RioGetItFix.pas

unit RioGetItFix;

interface

procedure Register;

implementation

uses
  Winapi.Windows, System.SysUtils, Vcl.Themes;

const
  PackageName = 'GetIt260.bpl';
  PatchOffset = $8AB14;
  OriginalCodes: array[0..4] of Byte = ($8B, $45, $F4, $8B, $10);

var
  IsHooked: Boolean;
  ReturnAddr1: Pointer;
  ReturnAddr2: Pointer;

function GetStyleServices: TCustomStyleServices;
begin
  Result := TStyleManager.ActiveStyle;
end;

procedure Trampoline;
asm
  MOV EAX,DWORD PTR [EBP-$C]
  TEST EAX,EAX
  JE @@1
  MOV EDX,DWORD PTR [EAX]
  JMP [ReturnAddr1]

@@1:
  CALL GetStyleServices
  JMP [ReturnAddr2]
end;

procedure Patch(Address: Pointer; const Data: array of Byte);
var
  oldProtect: DWORD;
begin
  VirtualProtect(Address, Length(Data), PAGE_READWRITE, oldProtect);
  Move(Data[0], Address^, Length(Data));
  VirtualProtect(Address, Length(Data), oldProtect, nil);
  FlushInstructionCache(GetCurrentProcess, Address, Length(Data));
end;

procedure Register;
var
  hModule: THandle;
  patchAddr: Pointer;
  jumpOffset: NativeInt;
  bytes: TBytes;
begin
  hModule := GetModuleHandle(PackageName);
  if hModule = 0 then Exit;

  patchAddr := Pointer(hModule + PatchOffset);
  if not CompareMem(patchAddr, @OriginalCodes[0], SizeOf(OriginalCodes)) then Exit;

  ReturnAddr1 := Pointer(hModule + PatchOffset + SizeOf(OriginalCodes));
  ReturnAddr2 := Pointer(hModule + PatchOffset + SizeOf(OriginalCodes) + 6);
  jumpOffset := NativeInt(@Trampoline) - NativeInt(ReturnAddr1);
  bytes := [$E9] + BytesOf(@jumpOffset, SizeOf(jumpOffset));
  Patch(patchAddr, bytes);
  IsHooked := True;
end;

procedure Unregister;
var
  hModule: THandle;
begin
  if not IsHooked then Exit;
  hModule := GetModuleHandle(PackageName);
  if hModule = 0 then Exit;
  Patch(Pointer(hModule + PatchOffset), OriginalCodes);
end;

initialization
finalization
  Unregister;
end.