.group->index);
-			last_group[0] = {a.group, GetString(STR_GROUP_NAME)};
-		}
-
-		if (b.group != last_group[1].first) {
-			SetDParam(0, b.group->index);
-			last_group[1] = {b.group, GetString(STR_GROUP_NAME)};
-		}
+		auto process_group = [&](size_t index, const Group *group) {
+			if (group != last_group[index].first) {
+				last_group[index].first = group;
+				last_group[index].second.clear();
+				SetDParam(0, group->index);
+				AppendStringInPlace(last_group[index].second, STR_GROUP_NAME);
+			}
+		};
+		process_group(0, a.group);
+		process_group(1, b.group);
 
 		int r = StrNaturalCompare(last_group[0].second, last_group[1].second); // Sort by name (natural sorting).
 		if (r == 0) return a.group->number < b.group->number;
@@ -197,18 +198,20 @@ void SortGUIGroupOnlyList(GUIGroupOnlyList &list)
 {
 	/* Sort the groups by their name */
 	const Group *last_group[2] = { nullptr, nullptr };
-	std::string last_name[2] = { {}, {} };
+	format_buffer last_name[2] = { {}, {} };
 	list.Sort([&](const Group * const &a, const Group * const &b) {
 		if (a != last_group[0]) {
 			last_group[0] = a;
 			SetDParam(0, a->index | GROUP_NAME_HIERARCHY);
-			last_name[0] = GetString(STR_GROUP_NAME);
+			last_name[0].clear();
+			AppendStringInPlace(last_name[0], STR_GROUP_NAME);
 		}
 
 		if (b != last_group[1]) {
 			last_group[1] = b;
 			SetDParam(0, b->index | GROUP_NAME_HIERARCHY);
-			last_name[1] = GetString(STR_GROUP_NAME);
+			last_name[1].clear();
+			AppendStringInPlace(last_name[1], STR_GROUP_NAME);
 		}
 
 		int r = StrNaturalCompare(last_name[0], last_name[1]); // Sort by name (natural sorting).

src/vehicle_gui.cpp

@@ -1624,18 +1624,20 @@ static bool VehicleNumberSorter(const Vehicle * const &a, const Vehicle * const
 /** Sort vehicles by their name */
 static bool VehicleNameSorter(const Vehicle * const &a, const Vehicle * const &b)
 {
-	static std::string last_name[2] = { {}, {} };
+	static format_buffer last_name[2] = { {}, {} };
 
 	if (a != _last_vehicle[0]) {
 		_last_vehicle[0] = a;
 		SetDParam(0, a->index);
-		last_name[0] = GetString(STR_VEHICLE_NAME);
+		last_name[0].clear();
+		AppendStringInPlace(last_name[0], STR_VEHICLE_NAME);
 	}
 
 	if (b != _last_vehicle[1]) {
 		_last_vehicle[1] = b;
 		SetDParam(0, b->index);
-		last_name[1] = GetString(STR_VEHICLE_NAME);
+		last_name[1].clear();
+		AppendStringInPlace(last_name[1], STR_VEHICLE_NAME);
 	}
 
 	int r = StrNaturalCompare(last_name[0], last_name[1]); // Sort by name (natural sorting).