p_sight.v

@[translated]
module main

//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005-2014 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// DESCRIPTION:
//	Simple basic typedefs, isolated here to make it easier
//	 separating modules.
//
// #define macros to provide functions missing in Windows.
// Outside Windows, we use strings.h for str[n]casecmp.
//
// The packed attribute forces structures to be packed into the minimum
// space necessary.  If this is not done, the compiler may align structure
// fields differently to optimize memory access, inflating the overall
// structure size.  It is important to use the packed attribute on certain
// structures where alignment is important, particularly data read/written
// to disk.
//
// C99 integer types; with gcc we just use this.  Other compilers
// should add conditional statements that define the C99 types.
// What is really wanted here is stdint.h; however, some old versions
// of Solaris don't have stdint.h and only have inttypes.h (the
// pre-standardisation version).  inttypes.h is also in the C99
// standard and defined to include stdint.h, so include this.
// Use builtin bool type with C++.
//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005-2014 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// DESCRIPTION:
//      System-specific timer interface
//
// Called by D_DoomLoop,
// returns current time in tics.
// returns current time in ms
// Pause for a specified number of ms
// Initialize timer
// Wait for vertical retrace or pause a bit.
//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005-2014 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// DESCRIPTION:
//   Functions and definitions relating to the game type and operational
//   mode.
//
// The "mission" controls what game we are playing.
// The "mode" allows more accurate specification of the game mode we are
// in: eg. shareware vs. registered.  So doom1.wad and doom.wad are the
// same mission, but a different mode.
// What version are we emulating?
// What IWAD variant are we using?
// Skill level.
// #ifndef __D_MODE__
//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005-2014 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// DESCRIPTION:
//  Internally used data structures for virtually everything,
//   lots of other stuff.
//
//
// Global parameters/defines.
//
// DOOM version
// Version code for cph's longtics hack ("v1.91")
// If rangecheck is undefined,
// most parameter validation debugging code will not be compiled
// The maximum number of players, multiplayer/networking.
// The current state of the game: whether we are
// playing, gazing at the intermission screen,
// the game final animation, or a demo.
//
// Difficulty/skill settings/filters.
//
// Skill flags.
// Deaf monsters/do not react to sound.
//
// Key cards.
//
// The defined weapons,
//  including a marker indicating
//  user has not changed weapon.
// Ammunition types defined.
// Power up artifacts.
//
// Power up durations,
//  how many seconds till expiration,
//  assuming TICRATE is 35 ticks/second.
//
// __DOOMDEF__
//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005-2014 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// DESCRIPTION:
//  all external data is defined here
//  most of the data is loaded into different structures at run time
//  some internal structures shared by many modules are here
//
// The most basic types we use, portability.
// Some global defines, that configure the game.
//
// Map level types.
// The following data structures define the persistent format
// used in the lumps of the WAD files.
//
// Lump order in a map WAD: each map needs a couple of lumps
// to provide a complete scene geometry description.


// A single Vertex.
// A separator, name, ExMx or MAPxx
// Monsters, items..
// LineDefs, from editing                   // A single Vertex.
// SideDefs, from editing                   typedef PACKED_STRUCT (
// Vertices, edited and BSP splits generated{
// LineSegs, from LineDefs split by BSP       short		x;
// SubSectors, list of LineSegs               short		y;
// BSP nodes                                }) mapvertex_t;
// Sectors, from editing
// LUT, sector-sector visibility	
// LUT, motion clipping, walls/grid element // A SideDef, defining the visual appearance of a wall,
// by setting textures and offsets.
// A LineDef, as used for editing, and as input
// to the BSP builder.
//
// LineDef attributes.
//
// Solid, is an obstacle.
// Blocks monsters only.
// Backside will not be present at all
//  if not two sided.
// If a texture is pegged, the texture will have
// the end exposed to air held constant at the
// top or bottom of the texture (stairs or pulled
// down things) and will move with a height change
// of one of the neighbor sectors.
// Unpegged textures allways have the first row of
// the texture at the top pixel of the line for both
// top and bottom textures (use next to windows).
// upper texture unpegged
// lower texture unpegged
// In AutoMap: don't map as two sided: IT'S A SECRET!
// Sound rendering: don't let sound cross two of these.
// Don't draw on the automap at all.
// Set if already seen, thus drawn in automap.
// Sector definition, from editing.
// SubSector, as generated by BSP.
// LineSeg, generated by splitting LineDefs
// using partition lines selected by BSP builder.
// BSP node structure.
// Indicate a leaf.
// Thing definition, position, orientation and type,
// plus skill/visibility flags and attributes.
