HdyHeaderBar: No way to center a squeezer, but still let the label move if it's too long.
These screenshots show
The label is placed inside a
HdySqueezer together with a
HdyViewSwitcher which is hidden since the window is too narrow.
Since the label is misplaced with loose centering, we want strict centering here, but the label is too wide to be shown exactly centered. Normally GtkHeaderBar shifts the title a little bit, but here it doesn't happen, and the title is ellipsized. Or, if it doesn't ellipsize, the window just can't reach the 360px width.
A reproducer: https://gitlab.gnome.org/exalm/sidebarexample