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Re: retain and graphics_level=2 [message #10196 is a reply to message #10194]

Wed, 29 October 1997 00:00

davidf
Messages: 2866
Registered: September 1996

Senior Member

R. Bauer (r.bauer@fz-juelich.de) writes:

> Sometimes, it has no effect if I use retain=2 in a draw_widget for
> object_graphics.
>
> What's are the reasons?

The IDL documentation states that the use of Retain=2 in
draw widgets used for object graphics is "strongly discouraged".
This might lead you to believe it's just a bad idea. In fact,
I've found that it is a disastrous idea on most of the platforms
I've used object graphics on. On my WindowsNT machine, for
example, use of Retain=2 with any resizeable graphics window
makes all of the axes labeling disappear on the resized plot!

The fact is, object graphics windows do not have to have
a pixmap around to "buffer" the window's contents. The
object graphics themselves *are* the buffer! In fact you
might say that the whole point of object graphics is that
they are persistent and that the object "scene" can be
reproduced at any time (albeit slowly sometimes).

I have gotten into the habit of setting Retain=0 and
Expose=1 on any window I create for object graphics
output. On any expose event I simply call the Draw
method on the Window. Simple. Easy. And it works
every time.

Cheers,

David

-----------------------------------------------------------
David Fanning, Ph.D.
Fanning Software Consulting
E-Mail: davidf@dfanning.com
Phone: 970-221-0438
Coyote's Guide to IDL Programming: http://www.dfanning.com/

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[Message index]

		Re: retain and graphics_level=2 By: Stein Vidar Hagfors H on Wed, 29 October 1997 00:00
		Re: retain and graphics_level=2 By: Stein Vidar Hagfors H on Wed, 29 October 1997 00:00
		Re: retain and graphics_level=2 By: davidf on Wed, 29 October 1997 00:00
		Re: retain and graphics_level=2 By: davidf on Wed, 29 October 1997 00:00
		Re: retain and graphics_level=2 By: Stein Vidar Hagfors H on Wed, 29 October 1997 00:00
		Re: retain and graphics_level=2 By: davidf on Wed, 29 October 1997 00:00

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