I just don't get it, what's with this->?

Geek Speak

I’m looking at some code to help me understand how to use the dbghelp.dll Windows stack walking and symbol discovery stuff and the code I’ve found on the net uses a programming style that I’ve seen a few times before and have never understood the reason for.

if (this->m_sw->pSGSFA(this->m_hProcess, s.AddrPC.Offset, 
      &(csEntry.offsetFromSmybol), pSym) != FALSE)
{
   strcpy_s(csEntry.name, pSym->Name);
   // UnDecorateSymbolName()
   this->m_sw->pUDSN( pSym->Name, 
      csEntry.undName, STACKWALK_MAX_NAMELEN, 
      UNDNAME_NAME_ONLY );
  
   this->m_sw->pUDSN( pSym->Name, csEntry.undFullName,
      STACKWALK_MAX_NAMELEN, 
      UNDNAME_COMPLETE );
}
else
{
   this->OnDbgHelpErr("SymGetSymFromAddr64", GetLastError(), s.AddrPC.Offset);
}

Why did the author feel it necessary to be explicit about his use of the current object by specifying this-> when accessing members? Where did this style come from and what purpose is it supposed to serve?