From: Aleksandar Andrejevic <aandrejevic@reactos.org>
Date: Fri, 9 May 2014 00:15:40 +0000 (+0000)
Subject: [NTVDM]
X-Git-Tag: backups/0.3.17@66124~1348
X-Git-Url: https://git.reactos.org/?p=reactos.git;a=commitdiff_plain;h=ef8bb583c95fadafabcc14d6d25ef7e8dac27722

[NTVDM]
Fix CGA emulation in shift interleave mode.
CORE-8177 #comment Possibly fixed. Can you redo your tests with r63199?


svn path=/trunk/; revision=63199
---

diff --git a/reactos/subsystems/ntvdm/hardware/vga.c b/reactos/subsystems/ntvdm/hardware/vga.c
index 4a4dc1b9237..81ef70b7540 100644
--- a/reactos/subsystems/ntvdm/hardware/vga.c
+++ b/reactos/subsystems/ntvdm/hardware/vga.c
@@ -1146,6 +1146,8 @@ static VOID VgaUpdateFramebuffer(VOID)
         /* Loop through the scanlines */
         for (i = 0; i < Resolution.Y; i++)
         {
+            BOOL RepeatScanline = FALSE;
+
             /* Loop through the pixels */
             for (j = 0; j < Resolution.X; j++)
             {
@@ -1199,10 +1201,23 @@ static VOID VgaUpdateFramebuffer(VOID)
                          * 2 bits shifted from plane 0 and 2 for the first 4 pixels,
                          * then 2 bits shifted from plane 1 and 3 for the next 4
                          */
-                        BYTE LowPlaneData = VgaMemory[((j / 4) % 2) * VGA_BANK_SIZE
-                                                      + (Address + (j / 8)) * AddressSize];
-                        BYTE HighPlaneData = VgaMemory[(((j / 4) % 2) + 2) * VGA_BANK_SIZE
-                                                       + (Address + (j / 8)) * AddressSize];
+                        DWORD BankNumber = (j / 4) % 2;
+                        DWORD Offset = Address + (j / 8);
+                        BYTE LowPlaneData, HighPlaneData;
+
+                        if (i % 2 == 0)
+                        {
+                            /* Odd-numbered line - add the CGA emulation offset */
+                            Offset += VGA_CGA_ODD_LINE_OFFSET;
+                        }
+                        else
+                        {
+                            /* Even-numbered line - use the same scanline */
+                            RepeatScanline = TRUE;
+                        }
+
+                        LowPlaneData = VgaMemory[BankNumber * VGA_BANK_SIZE + Offset * AddressSize];
+                        HighPlaneData = VgaMemory[(BankNumber + 2) * VGA_BANK_SIZE + Offset * AddressSize];
 
                         /* Extract the two bits from each plane */
                         LowPlaneData = (LowPlaneData >> (6 - ((j % 4) * 2))) & 3;
@@ -1296,7 +1311,7 @@ static VOID VgaUpdateFramebuffer(VOID)
             }
 
             /* Move to the next scanline */
-            Address += ScanlineSize;
+            if (!RepeatScanline) Address += ScanlineSize;
         }
 
         /*
diff --git a/reactos/subsystems/ntvdm/hardware/vga.h b/reactos/subsystems/ntvdm/hardware/vga.h
index 1f142c175a8..ba7884ee430 100644
--- a/reactos/subsystems/ntvdm/hardware/vga.h
+++ b/reactos/subsystems/ntvdm/hardware/vga.h
@@ -24,7 +24,7 @@
 #define VGA_MINIMUM_HEIGHT 300
 #define VGA_DAC_TO_COLOR(x) (((x) << 2) | ((x) >> 4))
 #define VGA_COLOR_TO_DAC(x) ((x) >> 2)
-
+#define VGA_CGA_ODD_LINE_OFFSET 0x1000
 
 
 /* Register I/O ports */