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Re: Keyboard events

"Doug Reynolds" <dsreyn@ll.mit.edu> wrote in message
> I'm in the process of writing a new application, and several of the likely
> users have requested that I allow various keyboard "shortcuts", as an
> alternative to clicking on various controls with the mouse.  For example,
> we will need to define a region in an image that will be zoomed in a
> separate draw window, and it would be nice to be able to use arrow keys
> to position and resize the zoom region.
> I've never tried to do this before in IDL (previously I've been content
> to handle mouse events), so I went looking through the manuals to figure
> out how to do it.  Unfortunately, the event handling routines seem to be
> limited to mouse and focus events.  The closest thing I could find was the
> get_kbrd function; someone here suggested putting a call to get_kbrd in
> the event handling function.  However, it would seem that this would cause
> keyboard events to queue up, unprocessed, until the user wiggled the
> In other words, it doesn't seem to be quite what I need.
> Is there something in the documentation that I have overlooked?  Any ideas
> would be most appreciated.
> Doug

I had a similar problem which I solved with a hack.  IDL UNFORTUNATLY does
pass the keyboard event on a draw window.
I got the idea from a previous posting.
What you do is create a text window behind the draw window and give it the
focus.  When the arrow keys are pressed, the event is for the text window
and you can
figure out which arrow key was pressed in the event handler.

My application turned out to be a little more complicated than that since on
UNIX (don't know about Windoze)
I wasn't able to get the keyboard events for the cursor keys. I ended up
creating a 3 by 3 text widget and putting
the cursor in the middle.  Every time the text cursor moved, i read the new
location and figure out which
arrow key was pressed then move the cursor back in the middle for the next
arrow key hit.

Told you it was a hack.

In the end it works very well.

Stephane Beland
Senior Application Programmer
Center for Astrophysics and Space Astronomy
University of Colorado - Boulder