... be used effectively.
We have had display pixel density detection for quite some time, but I
guess the step I set to switch to the "Huge" icon size (48px for the
toolbox icons) was too high at 300 PPI. Someone with a screen of about
280PPI reported the icons to be far too small on GIMP 2.9.8.
It seems that 240PPI is already even considered as XDPI already. Let's
just set our new "Huge" step at the 250PPI intermediate.

In any case, it seems GIMP 2.10 will have problems with even denser
displays, but the way GTK+2 handles icon sizes with a GTK_ICON_SIZE_*
enum is quite limited. That is quite a problem considering screens
getting denser in pixels nowadays. Hopefully GTK+ 3 will improve the
situation.