From ce2af4303ec5fd910701b0fc629705e663219838 Mon Sep 17 00:00:00 2001
From: tildearrow <tildearrow@protonmail.com>
Date: Fri, 18 Feb 2022 02:03:31 -0500
Subject: [PATCH] yay for more compatibility flags

ignore duplicate slides on .dmf
---
 papers/format.md        |  6 +++++-
 src/engine/engine.cpp   | 14 ++++++++++++--
 src/engine/engine.h     |  4 ++--
 src/engine/playback.cpp |  6 ++++++
 src/engine/song.h       |  4 +++-
 src/gui/gui.cpp         |  4 ++++
 6 files changed, 32 insertions(+), 6 deletions(-)

diff --git a/papers/format.md b/papers/format.md
index c4d9d8a6a..cfbe256a6 100644
--- a/papers/format.md
+++ b/papers/format.md
@@ -25,6 +25,9 @@ furthermore, an `or reserved` indicates this field is always present, but is res
 
 the format versions are:
 
+- 50: Furnace 0.5.7pre2
+- 49: Furnace 0.5.7pre1
+- 48: Furnace 0.5.6
 - 47: Furnace 0.5.6pre1
 - 46: Furnace 0.5.5
 - 45: Furnace 0.5.5pre3
@@ -166,7 +169,8 @@ size | description
   1  | arpeggio inhibits portamento (>=47) or reserved
   1  | wack algorithm macro (>=47) or reserved
   1  | broken shortcut slides (>=49) or reserved
-  8  | reserved
+  1  | ignore duplicate slides (>=50) or reserved
+  6  | reserved
  4?? | pointers to instruments
  4?? | pointers to wavetables
  4?? | pointers to samples
diff --git a/src/engine/engine.cpp b/src/engine/engine.cpp
index 86a5be350..6d2a31325 100644
--- a/src/engine/engine.cpp
+++ b/src/engine/engine.cpp
@@ -1565,6 +1565,7 @@ bool DivEngine::loadDMF(unsigned char* file, size_t len) {
     ds.arpNonPorta=false;
     ds.algMacroBehavior=false;
     ds.brokenShortcutSlides=false;
+    ds.ignoreDuplicateSlides=true;
 
     // Neo Geo detune
     if (ds.system[0]==DIV_SYSTEM_YM2610 || ds.system[0]==DIV_SYSTEM_YM2610_EXT) {
@@ -2117,6 +2118,9 @@ bool DivEngine::loadFur(unsigned char* file, size_t len) {
     if (ds.version<49) {
       ds.brokenShortcutSlides=true;
     }
+    if (ds.version<50) {
+      ds.ignoreDuplicateSlides=false;
+    }
 
     reader.readS(); // reserved
     int infoSeek=reader.readI();
@@ -2239,7 +2243,12 @@ bool DivEngine::loadFur(unsigned char* file, size_t len) {
       } else {
         reader.readC();
       }
-      for (int i=0; i<7; i++) reader.readC();
+      if (ds.version>=50) {
+        ds.ignoreDuplicateSlides=reader.readC();
+      } else {
+        reader.readC();
+      }
+      for (int i=0; i<6; i++) reader.readC();
     } else {
       for (int i=0; i<20; i++) reader.readC();
     }
@@ -2623,7 +2632,8 @@ SafeWriter* DivEngine::saveFur() {
   w->writeC(song.arpNonPorta);
   w->writeC(song.algMacroBehavior);
   w->writeC(song.brokenShortcutSlides);
-  for (int i=0; i<7; i++) {
+  w->writeC(song.ignoreDuplicateSlides);
+  for (int i=0; i<6; i++) {
     w->writeC(0);
   }
 
diff --git a/src/engine/engine.h b/src/engine/engine.h
index a1d4b0d37..44a05ca04 100644
--- a/src/engine/engine.h
+++ b/src/engine/engine.h
@@ -30,8 +30,8 @@
 #include <map>
 #include <queue>
 
-#define DIV_VERSION "0.5.7pre1"
-#define DIV_ENGINE_VERSION 49
+#define DIV_VERSION "0.5.7pre2"
+#define DIV_ENGINE_VERSION 50
 
 enum DivStatusView {
   DIV_STATUS_NOTHING=0,
diff --git a/src/engine/playback.cpp b/src/engine/playback.cpp
index 7d27edf20..63d3ab692 100644
--- a/src/engine/playback.cpp
+++ b/src/engine/playback.cpp
@@ -552,6 +552,8 @@ void DivEngine::processRow(int i, bool afterDelay) {
 
   chan[i].retrigSpeed=0;
 
+  short lastSlide=-1;
+
   // effects
   for (int j=0; j<song.pat[i].effectRows; j++) {
     short effect=pat->data[whatRow][4+(j<<1)];
@@ -583,6 +585,8 @@ void DivEngine::processRow(int i, bool afterDelay) {
         dispatchCmd(DivCommand(DIV_CMD_PANNING,i,effectVal));
         break;
       case 0x01: // ramp up
+        if (song.ignoreDuplicateSlides && lastSlide==0x01) break;
+        lastSlide=0x01;
         if (effectVal==0) {
           chan[i].portaNote=-1;
           chan[i].portaSpeed=-1;
@@ -600,6 +604,8 @@ void DivEngine::processRow(int i, bool afterDelay) {
         }
         break;
       case 0x02: // ramp down
+        if (song.ignoreDuplicateSlides && lastSlide==0x02) break;
+        lastSlide=0x02;
         if (effectVal==0) {
           chan[i].portaNote=-1;
           chan[i].portaSpeed=-1;
diff --git a/src/engine/song.h b/src/engine/song.h
index de57a78ff..0607c351e 100644
--- a/src/engine/song.h
+++ b/src/engine/song.h
@@ -246,6 +246,7 @@ struct DivSong {
   bool arpNonPorta;
   bool algMacroBehavior;
   bool brokenShortcutSlides;
+  bool ignoreDuplicateSlides;
 
   DivOrders orders;
   std::vector<DivInstrument*> ins;
@@ -304,7 +305,8 @@ struct DivSong {
     targetResetsSlides(true),
     arpNonPorta(false),
     algMacroBehavior(false),
-    brokenShortcutSlides(false) {
+    brokenShortcutSlides(false),
+    ignoreDuplicateSlides(false) {
     for (int i=0; i<32; i++) {
       system[i]=DIV_SYSTEM_NULL;
       systemVol[i]=64;
diff --git a/src/gui/gui.cpp b/src/gui/gui.cpp
index 715f32379..e5c912025 100644
--- a/src/gui/gui.cpp
+++ b/src/gui/gui.cpp
@@ -1810,6 +1810,10 @@ void FurnaceGUI::drawCompatFlags() {
     if (ImGui::IsItemHovered()) {
       ImGui::SetTooltip("when enabled, the slide effect is disabled after it reaches its target.");
     }
+    ImGui::Checkbox("Ignore duplicate slide effects",&e->song.ignoreDuplicateSlides);
+    if (ImGui::IsItemHovered()) {
+      ImGui::SetTooltip("if this is on, only the first slide of a row in a channel will be considered.");
+    }
 
     ImGui::Text("Loop modality:");
     if (ImGui::RadioButton("Reset channels",e->song.loopModality==0)) {