Main private entry point for building composite container components from template XML.
This is exported purely to let gtk-builder-tool validate templates, applications have no need to call this function.
the widget that is being extended
the type that the template is for
the string to parse
the length of @buffer (may be -1 if @buffer is nul-terminated)
A positive value on success, 0 if an error occurred
GException on failure.
See Implementation
Main private entry point for building composite container components from template XML.
This is exported purely to let gtk-builder-tool validate templates, applications have no need to call this function.