Re: Rotate Objects

[Lars Clausen <lrclause cs uiuc edu>]

On Fri, 10 Aug 2001, Cyrille Chepelov wrote:

> Le jeu, aoû 09, 2001, à 09:05:17 -0400, John Palmieri a écrit:
>
> > Is this going to be an object domain solution or Dia domain?  As it is,
> > UrShape will support arbitrary transforms (rotation and translations) of
> > all visual object except the Gtk stuff(unless GTK supports this).  Will
> > dia ask the object to rotate itself or will it do the transforms through
> > its own rendering interface?  I want to know so that we don't end up
> > with the UrShape code rotating itself and then Dia also doing the same.
>
> The primary thing holding rotation is rendering texts ; Lars' freetype
> code will eventually remove this limitation.

I have gotten so far as to find & load fonts, figure out widths, but not
quite render anything.  It's time we think seriously about how rotation
should be done.  We might even do a kludgy GTK-font based rotation quickly
(that just rotates the rendered pixmap), to get the rotation code in.

> Afterwards, I see two ways: either we teach each object (and/or object
> family) how to do this, or we monkey PostScript and teach transformations
> to renderers (perhaps not generalised transformation matrices, but simply
> stackable transformations, at least translations and rotations). In the
> latter case, we'll have to let objects know about rotations anyway.

I don't know if we want to have translations, even, just rotations.  If we
want to do rotations around different points (corner, center, etc), that
can be done with a normal move and a rotation.

> Either way, what counts is that the resulting code is well factored, and
> does not result in sprinking trigonometry in the whole tree... but the
> one who codes that will have the privilege to choose how to do this and
> where to draw lines, most certainly.

We shall certainly need a stack of rotations.  Maybe we can give the stack
to ddisplay_untransform_coords and the low-level renderers?  

-Lars

-- 
Lars Clausen (http://shasta.cs.uiuc.edu/~lrclause) | Hårdgrim of Numenor
"I do not agree with a word that you say, but I    | Retainer of Sir Kegg
will defend to the death your right to say it."    |   of Westfield
    --Evelyn Beatrice Hall paraphrasing Voltaire   | Chaos Berserker of Khorne