// __DOOMDATA__
//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 1993-2008 Raven Software
// Copyright(C) 2005-2014 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// DESCRIPTION:
//	System specific interface stuff.
//
// The data sampled per tick (single player)
// and transmitted to other peers (multiplayer).
// Mainly movements/button commands per game tick,
// plus a checksum for internal state consistency.
//
// Copyright(C) 2005-2014 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// DESCRIPTION:
//     SHA-1 digest.
//
// #ifndef __SHA1_H__
//
// Copyright(C) 2005-2014 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// DESCRIPTION:
//     Definitions for use in networking code.
//
// Absolute maximum number of "nodes" in the game.  This is different to
// NET_MAXPLAYERS, as there may be observers that are not participating
// (eg. left/right monitors)
// The maximum number of players, multiplayer/networking.
// This is the maximum supported by the networking code; individual games
// have their own values for MAXPLAYERS that can be smaller.
// Maximum length of a player's name.
// Networking and tick handling related.
// net_addr_t
// Magic number sent when connecting to check this is a valid client
// Old magic number used by Chocolate Doom versions before v3.0:
// header field value indicating that the packet is a reliable packet
// Supported protocols. If you're developing a fork of Chocolate
// Doom, you can add your own entry to this list while maintaining
// compatibility with Chocolate Doom servers. Higher-numbered enum values
// will be preferred when negotiating a protocol for the client and server
// to use, so the order matters.
// NOTE: The values in this enum do not have any special value outside of
// the program they're compiled in. What matters is the string representation.
// packet types
// Settings specified when the client connects to the server.
// Game settings sent by client to server when initiating game start,
// and received from the server by clients when the game starts.
// Complete set of ticcmds from all players
// Data sent in response to server queries
// Data sent by the server while waiting for the game to start.
// #ifndef NET_DEFS_H
//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005-2014 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// DESCRIPTION:
//	Main loop stuff.
//
// Callback function invoked while waiting for the netgame to start.
// The callback is invoked when new players are ready. The callback
// should return true, or return false to abort startup.
// Register callback functions for the main loop code to use.
// Create any new ticcmds and broadcast to other players.
// Broadcasts special packets to other players
//  to notify of game exit
//? how many ticks to run?
// Called at start of game loop to initialize timers
// Initialize networking code and connect to server.
// Start game with specified settings. The structure will be updated
// with the actual settings for the game.
// Check if it is permitted to record a demo with a non-vanilla feature.
// Check if it is permitted to play back a demo with a non-vanilla feature.
//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005-2014 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// DESCRIPTION:
//	Items: key cards, artifacts, weapon, ammunition.
//
// Weapon info: sprite frames, ammunition use.
// skipping global dup "weaponinfo"
//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005-2014 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// DESCRIPTION:
//	Fixed point arithemtics, implementation.
//
//
// Fixed point, 32bit as 16.16.
//
@[c: 'FixedMul']
fn fixed_mul(a int, b int) int

@[c: 'FixedDiv']
fn fixed_div(a int, b int) int

//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 1993-2008 Raven Software
// Copyright(C) 2005-2014 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// DESCRIPTION:
//	Lookup tables.
//	Do not try to look them up :-).
//	In the order of appearance:
//
//	int finetangent[4096]	- Tangens LUT.
//	 Should work with BAM fairly well (12 of 16bit,
//      effectively, by shifting).
//
//	int finesine[10240]		- Sine lookup.
//	 Guess what, serves as cosine, too.
//	 Remarkable thing is, how to use BAMs with this?
//
//	int tantoangle[2049]	- ArcTan LUT,
//	  maps tan(angle) to angle fast. Gotta search.	
//
// 0x100000000 to 0x2000
// Effective size is 10240.
// Re-use data, is just PI/2 pahse shift.
// Effective size is 4096.
// Gamma correction tables.
// Binary Angle Measument, BAM.
// Heretic code uses this definition as though it represents one
// degree, but it is not!  This is actually ~1.40 degrees.
// Effective size is 2049;
// The +1 size is to handle the case when x==y
//  without additional checking.
// Utility function,
//  called by R_PointToAngle.
//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005-2014 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// DESCRIPTION:
//  MapObj data. Map Objects or mobjs are actors, entities,
//  thinker, take-your-pick... anything that moves, acts, or
//  suffers state changes of more or less violent nature.
//
//
// Experimental stuff.
// To compile this as "ANSI C with classes"
//  we will need to handle the various
//  action functions cleanly.
//
// Historically, "think_t" is yet another
//  function pointer to a routine to handle
//  an actor.
// Doubly linked list of actors.
