Add wear bar color API (#13328)

---------

Co-authored-by: Muhammad Rifqi Priyo Susanto <muhammadrifqipriyosusanto@gmail.com>
Co-authored-by: Lars Müller <34514239+appgurueu@users.noreply.github.com>
Co-authored-by: grorp <gregor.parzefall@posteo.de>

doc/lua_api.md

@@ -7273,6 +7273,8 @@ an itemstring, a table or `nil`.
       the item breaks after `max_uses` times
     * Valid `max_uses` range is [0,65536]
     * Does nothing if item is not a tool or if `max_uses` is 0
+* `get_wear_bar_params()`: returns the wear bar parameters of the item,
+  or nil if none are defined for this item type or in the stack's meta
 * `add_item(item)`: returns leftover `ItemStack`
     * Put some item or stack onto this stack
 * `item_fits(item)`: returns `true` if item or stack can be fully added to
@@ -7314,6 +7316,10 @@ Can be obtained via `item:get_meta()`.
     * Overrides the item's tool capabilities
     * A nil value will clear the override data and restore the original
       behavior.
+* `set_wear_bar_params([wear_bar_params])`
+    * Overrides the item's wear bar parameters (see "Wear Bar Color" section)
+    * A nil value will clear the override data and restore the original
+      behavior.
 
 `MetaDataRef`
 -------------
@@ -8815,6 +8821,19 @@ Used by `minetest.register_node`, `minetest.register_craftitem`, and
         -- fallback behavior.
     },
 
+    -- Set wear bar color of the tool by setting color stops and blend mode
+    -- See "Wear Bar Color" section for further explanation including an example
+    wear_color = {
+        -- interpolation mode: 'constant' or 'linear'
+        -- (nil defaults to 'constant')
+        blend = "linear",
+        color_stops = {
+            [0.0] = "#ff0000",
+            [0.5] = "#ffff00",
+            [1.0] = "#00ff00",
+        }
+    },
+
     node_placement_prediction = nil,
     -- If nil and item is node, prediction is made automatically.
     -- If nil and item is not a node, no prediction is made.
@@ -9382,6 +9401,46 @@ Used by `minetest.register_node`.
 }
 ```
 
+Wear Bar Color
+--------------
+
+'Wear Bar' is a property of items that defines the coloring
+of the bar that appears under damaged tools.
+If it is absent, the default behavior of green-yellow-red is
+used.
+
+### Wear bar colors definition
+
+#### Syntax
+
+```lua
+{
+    -- 'constant' or 'linear'
+    -- (nil defaults to 'constant')
+    blend = "linear",
+    color_stops = {
+        [0.0] = "#ff0000",
+        [0.5] = "slateblue",
+        [1.0] = {r=0, g=255, b=0, a=150},
+    }
+}
+```
+
+#### Blend mode `blend`
+
+* `linear`: blends smoothly between each defined color point.
+* `constant`: each color starts at its defined point, and continues up to the next point
+
+#### Color stops `color_stops`
+
+Specified as `ColorSpec` color values assigned to `float` durability keys.
+
+"Durability" is defined as `1 - (wear / 65535)`.
+
+#### Shortcut usage
+
+Wear bar color can also be specified as a single `ColorSpec` instead of a table.
+
 Crafting recipes
 ----------------
 

games/devtest/mods/basetools/init.lua

@@ -420,36 +420,141 @@ minetest.register_tool("basetools:dagger_steel", {
 	}
 })
 
--- Test tool uses and punch_attack_uses
-local uses = { 1, 2, 3, 5, 10, 50, 100, 1000, 10000, 65535 }
-for i=1, #uses do
-	local u = uses[i]
-	local ustring
-	if i == 1 then
-		ustring = u.."-Use"
-	else
-		ustring = u.."-Uses"
-	end
-	local color = string.format("#FF00%02X", math.floor(((i-1)/#uses) * 255))
-	minetest.register_tool("basetools:pick_uses_"..string.format("%05d", u), {
+-- Test tool uses, punch_attack_uses, and wear bar coloring
+local tool_params = {
+	{uses = 1},
+	{uses = 2},
+	{uses = 3},
+	{
+		uses = 5,
+		wear_color = "#5865f2",
+		wear_description = "Solid color: #5865f2",
+	},
+	{
+		uses = 10,
+		wear_color = "slateblue",
+		wear_description = "Solid color: slateblue",
+	},
+	{
+		uses = 50,
+		wear_color = {
+			color_stops = {
+				[0] = "red",
+				[0.5] = "yellow",
+				[1.0] = "blue"
+			},
+			blend = "linear"
+		},
+		wear_description = "Ranges from blue to yellow to red",
+	},
+	{
+		uses = 100,
+		wear_color = {
+			color_stops = {
+				[0] = "#ffff00",
+				[0.2] = "#ff00ff",
+				[0.3] = "#ffff00",
+				[0.45] = "#c0ffee",
+				[0.6] = {r=255, g=255, b=0, a=100}, -- continues until the end
+			},
+			blend = "constant"
+		},
+		wear_description = "Misc. colors, constant interpolation",
+	},
+	{uses = 1e3},
+	{uses = 1e4},
+	{uses = 65535},
+}
+
+for i, params in ipairs(tool_params) do
+	local uses = params.uses
+	local ustring = uses.."-Use"..(uses == 1 and "" or "s")
+	local color = string.format("#FF00%02X", math.floor(((i-1)/#tool_params) * 255))
+	minetest.register_tool("basetools:pick_uses_"..string.format("%05d", uses), {
 		description = ustring.." Pickaxe".."\n"..
