From ba3110ca07808d5e6e1ec08c70479ccf59de4bc3 Mon Sep 17 00:00:00 2001
From: ripsaw8080 <ripsaw8080@users.sourceforge.net>
Date: Wed, 13 May 2015 01:35:39 +0000
Subject: [PATCH] Aspect correction fixes for CGA composite, Hercules graphics,
 350-line text modes, 400-line VESA modes, and VGA ModeX (God of Thunder, Lost
 Vikings, Wrath of Earth, etc.)

Imported-from: https://svn.code.sf.net/p/dosbox/code-0/dosbox/trunk@3913
---
 src/hardware/vga_draw.cpp | 8 +++++---
 src/ints/int10_modes.cpp  | 4 +++-
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/src/hardware/vga_draw.cpp b/src/hardware/vga_draw.cpp
index 254e826e..bd1cadc8 100644
--- a/src/hardware/vga_draw.cpp
+++ b/src/hardware/vga_draw.cpp
@@ -1310,7 +1310,9 @@ void VGA_SetupDrawing(Bitu /*val*/) {
 		break;
 	case 3:		//480 line mode, filled with 525 total
 	default:
-		pheight = (480.0 / 480.0) * ( 525.0 / vtotal );
+		//Allow 527 total ModeX to have exact 1:1 aspect
+		target_total = (vga.mode==M_VGA && vtotal==527) ? 527.0 : 525.0;
+		pheight = (480.0 / 480.0) * ( target_total / vtotal );
 		break;
 	}
 
@@ -1403,6 +1405,7 @@ void VGA_SetupDrawing(Bitu /*val*/) {
 		vga.draw.linear_mask = (vga.vmemwrap<<1) - 1;
 		break;
 	case M_CGA16:
+		aspect_ratio=1.2;
 		doubleheight=true;
 		vga.draw.blocks=width*2;
 		width<<=4;
@@ -1421,7 +1424,6 @@ void VGA_SetupDrawing(Bitu /*val*/) {
 		VGA_DrawLine=VGA_Draw_1BPP_Line;
 		break;
 	case M_TEXT:
-		aspect_ratio=1.2;
 		vga.draw.blocks=width;
 		doublewidth=(vga.seq.clocking_mode & 0x8) > 0;
 		if ((IS_VGA_ARCH) && (svgaCard==SVGA_None)) {
@@ -1444,9 +1446,9 @@ void VGA_SetupDrawing(Bitu /*val*/) {
 		}
 		break;
 	case M_HERC_GFX:
-		aspect_ratio=1.5;
 		vga.draw.blocks=width*2;
 		width*=16;
+		aspect_ratio=((double)width/(double)height)*(3.0/4.0);
 		VGA_DrawLine=VGA_Draw_1BPP_Line;
 		break;
 	case M_TANDY2:
diff --git a/src/ints/int10_modes.cpp b/src/ints/int10_modes.cpp
index 1e8c6d62..f68a7fc9 100644
--- a/src/ints/int10_modes.cpp
+++ b/src/ints/int10_modes.cpp
@@ -1006,7 +1006,9 @@ bool INT10_SetVideoMode(Bit16u mode) {
 	if (svgaCard == SVGA_S3Trio) {
 		/* Setup the correct clock */
 		if (CurMode->mode>=0x100) {
-			misc_output|=0xef;		//Select clock 3 
+			if (CurMode->vdispend>480)
+				misc_output|=0xc0;	//480-line sync
+			misc_output|=0x0c;		//Select clock 3 
 			Bitu clock=CurMode->vtotal*8*CurMode->htotal*70;
 			VGA_SetClock(3,clock/1000);
 		}