//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005-2014 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// DESCRIPTION:
//	Thing frame/state LUT,
//	generated by multigen utilitiy.
//	This one is the original DOOM version, preserved.
//
// Needed for action function pointer handling.
//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005-2014 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// DESCRIPTION:
//  Sprite animation.
//
// Basic data types.
// Needs fixed point, and BAM angles.
//
// Needs to include the precompiled
//  sprite animation tables.
// Header generated by multigen utility.
// This includes all the data for thing animation,
// i.e. the Thing Atrributes table
// and the Frame Sequence table.
//
// Frame flags:
// handles maximum brightness (torches, muzzle flare, light sources)
//
// flag in thing->frame
//
// Overlay psprites are scaled shapes
// drawn directly on the view screen,
// coordinates are given for a 320*200 view screen.
//
//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005-2014 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// DESCRIPTION:
//	Map Objects, MObj, definition and handling.
//
// Basics.
// We need the thinker_t stuff.
// We need the WAD data structure for Map things,
// from the THINGS lump.
// States are tied to finite states are
//  tied to animation frames.
// Needs precompiled tables/data structures.
//
// NOTES: mobj_t
//
// mobj_ts are used to tell the refresh where to draw an image,
// tell the world simulation when objects are contacted,
// and tell the sound driver how to position a sound.
//
// The refresh uses the next and prev links to follow
// lists of things in sectors as they are being drawn.
// The sprite, frame, and angle elements determine which patch_t
// is used to draw the sprite if it is visible.
// The sprite and frame values are allmost allways set
// from state_t structures.
// The statescr.exe utility generates the states.h and states.c
// files that contain the sprite/frame numbers from the
// statescr.txt source file.
// The xyz origin point represents a point at the bottom middle
// of the sprite (between the feet of a biped).
// This is the default origin position for patch_ts grabbed
// with lumpy.exe.
// A walking creature will have its z equal to the floor
// it is standing on.
//
// The sound code uses the x,y, and subsector fields
// to do stereo positioning of any sound effited by the mobj_t.
//
// The play simulation uses the blocklinks, x,y,z, radius, height
// to determine when mobj_ts are touching each other,
// touching lines in the map, or hit by trace lines (gunshots,
// lines of sight, etc).
// The mobj_t->flags element has various bit flags
// used by the simulation.
//
// Every mobj_t is linked into a single sector
// based on its origin coordinates.
// The subsector_t is found with R_PointInSubsector(x,y),
// and the sector_t can be found with subsector->sector.
// The sector links are only used by the rendering code,
// the play simulation does not care about them at all.
//
// Any mobj_t that needs to be acted upon by something else
// in the play world (block movement, be shot, etc) will also
// need to be linked into the blockmap.
// If the thing has the MF_NOBLOCK flag set, it will not use
// the block links. It can still interact with other things,
// but only as the instigator (missiles will run into other
// things, but nothing can run into a missile).
// Each block in the grid is 128*128 units, and knows about
// every line_t that it contains a piece of, and every
// interactable mobj_t that has its origin contained.
//
// A valid mobj_t is a mobj_t that has the proper subsector_t
// filled in for its xy coordinates and is linked into the
// sector from which the subsector was made, or has the
// MF_NOSECTOR flag set (the subsector_t needs to be valid
// even if MF_NOSECTOR is set), and is linked into a blockmap
// block or has the MF_NOBLOCKMAP flag set.
// Links should only be modified by the P_[Un]SetThingPosition()
// functions.
// Do not change the MF_NO? flags while a thing is valid.
//
// Any questions?
//
//
// Misc. mobj flags
//
// Map Object definition.
//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005-2014 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// DESCRIPTION:
//
//
// The player data structure depends on a number
// of other structs: items (internal inventory),
// animation states (closely tied to the sprites
// used to represent them, unfortunately).
// In addition, the player is just a special
// case of the generic moving object/actor.
// Finally, for odd reasons, the player input
// is buffered within the player data struct,
// as commands per game tick.
//
// Player states.
//
//
// Player internal flags, for cheats and debug.
//
//
// Extended player object info: player_t
//
//
// INTERMISSION
// Structure passed e.g. to WI_Start(wb)
//
//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005-2014 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// DESCRIPTION:
//   All the global variables that store the internal state.
//   Theoretically speaking, the internal state of the engine
//    should be found by looking at the variables collected
//    here, and every relevant module will have to include
//    this header file.
//   In practice, things are a bit messy.
//
// We need globally shared data structures,
//  for defining the global state variables.
// We need the playr data structure as well.
// Game mode/mission
// ------------------------
// Command line parameters.