-			"Digs cracky=3",
+			"Digs cracky=3"..
+			(params.wear_description and "\n".."Wear bar: " .. params.wear_description or ""),
 		inventory_image = "basetools_usespick.png^[colorize:"..color..":127",
 		tool_capabilities = {
 			max_drop_level=0,
 			groupcaps={
-				cracky={times={[3]=0.1, [2]=0.2, [1]=0.3}, uses=u, maxlevel=0}
+				cracky={times={[3]=0.1, [2]=0.2, [1]=0.3}, uses=uses, maxlevel=0}
 			},
 		},
+		wear_color = params.wear_color
 	})
 
-	minetest.register_tool("basetools:sword_uses_"..string.format("%05d", u), {
+	minetest.register_tool("basetools:sword_uses_"..string.format("%05d", uses), {
 		description = ustring.." Sword".."\n"..
 			"Damage: fleshy=1",
 		inventory_image = "basetools_usessword.png^[colorize:"..color..":127",
 		tool_capabilities = {
 			damage_groups = {fleshy=1},
-			punch_attack_uses = u,
+			punch_attack_uses = uses,
 		},
 	})
 end
+
+minetest.register_chatcommand("wear_color", {
+	params = "[idx]",
+	description = "Set wear bar color override",
+	func = function(player_name, param)
+		local player = minetest.get_player_by_name(player_name)
+		if not player then return end
+
+		local wear_color = nil
+		local wear_desc = "Reset override"
+
+		if param ~= "" then
+			local params = tool_params[tonumber(param)]
+			if not params then
+				return false, "idx out of bounds"
+			end
+			wear_color = params.wear_color
+			wear_desc = "Set override: "..(params.wear_description or "Default behavior")
+		end
+		local tool = player:get_wielded_item()
+		if tool:get_count() == 0 then
+			return false, "Tool not found"
+		end
+		tool:get_meta():set_wear_bar_params(wear_color)
+		player:set_wielded_item(tool)
+		return true, wear_desc
+	end
+})
+
+-- Punch handler to set random color & wear
+local wear_on_use = function(itemstack, user, pointed_thing)
+	local meta = itemstack:get_meta()
+	local color = math.random(0, 0xFFFFFF)
+	local colorstr = string.format("#%06x", color)
+	meta:set_wear_bar_params(colorstr)
+	minetest.log("action", "[basetool] Wear bar color of "..itemstack:get_name().." changed to "..colorstr)
+	itemstack:set_wear(math.random(0, 65535))
+	return itemstack
+end
+
+-- Place handler to clear item metadata color
+local wear_on_place = function(itemstack, user, pointed_thing)
+	local meta = itemstack:get_meta()
+	meta:set_wear_bar_params(nil)
+	return itemstack
+end
+
+minetest.register_tool("basetools:random_wear_bar", {
+	description = "Wear Bar Color Test\n" ..
+			"Punch: Set random color & wear\n" ..
