code: def get_text_width_height_descent(self, s, prop, ismath):
          
          #return 1, 1
          if ismath: s = self.strip_math(s)
  
          if self.gc is None:
              gc = self.new_gc()
          else:
              gc = self.gc
          gfx_ctx = gc.gfx_ctx
          font = self.get_wx_font(s, prop)
          gfx_ctx.SetFont(font, wx.BLACK)
          w, h, descent, leading = gfx_ctx.GetFullTextExtent(s)
  
          return w, h, descent
docs: get the width and height in display coords of the string s
          with FontPropertry prop