Use `function_ref` instead of `function`

`function_ref` is a lightweight function pointer,
whereas `std::function` always involves a heap allocation.

Source/DiabloUI/diabloui.cpp

@@ -762,11 +762,11 @@ void UiClearScreen()
 		SDL_FillRect(DiabloUiSurface(), nullptr, 0x000000);
 }
 
-void UiPollAndRender(std::function<bool(SDL_Event &)> eventHandler)
+void UiPollAndRender(std::optional<tl::function_ref<bool(SDL_Event &)>> eventHandler)
 {
 	SDL_Event event;
 	while (PollEvent(&event) != 0) {
-		if (eventHandler && eventHandler(event))
+		if (eventHandler && (*eventHandler)(event))
 			continue;
 		UiFocusNavigation(&event);
 		UiHandleEvents(&event);

Source/DiabloUI/diabloui.h

@@ -5,11 +5,14 @@
 #include <cstddef>
 #include <cstdint>
 
+#include <function_ref.hpp>
+
 #include "DiabloUI/ui_item.h"
 #include "engine/clx_sprite.hpp"
 #include "engine/load_pcx.hpp" // IWYU pragma: export
 #include "player.h"
 #include "utils/display.h"
+#include "utils/stdcompat/optional.hpp"
 
 namespace devilution {
 
@@ -105,7 +108,7 @@ void UiFocusNavigationEsc();
 void UiFocusNavigationYesNo();
 void UiInitList(void (*fnFocus)(int value), void (*fnSelect)(int value), void (*fnEsc)(), const std::vector<std::unique_ptr<UiItemBase>> &items, bool wraps = false, void (*fnFullscreen)() = nullptr, bool (*fnYesNo)() = nullptr, size_t selectedItem = 0);
 void UiClearScreen();
-void UiPollAndRender(std::function<bool(SDL_Event &)> eventHandler = nullptr);
+void UiPollAndRender(std::optional<tl::function_ref<bool(SDL_Event &)>> eventHandler = std::nullopt);
 void UiRenderItem(const UiItemBase &item);
 void UiRenderItems(const std::vector<UiItemBase *> &items);
 void UiRenderItems(const std::vector<std::unique_ptr<UiItemBase>> &items);

Source/DiabloUI/settingsmenu.cpp

@@ -1,5 +1,7 @@
 #include "selstart.h"
 
+#include <function_ref.hpp>
+
 #include "DiabloUI/diabloui.h"
 #include "DiabloUI/scrollbar.h"
 #include "control.h"
@@ -9,6 +11,7 @@
 #include "miniwin/misc_msg.h"
 #include "options.h"
 #include "utils/language.h"
+#include "utils/stdcompat/optional.hpp"
 #include "utils/utf8.hpp"
 
 namespace devilution {
@@ -268,7 +271,7 @@ void UiSettingsMenu()
 		vecDialog.push_back(std::make_unique<UiArtText>(optionDescription, MakeSdlRect(rectDescription), UiFlags::FontSize12 | UiFlags::ColorUiSilverDark | UiFlags::AlignCenter, 1, IsSmallFontTall() ? 22 : 18));
 
 		size_t itemToSelect = 1;
-		std::function<bool(SDL_Event &)> eventHandler;
+		std::optional<tl::function_ref<bool(SDL_Event &)>> eventHandler;
 
 		switch (shownMenu) {
 		case ShownMenuType::Settings: {

Source/engine/path.cpp

@@ -7,6 +7,8 @@
 
 #include <array>
 
+#include <function_ref.hpp>
+
 #include "levels/gendung.h"
 #include "lighting.h"
 #include "objects.h"
@@ -290,7 +292,7 @@ bool ParentPath(uint16_t pathIndex, Point candidatePosition, Point destinationPo
  *
  * @return false if we ran out of preallocated nodes to use, else true
  */
-bool GetPath(const std::function<bool(Point)> &posOk, uint16_t pathIndex, Point destination)
+bool GetPath(tl::function_ref<bool(Point)> posOk, uint16_t pathIndex, Point destination)
 {
 	for (Displacement dir : PathDirs) {
 		const PathNode &path = PathNodes[pathIndex];
@@ -362,7 +364,7 @@ bool IsTileOccupied(Point position)
 	return false;
 }
 
