From 457ca505f507922c7470e9e8daef5d8482f664b0 Mon Sep 17 00:00:00 2001
From: Fabian Greffrath <fabian@greffrath.com>
Date: Mon, 20 Jan 2020 11:32:27 +0100
Subject: [PATCH] make "3-key doors work with only 2 keys" bug optional (#45)

* make "3-key doors work with only 2 keys" bug optional, fixes #38

 * Introduce a compatibility flag for MBF's most famous bug and add it
   to the second menu page in the Doom Compatibility section.

* reverse comp[] logic

* add (config_t *) pointer casts

* improve menu item description

* rename 3keydoors to 3keydoor, matching the menu item

* comments
---
 Source/doomstat.h | 3 +++
 Source/m_menu.c   | 8 ++++++++
 Source/m_misc.c   | 9 +++++++++
 Source/p_spec.c   | 4 +++-
 4 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/Source/doomstat.h b/Source/doomstat.h
index e93986e9..b096ccda 100644
--- a/Source/doomstat.h
+++ b/Source/doomstat.h
@@ -111,6 +111,9 @@ enum {
   comp_stairs,
   comp_infcheat,
   comp_zerotags,
+  // [FG] 3-key door works with only 2 keys
+  // http://prboom.sourceforge.net/mbf-bugs.html
+  comp_3keydoor,
   COMP_TOTAL=32  // Some extra room for additional variables
 };
 
diff --git a/Source/m_menu.c b/Source/m_menu.c
index 7f422156..4d1ca1d7 100644
--- a/Source/m_menu.c
+++ b/Source/m_menu.c
@@ -3185,6 +3185,9 @@ enum
   compat_model,
   compat_zerotags,
   compat_menu,
+  // [FG] 3-key door works with only 2 keys
+  // http://prboom.sourceforge.net/mbf-bugs.html
+  compat_3keydoor,
 };
 
 setup_menu_t comp_settings1[] =  // Compatibility Settings screen #1
@@ -3260,6 +3263,11 @@ setup_menu_t comp_settings2[] =  // Compatibility Settings screen #2
   {"Use Doom's main menu ordering", S_YESNO, m_null, C_X,
    C_Y + compat_menu * COMP_SPC, {"traditional_menu"}, 0, 0, M_ResetMenu},
 
+  // [FG] 3-key door works with only 2 keys
+  // http://prboom.sourceforge.net/mbf-bugs.html
+  {"Fix 3-key door works with only 2 keys", S_YESNO, m_null, C_X,
+   C_Y + compat_3keydoor * COMP_SPC, {"comp_3keydoor"}},
+
   {"<- PREV", S_SKIP|S_PREV, m_null, KB_PREV, C_Y+C_NEXTPREV,{comp_settings1}},
 
   // Final entry
diff --git a/Source/m_misc.c b/Source/m_misc.c
index df963bdc..c3e50eb3 100644
--- a/Source/m_misc.c
+++ b/Source/m_misc.c
@@ -570,6 +570,15 @@ default_t defaults[] = {
     "Linedef effects work with sector tag = 0"
   },
 
+  // [FG] 3-key door works with only 2 keys
+  // http://prboom.sourceforge.net/mbf-bugs.html
+  {
+    "comp_3keydoor",
+    (config_t *) &default_comp[comp_3keydoor], (config_t *) &comp[comp_3keydoor],
+    {0}, {0,1}, number, ss_comp, wad_yes,
+    "Fix 3-key door works with only 2 keys"
+  },
+
   // For key bindings, the values stored in the key_* variables       // phares
   // are the internal Doom Codes. The values stored in the default.cfg
   // file are the keyboard codes. I_ScanCode2DoomCode converts from
diff --git a/Source/p_spec.c b/Source/p_spec.c
index 1f358281..a060e245 100644
--- a/Source/p_spec.c
+++ b/Source/p_spec.c
@@ -803,7 +803,9 @@ boolean P_CanUnlockGenDoor(line_t *line, player_t *player)
       if (skulliscard &&
           (!(player->cards[it_redcard] | player->cards[it_redskull]) ||
            !(player->cards[it_bluecard] | player->cards[it_blueskull]) ||
-           !(player->cards[it_yellowcard] | !player->cards[it_yellowskull])))
+           // [FG] 3-key door works with only 2 keys
+           // http://prboom.sourceforge.net/mbf-bugs.html
+           !(player->cards[it_yellowcard] | (!comp[comp_3keydoor] ? !player->cards[it_yellowskull] : player->cards[it_yellowskull]))))
         {
           player->message = s_PD_ALL3; // Ty 03/27/98 - externalized
           S_StartSound(player->mo,sfx_oof);             // killough 3/20/98