[aandrejevic] 60827: [NTVDM] Fix resolution calculation when scanline doubling is enabled.

Author: aandrejevic
Date: Sat Nov  2 01:51:27 2013
New Revision: 60827

URL: http://svn.reactos.org/svn/reactos?rev=60827&view=rev
Log:
[NTVDM]
Fix resolution calculation when scanline doubling is enabled.

Modified:
    branches/ntvdm/subsystems/ntvdm/vga.c
    branches/ntvdm/subsystems/ntvdm/vga.h

Modified: branches/ntvdm/subsystems/ntvdm/vga.c
URL: http://svn.reactos.org/svn/reactos/branches/ntvdm/subsystems/ntvdm/vga.c?rev...
==============================================================================
--- branches/ntvdm/subsystems/ntvdm/vga.c	[iso-8859-1] (original)
+++ branches/ntvdm/subsystems/ntvdm/vga.c	[iso-8859-1] Sat Nov  2 01:51:27 2013
@@ -802,6 +802,12 @@
         if (VgaAcRegisters[VGA_AC_CONTROL_REG] & VGA_AC_CONTROL_8BIT) Resolution.X /= 2;
     }

+    if (VgaCrtcRegisters[VGA_CRTC_MAX_SCAN_LINE_REG] & VGA_CRTC_MAXSCANLINE_DOUBLE)
+    {
+        /* Halve the vertical resolution */
+        Resolution.Y >>= 1;
+    }
+
     /* Divide the vertical resolution by the maximum scan line (== font size in text mode) */
     Resolution.Y /= MaximumScanLine;

Modified: branches/ntvdm/subsystems/ntvdm/vga.h
URL: http://svn.reactos.org/svn/reactos/branches/ntvdm/subsystems/ntvdm/vga.h?rev...
==============================================================================
--- branches/ntvdm/subsystems/ntvdm/vga.h	[iso-8859-1] (original)
+++ branches/ntvdm/subsystems/ntvdm/vga.h	[iso-8859-1] Sat Nov  2 01:51:27 2013
@@ -79,6 +79,9 @@

/* CRTC underline register bits */
 #define VGA_CRTC_UNDERLINE_DWORD (1 << 6)
+
+/* CRTC max scanline register bits */
+#define VGA_CRTC_MAXSCANLINE_DOUBLE (1 << 7)

/* CRTC mode control register bits */
 #define VGA_CRTC_MODE_CONTROL_WRAP (1 << 5)