Lua marker to create monsters on triggering

New lua marker MonsterOnTrigger, which creates a monster when the
triggering condition is met (which currently only includes a monster
dying).

Use it in the dis_mu Dis:7 vault to turn all of the iron statues into
iron golems when Dispater dies.

3 files changed, 126 insertions, 1 deletions

diff --git a/crawl-ref/source/dat/clua/lm_monst.lua b/crawl-ref/source/dat/clua/lm_monst.lua
new file mode 100644
index 0000000000..6700026fb4
--- /dev/null
+++ b/crawl-ref/source/dat/clua/lm_monst.lua
@@ -0,0 +1,118 @@
+---------------------------------------------------------------------------
+-- lm_monst.lua
+-- Create a monster on certain events
+--------------------------------------------------------------------------
+
+--------------------------------------------------------------------------------------
+-- This marker creates a monster on certain events.  It uses the following parameters:
+--
+-- * death_monster: The name of the monster who's death triggers the creation of
+--       the new monster.
+--
+-- * new_monster: The name of the monster to create.
+--
+-- * message: Message to give when monster is created, regardless of whether
+--       or not the player can see the marker.
+--
+-- * message_seen: Message to give if the player can see the marker.
+--
+-- * message_unseen: Message to give if the player can't see the marker.
+--
+-- NOTE: If the feature where the marker is isn't habitable by the new monster,
+-- the feature will be changed to the monster's primary habitat.
+--------------------------------------------------------------------------------------
+
+-- TODO:
+--  * Place more than one monster.
+--  * Place monster displaced from marker.
+
+MonsterOnTrigger = { CLASS = "MonsterOnTrigger" }
+MonsterOnTrigger.__index = MonsterOnTrigger
+
+function MonsterOnTrigger:_new()
+  local pm = { }
+  setmetatable(pm, self)
+  self.__index = self
+
+  return pm
+end
+
+function MonsterOnTrigger:new(pars)
+  pars = pars or { }
+
+  if not pars.death_monster or pars.death_monster == "" then
+    error("Must provide death_monster")
+  end
+
+  if not pars.new_monster or pars.new_monster == "" then
+    error("Must provide new_monster")
+  end
+
+  pars.message_seen   = pars.message_seen or pars.message or ""
+  pars.message_unseen = pars.message_unseen or pars.message or ""
+
+  local pm = self:_new()
+  pm.message_seen    = pars.message_seen
+  pm.message_unseen  = pars.message_unseen
+  pm.death_monster   = pars.death_monster
+  pm.new_monster     = pars.new_monster
+  pm.props           = pars
+
+  return pm
+end
+
+function MonsterOnTrigger:property(marker, pname)
+  return self.props[pname] or ''
+end
+
+function MonsterOnTrigger:write(marker, th)
+  lmark.marshall_table(th, self)
+end
+
+function MonsterOnTrigger:read(marker, th)
+  return MonsterOnTrigger:new(lmark.unmarshall_table(th))
+end
+
+function MonsterOnTrigger:activate(marker)
+  dgn.register_listener(dgn.dgn_event_type('monster_dies'), marker)
+end
+
+function MonsterOnTrigger:event(marker, ev)
+  local midx = ev:arg1()
+  local mons = dgn.mons_from_index(midx)
+
+  if not mons then
+    error("MonsterOnTrigger:event() didn't get a valid monster index")
+  end
+
+  if mons.name == self.death_monster then
+    local x,     y     = marker:pos()
+    local you_x, you_y = you.pos()
+
+    if x == you_x and y == you_y then
+      return
+    end
+
+    -- you.losight() seems to be necessary if the player has been moved by
+    -- a wizard command and then the marker triggered by another wizard
+    -- command, since then no turns will have been taken and the LOS info
+    -- won't have been updated.
+    you.losight()
+    local see_grid = you.see_grid(x, y)
+
+    if (not dgn.create_monster(x, y, self.new_monster)) then
+      return
+    elseif self.message_seen ~= "" and see_grid then
+      crawl.mpr(self.message_seen)
+    elseif self.message_unseen ~= "" and not see_grid then
+      crawl.mpr(self.message_unseen)
+    end
+
+    dgn.remove_listener(marker)
+    dgn.remove_marker(marker)
+  end
+end
+
+function monster_on_trigger(pars)
+  return MonsterOnTrigger:new(pars)
+end
diff --git a/crawl-ref/source/dat/clua/luamark.lua b/crawl-ref/source/dat/clua/luamark.lua
index cd9083e32d..43ec7f94ae 100644
--- a/crawl-ref/source/dat/clua/luamark.lua
+++ b/crawl-ref/source/dat/clua/luamark.lua
@@ -9,6 +9,7 @@ require('clua/lm_timed.lua')
 require('clua/lm_flags.lua')
 require('clua/lm_fog.lua')
 require('clua/lm_props.lua')
+require('clua/lm_monst.lua')
 
 function dlua_marker_function(table, name)
   return table[name]
diff --git a/crawl-ref/source/dat/hells.des b/crawl-ref/source/dat/hells.des
index dfad033c62..b2307a2387 100644
--- a/crawl-ref/source/dat/hells.des
+++ b/crawl-ref/source/dat/hells.des
@@ -454,6 +454,12 @@ SUBST:   4 = 4:20 7
 SUBST:   8 = 8o
 COLOUR:  o : cyan
 : dis_setup(_G)
+MARKER:  o = lua:monster_on_trigger { \
+            death_monster="Dispater", new_monster="generate_awake iron golem", \
+            message_seen="The iron statue comes to life!", \
+            message_unseen="You hear a grinding sound.", \
+            veto_fragmentation="veto", veto_disintegrate="veto" \
+         }
 MAP
 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
 xxxxxxvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvxxxxxx
@@ -1045,4 +1051,4 @@ xxxx.................................{xxxxBBBBxBBBBx.2..4..4...$$$$$xx
 xxxx................................[xxxxxBBBBxBBBBx..........$$$$$$xx  
 xxxx...............................(xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx  
 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
-ENDMAP
\ No newline at end of file
+ENDMAP