Messages from Usenet group comp.lang.idl-pvwave, compiled by Paulo Penteado
Draw Widget Object Graphics Scrolling, Confused
I want to scroll through a zoomed object graphics scene bigger than the viewport by dragging draw widget scrollbars. This works if RETAIN = 2, but performance is too slow, which is why it is not recommended in the documentation. If RETAIN is 0 or 1, the view only redraws itself *after* I release the scrollbars, so I can't really interactively scroll through my object graphics. While I'm dragging, until I release, the viewport goes almost all white, so I can't see where I am scrolling. I'm re-drawing with every expose or viewport event, as suggested in the help, but these events are not generated *while* I'm dragging the scrollbars. How do I use the draw widget scrollbars to scroll through an object graphics scene if RETAIN is 0, the recommended setting for object graphics windows? Thanks.
Re: Draw Widget Object Graphics Scrolling, Confused
On 8/9/10 12:04 PM, j.coenia@gmail.com wrote: > >> Is this because you are not getting events in your event >> handler (seems doubtful) or because you are not updating the >> scene in your event handler when you get a motion event? > > There are no events generated at all while scrolling (?), only when > the scrollbars are released (IDL 7.1, Windows 7 32). If there is > some switch I'm missing to turn on scrolling events so I could redraw, > that would solve my problem. How about an alternative approach? A "slippy map" type of control with the mouse, i.e., no scrollbars, you grab the image with your mouse and move: http://michaelgalloy.com/2006/04/15/idlgrimage-tiling-in-idl -62.html This above example talks a lot about JPEG 2000 and using IDLgrWindow's tiling capabilities, but you might be just interested in the portion of the event handler that handles motion events. Mike -- www.michaelgalloy.com Research Mathematician Tech-X Corporation
> How about an alternative approach? A "slippy map" type of control with > the mouse, i.e., no scrollbars, you grab the image with your mouse and move: > > http://michaelgalloy.com/2006/04/15/idlgrimage-tiling-in-idl -62.html > The slippy map is cool, and I'll definitely use idlgrimage tiling in the future if it increases zoom performance, but the mouse is being used to draw ROIs on the images right now. The interface can't be too creative -- the intended users aren't necessarily good with computers or with mice, and they'll expect scrollbars to scroll (not turn the screen white until released). It seems like window scrollbar dragging should generate viewport change events that I could use to redraw. Dr. Fanning's answer above suggests that he thinks I should be getting these events in my handler. I'm not, though. There must be some trick to using scrollbars when RETAIN = 0 that I just haven't found yet. Thanks