Re: simple rotate

[Lars Clausen <lrclause cs uiuc edu>]

On Sun, 24 Nov 2002, Martin Hans wrote:
> Hi, I've been following this list for a while. Every once in a while,
> someone asks about how to do rotation in dia and receives the answer,
> that this is not possible. It seems that the implementation of this
> feature is currently postponed because it would need quite some
> restructuring.
>
> If this is still so, how about implementing just some crude rotating in
> steps of 90 degrees? This would actually render the shapes in the logic
> sheet usable - now they are not (all pointing upwards).
>
> Would this be possible?

It's not so much a problem of the rendering anymore (we have a bit of code
to rotate text at an arbitrary angle), but how to structure the rotation
internally.  Especially when it comes to grouped objects.  A 90° rotation
mode would be a good start on this, since the rendering part would be
fairly easy.  Once the infrastructure is there, adding rendering for
arbitrary angles should be easy.

> One other idea: How about having a version of the zig-zag line that is
> rotated 90 degrees so that we'd get a down-left-down behaviour instead of
> the current left-down-left, which is a bad choice in about half of the
> cases.

I have code in the CVS that will do this somewhat intelligently at object
creation time, and there's a simple way to extend it to all.

The Box and Ellipse objects sets up allowable directions for each
connection point (in _update_data).  The Zigzagline, when created, looks at
those directions and makes itself either down-left-down or left-down-left
according to which are admissible.  To extend this to post-creation
movement, we need to make sure that midpoints stay where they are.  My idea
is to have it have one more segment when going horizontal at the end, and
one less when going vertical.  That way only one midpoint will be affected.

-Lars

-- 
Lars Clausen (http://shasta.cs.uiuc.edu/~lrclause)| Hårdgrim of Numenor
"I do not agree with a word that you say, but I   |----------------------------
will defend to the death your right to say it."   | Where are we going, and
    --Evelyn Beatrice Hall paraphrasing Voltaire  | what's with the handbasket?