//
// skipping global dup "nomonsters"
// checkparm of -nomonsters
// skipping global dup "respawnparm"
// checkparm of -respawn
// skipping global dup "fastparm"
// checkparm of -fast
// skipping global dup "devparm"
// DEBUG: launched with -devparm
// -----------------------------------------------------
// Game Mode - identify IWAD as shareware, retail etc.
//
// Convenience macro.
// 'gamemission' can be equal to pack_chex or pack_hacx, but these are
// just modified versions of doom and doom2, and should be interpreted
// as the same most of the time.
//
//#define logical_gamemission                             \
//    (gamemission == pack_chex ? doom :                  \
//     gamemission == pack_hacx ? doom2 : gamemission)
//
// Set if homebrew PWAD stuff has been added.
// -------------------------------------------
// Selected skill type, map etc.
//
// Defaults for menu, methinks.
// skipping global dup "startskill"
// skipping global dup "startepisode"
// skipping global dup "startmap"
// Savegame slot to load on startup.  This is the value provided to
// the -loadgame option.  If this has not been provided, this is -1.
// skipping global dup "startloadgame"
// skipping global dup "autostart"
// Selected by user.
// If non-zero, exit the level after this number of minutes
// Nightmare mode flag, single player.
// Netgame? Only true if >1 player.
// 0=Cooperative; 1=Deathmatch; 2=Altdeath
// -------------------------
// Internal parameters for sound rendering.
// These have been taken from the DOS version,
//  but are not (yet) supported with Linux
//  (e.g. no sound volume adjustment with menu.
// From m_menu.c:
//  Sound FX volume has default, 0 - 15
//  Music volume has default, 0 - 15
// These are multiplied by 8.
// Current music/sfx card - index useless
//  w/o a reference LUT in a sound module.
// Ideally, this would use indices found
//  in: /usr/include/linux/soundcard.h
// Config file? Same disclaimer as above.
// -------------------------
// Status flags for refresh.
//
// Depending on view size - no status bar?
// Note that there is no way to disable the
//  status bar explicitely.
// skipping global dup "automapactive"
// In AutoMap mode?
// Menu overlayed?
// Game Pause?
// This one is related to the 3-screen display mode.
// ANG90 = left side, ANG270 = right
// Player taking events, and displaying.
// -------------------------------------
// Scores, rating.
// Statistics on a given map, for intermission.
//
// Timer, for scores.
// gametic at level start
// tics in game play for par
// --------------------------------------
// DEMO playback/recording related stuff.
// No demo, there is a human player in charge?
// Disable save/end game?
//?
// Round angleturn in ticcmds to the nearest 256.  This is used when
// recording Vanilla demos in netgames.
// Quit after playing a demo from cmdline.
//?
//-----------------------------
// Internal parameters, fixed.
// These are set by the engine, and not changed
//  according to user inputs. Partly load from
//  WAD, partly set at startup time.
// Bookkeeping on players - state.
// Alive? Disconnected?
// Player spawn spots for deathmatch.
// skipping global dup "deathmatchstarts"
// skipping global dup "deathmatch_p"
// Player spawn spots.
// skipping global dup "playerstarts"
// skipping global dup "playerstartsingame"
// Intermission stats.
// Parameters for world map / intermission.
//-----------------------------------------
// Internal parameters, used for engine.
//
// File handling stuff.
// skipping global dup "savegamedir"
// if true, load all graphics at level load
// wipegamestate can be set to -1
//  to force a wipe on the next draw
// skipping global dup "wipegamestate"
// Needed to store the number of the dummy sky flat.
// Used for rendering,
//  as well as tracking projectiles etc.
// skipping global dup "skyflatnum"
// Netgame stuff (buffers and pointers, i.e. indices).
// skipping global dup "netcmds"
//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005-2014 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// DESCRIPTION:
//
//
//
// Event handling.
//
// Input event types.
// Event structure.
//
// Button/action code definitions.
//
// villsa [STRIFE] Strife specific buttons
// TODO - not finished
// Called by IO functions when input is detected.
// Read an event from the event queue
//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005-2014 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// DESCRIPTION:
//	System specific interface stuff.
//
// Called by DoomMain.
// Called by startup code
// to get the ammount of memory to malloc
// for the zone management.
// Asynchronous interrupt functions should maintain private queues
// that are read by the synchronous functions
// to be converted into events.
// Either returns a null ticcmd,
// or calls a loadable driver to build it.
// This ticcmd will then be modified by the gameloop
// for normal input.
// Called by M_Responder when quit is selected.
// Clean exit, displays sell blurb.
@[c: 'I_Error']
@[c2v_variadic]
fn i_error(error ...&i8)

// Schedule a function to be called when the program exits.
