Camera tilts globe up instead of down

The first middle mouse drag after clicking the home button tilts the globe up instead of down.
It seems like it might be dependent on the screen aspect ratio somehow?

It happens every time in a window like this (width > height):

But none of the time in a window like this:

No files, tests, or entry points are named. Start by reproducing the first middle-mouse drag after clicking Home in both wide and tall window shapes, then trace the globe camera and aspect-ratio handling. Done means the first drag tilts in the expected direction regardless of window shape.

Written by the indexing model from the issue text.