-int FindPath(const std::function<bool(Point)> &posOk, Point startPosition, Point destinationPosition, int8_t path[MaxPathLength])
+int FindPath(tl::function_ref<bool(Point)> posOk, Point startPosition, Point destinationPosition, int8_t path[MaxPathLength])
 {
 	/**
 	 * for reconstructing the path after the A* search is done. The longest
@@ -434,7 +436,7 @@ bool path_solid_pieces(Point startPosition, Point destinationPosition)
 	return rv;
 }
 
-std::optional<Point> FindClosestValidPosition(const std::function<bool(Point)> &posOk, Point startingPosition, unsigned int minimumRadius, unsigned int maximumRadius)
+std::optional<Point> FindClosestValidPosition(tl::function_ref<bool(Point)> posOk, Point startingPosition, unsigned int minimumRadius, unsigned int maximumRadius)
 {
 	return Crawl(minimumRadius, maximumRadius, [&](Displacement displacement) -> std::optional<Point> {
 		Point candidatePosition = startingPosition + displacement;

Source/engine/path.h

@@ -6,10 +6,10 @@
 #pragma once
 
 #include <cstdint>
-#include <functional>
 #include <limits>
 
 #include <SDL.h>
+#include <function_ref.hpp>
 
 #include "engine/direction.hpp"
 #include "engine/point.hpp"
@@ -36,7 +36,7 @@ bool IsTileOccupied(Point position);
  * @brief Find the shortest path from startPosition to destinationPosition, using PosOk(Point) to check that each step is a valid position.
  * Store the step directions (corresponds to an index in PathDirs) in path, which must have room for 24 steps
  */
-int FindPath(const std::function<bool(Point)> &posOk, Point startPosition, Point destinationPosition, int8_t path[MaxPathLength]);
+int FindPath(tl::function_ref<bool(Point)> posOk, Point startPosition, Point destinationPosition, int8_t path[MaxPathLength]);
 
 /**
  * @brief check if stepping from a given position to a neighbouring tile cuts a corner.
@@ -83,6 +83,6 @@ const Displacement PathDirs[8] = {
  * @param maximumRadius The maximum distance to check, defaults to 18 for vanilla compatibility but supports values up to 50
  * @return either the closest valid point or an empty optional
  */
-std::optional<Point> FindClosestValidPosition(const std::function<bool(Point)> &posOk, Point startingPosition, unsigned int minimumRadius = 0, unsigned int maximumRadius = 18);
+std::optional<Point> FindClosestValidPosition(tl::function_ref<bool(Point)> posOk, Point startingPosition, unsigned int minimumRadius = 0, unsigned int maximumRadius = 18);
 
 } // namespace devilution

Source/missiles.cpp

@@ -458,7 +458,7 @@ void CheckMissileCol(Missile &missile, int minDamage, int maxDamage, bool isDama
 		PlaySfxLoc(MissilesData[missile._mitype].miSFX, missile.position.tile);
 }
 
-bool MoveMissile(Missile &missile, const std::function<bool(Point)> &checkTile, bool ifCheckTileFailsDontMoveToTile = false)
+bool MoveMissile(Missile &missile, tl::function_ref<bool(Point)> checkTile, bool ifCheckTileFailsDontMoveToTile = false)
 {
 	Point prevTile = missile.position.tile;
 	missile.position.traveled += missile.position.velocity;

Source/monster.cpp

@@ -4049,7 +4049,7 @@ bool LineClearMissile(Point startPoint, Point endPoint)
 	return LineClear(PosOkMissile, startPoint, endPoint);
 }
 
-bool LineClear(const std::function<bool(Point)> &clear, Point startPoint, Point endPoint)
+bool LineClear(tl::function_ref<bool(Point)> clear, Point startPoint, Point endPoint)
 {
 	Point position = startPoint;
 

Source/monster.h

@@ -11,6 +11,8 @@
 #include <array>
 #include <functional>
 
+#include <function_ref.hpp>
+
 #include "engine.h"
 #include "engine/actor_position.hpp"
 #include "engine/animationinfo.h"
@@ -478,7 +480,7 @@ void FreeMonsters();
 bool DirOK(const Monster &monster, Direction mdir);
 bool PosOkMissile(Point position);
 bool LineClearMissile(Point startPoint, Point endPoint);
-bool LineClear(const std::function<bool(Point)> &clear, Point startPoint, Point endPoint);
+bool LineClear(tl::function_ref<bool(Point)> clear, Point startPoint, Point endPoint);
 void SyncMonsterAnim(Monster &monster);
 void M_FallenFear(Point position);
 void PrintMonstHistory(int mt);

