From b9b0a8110c307bdf8457fa66a83a193ad0008461 Mon Sep 17 00:00:00 2001
From: Monster Iestyn <iestynjealous@ntlworld.com>
Date: Wed, 16 Nov 2016 18:43:25 +0000
Subject: [PATCH] Add R_Draw2sMultiPatchTranslucentColumn_8, for columns of
 multi-patch textures used as midtextures on two-sided linedefs with both
 transparency AND translucency

...that was a mouthful
---
 src/r_draw.h  |  1 +
 src/r_draw8.c | 97 +++++++++++++++++++++++++++++++++++++++++++++++++++
 src/r_segs.c  |  2 ++
 src/screen.c  |  2 ++
 src/screen.h  |  1 +
 5 files changed, 103 insertions(+)

diff --git a/src/r_draw.h b/src/r_draw.h
index 6d85bd6a..9cf7e9d5 100644
--- a/src/r_draw.h
+++ b/src/r_draw.h
@@ -161,6 +161,7 @@ void R_DrawSplat_8(void);
 void R_DrawTranslucentSplat_8(void);
 void R_DrawTranslucentSpan_8(void);
 void R_Draw2sMultiPatchColumn_8(void);
+void R_Draw2sMultiPatchTranslucentColumn_8(void);
 void R_DrawFogSpan_8(void);
 void R_DrawFogColumn_8(void);
 void R_DrawColumnShadowed_8(void);
diff --git a/src/r_draw8.c b/src/r_draw8.c
index 800f28b6..e5dbe707 100644
--- a/src/r_draw8.c
+++ b/src/r_draw8.c
@@ -203,6 +203,103 @@ void R_Draw2sMultiPatchColumn_8(void)
 	}
 }
 
+void R_Draw2sMultiPatchTranslucentColumn_8(void)
+{
+	INT32 count;
+	register UINT8 *dest;
+	register fixed_t frac;
+	fixed_t fracstep;
+
+	count = dc_yh - dc_yl;
+
+	if (count < 0) // Zero length, column does not exceed a pixel.
+		return;
+
+#ifdef RANGECHECK
+	if ((unsigned)dc_x >= (unsigned)vid.width || dc_yl < 0 || dc_yh >= vid.height)
+		return;
+#endif
+
+	// Framebuffer destination address.
+	// Use ylookup LUT to avoid multiply with ScreenWidth.
+	// Use columnofs LUT for subwindows?
+
+	//dest = ylookup[dc_yl] + columnofs[dc_x];
+	dest = &topleft[dc_yl*vid.width + dc_x];
+
+	count++;
+
+	// Determine scaling, which is the only mapping to be done.
+	fracstep = dc_iscale;
+	//frac = dc_texturemid + (dc_yl - centery)*fracstep;
+	frac = (dc_texturemid + FixedMul((dc_yl << FRACBITS) - centeryfrac, fracstep))*(!dc_hires);
+
+	// Inner loop that does the actual texture mapping, e.g. a DDA-like scaling.
+	// This is as fast as it gets.
+	{
+		register const UINT8 *source = dc_source;
+		register const UINT8 *transmap = dc_transmap;
+		register const lighttable_t *colormap = dc_colormap;
+		register INT32 heightmask = dc_texheight-1;
+		register UINT8 val;
+		if (dc_texheight & heightmask)   // not a power of 2 -- killough
+		{
+			heightmask++;
+			heightmask <<= FRACBITS;
+
+			if (frac < 0)
+				while ((frac += heightmask) <  0);
+			else
+				while (frac >= heightmask)
+					frac -= heightmask;
+
+			do
+			{
+				// Re-map color indices from wall texture column
+				//  using a lighting/special effects LUT.
+				// heightmask is the Tutti-Frutti fix
+				val = source[frac>>FRACBITS];
+
+				if (val != TRANSPARENTPIXEL)
+					*dest = colormap[*(transmap + (val<<8) + (*dest))];
+
+				dest += vid.width;
+
+				// Avoid overflow.
+				if (fracstep > 0x7FFFFFFF - frac)
+					frac += fracstep - heightmask;
+				else
+					frac += fracstep;
+
+				while (frac >= heightmask)
+					frac -= heightmask;
+			} while (--count);
+		}
+		else
+		{
+			while ((count -= 2) >= 0) // texture height is a power of 2
+			{
+				val = source[(frac>>FRACBITS) & heightmask];
+				if (val != TRANSPARENTPIXEL)
+					*dest = colormap[*(transmap + (val<<8) + (*dest))];
+				dest += vid.width;
+				frac += fracstep;
+				val = source[(frac>>FRACBITS) & heightmask];
+				if (val != TRANSPARENTPIXEL)
+					*dest = colormap[*(transmap + (val<<8) + (*dest))];
+				dest += vid.width;
+				frac += fracstep;
+			}
+			if (count & 1)
+			{
+				val = source[(frac>>FRACBITS) & heightmask];
+				if (val != TRANSPARENTPIXEL)
+					*dest = colormap[*(transmap + (val<<8) + (*dest))];
+			}
+		}
+	}
+}
+
 /**	\brief The R_DrawShadeColumn_8 function
 	Experiment to make software go faster. Taken from the Boom source
 */
diff --git a/src/r_segs.c b/src/r_segs.c
index 502ff330..40184bdd 100644
--- a/src/r_segs.c
+++ b/src/r_segs.c
@@ -271,6 +271,8 @@ static void R_Render2sidedMultiPatchColumn(column_t *column)
 
 		if (colfunc == wallcolfunc)
 			twosmultipatchfunc();
+		else if (colfunc == fuzzcolfunc)
+			twosmultipatchtransfunc();
 		else
 			colfunc();
 	}
diff --git a/src/screen.c b/src/screen.c
index 2780edb6..58c38993 100644
--- a/src/screen.c
+++ b/src/screen.c
@@ -49,6 +49,7 @@ void (*splatfunc)(void); // span drawer w/ transparency
 void (*basespanfunc)(void); // default span func for color mode
 void (*transtransfunc)(void); // translucent translated column drawer
 void (*twosmultipatchfunc)(void); // for cols with transparent pixels
+void (*twosmultipatchtransfunc)(void); // for cols with transparent pixels AND translucency
 
 // ------------------
 // global video state
@@ -127,6 +128,7 @@ void SCR_SetMode(void)
 		fuzzcolfunc = R_DrawTranslucentColumn_8;
 		walldrawerfunc = R_DrawWallColumn_8;
 		twosmultipatchfunc = R_Draw2sMultiPatchColumn_8;
+		twosmultipatchtransfunc = R_Draw2sMultiPatchTranslucentColumn_8;
 #ifdef RUSEASM
 		if (R_ASM)
 		{
diff --git a/src/screen.h b/src/screen.h
index 2dff4590..a61de7f9 100644
--- a/src/screen.h
+++ b/src/screen.h
@@ -136,6 +136,7 @@ extern void (*basespanfunc)(void);
 extern void (*splatfunc)(void);
 extern void (*transtransfunc)(void);
 extern void (*twosmultipatchfunc)(void);
+extern void (*twosmultipatchtransfunc)(void);
 
 // -----
 // CPUID