typedef struct {
UINT8 Blue;
UINT8 Green;
UINT8 Red;
UINT8 Reserved;
} EFI_UGA_PIXEL;

typedef EFI_UGA_PIXEL EFI_GRAPHICS_OUTPUT_BLT_PIXEL;

.......

EFI_STATUS
EFIAPI
WinNtGopSetMode (
IN EFI_GRAPHICS_OUTPUT_PROTOCOL * This,
IN UINT32 ModeNumber
)
{
EFI_STATUS Status;
GOP_PRIVATE_DATA *Private;
GOP_MODE_DATA *ModeData;
EFI_GRAPHICS_OUTPUT_BLT_PIXEL Fill;
EFI_GRAPHICS_OUTPUT_BLT_PIXEL *NewFillLine;
RECT Rect;
UINTN Size;
UINTN Width;
UINTN Height;

Private = GOP_PRIVATE_DATA_FROM_THIS (This);

if (ModeNumber >= This->Mode->MaxMode) {
return EFI_UNSUPPORTED;
}

ModeData = &Private->ModeData[ModeNumber];
This->Mode->Mode = ModeNumber;
Private->GraphicsOutput.Mode->Info->HorizontalResolution = ModeData->HorizontalResolution;
Private->GraphicsOutput.Mode->Info->VerticalResolution = ModeData->VerticalResolution;
Private->GraphicsOutput.Mode->Info->PixelsPerScanLine = ModeData->HorizontalResolution;

if (Private->HardwareNeedsStarting) {
Status = WinNtGopStartWindow (
Private,
ModeData->HorizontalResolution,
ModeData->VerticalResolution,
ModeData->ColorDepth,
ModeData->RefreshRate
);
if (EFI_ERROR (Status)) {
return EFI_DEVICE_ERROR;
}

Private->HardwareNeedsStarting = FALSE;
} else {
//
// Change the resolution and resize of the window
//

//
// Free the old buffer. We do not save the content of the old buffer since the
// screen is to be cleared anyway. Clearing the screen is required by the EFI spec.
// See UEFI spec -EFI_GRAPHICS_OUTPUT_PROTOCOL.SetMode()
//
Private->WinNtThunk->HeapFree (Private->WinNtThunk->GetProcessHeap (), 0, Private->VirtualScreenInfo);

//
// Allocate DIB frame buffer directly from NT for performance enhancement
// This buffer is the virtual screen/frame buffer. This buffer is not the
// same a a frame buffer. The first row of this buffer will be the bottom
// line of the image. This is an artifact of the way we draw to the screen.
//
Size = ModeData->HorizontalResolution * ModeData->VerticalResolution * sizeof (RGBQUAD) + sizeof (BITMAPV4HEADER);
Private->VirtualScreenInfo = Private->WinNtThunk->HeapAlloc (
Private->WinNtThunk->GetProcessHeap (),
HEAP_ZERO_MEMORY,
Size
);

//
// Update the virtual screen info data structure
//
Private->VirtualScreenInfo->bV4Size = sizeof (BITMAPV4HEADER);
Private->VirtualScreenInfo->bV4Width = ModeData->HorizontalResolution;
Private->VirtualScreenInfo->bV4Height = ModeData->VerticalResolution;
Private->VirtualScreenInfo->bV4Planes = 1;
Private->VirtualScreenInfo->bV4BitCount = 32;
//
// uncompressed
//
Private->VirtualScreenInfo->bV4V4Compression = BI_RGB;

//
// The rest of the allocated memory block is the virtual screen buffer
//
Private->VirtualScreen = (RGBQUAD *) (Private->VirtualScreenInfo + 1);

//
// Use the AdjuctWindowRect fuction to calculate the real width and height
// of the new window including the border and caption
//
Rect.left = 0;
Rect.top = 0;
Rect.right = ModeData->HorizontalResolution;
Rect.bottom = ModeData->VerticalResolution;

Private->WinNtThunk->AdjustWindowRect (&Rect, WS_OVERLAPPEDWINDOW, 0);

Width = Rect.right - Rect.left;
Height = Rect.bottom - Rect.top;

//
// Retrieve the original window position information
//
Private->WinNtThunk->GetWindowRect (Private->WindowHandle, &Rect);

//
// Adjust the window size
//
Private->WinNtThunk->MoveWindow (Private->WindowHandle, Rect.left, Rect.top, Width, Height, TRUE);

}

NewFillLine = AllocatePool (sizeof (EFI_GRAPHICS_OUTPUT_BLT_PIXEL) * ModeData->HorizontalResolution);
if (NewFillLine == NULL) {
return EFI_DEVICE_ERROR;
}

if (Private->FillLine != NULL) {
FreePool (Private->FillLine);
}

Private->FillLine = NewFillLine;

Fill.Red = 0x00;
Fill.Green = 0x00;
Fill.Blue = 0x00;
This->Blt (
This,
&Fill,
EfiBltVideoFill,
0,
0,
0,
0,
ModeData->HorizontalResolution,
ModeData->VerticalResolution,
ModeData->HorizontalResolution * sizeof (EFI_GRAPHICS_OUTPUT_BLT_PIXEL)
);
return EFI_SUCCESS;
}