This is necessary for GtkNotebook so that the stack is always drawn
before the header.
And that is necessary so that the active tab can use negative
margins to overdraw the border of the stack to create a gap and
simulate old GTK2-style visuals for notebooks.
When we don't get a baseline passed in, we want to basically
center the children inside the allocation. There was an attempt
in the code to do 'internal baseline alignment', but it had the
side effect of moving the contents to the top when we don't get
a baseline passed in. Remove it for now, this needs some more
infrastructure to do properly.
https://bugzilla.gnome.org/show_bug.cgi?id=761363
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
