Fix libxmp GDM fine effects continue bug

AliceLR · Apr 11, 2020 · b279bd1 · b279bd1
1 parent a5fba89
commit b279bd1
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Showing 3 changed files with 118 additions and 2 deletions.
diff --git a/contrib/libxmp/src/loaders/gdm_load.c b/contrib/libxmp/src/loaders/gdm_load.c
@@ -60,6 +60,7 @@ static int gdm_test(HIO_HANDLE *f, char *t, const int start)
 
 void fix_effect(uint8 *fxt, uint8 *fxp)
 {
+	int h, l;
 	switch (*fxt) {
 	case 0x00:			/* no effect */
 		*fxp = 0;
@@ -80,9 +81,49 @@ void fix_effect(uint8 *fxt, uint8 *fxp)
 	case 0x0b:
 	case 0x0c:
 	case 0x0d:
-	case 0x0e:
 	case 0x0f:			/* same as protracker */
 		break;
+	case 0x0e:
+		/* Convert some extended effects to their S3M equivalents. This is
+		 * necessary because the continue effects were left as the original
+		 * effect (e.g. FX_VOLSLIDE for the fine volume slides) by 2GDM!
+		 * Otherwise, these should be the same as protracker.
+		 */
+		h = MSN(*fxp);
+		l = LSN(*fxp);
+		switch(h) {
+			case EX_F_PORTA_UP:
+				*fxt = FX_PORTA_UP;
+				*fxp = l | 0xF0;
+				break;
+			case EX_F_PORTA_DN:
+				*fxt = FX_PORTA_DN;
+				*fxp = l | 0xF0;
+				break;
+			case 0x8:	/* extra fine portamento up */
+				*fxt = FX_PORTA_UP;
+				*fxp = l | 0xE0;
+				break;
+			case 0x9:	/* extra fine portamento down */
+				*fxt = FX_PORTA_DN;
+				*fxp = l | 0xE0;
+				break;
+			case EX_F_VSLIDE_UP:
+				/* Don't convert 0 as it would turn into volume slide down... */
+				if (l) {
+					*fxt = FX_VOLSLIDE;
+					*fxp = (l << 4) | 0xF;
+				}
+				break;
+			case EX_F_VSLIDE_DN:
+				/* Don't convert 0 as it would turn into volume slide up... */
+				if (l) {
+					*fxt = FX_VOLSLIDE;
+					*fxp = l | 0xF0;
+				}
+				break;
+		}
+		break;
 	case 0x10:			/* arpeggio */
 		*fxt = FX_S3M_ARPEGGIO;
 		break;
@@ -367,7 +408,7 @@ static int gdm_load(struct module_data *m, HIO_HANDLE *f, const int start)
 			return -1;
 	}
 
-	m->quirk |= QUIRK_ARPMEM;
+	m->quirk |= QUIRK_ARPMEM | QUIRK_FINEFX;
 
 	return 0;
 }
diff --git a/contrib/patches/libxmp/16-libxmp-4.4.1-fix-gdm-fine-effects.patch b/contrib/patches/libxmp/16-libxmp-4.4.1-fix-gdm-fine-effects.patch
@@ -0,0 +1,72 @@
+diff --git a/src/loaders/gdm_load.c b/src/loaders/gdm_load.c
+index a326c9fc..30907f63 100644
+--- a/src/loaders/gdm_load.c
++++ b/src/loaders/gdm_load.c
+@@ -60,6 +60,7 @@ static int gdm_test(HIO_HANDLE *f, char *t, const int start)
+
+ void fix_effect(uint8 *fxt, uint8 *fxp)
+ {
++	int h, l;
+ 	switch (*fxt) {
+ 	case 0x00:			/* no effect */
+ 		*fxp = 0;
+@@ -80,9 +81,49 @@ void fix_effect(uint8 *fxt, uint8 *fxp)
+ 	case 0x0b:
+ 	case 0x0c:
+ 	case 0x0d:
+-	case 0x0e:
+ 	case 0x0f:			/* same as protracker */
+ 		break;
++	case 0x0e:
++		/* Convert some extended effects to their S3M equivalents. This is
++		 * necessary because the continue effects were left as the original
++		 * effect (e.g. FX_VOLSLIDE for the fine volume slides) by 2GDM!
++		 * Otherwise, these should be the same as protracker.
++		 */
++		h = MSN(*fxp);
++		l = LSN(*fxp);
++		switch(h) {
++			case EX_F_PORTA_UP:
++				*fxt = FX_PORTA_UP;
++				*fxp = l | 0xF0;
++				break;
++			case EX_F_PORTA_DN:
++				*fxt = FX_PORTA_DN;
++				*fxp = l | 0xF0;
++				break;
++			case 0x8:	/* extra fine portamento up */
++				*fxt = FX_PORTA_UP;
++				*fxp = l | 0xE0;
++				break;
++			case 0x9:	/* extra fine portamento down */
++				*fxt = FX_PORTA_DN;
++				*fxp = l | 0xE0;
++				break;
++			case EX_F_VSLIDE_UP:
++				/* Don't convert 0 as it would turn into volume slide down... */
++				if (l) {
++					*fxt = FX_VOLSLIDE;
++					*fxp = (l << 4) | 0xF;
++				}
++				break;
++			case EX_F_VSLIDE_DN:
++				/* Don't convert 0 as it would turn into volume slide up... */
++				if (l) {
++					*fxt = FX_VOLSLIDE;
++					*fxp = l | 0xF0;
++				}
++				break;
++		}
++		break;
+ 	case 0x10:			/* arpeggio */
+ 		*fxt = FX_S3M_ARPEGGIO;
+ 		break;
+@@ -367,7 +408,7 @@ static int gdm_load(struct module_data *m, HIO_HANDLE *f, const int start)
+ 			return -1;
+ 	}
+
+-	m->quirk |= QUIRK_ARPMEM;
++	m->quirk |= QUIRK_ARPMEM | QUIRK_FINEFX;
+
+ 	return 0;
+ }
diff --git a/docs/changelog.txt b/docs/changelog.txt
@@ -34,6 +34,9 @@ USERS
   decreased the size of the output HTML files somewhat.
 + Fixed libxmp playback for S3Ms containing ADPCM4 samples. This
   fixes mm2flash.s3m in ZeuxDrop.
++ Fixed libxmp playback for GDMs where 100/200/A00 should
+  continue the fine portamento and fine volume slide commands.
+  This fixes LB2_7.GDM from Kikan.
 + Windows builds now attempt to load and call SetProcessDPIAware
   on startup. This should fix undesirable DPI-related scaling
   and fullscreen bugs.