I am playing around some more with Tk::Canvas, and in particular, the scrolled variety. The scrollbar mechanisms seem really primitive.

    my $c = $parent->Scrolled('Canvas',
                  -width  => $width,
                  -height => $height,
                  -background => 'beige',
                  -scrollbars => 'osoe',
                  -scrollregion => [ 0, 0, $width, $height ]);

[download]

I've constructed a Scrolled Canvas, which apparently returns a ref of type Tk::Frame. That must have the children, including a Canvas and a couple of Scrollbars.

I also found the Tk::Autoscroll class, which didn't come with my build of Perl/Tk, but was easy enough to add.

When dragging around an item in a large scrolled canvas, I want to auto-scroll to keep the dragged item in view. This doesn't seem so hard, except knowing where the scroller is viewing at the current time.

I can't figure out the way to go from a blessed Canvas ref (given in the drag events), to calculate or query the area of the scrollregion that is currently visible.

Before I go digging farther, I bet someone already has some code that calculates the visible area.

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

In reply to getting visible area of Tk::Scrolled? by halley

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.