active-row-darken

Purpose

Provide a visual focus mechanism for vertically-scrolling lists. Rows near the focal center (typically canvas vertical center) appear in full opacity and bold weight; rows further away fade to a lighter, thinner state.

This is the "typographic dimmer" mechanic that gives SP-D editorial-magazine its hypnotic feel.

Params

{
  "focal_y_px": 960,                     // typically canvas_h / 2

  "distance_for_full_opacity_px": 0,     // rows AT focal are 100%
  "distance_for_50_opacity_px": 96,
  "distance_for_min_opacity_px": 240,

  "min_opacity": 0.18,