UEFI Shell - Graphics Output Protocol

Make use of GOP to write a GUI application under UEFI shell.

#include <Uefi.h>
#include <Protocol/GraphicsOutput.h>
#include <Library/MemoryAllocationLib.h>
#include <Library/UefiBootServicesTableLib.h>

EFI_GRAPHICS_OUTPUT_PROTOCOL *Gop;

EFI_STATUS Init() {
 EFI_STATUS status;
 UINTN handleCount;
 EFI_HANDLE *handleBuffer;

 status = gBS->LocateHandleBuffer(
 ByProtocol,
 &gEfiGraphicsOutputProtocolGuid,
 NULL,
 &handleCount,
 &handleBuffer);
 if (EFI_ERROR(status)) return status;

 status = gBS->HandleProtocol(
 handleBuffer[0], // TODO
 &gEfiGraphicsOutputProtocolGuid,
 (VOID **)&(Gop));
 if (EFI_ERROR(status)) return status;

 FreePool(handleBuffer);
 return status;
}