Re: Arrow questions

[Lars Clausen <lrclause cs uiuc edu>]

On Thu, 4 Apr 2002, Cyrille Chepelov wrote:
> Le Wed, Apr 03, 2002, à 05:52:15PM -0600, Lars Clausen a écrit:
>
> > Firstly, I notice explicit differences between hollow_ellipse and
> > filled_ellipse in whether to account for the line width.  Same for the
> > dots and boxes.  Shouldn't all of the account for the line width, so as
> > to line up nicely with the connection point?
>
> This was mostly kept from the previous behaviour (I believe that Alex
> wrote it that way). The current code is mostly mine, in a constant visual
> aspect refactoring.

Ok, I shall redo them so they act somewhat more consistently.

> > Second, I notice you're using beziers rather than ellipses to draw the
> > round shapes.  Any particular reason for that?  Beziers are notoriously
> > difficult to translate into other formats, as they aren't really
> > standard.
>
> non-horizontally aligned ellipses cause at least as many problems to
> uncapable renderers than Beziers. For Beziers, the approximation problem
> was already solved, so I re-used that code. And speed didn't seem to be
> an issue here for anyone, so in hindsight, this wasn't a too bad
> decision.

I see.  Since many of the arrows are horizontal or vertical, I'm thinking
using ellipses for those would improve rendering.  I guess a generic
draw_ellipse would be useful for the arrows.

> > Thirdly, I notice that the various objects have arrow information as
> > Arrow start_arrow, rather than Arrow *start_arrow.  Not only does that
> > waste some space, it also means that we can't add onto the Arrow
> > structure without causing binary incompatibilities.  Any reason to not
> > change that?
>
> None ! (though I care about binary incompatibility as much as of my first
> cent).

Uhm... how much do you care about your first cent?

> > Lastly, a general question.  With the upcoming arrow adjustment system,
> > it will be possible to have transparent arrowheads where the line
> > doesn't show through.  Is that desirable?  Better than the current
> > white-filled version?  Should we have both?
>
> This sounds very cool !
>
> We need to keep both versions, though: I can see areas where a hollow,
> transparent triangle head where the line doesn't show through is useful,
> as many as I can see areas where I'd want a bg-filled triangle head.

Ok.

> (do you have time to refactor the arrow selector code so that there is
> only one arrow selector widget instead of two, and one which uses the
> actual arrow-drawing code rather than custom, fixed-size code ? That'd
> help cut down the amount of code in a very nice way !)

I was wondering why the toolbox arrow selector didn't have tooltips.  Yes,
they should be combined.  I shall look into that.  Don't know if using the
actual arrow-drawing code is the best solution, I may want to use pixmaps
for some of them.

-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?