We don't want to let baseline adjustment shift the child
out of the original allocation. This is purely a sanity
measure - in practice, the baseline should always be bigger
than the child_baseline.
We were adjusting the allocation to line up baselines before
calling gtk_widget_size_allocate_with_baseline, but that function
is doing this alignment internally anyway and expects to be given
a 'fill' allocation.
Move the allocation adjustment code down into
gtk_box_gadget_allocate_child where it only affects child gadgets,
not child widgets.
When measuring children while distributing a given height,
we must measure them for the given width that goes with
the height. Otherwise, things will go wrong if some of the
children do actual width-for-height. This was showing up
as misaligned images in anaconda.
https://bugzilla.gnome.org/show_bug.cgi?id=760967
So far, the box gadget is always allocating all children the
full size in the cross axis. This behavior corresponds to the
align-items: stretch behavior in
https://www.w3.org/TR/css-flexbox-1/#align-items-property
This commit implements the other modes described there.
While widgets have halign/valign properties that we can use for
this, the API for inserting gadgets has to change to take an
extra align parameter. All callers have been updated to pass
GTK_ALIGN_FILL, since that corresponds to the previous behavior.
https://bugzilla.gnome.org/show_bug.cgi?id=760668
