From c9eb0378a5e91a36850c3582b3007b0bb497ad06 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sebastian=20Strohh=C3=A4cker?=
 <c2woody@users.sourceforge.net>
Date: Fri, 28 Sep 2007 21:06:18 +0000
Subject: [PATCH] add vret irq (ega only; fixes Gauntlet hanging)

Imported-from: https://svn.code.sf.net/p/dosbox/code-0/dosbox/trunk@3001
---
 include/vga.h             |  1 +
 src/hardware/vga_draw.cpp |  4 ++++
 src/hardware/vga_misc.cpp | 10 +++++++---
 3 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/include/vga.h b/include/vga.h
index d85b4042..d0500dbe 100644
--- a/include/vga.h
+++ b/include/vga.h
@@ -142,6 +142,7 @@ typedef struct {
 		Bit8u count,delay;
 		Bit8u enabled;
 	} cursor;
+	bool vret_triggered;
 } VGA_Draw;
 
 typedef struct {
diff --git a/src/hardware/vga_draw.cpp b/src/hardware/vga_draw.cpp
index 70693707..185e2a1d 100644
--- a/src/hardware/vga_draw.cpp
+++ b/src/hardware/vga_draw.cpp
@@ -617,6 +617,10 @@ static void VGA_VerticalTimer(Bitu val) {
 	//VGA_DrawPart( vga.draw.parts_lines );
 	PIC_AddEvent(VGA_DrawPart,(float)vga.draw.delay.parts,vga.draw.parts_lines);
 //	PIC_AddEvent(VGA_DrawPart,(float)(vga.draw.delay.parts/2),vga.draw.parts_lines); //Else tearline in Tyrian and second reality
+	if (GCC_UNLIKELY(machine==MCH_EGA)) {
+		PIC_ActivateIRQ(2);
+		vga.draw.vret_triggered=true;
+	}
 }
 
 void VGA_CheckScanLength(void) {
diff --git a/src/hardware/vga_misc.cpp b/src/hardware/vga_misc.cpp
index 4d9093b9..2da0c33e 100644
--- a/src/hardware/vga_misc.cpp
+++ b/src/hardware/vga_misc.cpp
@@ -139,11 +139,17 @@ static Bitu read_p3ca(Bitu port,Bitu iolen) {
 }
 
 static Bitu read_p3c2(Bitu port,Bitu iolen) {
-	return 0x70; 
+	Bitu retcode=0x70;
+	if (GCC_UNLIKELY(machine==MCH_EGA)) {
+		retcode |= (vga.draw.vret_triggered ? 0x80 : 0x00);
+		vga.draw.vret_triggered=false;
+	}
+	return retcode;
 }
 
 void VGA_SetupMisc(void) {
 	if (IS_EGAVGA_ARCH) {
+		vga.draw.vret_triggered=false;
 		IO_RegisterReadHandler(0x3c2,read_p3c2,IO_MB);
 		IO_RegisterWriteHandler(0x3c2,write_p3c2,IO_MB);
 		if (IS_VGA_ARCH) {
@@ -156,5 +162,3 @@ void VGA_SetupMisc(void) {
 		IO_RegisterReadHandler(0x3ba,vga_read_p3da,IO_MB);
 	}
 }
-
-