init.js

Hooks.on('canvasReady', (canvas) => {
  canvas.tokens.placeables.forEach((token) => {
    token.effects.addListener('childAdded', (child) => {
      fixEffectScale(token, child);
    });
    updateEffectScales(token);
  });
});

Hooks.on('createToken', (parent, tokenData) => {
  setTimeout(() => {
    const token = canvas.tokens.get(tokenData._id);
    if (token) {
      token.effects.addListener('childAdded', (child) => {
        fixEffectScale(token, child);
      });
      updateEffectScales(token);
    }
  }, 1000);
});

Hooks.on('updateToken', (parent, tokenData) => {
  setTimeout(() => {
    const token = canvas.tokens.get(tokenData._id);
    updateEffectScales(token);
  }, 1000);
});

let pendingUpdates = {};

function fixEffectScale(token, child) {
  clearTimeout(pendingUpdates[token.id]);
  pendingUpdates[token.id] = setTimeout(() => {
    updateEffectScales(token);
  }, 10);
}

function countEffects(token) {
  if(!token) {
    return 0;
  }
  const tokenEffects = token.data.effects;
  const actorEffects = token.actor && token.actor.temporaryEffects || [];
  let numEffects = tokenEffects.length;
  actorEffects.forEach(actorEffect => {
    if ( !actorEffect.getFlag("core", "overlay") ) {
      numEffects++;
    }
  });
  return numEffects;
}

function updateEffectScales(token) {
  const numEffects = countEffects(token);
  if (numEffects > 0 && token.effects.children.length > 0) {
    const w = Math.floor(token.w / 3) - 1;
    const bg = token.effects.children[0];
    bg.clear();
    bg.beginFill(0x000000, 0.6).lineStyle(1.0, 0x000000);
    token.effects.children.forEach((effectIcon, i) => {
      if (i === 0) {
        // BG
      } else if (i <= numEffects) {
        // Effect icon
        const ei = i - 1;
        const x = (ei % 3) * w;
        const y = Math.floor(ei / 3) * w;
        effectIcon.width = effectIcon.height = w;
        effectIcon.position.x = x;
        effectIcon.position.y = y;
        bg.drawRoundedRect(
          effectIcon.position.x,
          effectIcon.position.y,
          effectIcon.width,
          effectIcon.width,
          2
        );
      } else {
        // Overlay icon
      }
    });
  }
}