+			"Place: Clear color",
+	-- Base texture: A grayscale square (can be colorized)
+	inventory_image = "basetools_usespick.png^[colorize:#FFFFFF:127",
+	tool_capabilities = {
+		max_drop_level=0,
+		groupcaps={
+			cracky={times={[3]=0.1, [2]=0.2, [1]=0.3}, uses=1000, maxlevel=0}
+		},
+	},
+
+	on_use = wear_on_use,
+	on_place = wear_on_place,
+	on_secondary_use = wear_on_place,
+})

games/devtest/mods/util_commands/init.lua

@@ -210,6 +210,29 @@ minetest.register_chatcommand("dump_item", {
 	end,
 })
 
+minetest.register_chatcommand("dump_itemdef", {
+	params = "",
+	description = "Prints a dump of the wielded item's definition in table form",
+	func = function(name, param)
+		local player = minetest.get_player_by_name(name)
+		local str = dump(player:get_wielded_item():get_definition())
+		print(str)
+		return true, str
+	end,
+})
+
+minetest.register_chatcommand("dump_wear_bar", {
+	params = "",
+	description = "Prints a dump of the wielded item's wear bar parameters in table form",
+	func = function(name, param)
+		local player = minetest.get_player_by_name(name)
+		local item = player:get_wielded_item()
+		local str = dump(item:get_wear_bar_params())
+		print(str)
+		return true, str
+	end,
+})
+
 core.register_chatcommand("set_saturation", {
     params = "<saturation>",
     description = "Set the saturation for current player.",

src/client/hud.cpp

@@ -1179,17 +1179,26 @@ void drawItemStack(
 			(1 - wear) * progressrect.LowerRightCorner.X;
 
 		// Compute progressbar color
+		// default scheme:
 		//   wear = 0.0: green
 		//   wear = 0.5: yellow
 		//   wear = 1.0: red
-		video::SColor color(255, 255, 255, 255);
-		int wear_i = MYMIN(std::floor(wear * 600), 511);
-		wear_i = MYMIN(wear_i + 10, 511);
 
-		if (wear_i <= 255)
-			color.set(255, wear_i, 255, 0);
-		else
-			color.set(255, 255, 511 - wear_i, 0);
+		video::SColor color;
+		auto barParams = item.getWearBarParams(client->idef());
+		if (barParams.has_value()) {
+			f32 durabilityPercent = 1.0 - wear;
+			color = barParams->getWearBarColor(durabilityPercent);
+		} else {
+			color = video::SColor(255, 255, 255, 255);
+			int wear_i = MYMIN(std::floor(wear * 600), 511);
+			wear_i = MYMIN(wear_i + 10, 511);
+
+			if (wear_i <= 255)
+				color.set(255, wear_i, 255, 0);
+			else
+				color.set(255, 255, 511 - wear_i, 0);
+		}
 
 		core::rect<s32> progressrect2 = progressrect;
 		progressrect2.LowerRightCorner.X = progressmid;

src/inventory.h

@@ -131,6 +131,15 @@ struct ItemStack
 		return metadata.getToolCapabilities(*item_cap); // Check for override
 	}
 
+	const std::optional<WearBarParams> &getWearBarParams(
+			const IItemDefManager *itemdef) const
+	{
+		auto &meta_override = metadata.getWearBarParamOverride();
+		if (meta_override.has_value())
+			return meta_override;
+		return itemdef->get(name).wear_bar_params;
+	}
+
 	// Wear out (only tools)
 	// Returns true if the item is (was) a tool
 	bool addWear(s32 amount, const IItemDefManager *itemdef)

src/itemdef.cpp

@@ -125,6 +125,7 @@ ItemDefinition& ItemDefinition::operator=(const ItemDefinition &def)
 	pointabilities = def.pointabilities;
 	if (def.tool_capabilities)
 		tool_capabilities = new ToolCapabilities(*def.tool_capabilities);
+	wear_bar_params = def.wear_bar_params;
 	groups = def.groups;
 	node_placement_prediction = def.node_placement_prediction;
 	place_param2 = def.place_param2;
@@ -149,6 +150,7 @@ void ItemDefinition::resetInitial()
 {
 	// Initialize pointers to NULL so reset() does not delete undefined pointers
 	tool_capabilities = NULL;
+	wear_bar_params = std::nullopt;
 	reset();
 }
 
@@ -171,6 +173,7 @@ void ItemDefinition::reset()
 	pointabilities = std::nullopt;
 	delete tool_capabilities;
