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Re: vertical line that moves with cursor in draw widget [message #60727 is a reply to message #60724]

Fri, 06 June 2008 14:55

Rick Towler
Messages: 821
Registered: August 1998

Senior Member

cgoethel wrote:
> Hello, I have a draw_widget with motion events set up. I draw a
> vertical line (using plots) which follows the cursor as it moves
> through the draw area. I can get the vertical line to follow the
> cursor easily enough - but I can't seem to figure out how to erase the
> previous lines. All the lines remain drawn. Any suggestions?

The easiest way is to redraw your background before you draw the new
vertical line in your motion event handler. Depending on what your
doing this can be quite costly in direct graphics. If re-plotting is
too slow you can create a copy of your draw widget background (using
something like tvread from www.dfanning.com) and simply re-draw this
image instead of running thru all of your plotting code. Either way
you'll want to work hard to minimize the drawing to only when it is
absolutely necessary.

The best way to do this is to use object graphics which is far better
suited for this type of application. The problem here is that there's a
bit of a learning curve...

-Rick

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[Message index]

		Re: vertical line that moves with cursor in draw widget By: Michael Galloy on Sun, 08 June 2008 15:56
		Re: vertical line that moves with cursor in draw widget By: Craig Markwardt on Sat, 07 June 2008 00:49
		Re: vertical line that moves with cursor in draw widget By: ben.bighair on Fri, 06 June 2008 19:51
		Re: vertical line that moves with cursor in draw widget By: Rick Towler on Fri, 06 June 2008 14:55
		Re: vertical line that moves with cursor in draw widget By: Jean H. on Fri, 06 June 2008 14:28

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