// If run_if_error is true, the function is called if the exit
// is due to an error (I_Error)
// Add all system-specific config file variable bindings.
// Print startup banner copyright message.
// Print a centered text banner displaying the given string.
// Print a dividing line for startup banners.
//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005-2014 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// DESCRIPTION:
//	System specific interface stuff.
//
// Screen width and height.
// Screen height used when aspect_ratio_correct=true.
// Called by D_DoomMain,
// determines the hardware configuration
// and sets up the video mode
// Takes full 8 bit values.
// Called before processing any tics in a frame (just after displaying a frame).
// Time consuming syncronous operations are performed here (joystick reading).
// Called before processing each tic in a frame.
// Quick syncronous operations are performed here.
// Enable the loading disk image displayed when reading from disk.
// Joystic/gamepad hysteresis
//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005-2014 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// DESCRIPTION:
//      Refresh/rendering module, shared data struct definitions.
//
// Screenwidth.
// Some more or less basic data types
// we depend on.
// We rely on the thinker data struct
// to handle sound origins in sectors.
// SECTORS do store MObjs anyway.
// Silhouette, needed for clipping Segs (mainly)
// and sprites representing things.
//
// INTERNAL MAP TYPES
//  used by play and refresh
//
//
// Your plain vanilla vertex.
// Note: transformed values not buffered locally,
//  like some DOOM-alikes ("wt", "WebView") did.
//
// Forward of LineDefs, for Sectors.
// Each sector has a degenmobj_t in its center
//  for sound origin purposes.
// I suppose this does not handle sound from
//  moving objects (doppler), because
//  position is prolly just buffered, not
//  updated.
//
// The SECTORS record, at runtime.
// Stores things/mobjs.
//
//
// The SideDef.
//
//
// Move clipping aid for LineDefs.
//
//
// A SubSector.
// References a Sector.
// Basically, this is a list of LineSegs,
//  indicating the visible walls that define
//  (all or some) sides of a convex BSP leaf.
//
//
// The LineSeg.
//
//
// BSP node.
//
// PC direct to screen pointers
// B UNUSED - keep till detailshift in r_draw.c resolved
// extern byte*	destview;
// extern byte*	destscreen;
//
// OTHER TYPES
//
// This could be wider for >8 bit display.
// Indeed, true color support is posibble
//  precalculating 24bpp lightmap/colormap LUT.
//  from darkening PLAYPAL to all black.
// Could even us emore than 32 levels.
// typedef pixel_t		lighttable_t;
// XTODO  alias to alias
//
// ?
//
// A vissprite_t is a thing
//  that will be drawn during a refresh.
// I.e. a sprite object that is partly visible.
//	
// Sprites are patches with a special naming convention
//  so they can be recognized by R_InitSprites.
// The base name is NNNNFx or NNNNFxFx, with
//  x indicating the rotation, x = 0, 1-7.
// The sprite and frame specified by a thing_t
//  is range checked at run time.
// A sprite is a patch_t that is assumed to represent
//  a three dimensional object and may have multiple
//  rotations pre drawn.
// Horizontal flipping is used to save space,
//  thus NNNNF2F5 defines a mirrored patch.
// Some sprites will only have one picture used
// for all views: NNNNF0
//
//
// A sprite definition:
//  a number of animation frames.
//
//
// Now what is a visplane, anyway?
//
//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005-2014 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// DESCRIPTION:
//	Refresh/render internal state variables (global).
//
// Need data structure definitions.
//
// Refresh internal data structures,
//  for rendering.
//
// needed for texture pegging
// needed for pre rendering (fracs)
// for global animation
// Sprite....
//
// Lookup tables for map data.
//
// skipping global dup "numvertexes"
// skipping global dup "vertexes"
// skipping global dup "numsegs"
// skipping global dup "segs"
// skipping global dup "numsectors"
// skipping global dup "sectors"
// skipping global dup "numsubsectors"
// skipping global dup "subsectors"
// skipping global dup "numnodes"
// skipping global dup "nodes"
// skipping global dup "numlines"
// skipping global dup "lines"
// skipping global dup "numsides"
// skipping global dup "sides"
//
// POV data.
//
// ?
// extern fixed_t		finetangent[FINEANGLES/2];
// angle to line origin
// Segs count?
//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005-2014 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// DESCRIPTION:
//  Refresh module, data I/O, caching, retrieval of graphics
//  by name.
//
// Retrieve column data for span blitting.
// I/O, setting up the stuff.
// Retrieval.
// Floor/ceiling opaque texture tiles,
// lookup by name. For animation?
// Called by P_Ticker for switches and animations,
// returns the texture number for the texture name.