Source/panels/charpanel.cpp

@@ -3,6 +3,7 @@
 #include <string>
 
 #include <fmt/format.h>
+#include <function_ref.hpp>
 
 #include "control.h"
 #include "engine/load_clx.hpp"
@@ -42,8 +43,8 @@ struct PanelEntry {
 	std::string label;
 	Point position;
 	int length;
-	int labelLength;                                       // max label's length - used for line wrapping
-	std::function<StyledText()> statDisplayFunc = nullptr; // function responsible for displaying stat
+	int labelLength;                                               // max label's length - used for line wrapping
+	std::optional<tl::function_ref<StyledText()>> statDisplayFunc; // function responsible for displaying stat
 };
 
 UiFlags GetBaseStatColor(CharacterAttribute attr)
@@ -145,8 +146,8 @@ PanelEntry panelEntries[] = {
 	        return StyledText { UiFlags::ColorWhite, FormatInteger(MyPlayer->_pNextExper), spacing };
 	    } },
 
-	{ N_("Base"), { LeftColumnLabelX, /* set dynamically */ 0 }, 0, 44 },
-	{ N_("Now"), { 135, /* set dynamically */ 0 }, 0, 44 },
+	{ N_("Base"), { LeftColumnLabelX, /* set dynamically */ 0 }, 0, 44, {} },
+	{ N_("Now"), { 135, /* set dynamically */ 0 }, 0, 44, {} },
 	{ N_("Strength"), { LeftColumnLabelX, 135 }, 45, LeftColumnLabelWidth,
 	    []() { return StyledText { GetBaseStatColor(CharacterAttribute::Strength), StrCat(MyPlayer->_pBaseStr) }; } },
 	{ "", { 135, 135 }, 45, 0,
@@ -167,7 +168,7 @@ PanelEntry panelEntries[] = {
 	        return StyledText { UiFlags::ColorRed, (MyPlayer->_pStatPts > 0 ? StrCat(MyPlayer->_pStatPts) : "") };
 	    } },
 
-	{ N_("Gold"), { TopRightLabelX, /* set dynamically */ 0 }, 0, 98 },
+	{ N_("Gold"), { TopRightLabelX, /* set dynamically */ 0 }, 0, 98, {} },
 	{ "", { TopRightLabelX, 127 }, 99, 0,
 	    []() { return StyledText { UiFlags::ColorWhite, FormatInteger(MyPlayer->_pGold) }; } },
 
@@ -283,7 +284,7 @@ void LoadCharPanel()
 		panelEntries[GoldHeaderEntryIndex].position.y = isSmallFontTall ? 105 : 106;
 
 		for (auto &entry : panelEntries) {
-			if (entry.statDisplayFunc != nullptr) {
+			if (entry.statDisplayFunc) {
 				DrawPanelField(out, entry.position, entry.length, boxLeft[0], boxMiddle[0], boxRight[0]);
 			}
 			DrawShadowString(out, entry);
@@ -303,8 +304,8 @@ void DrawChr(const Surface &out)
 	Point pos = GetPanelPosition(UiPanels::Character, { 0, 0 });
 	RenderClxSprite(out, (*Panel)[0], pos);
 	for (auto &entry : panelEntries) {
-		if (entry.statDisplayFunc != nullptr) {
-			StyledText tmp = entry.statDisplayFunc();
+		if (entry.statDisplayFunc) {
+			StyledText tmp = (*entry.statDisplayFunc)();
 			DrawString(
 			    out,
 			    tmp.text,

Source/platform/vita/CMakeLists.txt

@@ -23,4 +23,5 @@ target_link_libraries(libdevilutionx_vita PUBLIC
   SceAppUtil_stub
   SceNet_stub
   SceNetCtl_stub
+  tl
 )

Source/utils/language.cpp

@@ -1,10 +1,11 @@
 #include "utils/language.h"
 
-#include <functional>
 #include <memory>
 #include <unordered_map>
 #include <vector>
 
+#include <function_ref.hpp>
+
 #include "engine/assets.hpp"
 #include "options.h"
 #include "utils/file_util.h"
@@ -104,7 +105,7 @@ string_view TrimRight(string_view str)
 
 // English, Danish, Spanish, Italian, Swedish
 unsigned PluralForms = 2;
-std::function<int(int n)> GetLocalPluralId = [](int n) -> int { return n != 1 ? 1 : 0; };
+tl::function_ref<int(int n)> GetLocalPluralId = [](int n) -> int { return n != 1 ? 1 : 0; };
 
 /**
  * Match plural=(n != 1);"