Intercepting directx DrawText calls

[scframble]

Hello,
I would like to intercept DrawText calls in my game. Is it something that inner space can help me with or should I find another way ?

[Lax]

There actually isnt a Direct3D DrawText function. Assuming the game uses D3DX, it would use the gdi32 ExtTextOutA/ExtTextOutW, but there's no guarantee of that. A lot of games use their own routines, some even use maps of textures for fonts. But, you can certainly try using a detour of ExtTextOutA and ExtTextOutW in an extension.

Code: Select all

EzDetour(ExtTextOutA,ExtTextOutA_detour,ExtTextOutA_trampoline);

[scframble]

There actually isnt a Direct3D DrawText function. Assuming the game uses D3DX, it would use the gdi32 ExtTextOutA/ExtTextOutW, but there's no guarantee of that. A lot of games use their own routines, some even use maps of textures for fonts. But, you can certainly try using a detour of ExtTextOutA and ExtTextOutW in an extension.

Code: Select all

EzDetour(ExtTextOutA,ExtTextOutA_detour,ExtTextOutA_trampoline);

Lax, I really appreciate your prompt response.

Is there any documentation/sample how to use it ? I tried to search wiki but has not found anything about it.

What is exactly trampoline in this case ? I thought a trampoline would be automatically generated for me ? So if I need to supply it myself how to go about writing it ?

Thanks

[Lax]

Well, I didn't want to do all the work for you

Code: Select all

DETOUR_TRAMPOLINE_EMPTY(BOOL WINAPI ExtTextOutA_tramopline(
  HDC hdc,          // handle to DC
  int X,            // x-coordinate of reference point
  int Y,            // y-coordinate of reference point
  UINT fuOptions,   // text-output options
  CONST RECT* lprc, // optional dimensions
  LPCTSTR lpString, // string
  UINT cbCount,     // number of characters in string
  CONST INT* lpDx   // array of spacing values
));
BOOL WINAPI ExtTextOutA_detour(
  HDC hdc,          // handle to DC
  int X,            // x-coordinate of reference point
  int Y,            // y-coordinate of reference point
  UINT fuOptions,   // text-output options
  CONST RECT* lprc, // optional dimensions
  LPCTSTR lpString, // string
  UINT cbCount,     // number of characters in string
  CONST INT* lpDx   // array of spacing values
)
{
  // do any stuff you want to do during the intercept
   printf("ExtTextOutA(%s)",lpString);

  // call the trampoline with the original data (or your own data, but original here)
  return ExtTextOutA_trampoline(hdc,X,Y,fuOptions,lprc,lpString,cbCount,lpDx);
}

[scframble]

Well, I didn't want to do all the work for you

Thx a lot Lax. It worked. As i am struggling to learn c++ every bit of working code helps a lot.

As you expected my game does not use this call for rendering its ingame text. I know that interception worked because i got echo of some inner space text on the console.

That brings a couple more questions. Is there any other standard way of outputting text in games ? i found this reference in msdn:
ID3DXFont::DrawText

http://msdn.microsoft.com/archive/defau ... awText.asp

Any chance to intercept this call also in a similar way to ExtTextOut ?

Is there any tool that shows directx call made by an app ?

[Lax]

That is the call used by ID3DXFont::DrawTextA. ID3DXFont::DrawTextW uses ExtTextOutW, which you should try instead of A since it didnt work for the game you're trying. There are two versions of every text-related function in Windows, one uses ANSI encoding (A is for ANSI) and the other uses unicode (W is for Wide, as in unicode).

Try this instead.

Code: Select all

DETOUR_TRAMPOLINE_EMPTY(BOOL WINAPI ExtTextOutW_tramopline(
  HDC hdc,          // handle to DC
  int X,            // x-coordinate of reference point
  int Y,            // y-coordinate of reference point
  UINT fuOptions,   // text-output options
  CONST RECT* lprc, // optional dimensions
  LPCWSTR lpString, // string
  UINT cbCount,     // number of characters in string
  CONST INT* lpDx   // array of spacing values
));
BOOL WINAPI ExtTextOutW_detour(
  HDC hdc,          // handle to DC
  int X,            // x-coordinate of reference point
  int Y,            // y-coordinate of reference point
  UINT fuOptions,   // text-output options
  CONST RECT* lprc, // optional dimensions
  LPCWSTR lpString, // string
  UINT cbCount,     // number of characters in string
  CONST INT* lpDx   // array of spacing values
)
{
  // do any stuff you want to do during the intercept
   printf("ExtTextOutW(%S)",lpString);

  // call the trampoline with the original data (or your own data, but original here)
  return ExtTextOutW_trampoline(hdc,X,Y,fuOptions,lprc,lpString,cbCount,lpDx);
} 

[scframble]

That is the call used by ID3DXFont::DrawTextA. ID3DXFont::DrawTextW uses ExtTextOutW, which you should try instead of A since it didnt work for the game you're trying. There are two versions of every text-related function in Windows, one uses ANSI encoding (A is for ANSI) and the other uses unicode (W is for Wide, as in unicode).

Thx again Lax, unicode version does not work either. Seems the game uses their own custom way for drawing text.