const nsFont* font; fm->GetFont(font); emHeight = NSToCoordRound(float(font->size));
emHeight = NSToCoordRound(float(fm->Font().size));
  GetEmHeight(nsIFontMetrics* fm,              nscoord&        emHeight)  {#if 0     // should switch to this API in order to scale with changes of TextZoom    fm->GetEmHeight(emHeight);#else    const nsFont* font;    fm->GetFont(font);    emHeight = NSToCoordRound(float(font->size));#endif  }