Re: [boost] GUI library - another one

4 Mar 2004

      Me and Daniel Walling have been toying some with a gui library approach
where the user would build the gui trees using a DSEL. Something like
this:

void clicked_ok(button::clicked_event e)
{ /* .. */ }

void clicked_cancel(button::clicked_event e)
{ /* .. */ }

int main()
{
     window w("my gui");

     gadget my_gui =
         + vgroup()
             + "Buttons below me!"
             + hgroup()
                 + button("OK") [ button::clicked = &clicked_ok ]
                 + space()
                 + button("Cancel") [ button::clicked = &clicked_cancel ]
             - hgroup()
                 + button("Maybe") [ button::clicked = &clicked_maybe ]
                 + space()
                 + button("Foobar") [ button::clicked = &clicked_foobar ]
         ;

     w.set_gadget(my_gui);
     w.show();

     /* ... */
}

which would produce a gui like this:

     +---------------------------+
     |     Buttons below me!     |
     |                           |
     | +----------+ +----------+ |
     | |    OK    | |  Cancel  | |
     | +----------+ +----------+ |
     | +----------+ +----------+ |
     | |   Maybe  | |  Foobar  | |
     | +----------+ +----------+ |
     +---------------------------+

of course the functions would be boost::function and possible to
boost::bind to member functions. The expressions within the
[]-operators should of course be a list where it's possible to
assign callbacks for more than one event.

One important requirement I see with a gui lib is to be able to
easily create dynamic guis. Where sub-trees can be exchanged, removed
or added on the fly.

-- 
Arvid Norberg

David Turner wrote:
...
Hello
It seems that the idea of adding a medium-complexity GUI library to boost
is popular, but that there are widely varying opinions on how it should be
done.
I've written a first draft of a library that fulfils most of my
expectations.  It's available at http://www.turn.co.za/david/gui.  It
supports two platforms (Win32 and GTK2), and four user interface elements
or widgets (window, label, button, text-entry).  The design is such that
it is extremely easy to support new platforms or widgets.
These are my expectations of how a good C++ GUI library should behave:
1.  It should be a consistent yet thin wrapper around the platform's
native functionality.
2.  It should degrade gracefully in the absence of certain features on the
platform.
3.  It should be extensible through the factory pattern.
4.  It should couple loosely with user code - this means no inheriting
from an abstract Window class.
5.  It should do what the user (programmer) expects, whenever possible
(i.e. no leaky metaphors).
6.  Widgets that contain things should behave like containers, whenever
this is practical.
7.  It should not use device-specific units like pixels, wherever this is
practical.
and finally
8.  It should be extremely easy to use.
The library at the link above fulfils most of these requirements.  But
it's not perfect.  There are some interesting design choices.
In many respects the most difficult design work is still to be done (list
boxes, menus, drawing areas).  However, the code that exists has the great
advantage of working.
I'd like to know what the boost community thinks before proceeding.
Regards
David Turner