[PATCH] OvmfPkg/Gop: clear the screen to black in SetMode()

[Ruiyu Ni <ruiyu.ni@intel.com>]

Today's implementation forgot to clear the screen to black in
SetMode(). It causes SCT SetMode() test fails.

The patch adds the clear screen operation in SetMode() to fix
the SCT failure.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 OvmfPkg/QemuVideoDxe/Gop.c | 23 ++++++++++++++++++-----
 1 file changed, 18 insertions(+), 5 deletions(-)

diff --git a/OvmfPkg/QemuVideoDxe/Gop.c b/OvmfPkg/QemuVideoDxe/Gop.c
index 512fd27acb..f573f7011a 100644
--- a/OvmfPkg/QemuVideoDxe/Gop.c
+++ b/OvmfPkg/QemuVideoDxe/Gop.c
@@ -1,7 +1,7 @@
 /** @file
   Graphics Output Protocol functions for the QEMU video controller.
 
-  Copyright (c) 2007 - 2017, Intel Corporation. All rights reserved.<BR>
+  Copyright (c) 2007 - 2018, Intel Corporation. All rights reserved.<BR>
 
   This program and the accompanying materials
   are licensed and made available under the terms and conditions of the BSD License
@@ -196,9 +196,10 @@ Routine Description:
 
 --*/
 {
-  QEMU_VIDEO_PRIVATE_DATA    *Private;
-  QEMU_VIDEO_MODE_DATA       *ModeData;
-  RETURN_STATUS              Status;
+  QEMU_VIDEO_PRIVATE_DATA       *Private;
+  QEMU_VIDEO_MODE_DATA          *ModeData;
+  RETURN_STATUS                 Status;
+  EFI_GRAPHICS_OUTPUT_BLT_PIXEL Black;
 
   Private = QEMU_VIDEO_PRIVATE_DATA_FROM_GRAPHICS_OUTPUT_THIS (This);
 
@@ -271,7 +272,19 @@ Routine Description:
   }
   ASSERT (Status == RETURN_SUCCESS);
 
-  return EFI_SUCCESS;
+  //
+  // Per UEFI Spec, need to clear the visible portions of the output display to black.
+  //
+  ZeroMem (&Black, sizeof (Black));
+  return FrameBufferBlt (
+           Private->FrameBufferBltConfigure,
+           &Black,
+           EfiBltVideoFill,
+           0, 0,
+           0, 0,
+           This->Mode->Info->HorizontalResolution, This->Mode->Info->VerticalResolution,
+           0
+           );
 }
 
 EFI_STATUS
-- 
2.16.1.windows.1