One requirement of .ui files is that each object must have an ID,
even if it is never referred to or directly loaded from the code.
This makes editing .ui files much more onerous than it has to be,
due to the frequent need to invent new IDs, while avoiding
clashes.
This commit makes IDs optional in the XML. They only need to
be provided for objects which are referred to or explictly loaded
from the code. Since GtkBuilder needs IDs for its own internal
accounting, we create IDs of the form ___object_N___ if not
specified in the XML.
https://bugzilla.gnome.org/show_bug.cgi?id=712553
This adds the definition of the <template> tag with some documentation
on the variant of the format.
_gtk_builder_extend_with_template() is to be used while GtkContainer
builds from composite templates. A couple of error codes are also added
to handle a few new possible failure cases.
DTD Files gtkbuilder.rnc and gtkbuilder.rng have been updated to include
the new <template> tag and it's attributes.
Replace the (invalid) DTD in the GtkBuilder docs by a
RELAX NG schema. Also install the schema in /usr/share/gtk-3.0,
so it can be used to validate GtkBuilder ui files.