//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005-2014 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// DESCRIPTION:
//	System specific interface stuff.
//
//
// POV related.
//
//
// Lighting LUT.
// Used for z-depth cuing per column/row,
//  and other lighting effects (sector ambient, flash).
//
// Lighting constants.
// Now why not 32 levels here?
// Number of diminishing brightness levels.
// There a 0-31, i.e. 32 LUT in the COLORMAP lump.
// Blocky/low detail mode.
// B remove this?
//  0 = high, 1 = low
//
// Function pointers to switch refresh/drawing functions.
// Used to select shadow mode etc.
//
// No shadow effects on floors.
//
// Utility functions.
//
// REFRESH - the actual rendering functions.
//
// Called by G_Drawer.
// Called by startup code.
// Called by M_Responder.
//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005-2014 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// DESCRIPTION:
//	Refresh module, BSP traversal and handling.
//
// false if the back side is the same plane
// BSP?
//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005-2014 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// DESCRIPTION:
//	Refresh module, drawing LineSegs from BSP.
//
//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005-2014 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// DESCRIPTION:
//	Refresh, visplane stuff (floor, ceilings).
//
// Visplane related.
//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005-2014 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// DESCRIPTION:
//	Rendering of moving objects, sprites.
//
// Constant arrays used for psprite clipping
//  and initializing clipping.
// vars for R_DrawMaskedColumn
//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005-2014 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// DESCRIPTION:
//	System specific interface stuff.
//
// first pixel in a column
// The span blitting interface.
// Hook in assembler or system specific BLT
//  here.
// The Spectre/Invisibility effect.
// Draw with color translation tables,
//  for player sprite rendering,
//  Green/Red/Blue/Indigo shirts.
// start of a 64*64 tile image
// Span blitting for rows, floor/ceiling.
// No Sepctre effect needed.
// Low resolution mode, 160x200?
// Initialize color translation tables,
//  for player rendering etc.
// Rendering function.
// If the view size is not full screen, draws a border around it.
//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005-2014 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// DESCRIPTION:
//	Play functions, animation, global header.
//
// mapblocks are used to check movement
// against lines and things
// player radius for movement checking
// MAXRADIUS is for precalculated sector block boxes
// the spider demon is larger,
// but we do not have any moving sectors nearby
// follow a player exlusively for 3 seconds
//
// P_TICK
//
// both the head and tail of the thinker list
//
// P_PSPR
//
//
// P_USER
//
//
// P_MOBJ
//
// Time interval for item respawning.
// skipping global dup "itemrespawnque"
// skipping global dup "itemrespawntime"
// skipping global dup "iquehead"
// skipping global dup "iquetail"
//
// P_ENEMY
//
//
// P_MAPUTL
//
// Extended MAXINTERCEPTS, to allow for intercepts overrun emulation.
@[c: 'P_LineOpening']
fn p_line_opening(linedef &Line_t)

@[c: 'P_PathTraverse']
fn p_path_traverse(x1 int, y1 int, x2 int, y2 int, flags int, trav fn (&Intercept_t) bool) bool

//
// P_MAP
//
// If "floatok" true, move would be ok
// if within "tmfloorz - tmceilingz".
// fraggle: I have increased the size of this buffer.  In the original Doom,
// overrunning past this limit caused other bits of memory to be overwritten,
// affecting demo playback.  However, in doing so, the limit was still
// exceeded.  So we have to support more than 8 specials.
//
// We keep the original limit, to detect what variables in memory were
// overwritten (see SpechitOverrun())
@[c: 'P_CheckSight']
fn p_check_sight(t1 &Mobj_t, t2 &Mobj_t) bool

// who got hit (or NULL)
//
// P_SETUP
//
// skipping global dup "rejectmatrix"
// for fast sight rejection
// skipping global dup "blockmaplump"
// offsets in blockmap are from here
// skipping global dup "blockmap"
// skipping global dup "bmapwidth"
// skipping global dup "bmapheight"
// in mapblocks
// skipping global dup "bmaporgx"
// skipping global dup "bmaporgy"
// origin of block map
// skipping global dup "blocklinks"
// for thing chains
//
// P_INTER
//
//
// P_SPEC
//
// __P_LOCAL__
//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005-2014 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// DESCRIPTION:  none
//	Implements special effects:
//	Texture animation, height or lighting changes
//	 according to adjacent sectors, respective
//	 utility functions, etc.
