Prevent crashes when DOS program tries to access console and no

dlls/winedos/int10.c

@@ -489,7 +489,10 @@ void WINAPI DOSVM_Int10Handler( CONTEXT86 *context )
            {
                 BYTE ascii, attr;
                 TRACE("Read Character and Attribute at Cursor Position\n");
-                VGA_GetCharacterAtCursor(&ascii, &attr);
+                if(!VGA_GetCharacterAtCursor(&ascii, &attr)) {
+                    ascii = 0;
+                    attr = 0;
+                }
                 SET_AL( context, ascii );
                 SET_AH( context, attr );
             }
@@ -845,6 +848,6 @@ void WINAPI DOSVM_PutChar(BYTE ascii)
   TRACE("char: 0x%02x(%c)\n", ascii, ascii);
 
   VGA_PutChar(ascii);
-  VGA_GetCursorPos(&xpos, &ypos);
-  BIOS_SetCursorPos(data, 0, xpos, ypos);
+  if(VGA_GetCursorPos(&xpos, &ypos))
+      BIOS_SetCursorPos(data, 0, xpos, ypos);
 }

dlls/winedos/vga.c

@@ -627,12 +627,17 @@ void VGA_SetCursorPos(unsigned X,unsigned Y)
     SetConsoleCursorPosition(VGA_AlphaConsole(),pos);
 }
 
-void VGA_GetCursorPos(unsigned*X,unsigned*Y)
+BOOL VGA_GetCursorPos(unsigned*X,unsigned*Y)
 {
     CONSOLE_SCREEN_BUFFER_INFO info;
-    GetConsoleScreenBufferInfo(VGA_AlphaConsole(),&info);
-    if (X) *X=info.dwCursorPosition.X;
-    if (Y) *Y=info.dwCursorPosition.Y;
+    if(!GetConsoleScreenBufferInfo(VGA_AlphaConsole(),&info))
+    {
+        return FALSE;
+    } else {
+        if (X) *X=info.dwCursorPosition.X;
+        if (Y) *Y=info.dwCursorPosition.Y;
+        return TRUE;
+    }
 }
 
 void VGA_WriteChars(unsigned X,unsigned Y,unsigned ch,int attr,int count)
@@ -643,6 +648,9 @@ void VGA_WriteChars(unsigned X,unsigned Y,unsigned ch,int attr,int count)
     unsigned XR, YR;
     char *dat;
 
+    if(!VGA_GetAlphaMode(&XR, &YR))
+        return;
+
     EnterCriticalSection(&vga_lock);
 
     info.Char.AsciiChar = ch;
@@ -654,7 +662,6 @@ void VGA_WriteChars(unsigned X,unsigned Y,unsigned ch,int attr,int count)
     dest.Top=Y;
     dest.Bottom=Y;
 
-    VGA_GetAlphaMode(&XR, &YR);
     dat = VGA_AlphaBuffer() + ((XR*Y + X) * 2);
     while (count--) {
         dest.Left = X + count;
@@ -688,9 +695,13 @@ void VGA_PutChar(BYTE ascii)
 {
     unsigned width, height, x, y, nx, ny;
 
+    if(!VGA_GetAlphaMode(&width, &height)) {
+        WriteFile(VGA_AlphaConsole(), &ascii, 1, NULL, NULL);
+        return;
+    }
+
     EnterCriticalSection(&vga_lock);
 
-    VGA_GetAlphaMode(&width, &height);
     VGA_GetCursorPos(&x, &y);
 
     switch(ascii) {
@@ -753,10 +764,7 @@ BOOL VGA_ClearText(unsigned row1, unsigned col1,
 
     /* return if we fail to get the height and width of the window */
     if(!VGA_GetAlphaMode(&width, &height))
-    {
-        ERR("failed\n");
         return FALSE;
-    }
 
     TRACE("dat = %p, width = %d, height = %d\n", dat, width, height);
 
@@ -794,17 +802,20 @@ void VGA_ScrollDownText(unsigned row1, unsigned col1,
     FIXME("not implemented\n");
 }
 
-void VGA_GetCharacterAtCursor(BYTE *ascii, BYTE *attr)
+BOOL VGA_GetCharacterAtCursor(BYTE *ascii, BYTE *attr)
 {
     unsigned width, height, x, y;
     char *dat;
 
-    VGA_GetAlphaMode(&width, &height);
-    VGA_GetCursorPos(&x, &y);
+    if(!VGA_GetAlphaMode(&width, &height) || !VGA_GetCursorPos(&x, &y))
+        return FALSE;
+
     dat = VGA_AlphaBuffer() + ((width*y + x) * 2);
 
     *ascii = dat[0];
     *attr = dat[1];
+
+    return TRUE;
 }
 
 

dlls/winedos/vga.h

@@ -44,7 +44,7 @@ int VGA_SetAlphaMode(unsigned Xres,unsigned Yres);
 BOOL VGA_GetAlphaMode(unsigned*Xres,unsigned*Yres);
 void VGA_SetCursorShape(unsigned char start_options,unsigned char end);
 void VGA_SetCursorPos(unsigned X,unsigned Y);
-void VGA_GetCursorPos(unsigned*X,unsigned*Y);
+BOOL VGA_GetCursorPos(unsigned*X,unsigned*Y);
 void VGA_WriteChars(unsigned X,unsigned Y,unsigned ch,int attr,int count);
 void VGA_PutChar(BYTE ascii);
 void VGA_SetTextAttribute(BYTE attr);
@@ -57,7 +57,7 @@ void VGA_ScrollUpText(unsigned row1, unsigned col1,
 void VGA_ScrollDownText(unsigned row1, unsigned col1,
                        unsigned row2, unsigned col2,
                        unsigned lines, BYTE attr);
-void VGA_GetCharacterAtCursor(BYTE *ascii, BYTE *attr);
+BOOL VGA_GetCharacterAtCursor(BYTE *ascii, BYTE *attr);
 
 /* control */
 void VGA_ioport_out(WORD port, BYTE val);