| moving to objects / IDL objects and object graphics [message #56146] |
Sat, 06 October 2007 13:19  |
markb77
Messages: 217
Registered: July 2006
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Senior Member |
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I'm trying to get a feel for object programming in IDL. I'm reading
the last chapter of David Fanning's book on the subject. Here's what
I'm wondering:
I like the object graphics system in IDL. I also like the concept of
writing my own objects. For example, I currently have a widget
program containing a draw window. The draw window is set to object
graphics mode. I define an IDLgrView object and in the view I place
an IDLgrImage object.
The data that I'm working with isn't an image, however, it's a movie.
What if I were to create my own MBgrMovie object? This object could
contain all of the relevant information about the movie.. number of
frames, dimensions, and many other application specific tags. I could
write methods that would act on the movie, etc, etc. The movie could
make use of image objects, too.
But could this be integrated with IDL object graphics? For instance,
would the IDLgrView know what to do if I were to Add my Movie object
to it? And would the IDLgrWindow know how to draw it?
that's my question of the moment. I'm going to keep reading on this
object stuff, but I'm wondering about integration with object
graphics...
thanks
Mark Bates
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| Re: moving to objects / IDL objects and object graphics [message #56251 is a reply to message #56146] |
Tue, 09 October 2007 09:09  |
Rick Towler
Messages: 821
Registered: August 1998
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Senior Member |
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markb77 wrote:
I would suggest creating your MBgrMovie object as a subclass of
IDLgrImage. Keep it simple. All you really need to add are the
properties you have mentioned, a timer as Robbie mentioned, a pointer to
the movie data, and some methods to make it all work (stop, start, fwd,
rev, go to, etc).
I personally would separate the GUI from the movie object so I would
only include one hidden base widget which would handle the timer events.
Your object's timer event will do two things. Update your DATA
property with "this" frames image data and optionally call a callback.
Create a property that contains the name of the callback that your
hidden timer event calls when your movie object needs to draw the next
frame (check out call_function and call_procedure). Construct your
callback such that you pass your movie object reference as well as a
pointer to "this" frames image data. Including the pointer to the image
data would allow you to use it in direct graphics applications as well.
> But could this be integrated with IDL object graphics? For instance,
> would the IDLgrView know what to do if I were to Add my Movie object
> to it? And would the IDLgrWindow know how to draw it?
Your object will be a subclass of IDLgrWindow so all you need to do is
add it into your object hierarchy. In this case I don't think you need
to override the DRAW method as David suggests. Your movie is ruled by
the timer. Just get the proper frame into the image object at the right
time and let the callback routine know. It will be the application's
responsibility to call the draw method for the view.
At some point you may want to consider more elegant methods to handle
the image data. Holding the entire movie in RAM may not always be an
option.
-Rick
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