Re: Widgets

[Liam Gumley <Liam.Gumley(at)ssec.wisc.edu>]

Robert LeeJoice wrote:
> Question for Widget Gurus:  Can I put Widget creation items in an event
> procedure?  I want to be able to able to have a menu item open a new window
> that consists of a table to display some data.  I have put the following in
> and it seems to work, but I'm concerned about how xmanager sees/doesn't see
> this since the widget statements are not in the "Widget Definition file".
> Is it okay and prudent to do this?  I assume as long as there are no
> event_procedures in the code?

Robert,

Anytime you create a new window, the best approach is to create a
separate program to create the widgets in the window and manage events.
For example:

Main program
- Create widgets
- Manage events
  - If new window is requested, call new window program

New window program
- Create widgets
- Manage events

Here's an example which creates a simple launcher for XLOADCT, which is
a separate program (see the lib directory in your IDL installation):

;---cut here---
PRO TEST_EVENT, EVENT

;- Get user value from the widget which caused the event

widget_control, event.id, get_uvalue=uvalue

;- Act on the user value

case uvalue of
  'Color Table' : xloadct
  else          : print, 'Unrecognized widget event'
endcase

END

PRO TEST

;- Create widgets

base = widget_base(/column)
butt = widget_button(base, value='Color Table', uvalue='Color Table')
widget_control, base, /realize

;- Manage events

xmanager, 'test', base

END
;---cut here---

In the event handler procedure TEST_EVENT, XLOADCT is called if an event
is received from the 'Color Table' button. XLOADCT is written as a
separate main program so that it can be called from different modes,
such as the command line, or from within a widget program.

Even when you are creating a utility widget which is specific to your
application, it is still much better to code it as a separate IDL
program (like XLOADCT), because you can code and test it as a unit,
separate from the main program.

Cheers,
Liam.