//
//
// End-level timer (-TIMER option)
//
// skipping global dup "levelTimer"
// skipping global dup "levelTimeCount"
//      Define values for map objects
// at game start
// at map load
// every tic
// when needed
//
// SPECIAL
//
//
// P_LIGHTS
//
//
// P_SWITCH
//
// max # of wall switches in a level
// 4 players, 4 buttons each at once, max.
// 1 second, in ticks.
// skipping global dup "buttonlist"
//
// P_PLATS
//
//
// P_DOORS
//
// UNUSED
//
//      Sliding doors...
//
// how many frames of animation
// how many diff. types of anims
//
// P_CEILNG
//
// skipping global dup "activeceilings"
//
// P_FLOOR
//
//
// P_TELEPT
//
//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005-2014 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// DESCRIPTION:
//	LineOfSight/Visibility checks, uses REJECT Lookup Table.
//
// State.
//
// P_CheckSight
//
// eye z of looker
// slopes to top and bottom of target
// from t1 to t2
// PTR_SightTraverse() for Doom 1.2 sight calculations
// taken from prboom-plus/src/p_sight.c:69-102
@[c: 'PTR_SightTraverse']
fn ptr_sight_traverse(in_ &Intercept_t) bool {
	li := &Line_t(0)
	slope := 0
	li = in_.d.line
	//
	// crosses a two sided line
	//
	p_line_opening(li)
	if openbottom >= opentop // quick test for totally closed doors
	  {
		return false
	}
	// stop
	if li.frontsector.floorheight != li.backsector.floorheight {
		slope = fixed_div(openbottom - sightzstart, in_.frac)
		if slope > bottomslope {
			bottomslope = slope
		}
	}
	if li.frontsector.ceilingheight != li.backsector.ceilingheight {
		slope = fixed_div(opentop - sightzstart, in_.frac)
		if slope < topslope {
			topslope = slope
		}
	}
	if topslope <= bottomslope {
		return false
	}
	// stop
	return true
	// keep going
}

//
// P_DivlineSide
// Returns side 0 (front), 1 (back), or 2 (on).
//
@[c: 'P_DivlineSide']
fn p_divline_side(x int, y int, node &Divline_t) int {
	dx := 0
	dy := 0
	left := 0
	right := 0
	if !node.dx {
		if x == node.x {
			return 2
		}
		if x <= node.x {
			return node.dy > 0
		}
		return node.dy < 0
	}
	if !node.dy {
		if x == node.y {
			return 2
		}
		if y <= node.y {
			return node.dx < 0
		}
		return node.dx > 0
	}
	dx = (x - node.x)
	dy = (y - node.y)
	left = (node.dy >> 16) * (dx >> 16)
	right = (dy >> 16) * (node.dx >> 16)
	if right < left {
		return 0
	}
	// front side
	if left == right {
		return 2
	}
	return 1
	// back side
}

//
// P_InterceptVector2
// Returns the fractional intercept point
// along the first divline.
// This is only called by the addthings and addlines traversers.
//
@[c: 'P_InterceptVector2']
fn p_intercept_vector2(v2 &Divline_t, v1 &Divline_t) int {
	frac := 0
	num := 0
	den := 0
	den = fixed_mul(v1.dy >> 8, v2.dx) - fixed_mul(v1.dx >> 8, v2.dy)
	if den == 0 {
		return 0
	}
	//	I_Error ("P_InterceptVector: parallel");
	num = fixed_mul((v1.x - v2.x) >> 8, v1.dy) + fixed_mul((v2.y - v1.y) >> 8, v1.dx)
	frac = fixed_div(num, den)
	return frac
}

//
// P_CrossSubsector
// Returns true
//  if strace crosses the given subsector successfully.
//
@[c: 'P_CrossSubsector']
fn p_cross_subsector(num int) bool {
	seg := &Seg_t(0)
	line := &Line_t(0)
	s1 := 0
	s2 := 0
	count := 0
	sub := &Subsector_t(0)
	front := &Sector_t(0)
	back := &Sector_t(0)
	opentop := 0
	openbottom := 0
	divl := Divline_t{}
	v1 := &Vertex_t(0)
	v2 := &Vertex_t(0)
	frac := 0
	slope := 0
	if num >= numsubsectors {
		i_error(c'P_CrossSubsector: ss %i with numss = %i', num, numsubsectors)
	}
	sub = &subsectors[num]
	// check lines
	count = sub.numlines
	seg = &segs[sub.firstline]
	for ; count; seg++ {
		line = seg.linedef
		// allready checked other side?
		if line.validcount == validcount {
			count--
			continue
		}
		line.validcount = validcount
		v1 = line.v1
		v2 = line.v2
		s1 = p_divline_side(v1.x, v1.y, &strace)
		s2 = p_divline_side(v2.x, v2.y, &strace)
		// line isn't crossed?
