257) What is UIL and why is it so popular?

[Last modified: Sept 94]

Answer:

UIL is the acronym for "User Interface Language", a Motif standard which
permits separation of the user interface from application code.  UIL is a
textual description of the user interface which is compiled into binary form
called UID ("User Interface Definition") using the Motif-provided compiler
called "uil".

It is important to realize that UIL is a static description of the UI in that
connections between buttons and the dialogs they invoke, for example, is not
expressed here; dynamic UI behavior appears in C code.

The Period Table of Widgets, called "periodic" (delivered by many Motif
vendors) is an example of a UIL application.

There are many advantages and disadvantages of UIL applications.  A few of the
advantages are:

    UIL is a standard format which encourages separation of the
    user interface from application code.

    UIL can be read and/or written by many of the GUI builders and UIMS
    tools mentioned elsewhere in this FAQ, making your interface portable
    (to a degree) across builder tools.

    UIL is a much better language than C for defining a widget
    hierarchy: in C, the widget hierarchy is expressed "linearly"
    by referencing a previously-created parent widget when creating
    a child widget; in UIL, widget trees are defined more naturally
    using nesting.

    With UIL, you separate the definition of the widget tree from
    the application.  You can make major changes to the look-and-feel
    without re-building the application.

    It is possible to write a "general-purpose" application that defines
    a library of callbacks.  The application may "execute" any UIL file
    that references callbacks from the library.


For a good UIL reference, see "Motif Programming Manual", Volume 6A, published
by O'Reilly and Associates. [See "BOOKS" for details.]