[NTVDM]

The highest bit of the mode number is used to determine whether or not we need to clear the screen. Fix the existing code that was disabled in revision 61907 because it was completely wrong. Now we correctly support this feature. Also check the mode number limit and fail if it is unsupported.

svn path=/trunk/; revision=64431

diff --git a/reactos/subsystems/ntvdm/bios/vidbios.c b/reactos/subsystems/ntvdm/bios/vidbios.c
index b7ccc17..2b894d6 100644 (file)
--- a/reactos/subsystems/ntvdm/bios/vidbios.c
+++ b/reactos/subsystems/ntvdm/bios/vidbios.c
@@ -1003,11 +1003,23 @@ BYTE VidBiosGetVideoMode(VOID)
 static BOOLEAN VidBiosSetVideoMode(BYTE ModeNumber)
 {
     BYTE Page;
-
     COORD Resolution;
-    PVGA_REGISTERS VgaMode = VideoModes[ModeNumber];
+    BOOLEAN DoNotClear = !!(ModeNumber & 0x80);
+    PVGA_REGISTERS VgaMode;
+
+    /* Retrieve the real mode number and check its validity */
+    ModeNumber &= 0x7F;
+    // if (ModeNumber >= sizeof(VideoModes)/sizeof(VideoModes[0]))
+    if (ModeNumber > BIOS_MAX_VIDEO_MODE)
+    {
+        DPRINT1("VidBiosSetVideoMode -- Mode %02Xh invalid\n", ModeNumber);
+        return FALSE;
+    }
+
+    VgaMode = VideoModes[ModeNumber];
 
-    DPRINT1("Switching to mode %Xh; VgaMode = 0x%p\n", ModeNumber, VgaMode);
+    DPRINT1("Switching to mode %02Xh %s clearing the screen; VgaMode = 0x%p\n",
+            ModeNumber, (DoNotClear ? "without" : "and"), VgaMode);
 
     if (!VgaSetRegisters(VgaMode)) return FALSE;
 
@@ -1019,8 +1031,7 @@ static BOOLEAN VidBiosSetVideoMode(BYTE ModeNumber)
      * See Ralf Brown: http://www.ctyme.com/intr/rb-0069.htm
      * for more information.
      */
-    // if ((ModeNumber & 0x08) == 0) VgaClearMemory();
-    VgaClearMemory();
+    if (!DoNotClear) VgaClearMemory();
 
     // Bda->CrtModeControl;
     // Bda->CrtColorPaletteMask;