Minor log tick labels are set depending on number of major log ticks, not on number of decades spanned

Previously, by default, on a log-scaled axis, the minor ticks would be unlabeled if the axis limits spanned more than one decade. The meaning of the minor_thresholds parameter to LogFormatter has been altered so that the decision of whether to label the minor ticks is now based on the number of major ticks drawn within the axis limits.

For example, for an axis spanning from 4 to 60 (with thus a single major log tick, at 10), minor ticks are now labeled, even though the axis spans more than one decade.