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Re: Trouble with IDL 5.0.2 (filled contours) unsolved? [message #11045]

Thu, 05 March 1998 00:00

rivers
Messages: 228
Registered: March 1991

Senior Member

In article <34FD2406.D7CD49EC@gmx.net>, Reinhold Schaaf <Kakadu42@gmx.net>
writes:

> A third remark concernes event handling: It is not possible to define a
> method of a class as the event handler of a widget. Consider:
>
> PRO CFrame__Define
> struct = { CFrame, $
> wBase:0L, $
> wDraw:0L $
> }
> END
>
> FUNCTION CFrame::Init
> self.wBase = WIDGET_BASE()
> self.wDraw = WIDGET_DRAW(self.wBase)
> WIDGET_CONTROL, self.wBase, EVENT_PRO='CFrame::Event'; Not allowed!
> WIDGET_CONTROL, self.wBase, /REALIZE
> RETURN, 1
> END
>
> PRO CFrame::Event, sEvent
> ;handle events
> END
>
> This leads to the runtime error:
>
> % WIDGET_CONTROL: Object method is not allowed in this context.
>
> As a consequence, one is forced to make the event handler a global
> function. But global functions cannot access members of objects, so one
> has to add methods to the class which would be unnecessary otherwise.

I agree that this is somewhat inconvenient, but the workaround is really pretty
easy. The trick I use is to stick the object itself in the uvalue of the top
level base for this object. There is no need to keep the list of objects.
Here is an example:

;*********************************************************** ******************
pro mca_display_event, event ; event processing for MCA application

widget_control, event.top, get_uvalue = mca_display
mca_display->event, event
end

;*********************************************************** ******************
pro mca_display::event, event ; event processing for MCA application

case event.id of

.... Rest of event processing goes here.

;*********************************************************** ******************
function mca_display::init, font_size=font_size, parent=parent
...
base = self.widgets.base
widget_control, base, set_uvalue=self
xmanager, 'mca_display::init', base, event='mca_display_event', $
cleanup = 'mca_display_cleanup', /no_block
...

____________________________________________________________
Mark Rivers (773) 702-2279 (office)
CARS (773) 702-9951 (secretary)
Univ. of Chicago (773) 702-5454 (FAX)
5640 S. Ellis Ave. (708) 922-0499 (home)
Chicago, IL 60637 rivers@cars.uchicago.edu (e-mail)

or:
Argonne National Laboratory (630) 252-0422 (office)
Building 434A (630) 252-0405 (lab)
9700 South Cass Avenue (630) 252-1713 (beamline)
Argonne, IL 60439 (630) 252-0443 (FAX)

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[Message index]

		Re: Trouble with IDL 5.0.2 (filled contours) unsolved? By: rivers on Thu, 05 March 1998 00:00
		Re: Trouble with IDL 5.0.2 (filled contours) unsolved? By: Reinhold Schaaf on Wed, 04 March 1998 00:00
		Re: Trouble with IDL 5.0.2 (filled contours) unsolved? By: hcp on Wed, 04 March 1998 00:00
		Re: Trouble with IDL 5.0.2 (filled contours) unsolved? By: Andy Loughe on Tue, 03 March 1998 00:00
		Re: Trouble with IDL 5.0.2 (filled contours) unsolved? By: davidf on Tue, 03 March 1998 00:00
		Re: Trouble with IDL 5.0.2 (filled contours) unsolved? By: Andy Loughe on Tue, 03 March 1998 00:00
		Re: Trouble with IDL 5.0.2 (filled contours) unsolved? By: Mikael Barfred on Tue, 03 March 1998 00:00
		Re: Trouble with IDL 5.0.2 (filled contours) unsolved? By: Mikael Barfred on Tue, 03 March 1998 00:00

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