		if s1 == s2 {
			count--
			continue
		}
		divl.x = v1.x
		divl.y = v1.y
		divl.dx = v2.x - v1.x
		divl.dy = v2.y - v1.y
		s1 = p_divline_side(strace.x, strace.y, &divl)
		s2 = p_divline_side(t2x, t2y, &divl)
		// line isn't crossed?
		if s1 == s2 {
			count--
			continue
		}
		// Backsector may be NULL if this is an "impassible
		// glass" hack line.
		if line.backsector == (unsafe { nil }) {
			return false
		}
		// stop because it is not two sided anyway
		// might do this after updating validcount?
		if !(line.flags & 4) {
			return false
		}
		// crosses a two sided line
		front = seg.frontsector
		back = seg.backsector
		// no wall to block sight with?
		if front.floorheight == back.floorheight && front.ceilingheight == back.ceilingheight {
			count--
			continue
		}
		// possible occluder
		// because of ceiling height differences
		if front.ceilingheight < back.ceilingheight {
			opentop = front.ceilingheight
		} else { // 3
			opentop = back.ceilingheight
		}
		// because of ceiling height differences
		if front.floorheight > back.floorheight {
			openbottom = front.floorheight
		} else { // 3
			openbottom = back.floorheight
		}
		// quick test for totally closed doors
		if openbottom >= opentop {
			return false
		}
		// stop
		frac = p_intercept_vector2(&strace, &divl)
		if front.floorheight != back.floorheight {
			slope = fixed_div(openbottom - sightzstart, frac)
			if slope > bottomslope {
				bottomslope = slope
			}
		}
		if front.ceilingheight != back.ceilingheight {
			slope = fixed_div(opentop - sightzstart, frac)
			if slope < topslope {
				topslope = slope
			}
		}
		if topslope <= bottomslope {
			return false
		}
		// stop				
		count--
	}
	// passed the subsector ok
	return true
}

//
// P_CrossBSPNode
// Returns true
//  if strace crosses the given node successfully.
//
@[c: 'P_CrossBSPNode']
fn p_cross_bspn_ode(bspnum int) bool {
	bsp := &Node_t(0)
	side := 0
	if bspnum & 32768 {
		// XTODO
		if bspnum == -1 {
			return p_cross_subsector(0)
		} else {
			return p_cross_subsector(bspnum & (~32768))
		}
	}
	bsp = &nodes[bspnum]
	// decide which side the start point is on
	side = p_divline_side(strace.x, strace.y, &Divline_t(bsp))
	if side == 2 {
		side = 0
	}
	// an "on" should cross both sides
	// cross the starting side
	if !p_cross_bspn_ode(bsp.children[side]) {
		return false
	}
	// the partition plane is crossed here
	if side == p_divline_side(t2x, t2y, &Divline_t(bsp)) {
		// the line doesn't touch the other side
		return true
	}
	// cross the ending side		
	return p_cross_bspn_ode(bsp.children[side ^ 1])
}

//
// P_CheckSight
// Returns true
//  if a straight line between t1 and t2 is unobstructed.
// Uses REJECT.
//
@[c: 'P_CheckSight']
fn p_check_sight(t1 &Mobj_t, t2 &Mobj_t) bool {
	s1 := 0
	s2 := 0
	pnum := 0
	bytenum := 0
	bitnum := 0
	// First check for trivial rejection.
	// Determine subsector entries in REJECT table.
	s1 = (t1.subsector.sector - sectors)
	s2 = (t2.subsector.sector - sectors)
	pnum = s1 * numsectors + s2
	bytenum = pnum >> 3
	bitnum = 1 << (pnum & 7)
	// Check in REJECT table.
	if rejectmatrix[bytenum] & bitnum {
		sightcounts[0]++
		// can't possibly be connected
		return false
	}
	// An unobstructed LOS is possible.
	// Now look from eyes of t1 to any part of t2.
	sightcounts[1]++
	validcount++
	sightzstart = t1.z + t1.height - (t1.height >> 2)
	topslope = (t2.z + t2.height) - sightzstart
	bottomslope = (t2.z) - sightzstart
	if gameversion <= GameVersion_t.exe_doom_1_2 {
		return p_path_traverse(t1.x, t1.y, t2.x, t2.y, 4 | 1, ptr_sight_traverse)
	}
	strace.x = t1.x
	strace.y = t1.y
	t2x = t2.x
	t2y = t2.y
	strace.dx = t2.x - t1.x
	strace.dy = t2.y - t1.y
	// the head node is the last node output
	return p_cross_bspn_ode(numnodes - 1)
}