galleryColumnSpan function
How many COLUMNS a tile of the given aspect (width/height) spans in the
CSS-grid base — wider artwork spans more columns. The opt-in packer refines.
Implementation
int galleryColumnSpan(double aspect) {
final double a = _clampAspect(aspect);
if (a >= 1.68) return 3; // panorama
if (a >= 1.28) return 2; // wide
return 1;
}