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From: <pukite@daina.com>
Newsgroups: comp.lang.ada
Subject: Re: Graphical interface for Ada programs
Date: Thu, 16 Mar 95 20:25:21 CST
Organization: DAINA Engineering
Message-ID: <83597.pukite@daina.com>
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Date: 1995-03-16T20:25:21-06:00
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ab@captblood.armstrong.edu  <ab@captblood.armstrong.edu> wrote:
> I would like to build a graphical interface to an
> Ada program. The interface would have the usual buttons,
> menus, multiple choices, as well as edit subwindows and a
> animated display subwindow. 
>
> What do you use for such a combination? Are there any
> PD packagages that provide some/all of these 
> interface-design objects?

I will try to explain one method of designing an Ada GUI.

Suppose that I want to design an interactive dialog box.  I plan to provide 
initial data to the dialog, then perform some procedures or updates while 
it is instantiated, and then return some data upon closure. 

To accomplish all this, I will eventually have to code (either visually or 
textually) various edit subwindows, check boxes, buttons, etc. to the 
basic dialog.  Here is the list of controls (widgets) that a dialog 
might contain:

   Check box    : BOOLEAN indication (yes or no)
   Radio button : set of TYPED (enumerated) values with only one chosen
   Edit box     : text STRING or INTEGER value or FLOAT
   Slider/Scroll: RANGE of discrete values
   Push button  : PROCEDURE that gets invoked
   List box     : UNCONSTRAINED ARRAY of items
   Combo box    : UNCONSTRAINED ARRAY of items with 0th item separate
     
I can also have composites of these controls:
   Group box    : A RECORD of related controls surrounded by a rectangle
   Array        : A CONSTRAINED ARRAY of check boxes, edits, etc

And I can trigger events by clicking on one control which updates another:
   Event click  : A FUNCTION that returns a value to a specific control

Notice that I have intentionally upper-cased certain words.  In fact, 
these keywords and a parser allow me a way to map directly from Ada 
constructs to the appropriate dialog controls.  

I will give an example of how this works.  The Ada package below 
uniquely specifies a dialog box:

with Wintypes;
package Select_Shape is

   subtype Shape_Name is STRING (1..20);
   type Shapes is array ( POSITIVE range <> ) of Shape_Name;

   type Intensities is range 1..10;

   type Colors is ( Red, Green, Blue );
   
   type Dimensions is range 1..3;
   type Scaling is array ( Dimensions ) of INTEGER;
   
   generic
      with procedure Help 
        ( Window     : in Wintypes.HWND );    -- Push button 
   procedure Box 
        ( Window     : in     Wintypes.HWND;  -- parent Window handle
          List_Name  : in     STRING;         -- Static text
          List       : in out Shapes;         -- List box
          Intensity  : in out Intensities;    -- Scroll bar or slider
          Fill       :    out BOOLEAN;        -- Check box
          Color      : in out Colors;         -- 3 Radio buttons
          Scale      : in out Scaling );      -- Array of 3 Edits

end Select_Shape;

This dialog prompts for input on how to display and scale a certain shape.
Note that this also gives the directional modes of the data. 
This specific example may be a bit contrived, but I can usually map a fair 
share of dialog boxes that I have seen out there with this technique.

Of course, finishing up the coding task requires manual effort or a tool.
The Ada package body will contain interfacing code; and a resource script 
file will contain the dialog layout.  Plenty of tedious work is involved 
in interfacing so I prefer to use the automated approach.  

Fortunately, you can get an automated ("declareware") tool from the PAL if 
you happen to be Ada coding for Windows.  Check out CanAda in the 
/languages/Ada/swtools directory and make sure you have a floating-point 
coprocessor enabled PC.  It contains a Windows hypertext help file 
as documentation.