A single price-axis grid line: the price it sits at, its Y pixel, and
a pre-formatted label. label is null for price-based modes
(linear/log) so the renderer can apply the host's custom price
formatter; it is a ready string for percentage/indexed modes whose
axis reads percentages, not prices.
A single price-axis grid line: the price it sits at, its Y pixel, and a pre-formatted label.
labelisnullfor price-based modes (linear/log) so the renderer can apply the host's custom price formatter; it is a ready string for percentage/indexed modes whose axis reads percentages, not prices.