 	tool_capabilities = NULL;
+	wear_bar_params.reset();
 	groups.clear();
 	sound_place = SoundSpec();
 	sound_place_failed = SoundSpec();
@@ -251,6 +254,13 @@ void ItemDefinition::serialize(std::ostream &os, u16 protocol_version) const
 		pointabilities_s = tmp_os.str();
 	}
 	os << serializeString16(pointabilities_s);
+
+	if (wear_bar_params.has_value()) {
+		writeU8(os, 1);
+		wear_bar_params->serialize(os);
+	} else {
+		writeU8(os, 0);
+	}
 }
 
 void ItemDefinition::deSerialize(std::istream &is, u16 protocol_version)
@@ -333,6 +343,10 @@ void ItemDefinition::deSerialize(std::istream &is, u16 protocol_version)
 			pointabilities = std::make_optional<Pointabilities>();
 			pointabilities->deSerialize(tmp_is);
 		}
+
+		if (readU8(is)) {
+			wear_bar_params = WearBarParams::deserialize(is);
+		}
 	} catch(SerializationError &e) {};
 }
 

src/itemdef.h

@@ -28,6 +28,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "itemgroup.h"
 #include "sound.h"
 #include "texture_override.h" // TextureOverride
+#include "tool.h"
 #include "util/pointabilities.h"
 class IGameDef;
 class Client;
@@ -103,6 +104,8 @@ struct ItemDefinition
 	// They may be NULL. If non-NULL, deleted by destructor
 	ToolCapabilities *tool_capabilities;
 
+	std::optional<WearBarParams> wear_bar_params;
+
 	ItemGroupList groups;
 	SoundSpec sound_place;
 	SoundSpec sound_place_failed;

src/itemstackmetadata.cpp

@@ -21,7 +21,9 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "itemstackmetadata.h"
 #include "util/serialize.h"
 #include "util/strfnd.h"
+
 #include <algorithm>
+#include <optional>
 
 #define DESERIALIZE_START '\x01'
 #define DESERIALIZE_KV_DELIM '\x02'
@@ -31,11 +33,13 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #define DESERIALIZE_PAIR_DELIM_STR "\x03"
 
 #define TOOLCAP_KEY "tool_capabilities"
+#define WEAR_BAR_KEY "wear_color"
 
 void ItemStackMetadata::clear()
 {
 	SimpleMetadata::clear();
 	updateToolCapabilities();
+	updateWearBarParams();
 }
 
 static void sanitize_string(std::string &str)
@@ -55,6 +59,8 @@ bool ItemStackMetadata::setString(const std::string &name, const std::string &va
 	bool result = SimpleMetadata::setString(clean_name, clean_var);
 	if (clean_name == TOOLCAP_KEY)
 		updateToolCapabilities();
+	else if (clean_name == WEAR_BAR_KEY)
+		updateWearBarParams();
 	return result;
 }
 
@@ -91,6 +97,7 @@ void ItemStackMetadata::deSerialize(std::istream &is)
 		}
 	}
 	updateToolCapabilities();
+	updateWearBarParams();
 }
 
 void ItemStackMetadata::updateToolCapabilities()
@@ -116,3 +123,25 @@ void ItemStackMetadata::clearToolCapabilities()
 {
 	setString(TOOLCAP_KEY, "");
 }
+
+void ItemStackMetadata::updateWearBarParams()
+{
+	if (contains(WEAR_BAR_KEY)) {
+		std::istringstream is(getString(WEAR_BAR_KEY));
+		wear_bar_override = WearBarParams::deserializeJson(is);
+	} else {
+		wear_bar_override.reset();
+	}
+}
+
+void ItemStackMetadata::setWearBarParams(const WearBarParams &params)
+{
+	std::ostringstream os;
+	params.serializeJson(os);
+	setString(WEAR_BAR_KEY, os.str());
+}
+
+void ItemStackMetadata::clearWearBarParams()
+{
+	setString(WEAR_BAR_KEY, "");
+}

src/itemstackmetadata.h

@@ -22,13 +22,17 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "metadata.h"
 #include "tool.h"
 
+#include <optional>
+
 class Inventory;
 class IItemDefManager;
 
 class ItemStackMetadata : public SimpleMetadata
 {
 public:
-	ItemStackMetadata() : toolcaps_overridden(false) {}
+	ItemStackMetadata():
+			toolcaps_overridden(false)
+	{}
 
 	// Overrides
 	void clear() override;
@@ -46,9 +50,20 @@ public:
 	void setToolCapabilities(const ToolCapabilities &caps);
 	void clearToolCapabilities();
 
+	const std::optional<WearBarParams> &getWearBarParamOverride() const
