More interesting Gehennom levels

Instead of just plain old boring mazes, spice up Gehennom by
occasionally adding lava, iron bars, or even mines-style levels
(with lava, of course).

Of the fixed Gehennom levels, only Asmodeus' lair has been changed
to add some random lava pools.

Also some lua fixes and changes:
- Fixed a selection negation bounding box being wrong.
- Fixed a selection negated and ORed returning wrong results.
- des.map now returns a selection of the map grids it touched.
- When using des.map contents-function the commands following the
  map are not relative to it.

dat/hellfill.lua

@@ -0,0 +1,155 @@
+-- NetHack 3.7	hellfill.des	$NHDT-Date: 1432512783 2015/05/25 00:13:03 $  $NHDT-Branch: master $:$NHDT-Revision: 1.25 $
+--	Copyright (c) 2022 by Pasi Kallinen
+-- NetHack may be freely redistributed.  See license for details.
+--
+--
+
+--	The "fill" level for gehennom.
+--
+--	This level is used to fill out any levels not occupied by
+--	specific levels.
+--
+
+function hellobjects()
+   local objclass = { "(", "/", "=", "+", ")", "[", "?", "*", "%" };
+   shuffle(objclass);
+
+   des.object(objclass[1]);
+   des.object(objclass[1]);
+   des.object(objclass[2]);
+   des.object(objclass[3]);
+   des.object(objclass[4]);
+   des.object(objclass[5]);
+   des.object()
+   des.object()
+end
+
+--
+
+function hellmonsters()
+   local monclass = { "V", "D", " ", "&", "Z" };
+   shuffle(monclass);
+
+   des.monster({ class = monclass[1], peaceful = 0 });
+   des.monster({ class = monclass[1], peaceful = 0 });
+   des.monster({ class = monclass[2], peaceful = 0 });
+   des.monster({ class = monclass[2], peaceful = 0 });
+   des.monster({ class = monclass[3], peaceful = 0 });
+   des.monster({ class = monclass[4], peaceful = 0 });
+   des.monster({ peaceful = 0 });
+   des.monster({ class = "H", peaceful = 0 });
+end
+
+--
+
+function helltraps()
+   for i = 1, 12 do
+      des.trap()
+   end
+end
+
+--
+
+function populatemaze()
+   for i = 1, math.random(8) + 11 do
+      if (percent(50)) then
+         des.object("*");
+      else
+         des.object();
+      end
+   end
+
+   for i = 1, math.random(10) + 2 do
+      des.object("`");
+   end
+
+   for i = 1, math.random(3) do
+      des.monster({ id = "minotaur", peaceful = 0 });
+   end
+
+   for i = 1, math.random(5) + 7 do
+      des.monster({ peaceful = 0 });
+   end
+
+   for i = 1, math.random(6) + 7 do
+      des.gold();
+   end
+
+   for i = 1, math.random(6) + 7 do
+      des.trap();
+   end
+end
+
+--
+
+-- TODO: cold hells? (ice & water instead of lava. sometimes floor = ice)
+-- TODO: more hell_tweaks:
+--    - replacing walls with iron bars
+--    - random prefab areas
+--    - replace all walls (in a full level width/height) in a small area
+
+hells = {
+   -- 1: "mines" style with lava
+   function ()
+      des.level_init({ style = "solidfill", fg = " " });
+      des.level_flags("mazelevel", "noflip");
+      des.level_init({ style="mines", fg=".", smoothed=true ,joined=true, lit=0, walled=true });
+      des.replace_terrain({ fromterrain = " ", toterrain = "L" });
+      des.replace_terrain({ fromterrain = ".", toterrain = "L", chance = 5 });
+      des.replace_terrain({ mapfragment = [[w]], toterrain = "L", chance = 20 });
+      des.replace_terrain({ mapfragment = [[w]], toterrain = ".", chance = 15 });
+   end,
+
+   -- 2: mazes like original, with some hell_tweaks
+   function ()
+      des.level_flags("mazelevel", "noflip");
+      des.level_init({ style = "mazegrid", bg = "-" });
+      des.mazewalk(01,10,"east");
+      local tmpbounds = selection.match("-");
+      local bnds = tmpbounds:bounds();
+      local protected_area = selection.fillrect(bnds.lx, bnds.ly + 1, bnds.hx - 2, bnds.hy - 1);
+      hell_tweaks(protected_area:negate());
+   end,
+
+   -- 3: mazes, style 1: wall thick = 1, random wid corr
+   function ()
+      des.level_init({ style = "solidfill", fg = " " });
+      des.level_flags("mazelevel", "noflip");
+      des.level_init({ style = "maze", wallthick = 1 });
+   end,
+
+   -- 4: mazes, style 2: replace wall with iron bars of lava
+   function ()
+      des.level_init({ style = "solidfill", fg = " " });
+      des.level_flags("mazelevel", "noflip");
+      des.level_init({ style = "maze", wallthick = 1 });
+      local outside_walls = selection.match(" ");
+      local wallterrain = { "F", "L" };
+      shuffle(wallterrain);
+      des.replace_terrain({ mapfragment = "w", toterrain = wallterrain[1] });
+      des.terrain(outside_walls, " ");  -- return the outside back to solid wall
+   end,
+
+   -- 5: mazes, thick walls, occasionally lava instead of walls
+   function ()
+      des.level_init({ style = "solidfill", fg = " " });
+      des.level_flags("mazelevel", "noflip");
+      des.level_init({ style = "maze", wallthick = 1 + math.random(2), corrwid = math.random(2) });
+      if (percent(50)) then
+         local outside_walls = selection.match(" ");
+         des.replace_terrain({ mapfragment = "w", toterrain = "L" });
+         des.terrain(outside_walls, " ");  -- return the outside back to solid wall
+      end
+   end,
+};
+
+local hellno = math.random(1, #hells);
+hells[hellno]();
+
+--
+
+des.stair("up")
+des.stair("down")
+
+des.region(selection.area(00,00,77,21),"unlit");
+populatemaze();