Re: Ada and graphics

[jgoodsen@trinidad.ny (John Goodsen)]

In article <3avnif$gkv@babyblue.cs.yale.edu> cosby@greatwall.cctt.com (John Cosby) writes:

   andrej@dec1 (J.C. ANDRE (Progfou)) wrote:
   >Boullier Marc (boulliem@mines.u-nancy.fr) a ecrit :
   >> I want to make graphics with ada but I have no library to help me 
   >> Does someone know a little about X libraries for ada ?
   <snip>
   >P.S.: we use X11R5, DEC ADA.

   Ada bindings for Xlib and Xt exist, out there somewhere in Net.land.  Check
   the Public Ada Library at wuarchive (info about it pops up in this newsgroup
   often).  There may also be some in the ASSET repository; I haven't checked.

   Most Ada vendors will recommend a bindings vendor on request; try them.  If
   you don't want to pay, you're going to be stuck with what you can get off
   the Internet; if you do want to pay, contact a bindings vendor (ATC, SERC,
   and Top GraphX come to mind).  Each set of bindings has its own pros and
   cons; do some research before you pay.

Bindings to Xlib/Xt are not often the solution you need, but many 
inexperienced developers take off down this path and waste a lot
of time and money rebuilding something they would have been better
off buying to get the graphics implemented.

You should take a serious look at a *real* structured graphics engine,
rather than hitting the low level Xlib intrinsics for your graphics.
Unless you are doing anything but the most trivial graphics application,
you will quickly have a need for a structured graphics toolkit...
Ask yourself the following questions:

   1.  Will I require pointer hit detection on graphical objects?
       (e.g. click on a graphical object and detect which object
        was clicked upon)

   2.  Will you ever have to redraw the screen?  
       (using raw xlib, graphics are not redrawn.  You have to remember
        what you drew and always be prepared to redraw it whenever a user
        moves a window over your graphics)

   4.  Do you have the need to scale, rotate or otherwise deform your
       graphical objects?

   3.  Do you have a need for hierarchical graphical objects?
       (e.g. do you want composite graphical objects which allow you to
        scale, move, rotate a set of graphical objects independently from
        other graphical objects)

   5.  Will you ever need to run your application on a non X-window platform?
       (e.g. Windows, NT, etc...)  too often this is the case, but is ignored
       until it becomes a problem at which point it can't be handled well.

Check out HeraGraph from EVB Software Engineering (info@evb.com) if you
want to see how snazzy, portable Ada graphics applications can be built in tens of
lines of pure Ada code.  Haven't seen anything else written in Ada that even
compares closely to it...

-- 
--
John Goodsen                         Currently on-site at:
The Dalmatian Group                       JP Morgan 
User Interface Specialists                60 Wall St., New York City
jgoodsen@radsoft.com                      jgoodsen@jpmorgan.com