+	{
+		return wear_bar_override;
+	}
+
+
+	void setWearBarParams(const WearBarParams &params);
+	void clearWearBarParams();
+
 private:
 	void updateToolCapabilities();
+	void updateWearBarParams();
 
 	bool toolcaps_overridden;
 	ToolCapabilities toolcaps_override;
+	std::optional<WearBarParams> wear_bar_override;
 };

src/script/common/c_content.cpp

@@ -35,6 +35,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "server/player_sao.h"
 #include "util/pointedthing.h"
 #include "debug.h" // For FATAL_ERROR
+#include <SColor.h>
 #include <json/json.h>
 
 struct EnumString es_TileAnimationType[] =
@@ -94,6 +95,15 @@ void read_item_definition(lua_State* L, int index,
 		def.tool_capabilities = new ToolCapabilities(
 				read_tool_capabilities(L, -1));
 	}
+	lua_getfield(L, index, "wear_color");
+	if (lua_istable(L, -1)) {
+		def.wear_bar_params = read_wear_bar_params(L, -1);
+	} else if (lua_isstring(L, -1)) {
+		video::SColor color;
+		read_color(L, -1, &color);
+		def.wear_bar_params = WearBarParams({{0.0, color}},
+				WearBarParams::BLEND_MODE_CONSTANT);
+	}
 
 	// If name is "" (hand), ensure there are ToolCapabilities
 	// because it will be looked up there whenever any other item has
@@ -213,6 +223,10 @@ void push_item_definition_full(lua_State *L, const ItemDefinition &i)
 		push_tool_capabilities(L, *i.tool_capabilities);
 		lua_setfield(L, -2, "tool_capabilities");
 	}
+	if (i.wear_bar_params.has_value()) {
+		push_wear_bar_params(L, *i.wear_bar_params);
+		lua_setfield(L, -2, "wear_color");
+	}
 	push_groups(L, i.groups);
 	lua_setfield(L, -2, "groups");
 	push_simplesoundspec(L, i.sound_place);
@@ -1454,6 +1468,22 @@ void push_tool_capabilities(lua_State *L,
 		lua_setfield(L, -2, "damage_groups");
 }
 
+/******************************************************************************/
+void push_wear_bar_params(lua_State *L,
+		const WearBarParams &params)
+{
+	lua_newtable(L);
+	setstringfield(L, -1, "blend", WearBarParams::es_BlendMode[params.blend].str);
+
+	lua_newtable(L);
+	for (const std::pair<const f32, const video::SColor> item: params.colorStops) {
+		lua_pushnumber(L, item.first); // key
+		push_ARGB8(L, item.second);
+		lua_rawset(L, -3);
+	}
+	lua_setfield(L, -2, "color_stops");
+}
+
 /******************************************************************************/
 void push_inventory_list(lua_State *L, const InventoryList &invlist)
 {
@@ -1732,6 +1762,54 @@ void push_pointabilities(lua_State *L, const Pointabilities &pointabilities)
 	}
 }
 
+/******************************************************************************/
+WearBarParams read_wear_bar_params(
+		lua_State *L, int stack_idx)
+{
+	if (lua_isstring(L, stack_idx)) {
+		video::SColor color;
+		read_color(L, stack_idx, &color);
+		return WearBarParams(color);
+	}
+
+	if (!lua_istable(L, stack_idx))
+		throw LuaError("Expected wear bar color table or colorstring");
+
+	lua_getfield(L, stack_idx, "color_stops");
+	if (!check_field_or_nil(L, -1, LUA_TTABLE, "color_stops"))
+		throw LuaError("color_stops must be a table");
+
+	std::map<f32, video::SColor> colorStops;
+	// color stops table is on the stack
+	int table_values = lua_gettop(L);
+	lua_pushnil(L);
+	while (lua_next(L, table_values) != 0) {
+		// key at index -2 and value at index -1 within table_values
+		f32 point = luaL_checknumber(L, -2);
+		if (point < 0 || point > 1)
+			throw LuaError("Wear bar color stop key out of range");
+		video::SColor color;
+		read_color(L, -1, &color);
+		colorStops.emplace(point, color);
+
+		// removes value, keeps key for next iteration
+		lua_pop(L, 1);
+	}
+	lua_pop(L, 1); // pop color stops table
+
+	auto blend = WearBarParams::BLEND_MODE_CONSTANT;
