From e8d514701f7b3f90da66e59131c1b803207cc840 Mon Sep 17 00:00:00 2001
From: Jonathan Campbell <jonathan@castus.tv>
Date: Mon, 8 Jul 2024 06:49:24 -0700
Subject: [PATCH] XGA: Rectangle command needs to obey -/+ X and Y direction
 bits. If someone wants to draw a bitmap bottom up, then do it

---
 src/hardware/vga_xga.cpp | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/src/hardware/vga_xga.cpp b/src/hardware/vga_xga.cpp
index 6a484d39e76..6a0468c7e80 100644
--- a/src/hardware/vga_xga.cpp
+++ b/src/hardware/vga_xga.cpp
@@ -83,7 +83,7 @@ struct XGAStatus {
 		bool newline;
 		bool wait;
 		uint16_t cmd;
-		uint16_t curx, cury;
+		uint16_t curx, cury, curdx, curdy;
 		uint16_t x1, y1, x2, y2, sizex, sizey;
 		uint32_t data; /* transient data passed by multiple calls */
 		Bitu datasize;
@@ -802,7 +802,7 @@ bool XGA_CheckX(void) {
 	
 	if((xga.waitcmd.curx<2048) && xga.waitcmd.curx > (xga.waitcmd.x2)) {
 		xga.waitcmd.curx = xga.waitcmd.x1;
-		xga.waitcmd.cury++;
+		xga.waitcmd.cury += xga.waitcmd.curdy;
 		xga.waitcmd.cury&=0x0fff;
 		newline = true;
 		xga.waitcmd.newline = true;
@@ -814,7 +814,7 @@ bool XGA_CheckX(void) {
 			uint16_t realxend=4096-xga.waitcmd.x2;
 			if(realx==realxend) {
 				xga.waitcmd.curx = xga.waitcmd.x1;
-				xga.waitcmd.cury++;
+				xga.waitcmd.cury += xga.waitcmd.curdy;
 				xga.waitcmd.cury&=0x0fff;
 				newline = true;
 				xga.waitcmd.newline = true;
@@ -824,7 +824,7 @@ bool XGA_CheckX(void) {
 		} else { // else overlapping
 			if(realx==xga.waitcmd.x2) {
 				xga.waitcmd.curx = xga.waitcmd.x1;
-				xga.waitcmd.cury++;
+				xga.waitcmd.cury += xga.waitcmd.curdy;
 				xga.waitcmd.cury&=0x0fff;
 				newline = true;
 				xga.waitcmd.newline = true;
@@ -834,7 +834,7 @@ bool XGA_CheckX(void) {
 			}
 		}
 	} else {
-        xga.waitcmd.newline = false;
+		xga.waitcmd.newline = false;
 	}
 	return newline;
 }
@@ -847,7 +847,7 @@ void XGA_DrawWaitSub(Bitu mixmode, Bitu srcval) {
 	//LOG_MSG("XGA: DrawPattern: Mixmode: %x srcval: %x", mixmode, srcval);
 
 	XGA_DrawPoint(xga.waitcmd.curx, xga.waitcmd.cury, destval);
-	xga.waitcmd.curx++;
+	xga.waitcmd.curx += xga.waitcmd.curdx;
 	xga.waitcmd.curx&=0x0fff;
 	XGA_CheckX();
 }
@@ -1236,7 +1236,7 @@ void XGA_DrawCmd(Bitu val, Bitu len) {
 #if XGA_SHOW_COMMAND_TRACE == 1
 					LOG_MSG("XGA: Drawing Bresenham line");
 #endif
-                    XGA_DrawLineBresenham(val);
+					XGA_DrawLineBresenham(val);
 				} else {
 #if XGA_SHOW_COMMAND_TRACE == 1
 					LOG_MSG("XGA: Drawing vector line");
@@ -1262,6 +1262,13 @@ void XGA_DrawCmd(Bitu val, Bitu len) {
 				xga.waitcmd.wait = true;
 				xga.waitcmd.curx = xga.curx;
 				xga.waitcmd.cury = xga.cury;
+
+				/* Windows will always use 101b (+X +Y) to draw left to right, top to bottom.
+				 * Apparently there is an MS-DOS CAD program out there that wants to draw
+				 * (+X -Y) left to right, bottom to top. */
+				xga.waitcmd.curdx = ((val>>5)&1) ? 1 : uint16_t(~0u)/*equiv -1*/;
+				xga.waitcmd.curdy = ((val>>7)&1) ? 1 : uint16_t(~0u)/*equiv -1*/;
+
 				xga.waitcmd.x1 = xga.curx;
 				xga.waitcmd.y1 = xga.cury;
 				xga.waitcmd.x2 = (uint16_t)((xga.curx + xga.MAPcount)&0x0fff);