Question

I want to use the windows detours library to detour a non win api function. The function is part of the Qt library (QtGui4.dll). I am wondering how I would set up the function signature for :

void QPainter::drawText ( const QPointF & position, const QString & text )

I had a go with this and it received my usual share of errors, a little explanation of requirements would be interesting as well:

void (QPainter * real_drawText)(const QPointF & position, const QString & text) = drawText

This is what they look like for TextOut, under the windows API:

BOOL (WINAPI * Real_TextOut)(HDC a0, int a1, int a2, LPCWSTR a3, int a4) = TextOutW;
BOOL WINAPI Mine_TextOut(HDC hdc,int X,int Y,LPCWSTR text,int textLen)
{
BOOL rv = Real_TextOut(hdc, X, Y, text, textLen);

HWND hWindow = WindowFromDC(hdc);

SendTextMessage(hWindow, text);

return rv;
}

So, following on from Gene’s suggestion I tried:

typedef void (QPainter::* Real_qp_drawText)(const QPointF & position, const QString & text);

void Mine_drawText(const QPointF & position, const QString & text)
{

    Real_qp_drawText(position,text);

}

But got the error, ‘a function-style conversion to a built-in type can only take one parameter.

So anyway, they say a little public humiliation is good for the soul, my soul must be having the best time…

Thanks.

Answer 1

The type of your functions is FnType:

typedef void (QPainter::*FnType)(const QPointF &, const QString &);

but it looks like what they expect is a WINIAPI = __stdcall C function instead. You might think if you can wrap your function into a C function.