From c614c13e0edcd9675b990505c03a19dc33743417 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sebastian=20Strohh=C3=A4cker?=
 <c2woody@users.sourceforge.net>
Date: Sun, 23 Oct 2005 19:47:18 +0000
Subject: [PATCH] fix INT10_GetDACBlock; add gray scale summing (from VGABIOS)

Imported-from: https://svn.code.sf.net/p/dosbox/code-0/dosbox/trunk@2353
---
 src/ints/int10.cpp       | 21 +++++++++++++++------
 src/ints/int10.h         |  2 +-
 src/ints/int10_modes.cpp |  6 ++++++
 src/ints/int10_pal.cpp   | 17 ++++++++++++++++-
 4 files changed, 38 insertions(+), 8 deletions(-)

diff --git a/src/ints/int10.cpp b/src/ints/int10.cpp
index 90ff9fc8..6edfe462 100644
--- a/src/ints/int10.cpp
+++ b/src/ints/int10.cpp
@@ -176,6 +176,9 @@ static Bitu INT10_Handler(void) {
 		case 0x1A:							/* GET VIDEO DAC COLOR PAGE */
 			INT10_GetDACPage(&reg_bl,&reg_bh);
 			break;
+		case 0x1B:							/* PERFORM GRAY-SCALE SUMMING */
+			INT10_PerformGrayScaleSumming(reg_bx,reg_cx);
+			break;
 		default:
 			LOG(LOG_INT10,LOG_ERROR)("Function 10:Unhandled EGA/VGA Palette Function %2X",reg_al);
 		}
@@ -274,12 +277,18 @@ graphics_chars:
 		if (machine<MCH_VGA) break;
 		switch (reg_bl) {
 		case 0x10:							/* Get EGA Information */
-			{
-				reg_bh=(real_readw(BIOSMEM_SEG,BIOSMEM_CRTC_ADDRESS)==0x3B4);	
-				reg_bl=3;	//256 kb
-				reg_cx=real_readb(BIOSMEM_SEG,BIOSMEM_SWITCHES) & 0x0F;
-				break;
-			}
+			reg_bh=(real_readw(BIOSMEM_SEG,BIOSMEM_CRTC_ADDRESS)==0x3B4);	
+			reg_bl=3;	//256 kb
+			reg_cx=real_readb(BIOSMEM_SEG,BIOSMEM_SWITCHES) & 0x0F;
+			break;
+		case 0x33: /* SWITCH GRAY-SCALE SUMMING */
+			{   
+				Bit8u temp = real_readb(BIOSMEM_SEG,BIOSMEM_MODESET_CTL) & 0xfd;
+				if (!(reg_al&1)) temp|=2;		// enable if al=0
+				real_writeb(BIOSMEM_SEG,BIOSMEM_MODESET_CTL,temp);
+				reg_al=0x12;
+				break;	
+			}		
 		case 0x34: /* ALTERNATE FUNCTION SELECT (VGA) - CURSOR EMULATION */
 			{   
 				// bit 0: 0=enable, 1=disable
diff --git a/src/ints/int10.h b/src/ints/int10.h
index abdb7110..bc769198 100644
--- a/src/ints/int10.h
+++ b/src/ints/int10.h
@@ -179,7 +179,7 @@ void INT10_SelectDACPage(Bit8u function,Bit8u mode);
 void INT10_GetDACPage(Bit8u* mode,Bit8u* page);
 void INT10_SetPelMask(Bit8u mask);
 void INT10_GetPelMask(Bit8u & mask);
-
+void INT10_PerformGrayScaleSumming(Bit16u start_reg,Bit16u count);
 
 
 /* Vesa Group */
diff --git a/src/ints/int10_modes.cpp b/src/ints/int10_modes.cpp
index 06db9fdd..925e63c5 100644
--- a/src/ints/int10_modes.cpp
+++ b/src/ints/int10_modes.cpp
@@ -781,6 +781,12 @@ dac_text16:
 		}
 		break;
 	}
+	if (machine==MCH_VGA) {
+		/* check if gray scale summing is enabled */
+		if (real_readb(BIOSMEM_SEG,BIOSMEM_MODESET_CTL) & 2) {
+			INT10_PerformGrayScaleSumming(0,256);
+		}
+	}
 	/* Setup some special stuff for different modes */
 	Bit8u feature=real_readb(BIOSMEM_SEG,BIOSMEM_INITIAL_MODE);
 	switch (CurMode->type) {
diff --git a/src/ints/int10_pal.cpp b/src/ints/int10_pal.cpp
index 480d3d76..ed13342f 100644
--- a/src/ints/int10_pal.cpp
+++ b/src/ints/int10_pal.cpp
@@ -154,7 +154,7 @@ void INT10_SetDACBlock(Bit16u index,Bit16u count,PhysPt data) {
 }
 
 void INT10_GetDACBlock(Bit16u index,Bit16u count,PhysPt data) {
- 	IO_Write(VGAREG_DAC_WRITE_ADDRESS,(Bit8u)index);
+ 	IO_Write(VGAREG_DAC_READ_ADDRESS,(Bit8u)index);
 	for (;count>0;count--) {
 		mem_writeb(data++,IO_Read(VGAREG_DAC_DATA));
 		mem_writeb(data++,IO_Read(VGAREG_DAC_DATA));
@@ -239,3 +239,18 @@ void INT10_SetColorSelect(Bit8u val) {
 		INT10_SetSinglePaletteRegister( 3, val );
 	}
 }
+
+void INT10_PerformGrayScaleSumming(Bit16u start_reg,Bit16u count) {
+	if (count>0x100) count=0x100;
+	for (Bitu ct=0; ct<count; ct++) {
+		IO_Write(VGAREG_DAC_READ_ADDRESS,start_reg+ct);
+		Bit8u red=IO_Read(VGAREG_DAC_DATA);
+		Bit8u green=IO_Read(VGAREG_DAC_DATA);
+		Bit8u blue=IO_Read(VGAREG_DAC_DATA);
+
+		/* calculate clamped intensity, taken from VGABIOS */
+		Bit32u i=(( 77*red + 151*green + 28*blue ) + 0x80) >> 8;
+		Bit8u ic=(i>0x3f) ? 0x3f : ((Bit8u)(i & 0xff));
+		INT10_SetSingleDacRegister(start_reg+ct,ic,ic,ic);
+	}
+}