MdeModulePkg/Application/HelloWorld/HelloWorld.c

/** @file
  This sample application bases on HelloWorld PCD setting
  to print "UEFI Hello World!" to the UEFI Console.

  Copyright (c) 2006 - 2018, Intel Corporation. All rights reserved.<BR>
  SPDX-License-Identifier: BSD-2-Clause-Patent

**/

#include <Uefi.h>
#include <Library/PcdLib.h>
#include <Library/UefiLib.h>
#include <Library/UefiApplicationEntryPoint.h>
#include <Library/UefiBootServicesTableLib.h>
#include <Protocol/GraphicsOutput.h>

//
// String token ID of help message text.
// Shell supports to find help message in the resource section of an application image if
// .MAN file is not found. This global variable is added to make build tool recognizes
// that the help string is consumed by user and then build tool will add the string into
// the resource section. Thus the application can use '-?' option to show help message in
// Shell.
//
GLOBAL_REMOVE_IF_UNREFERENCED EFI_STRING_ID  mStringHelpTokenId = STRING_TOKEN (STR_HELLO_WORLD_HELP_INFORMATION);

/**
  The user Entry Point for Application. The user code starts with this function
  as the real entry point for the application.

  @param[in] ImageHandle    The firmware allocated handle for the EFI image.
  @param[in] SystemTable    A pointer to the EFI System Table.

  @retval EFI_SUCCESS       The entry point is executed successfully.
  @retval other             Some error occurs when executing this entry point.

**/
EFI_STATUS
EFIAPI
UefiMain (
  IN EFI_HANDLE        ImageHandle,
  IN EFI_SYSTEM_TABLE  *SystemTable
  )
{
  UINT32                           Index;
  EFI_STATUS                       Status;
  EFI_GRAPHICS_OUTPUT_PROTOCOL     *GraphicsOutput;
  EFI_GRAPHICS_OUTPUT_MODE_INFORMATION *ModeInfo;
  UINTN                            SizeOfInfo;

  Index = 0;

  //
  // Three PCD type (FeatureFlag, UINT32 and String) are used as the sample.
  //
  if (FeaturePcdGet (PcdHelloWorldPrintEnable)) {
    for (Index = 0; Index < PcdGet32 (PcdHelloWorldPrintTimes); Index++) {
      //
      // Use UefiLib Print API to print string to UEFI console
      //
      Print ((CHAR16 *)PcdGetPtr (PcdHelloWorldPrintString));
    }
  }

  //
  // Get current screen resolution
  //
  Status = gBS->LocateProtocol(
                  &gEfiGraphicsOutputProtocolGuid,
                  NULL,
                  (VOID **)&GraphicsOutput
                  );
  
  if (EFI_ERROR(Status)) {
    Print(L"Failed to locate Graphics Output Protocol: %r\n", Status);
  } else {
    // Get current mode information
    Status = GraphicsOutput->QueryMode(
                               GraphicsOutput,
                               GraphicsOutput->Mode->Mode,
                               &SizeOfInfo,
                               &ModeInfo
                               );
    
    if (EFI_ERROR(Status)) {
      Print(L"Failed to query current mode: %r\n", Status);
    } else {
      // Print current screen resolution
      Print(L"Current Screen Resolution: %dx%d\n", 
            ModeInfo->HorizontalResolution, 
            ModeInfo->VerticalResolution);
      
      // Free the buffer allocated by QueryMode
      gBS->FreePool(ModeInfo);
    }
  }

  return EFI_SUCCESS;
}