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Re^2: getting visible area of Tk::Scrolled?

by halley (Prior)
on Sep 17, 2011 at 12:52 UTC ( #926537=note: print w/replies, xml ) Need Help??


in reply to Re: getting visible area of Tk::Scrolled?
in thread getting visible area of Tk::Scrolled?

Partly there. What are the screen X, Y of the lower right corner of the canvas window? Accurately taking into account whether scrollbars have appeared or not?

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Re^3: getting visible area of Tk::Scrolled?
by BrowserUk (Pope) on Sep 17, 2011 at 13:06 UTC

    Use $canvas->get_corners to obtain the bounding box of the visible portion of the canvas.

    See also the return lists from the ->xview() & ->yview() methods which are useful for manipulating the scrollbars.


    Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
    "Science is about questioning the status quo. Questioning authority".
    In the absence of evidence, opinion is indistinguishable from prejudice.

      Thanks again for your help, BrowserUk. This is the heart of a drag-an-item handler, so that when dragging near the edge of the scrollable canvas, the canvas automatically scrolls more into view. Otherwise the user must drop, scroll, and grab the item again.

      # move all associated items... $c->move($group, $dx, $dy); # consider moving the visible area in the scrollregion my @corners = $c->get_corners(); my @bb = $c->bbox($group); if ($bb[0] < $corners[0]) { $c->xviewScroll(-1, 'units'); } if ($bb[1] < $corners[1]) { $c->yviewScroll(-1, 'units'); } if ($bb[2] >= $corners[2]) { $c->xviewScroll(+1, 'units'); } if ($bb[3] >= $corners[3]) { $c->yviewScroll(+1, 'units'); }

      Without starting any timers or anything, it's a little chunky, but it's pretty useful and dead simple.

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      [ e d @ h a l l e y . c c ]

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