+	lua_getfield(L, stack_idx, "blend");
+	if (check_field_or_nil(L, -1, LUA_TSTRING, "blend")) {
+		int blendInt;
+		if (!string_to_enum(WearBarParams::es_BlendMode, blendInt, std::string(lua_tostring(L, -1))))
+			throw LuaError("Invalid wear bar color blend mode");
+		blend = static_cast<WearBarParams::BlendMode>(blendInt);
+	}
+	lua_pop(L, 1);
+
+	return WearBarParams(colorStops, blend);
+}
+
 /******************************************************************************/
 void push_dig_params(lua_State *L,const DigParams &params)
 {

src/script/common/c_content.h

@@ -116,6 +116,9 @@ void               push_pointabilities       (lua_State *L, const Pointabilities
 ToolCapabilities   read_tool_capabilities    (lua_State *L, int table);
 void               push_tool_capabilities    (lua_State *L,
                                               const ToolCapabilities &prop);
+WearBarParams      read_wear_bar_params      (lua_State *L, int table);
+void               push_wear_bar_params      (lua_State *L,
+                                              const WearBarParams &prop);
 
 void read_item_definition (lua_State *L, int index, const ItemDefinition &default_def,
 		ItemDefinition &def);

src/script/lua_api/l_item.cpp

@@ -376,6 +376,22 @@ int LuaItemStack::l_add_wear_by_uses(lua_State *L)
 	return 1;
 }
 
+// get_wear_bar_params(self) -> table
+// Returns the effective wear bar parameters.
+// Returns nil if this item has none associated.
+int LuaItemStack::l_get_wear_bar_params(lua_State *L)
+{
+	NO_MAP_LOCK_REQUIRED;
+	LuaItemStack *o = checkObject<LuaItemStack>(L, 1);
+	ItemStack &item = o->m_stack;
+	auto params = item.getWearBarParams(getGameDef(L)->idef());
+	if (params.has_value()) {
+		push_wear_bar_params(L, *params);
+		return 1;
+	}
+	return 0;
+}
+
 // add_item(self, itemstack or itemstring or table or nil) -> itemstack
 // Returns leftover item stack
 int LuaItemStack::l_add_item(lua_State *L)
@@ -551,6 +567,7 @@ const luaL_Reg LuaItemStack::methods[] = {
 	luamethod(LuaItemStack, get_tool_capabilities),
 	luamethod(LuaItemStack, add_wear),
 	luamethod(LuaItemStack, add_wear_by_uses),
+	luamethod(LuaItemStack, get_wear_bar_params),
 	luamethod(LuaItemStack, add_item),
 	luamethod(LuaItemStack, item_fits),
 	luamethod(LuaItemStack, take_item),

src/script/lua_api/l_item.h

@@ -125,6 +125,11 @@ private:
 	// Returns true if the item is (or was) a tool.
 	static int l_add_wear_by_uses(lua_State *L);
 
+	// get_wear_bar_params(self) -> table
+	// Returns the effective wear bar parameters.
+	// Returns nil if this item has none associated.
+	static int l_get_wear_bar_params(lua_State *L);
+
 	// add_item(self, itemstack or itemstring or table or nil) -> itemstack
 	// Returns leftover item stack
 	static int l_add_item(lua_State *L);

src/script/lua_api/l_itemstackmeta.cpp

@@ -22,6 +22,8 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "lua_api/l_itemstackmeta.h"
 #include "lua_api/l_internal.h"
 #include "common/c_content.h"
+#include "common/c_converter.h"
+#include "tool.h"
 
 /*
 	ItemStackMetaRef
@@ -58,6 +60,20 @@ int ItemStackMetaRef::l_set_tool_capabilities(lua_State *L)
 	return 0;
 }
 
+int ItemStackMetaRef::l_set_wear_bar_params(lua_State *L)
+{
+	ItemStackMetaRef *metaref = checkObject<ItemStackMetaRef>(L, 1);
+	if (lua_isnoneornil(L, 2)) {
+		metaref->clearWearBarParams();
+	} else if (lua_istable(L, 2) || lua_isstring(L, 2)) {
+		metaref->setWearBarParams(read_wear_bar_params(L, 2));
+	} else {
+		luaL_typerror(L, 2, "table, ColorString, or nil");
+	}
+
+	return 0;
+}
+
 ItemStackMetaRef::ItemStackMetaRef(LuaItemStack *istack): istack(istack)
 {
 	istack->grab();
