Re: Gnome2::Canvas --> do I really need to worry about pixels_per_unit?

[zentara <zentara1 sbcglobal net>]

On Mon, 23 Jun 2008 11:18:57 -0700
walt <w41ter gmail com> wrote:

> zentara wrote:
> > On Sun, 22 Jun 2008 20:20:33 -0700
> > walt<w41ter gmail com>  wrote:
> >
> > > ...
> > > The problem is that the vertical scroll region will just ignore
> > > any height value below some arbitrary limit.
> > > ...
>
> > Could you post a small example where the data point can't
> > be scrolled to, and the "arbitrary limit" is hit?
> >
> > It sounds to me like you have a predefined size set somewhere,
> > like a set_default_size in your mainwindow, or something.
> >
> > I just posted a similar question recently, where my coordinates
> > seemed way off, and I couldn't explain it..... I figured it out as follows
> >
> > ################################
> > Doh!!!  Sorry I see the mistake. If the scrollregion is smaller than the default
> > canvas size, weird coordinate transforms occur. Maybe a bug?
> >
> > $scroller->add( $canvas );
> > $window->add( $scroller );
> > $window->set_default_size( 500, 500 );
> >
> > #if scrollregion is smaller than default size, odd
> > # coordinate problems occur
> > #$canvas->set_scroll_region( 0, 0, 400, 400 ); #bad
> >
> > $canvas->set_scroll_region( 0, 0, 700, 700 );   #good and works fine
> >
> > It would be a good "trick" question to throw at someone. :-)
> > ########################################
> >
> >
> > See if that is it, otherwise post a minimal example.
>
> My example is very similar to yours, but the numbers are smaller to show
> the problem in an exaggerated way:
>
> my $line = Gnome2::Canvas::Item->new
>                             (
>                             $root,
>                              'Gnome2::Canvas::Line',
>                              points=> [0,0,50,50],
>                              width_pixels=> 1,
>                              fill_color => 'black',
>                              line_style => 'solid'
>                             );
>
> $window->set_default_size (500, 500);
> $canvas->set_scroll_region(0,0,50,50);
>
> my @region = $canvas->get_scroll_region;
> print "@region\n";


Didn't you read the code fragment I sent?

> > $window->set_default_size( 500, 500 );
> >
> > #if scrollregion is smaller than default size, odd
> > # coordinate problems occur
> > #$canvas->set_scroll_region( 0, 0, 400, 400 ); #bad
> >
> > $canvas->set_scroll_region( 0, 0, 700, 700 );   #good and works fine

Your scroll region 50,50 is less than 500,500 so a weird
coordinate transform occurs. 

Either make sure your scroll_region is greater than the default_size
OR
don't use default_size, try set_size
$window->set_size_request(300,200);

set_default_size is very strong, and usually not wanted.  


zentara





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