From bf3e6ab0efbb8c4357852583022b719ddfcf1fd9 Mon Sep 17 00:00:00 2001
From: Ralf Grillenberger <h-a-l-9000@users.sourceforge.net>
Date: Mon, 29 Nov 2010 22:26:32 +0000
Subject: [PATCH] Potentially resize the screen when vertical blanking end
 changes. Fixes Threat v1.40 Intro.

Imported-from: https://svn.code.sf.net/p/dosbox/code-0/dosbox/trunk@3662
---
 src/hardware/vga_crtc.cpp | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/hardware/vga_crtc.cpp b/src/hardware/vga_crtc.cpp
index aab7b888..6868f634 100644
--- a/src/hardware/vga_crtc.cpp
+++ b/src/hardware/vga_crtc.cpp
@@ -302,10 +302,14 @@ void vga_write_p3d5(Bitu port,Bitu val,Bitu iolen) {
 		*/
 		break;
 	case 0x16:	/*  End Vertical Blank Register */
-		crtc(end_vertical_blanking)=val;
-		 /*
+		if (val!=crtc(end_vertical_blanking)) {
+			crtc(end_vertical_blanking)=val;
+			VGA_StartResize();
+		}
+		/*
 			0-6	Vertical blanking stops when the lower 7 bits of the line counter
 				equals this field. Some SVGA chips uses all 8 bits!
+				IBM actually says bits 0-7.
 		*/
 		break;
 	case 0x17:	/* Mode Control Register */