@@ -102,5 +118,6 @@ const luaL_Reg ItemStackMetaRef::methods[] = {
 	luamethod(MetaDataRef, from_table),
 	luamethod(MetaDataRef, equals),
 	luamethod(ItemStackMetaRef, set_tool_capabilities),
+	luamethod(ItemStackMetaRef, set_wear_bar_params),
 	{0,0}
 };

src/script/lua_api/l_itemstackmeta.h

@@ -49,8 +49,19 @@ private:
 		istack->getItem().metadata.clearToolCapabilities();
 	}
 
+	void setWearBarParams(const WearBarParams &params)
+	{
+		istack->getItem().metadata.setWearBarParams(params);
+	}
+
+	void clearWearBarParams()
+	{
+		istack->getItem().metadata.clearWearBarParams();
+	}
+
 	// Exported functions
 	static int l_set_tool_capabilities(lua_State *L);
+	static int l_set_wear_bar_params(lua_State *L);
 public:
 	// takes a reference
 	ItemStackMetaRef(LuaItemStack *istack);

src/tool.cpp

@@ -26,7 +26,10 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "convert_json.h"
 #include "util/serialize.h"
 #include "util/numeric.h"
+#include "util/hex.h"
+#include "common/c_content.h"
 #include <json/json.h>
+	
 
 void ToolGroupCap::toJson(Json::Value &object) const
 {
@@ -183,6 +186,127 @@ void ToolCapabilities::deserializeJson(std::istream &is)
 	}
 }
 
+void WearBarParams::serialize(std::ostream &os) const
+{
+	writeU8(os, 1); // Version for future-proofing
+	writeU8(os, blend);
+	writeU16(os, colorStops.size());
+	for (const std::pair<f32, video::SColor> item : colorStops) {
+		writeF32(os, item.first);
+		writeARGB8(os, item.second);
+	}
+}
+
+WearBarParams WearBarParams::deserialize(std::istream &is)
+{
+	u8 version = readU8(is);
+	if (version > 1)
+		throw SerializationError("unsupported WearBarParams version");
+
+	auto blend = static_cast<WearBarParams::BlendMode>(readU8(is));
+	if (blend >= BlendMode_END)
+		throw SerializationError("invalid blend mode");
+	u16 count = readU16(is);
+	if (count == 0)
+		throw SerializationError("no stops");
+	std::map<f32, video::SColor> colorStops;
+	for (u16 i = 0; i < count; i++) {
+		f32 key = readF32(is);
+		if (key < 0 || key > 1)
+			throw SerializationError("key out of range");
+		video::SColor color = readARGB8(is);
+		colorStops.emplace(key, color);
+	}
+	return WearBarParams(colorStops, blend);
+}
+
+void WearBarParams::serializeJson(std::ostream &os) const
+{
+	Json::Value root;
+	Json::Value color_stops;
+	for (const std::pair<f32, video::SColor> item : colorStops) {
+		color_stops[ftos(item.first)] = encodeHexColorString(item.second);
+	}
+	root["color_stops"] = color_stops;
+	root["blend"] = WearBarParams::es_BlendMode[blend].str;
+
+	fastWriteJson(root, os);
+}
+
+std::optional<WearBarParams> WearBarParams::deserializeJson(std::istream &is)
+{
+	Json::Value root;
+	is >> root;
+	if (!root.isObject() || !root["color_stops"].isObject() || !root["blend"].isString())
+		return std::nullopt;
+
+	int blendInt;
+	WearBarParams::BlendMode blend;
+	if (string_to_enum(WearBarParams::es_BlendMode, blendInt, root["blend"].asString()))
+		blend = static_cast<WearBarParams::BlendMode>(blendInt);
+	else
+		return std::nullopt;
+	
+	const Json::Value &color_stops_object = root["color_stops"];
+	std::map<f32, video::SColor> colorStops;
+	for (const std::string &key : color_stops_object.getMemberNames()) {
+		f32 stop = stof(key);
+		if (stop < 0 || stop > 1)
+			return std::nullopt;
+		const Json::Value &value = color_stops_object[key];
+		if (value.isString()) {
+			video::SColor color;
+			parseColorString(value.asString(), color, false);
+			colorStops.emplace(stop, color);
+		}
+	}
+	if (colorStops.empty())
+		return std::nullopt;
+	return WearBarParams(colorStops, blend);
+}
+
+video::SColor WearBarParams::getWearBarColor(f32 durabilityPercent) {
+	if (colorStops.empty())
+		return video::SColor();
+
+	/*
