From 9c7e1fbd6c8ffba3c0d0006b6740398b851fb4ce Mon Sep 17 00:00:00 2001
From: kraflab <kraflab@gmail.com>
Date: Sat, 17 Apr 2021 17:55:29 +0200
Subject: [PATCH 1/2] Add better scroll control line special

---
 prboom2/src/p_spec.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/prboom2/src/p_spec.c b/prboom2/src/p_spec.c
index c944ae530..363e28325 100644
--- a/prboom2/src/p_spec.c
+++ b/prboom2/src/p_spec.c
@@ -3098,6 +3098,27 @@ static void P_SpawnScrollers(void)
                        sides[s].rowoffset, -1, s, accel);
           break;
 
+        case 1024: // special 255 with tag control
+        case 1025:
+        case 1026:
+          if (l->tag == 0)
+            I_Error("Line %d is missing a tag!", i);
+
+          if (special > 1024)
+            control = sides[*l->sidenum].sector->iSectorID;
+
+          if (special == 1026)
+            accel = 1;
+
+          s = lines[i].sidenum[0];
+          dx = -sides[s].textureoffset;
+          dy = sides[s].rowoffset;
+          for (s = -1; (s = P_FindLineFromLineTag(l, s)) >= 0;)
+            if (s != i)
+              Add_Scroller(sc_side, dx, dy, control, lines[s].sidenum[0], accel);
+
+          break;
+
         case 48:                  // scroll first side
           Add_Scroller(sc_side,  FRACUNIT, 0, -1, lines[i].sidenum[0], accel);
           break;

From 42349cb7698d57dbead9472f4a018f8da1ec4930 Mon Sep 17 00:00:00 2001
From: kraflab <kraflab@gmail.com>
Date: Sat, 17 Apr 2021 18:00:18 +0200
Subject: [PATCH 2/2] Update mbf21 readme

---
 prboom2/src/mbf21.md | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/prboom2/src/mbf21.md b/prboom2/src/mbf21.md
index 4f1639ba9..0729e19cc 100644
--- a/prboom2/src/mbf21.md
+++ b/prboom2/src/mbf21.md
@@ -46,6 +46,13 @@ This is proof-of-concept implemented in dsda-doom.
 #### Fix generalized crusher walkover lines
 - [commit](https://github.com/kraflab/dsda-doom/commit/76776f721b5d1d8a1a0ae95daab525cf8183ce44)
 
+#### Line scroll special variants
+- [PR](https://github.com/kraflab/dsda-doom/pull/29)
+- Scroll like special 255, but the special line determines the speed / direction with which all tagged lines scroll.
+- 1024 is without control sector / acceleration.
+- 1025 uses control sector.
+- 1026 uses control sector + acceleration.
+
 #### Fix negative ammo counts
 - [PR](https://github.com/kraflab/dsda-doom/pull/24)