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Re: drawing lines interactively [message #30538 is a reply to message #30536]

Fri, 03 May 2002 09:05

James Kuyper
Messages: 425
Registered: March 2000

Senior Member

What you have to do is to capture all mouse movements, not just clicks.
You do this by choosing the "/MOTION_EVENTS" option when creating your
draw widget. Alternatively, you can use the DRAW_MOTION_EVENTS option of
WIDGET_CONTROL to turn the reporting of motion events on and off.
Each time your event handler recieves a new WIDGET_DRAW event with
TYPE=2, it's a report of a new mouse position. You can then draw your line.

The tricky part is making the line temporary. That means you have to
keep track of where you drew it, and then "undraw" it when the next
mouse position event comes in. There's probably other ways to do it, but
I know of only one simple way, that involves putting graphics into XOR mode:

DEVICE, GET_GRAPHICS=oldg, SET_GRAPHICS=6
PLOT,[x0,x1],[y0,y1], /DATA,/NOERASE
DEVICE, SET_GRAPHICS=oldg

If you draw the same line in that mode twice in a row, the second
occurance will un-draw the first.

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[Message index]

		Re: drawing lines interactively By: R.Bauer on Sun, 05 May 2002 11:45
		Re: drawing lines interactively By: David Fanning on Fri, 03 May 2002 14:51
		Re: drawing lines interactively By: James Kuyper on Fri, 03 May 2002 09:05
		Re: drawing lines interactively By: nobody@nowhere.com (S on Fri, 03 May 2002 09:33

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