pointToCell

pub fn pointToCell(self: *GridWidget, point: Point.Physical) ?Cell {
    if (self.init_opts.row_height_variable) return null;
    if (self.resizing or self.init_opts.resize_cols) return null;
    if (self.row_height < 1) return null;

    if (self.pointToBodyRelative(point)) |point_rel| {
        const row_num: usize = @trunc((self.frame_viewport.y + point_rel.y) / self.row_height);
        const col_num = blk: {
            var total_w: f32 = 0;
            for (self.col_widths, 0..) |w, col| {
                total_w += w;
                if (point_rel.x < total_w) {
                    break :blk col;
                }
            }
            return null;
        };
        return .{ .col_num = col_num, .row_num = row_num };
    }
    return null;
}