Respect object property hp_max field for players (#6287)

* Respect object property hp_max field for players
This allows modders to configure the maximal HP per player

* Statbars: Downscale bar to full 20 HP when exceeding this value
Add default max HP for players and breath constants to builtin
Document the constants

* Rename PLAYER_MAX_HP -> PLAYER_MAX_HP_DEFAULT

2 files changed, 34 insertions, 19 deletions

diff --git a/builtin/game/constants.lua b/builtin/game/constants.lua
index 50c515b24..29eeb8330 100644
--- a/builtin/game/constants.lua
+++ b/builtin/game/constants.lua
@@ -21,6 +21,10 @@ core.EMERGE_GENERATED   = 4
 -- constants.h
 -- Size of mapblocks in nodes
 core.MAP_BLOCKSIZE = 16
+-- Default maximal HP of a player
+core.PLAYER_MAX_HP_DEFAULT = 20
+-- Maximal breath of a player
+core.PLAYER_MAX_BREATH = 11
 
 -- light.h
 -- Maximum value for node 'light_source' parameter
diff --git a/builtin/game/statbars.lua b/builtin/game/statbars.lua
index 6aa106140..1b83dd4ac 100644
--- a/builtin/game/statbars.lua
+++ b/builtin/game/statbars.lua
@@ -6,7 +6,7 @@ local health_bar_definition =
 	hud_elem_type = "statbar",
 	position = { x=0.5, y=1 },
 	text = "heart.png",
-	number = 20,
+	number = core.PLAYER_MAX_HP_DEFAULT,
 	direction = 0,
 	size = { x=24, y=24 },
 	offset = { x=(-10*24)-25, y=-(48+24+16)},
@@ -37,39 +37,45 @@ local function initialize_builtin_statbars(player)
 		return
 	end
 
-	if (hud_ids[name] == nil) then
+	if not hud_ids[name] then
 		hud_ids[name] = {}
 		-- flags are not transmitted to client on connect, we need to make sure
 		-- our current flags are transmitted by sending them actively
 		player:hud_set_flags(player:hud_get_flags())
 	end
+	local hud = hud_ids[name]
 
 	if player:hud_get_flags().healthbar and enable_damage then
- 		if hud_ids[name].id_healthbar == nil then
-			health_bar_definition.number = player:get_hp()
-			hud_ids[name].id_healthbar  = player:hud_add(health_bar_definition)
+ 		if hud.id_healthbar == nil then
+ 			local hp = player:get_hp()
+ 			local max_display_hp = math.max(core.PLAYER_MAX_HP_DEFAULT,
+ 				math.max(player:get_properties().hp_max, hp))
+ 			-- Limit width of health bar: Scale to the default maximal HP
+			health_bar_definition.number =
+				hp / max_display_hp * core.PLAYER_MAX_HP_DEFAULT
+			hud.id_healthbar  = player:hud_add(health_bar_definition)
 		end
 	else
-		if hud_ids[name].id_healthbar ~= nil then
-			player:hud_remove(hud_ids[name].id_healthbar)
-			hud_ids[name].id_healthbar = nil
+		if hud.id_healthbar ~= nil then
+			player:hud_remove(hud.id_healthbar)
+			hud.id_healthbar = nil
 		end
 	end
 
-	if (player:get_breath() < 11) then
+	if player:get_breath() < core.PLAYER_MAX_BREATH then
 		if player:hud_get_flags().breathbar and enable_damage then
-			if hud_ids[name].id_breathbar == nil then
-				hud_ids[name].id_breathbar = player:hud_add(breath_bar_definition)
+			if hud.id_breathbar == nil then
+				hud.id_breathbar = player:hud_add(breath_bar_definition)
 			end
 		else
-			if hud_ids[name].id_breathbar ~= nil then
-				player:hud_remove(hud_ids[name].id_breathbar)
-				hud_ids[name].id_breathbar = nil
+			if hud.id_breathbar ~= nil then
+				player:hud_remove(hud.id_breathbar)
+				hud.id_breathbar = nil
 			end
 		end
-	elseif hud_ids[name].id_breathbar ~= nil then
-		player:hud_remove(hud_ids[name].id_breathbar)
-		hud_ids[name].id_breathbar = nil
+	elseif hud.id_breathbar ~= nil then
+		player:hud_remove(hud.id_breathbar)
+		hud.id_breathbar = nil
 	end
 end
 
@@ -101,7 +107,12 @@ local function player_event_handler(player,eventname)
 		initialize_builtin_statbars(player)
 
 		if hud_ids[name].id_healthbar ~= nil then
-			player:hud_change(hud_ids[name].id_healthbar,"number",player:get_hp())
+ 			local hp = player:get_hp()
+ 			local max_display_hp = math.max(core.PLAYER_MAX_HP_DEFAULT,
+ 				math.max(player:get_properties().hp_max, hp))
+ 			-- Limit width of health bar: Scale to the default maximal HP
+			local hp_count = hp / max_display_hp * core.PLAYER_MAX_HP_DEFAULT
+			player:hud_change(hud_ids[name].id_healthbar, "number", hp_count)
 			return true
 		end
 	end
@@ -110,7 +121,7 @@ local function player_event_handler(player,eventname)
 		initialize_builtin_statbars(player)
 
 		if hud_ids[name].id_breathbar ~= nil then
-			player:hud_change(hud_ids[name].id_breathbar,"number",player:get_breath()*2)
+			player:hud_change(hud_ids[name].id_breathbar, "number", player:get_breath() * 2)
 			return true
 		end
 	end