code: function setArrowFromButton(obj) {
  		
  		var parts = this.id.split('_');
  		var pos = parts[1];
  		var val = parts[2];
  		if (parts[3]) { val += '_' + parts[3];}
  		
  		if (val != 'textmarker') {
  			triggerTextEntry(pos, '\\'+val);
  		} else {
  			showTextPrompt(pos);
  		}
  	}
docs: /*
  function setMarkerSet(obj) {
  var parts = this.id.split('_');
  var set = parts[2];
  switch (set) {
  case 'off':
  triggerTextEntry('start','\\nomarker');
  triggerTextEntry('mid','\\nomarker');
  triggerTextEntry('end','\\nomarker');
  break;
  case 'dimension':
  triggerTextEntry('start','\\leftarrow');
  triggerTextEntry('end','\\rightarrow');
  showTextPrompt('mid');
  break;
  case 'label':
  triggerTextEntry('mid','\\nomarker');
  triggerTextEntry('end','\\rightarrow');
  showTextPrompt('start');
  break;
  }
  }
   callback function for a toolbar button click