+	 * Strategy:
+	 * Find upper bound of durabilityPercent
+	 *
+	 * if it == stops.end() -> return last color in the map
+	 * if it == stops.begin() -> return first color in the map
+	 *
+	 * else:
+	 * 	lower_bound = it - 1
+	 * 	interpolate/do constant
+	 */
+	auto upper = colorStops.upper_bound(durabilityPercent);
+
+	if (upper == colorStops.end()) // durability is >= the highest defined color stop
+		return std::prev(colorStops.end())->second; // return last element of the map
+
+	if (upper == colorStops.begin()) // durability is <= the lowest defined color stop
+		return upper->second;
+
+	auto lower = std::prev(upper);
+	f32 lower_bound = lower->first;
+	video::SColor lower_color = lower->second;
+	f32 upper_bound = upper->first;
+	video::SColor upper_color = upper->second;
+
+	f32 progress = (durabilityPercent - lower_bound) / (upper_bound - lower_bound);
+
+	switch (blend) {
+		case BLEND_MODE_CONSTANT:
+			return lower_color;
+		case BLEND_MODE_LINEAR:
+			return upper_color.getInterpolated(lower_color, progress);
+		case BlendMode_END:
+			throw std::logic_error("dummy value");
+	}
+	throw std::logic_error("invalid blend value");
+}
+
 u32 calculateResultWear(const u32 uses, const u16 initial_wear)
 {
 	if (uses == 0) {

src/tool.h

@@ -20,10 +20,15 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #pragma once
 
 #include "irrlichttypes.h"
-#include <string>
-#include <iostream>
 #include "itemgroup.h"
 #include "json-forwards.h"
+#include "common/c_types.h"
+#include <json/json.h>
+#include <SColor.h>
+
+#include <string>
+#include <iostream>
+#include <optional>
 
 struct ItemDefinition;
 
@@ -82,6 +87,37 @@ struct ToolCapabilities
 	void deserializeJson(std::istream &is);
 };
 
+struct WearBarParams
+{
+	std::map<f32, video::SColor> colorStops;
+	enum BlendMode: u8 {
+	    BLEND_MODE_CONSTANT,
+	    BLEND_MODE_LINEAR,
+	    BlendMode_END // Dummy for validity check
+	};
+	constexpr const static EnumString es_BlendMode[3] = {
+		{WearBarParams::BLEND_MODE_CONSTANT, "constant"},
+		{WearBarParams::BLEND_MODE_LINEAR, "linear"},
+		{0, NULL}
+	};
+	BlendMode blend;
+
+	WearBarParams(const std::map<f32, video::SColor> &colorStops, BlendMode blend):
+		colorStops(colorStops),
+		blend(blend)
+	{}
+
+	WearBarParams(const video::SColor color):
+		WearBarParams({{0.0, color}}, WearBarParams::BLEND_MODE_CONSTANT)
+	{};
+
+	void serialize(std::ostream &os) const;
+	static WearBarParams deserialize(std::istream &is);
+	void serializeJson(std::ostream &os) const;
+	static std::optional<WearBarParams> deserializeJson(std::istream &is);
+	video::SColor getWearBarColor(f32 durabilityPercent);
+};
+
 struct DigParams
 {
 	bool diggable;

src/util/string.cpp

@@ -574,6 +574,20 @@ bool parseColorString(const std::string &value, video::SColor &color, bool quiet
 	return success;
 }
 
+std::string encodeHexColorString(const video::SColor &color)
+{
+	std::string color_string = "#";
+	const char red = color.getRed();
+	const char green = color.getGreen();
+	const char blue = color.getBlue();
+	const char alpha = color.getAlpha();
+	color_string += hex_encode(&red, 1);
+	color_string += hex_encode(&green, 1);
+	color_string += hex_encode(&blue, 1);
+	color_string += hex_encode(&alpha, 1);
+	return color_string;
+}
+
 void str_replace(std::string &str, char from, char to)
 {
 	std::replace(str.begin(), str.end(), from, to);

src/util/string.h

@@ -88,6 +88,7 @@ char *mystrtok_r(char *s, const char *sep, char **lasts) noexcept;
 u64 read_seed(const char *str);
 bool parseColorString(const std::string &value, video::SColor &color, bool quiet,
 		unsigned char default_alpha = 0xff);
+std::string encodeHexColorString(const video::SColor &color);
 
 
 /**