revealText = () => {
const leaf = d3.select(treemap).selectAll('g.leaf')
leaf.each((d, i, arr) => {
const current = arr[i]
const left = d.x0,
right = d.x1,
width = (right - left) * d3.event.transform.k,
top = d.y0,
bottom = d.y1,
height = (d.y1 - d.y0) * d3.event.transform.k
const tooSmall = width < 34 || height < 25
d3.select( current ).select('text')
.attr('opacity', tooSmall ? 0 : 0.9)
})
}