If a comment is needed in this function it's probably here.  If the `toolTipContainer` width is bigger than the `graph.option.tooltip.width` we're going to resize by a magic number (`20`), but from looking at this code I have no sense of why.  Do you mind adding a comment to this block or maybe better, maybe to the function, either by bumping it to a named function, or providing a short block on the first line of the anonymous block?