| Re: problem with corrupted pix-maps [message #12165 is a reply to message #12160] |
Mon, 29 June 1998 00:00  |
davidf
Messages: 2866
Registered: September 1996
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Senior Member |
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Mirko Vukovic (mirko_vukovic@notes.mrc.sony.com) offers us
a programming puzzle when he writes:
> following instructions of some of our more esteemed colleagues on this group,
> I created copies of two windows in memory.
>
> The purpose was to animate a marker. This is a gui application in which
> with a cursor on one plot, the code finds the closest point on the curve,
> puts a marker there, *and* a marker on the corresponding point on the curve
> on the other plot.
>
> I use the memory resident copies to restore the plots prior to re-plotting
> the markers when the cursor moves.
>
> It almost works in practice, except that on one of the plots, if I put the
> marker close to the left axis, it seems to *corrupt* (ie, make its way into)
> the memory resident copy of the plot.
>
> Now, in such situations,the first thought that comes to mind is a bug in IDL.
> The second (and usually more correct thought) is that I overlooked something.
Uh, I vote for the more correct thought. :-)
> But it must be something truly peculiar, as the plot gets corrupted only
> when the cursor and marker move into that particular region of the plot
> (say leftmost 20% of the plot region).
Humm. Every good mystery has a seminal clue. I think this is it.
In my experience things creeping into a particular region of the
plot means that something has gone wrong with the Device, Copy
coordinates. My guess is that you are not copying the entire window,
but only a portion of it with Device, Copy. With two pixmaps you
are probably doing a lot of switching back and forth. I would make
sure you are copying the region of the window you *think* you are
copying. A simple switch of an x coordinate in place of a y coordinate
has been known to produce effects such as this. Does the problem go
away if your window is square?
> Any thoughts out there on what I may be missing? I contacted RSI, and
> other than suggesting that I send them the code, they could not offer any
> advice.
Don't you wish technical support people had more imagination? How
dreary. I would have made up something wild and extravagant. :-)
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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