How to draw a rectangle with rounded corners ?

> Message du 29/10/10 07:07
> De : "Travis Griggs"
> A : "VisualWorks non commercial mailing list"
> Copie à :
> Objet : Re: [vwnc] How to draw a rectangle with rounded corners ?
>
> On Oct 28, 2010, at 7:32 AM, Josef Springer wrote:
>
> > Hello everybody,
> >
> > i have a graphical question, may be anybody can give me an assist:
> >
> > I want to draw a rectangle with rounded corners. "aGrahicsContext
> > joinStyle: GraphicsContext joinRound" does not work for me, because
> > the
> > width of the rectangle's border is < 5 and so makes no good visual
> > picture. I want to use smooth round corners for the rectangle so, i
> > must
> > use soething like class EllipticalArc, i think. Where can i find
> > examples of drawing reclangle with smooth rounded corners ?
>
> For standard VisualWorks, you'll have to do the work yourself. It's
> common to do as HotDraw has done and create a subclass of Rectangle
> with a fillet/round instance variable, and then define it's strokeOn:/
> fillOn: methods appropriately. What is appropriate for your context
> depends.
>
> If your expected rounding is low, then you can just cut diagonal
> corners. The various "rounded" shapes drawn in the various new tools
> (prerequisite, bundle structure, and comparison) are all done so.
> Something like
>
> poly := (OrderedCollect new) add: (myRect topLeft rightBy: 3); add:
> (myRect topRight leftBy: 3); add: (myRect topRight downBy: 3); add:
> (myRect bottomRight upBy: 3); add: (myRect bottomRight leftBy: 3);
> add: (myRect bottomLeft rightBy: 3); add: (myRect bottomLeft upBy: 3);
> add: (myRect topLeft downBy: 3); add: (myRect topLeft rightBy: 3);
> yourself.
>
> and then either aGC displayPolyline: poly or aGC displayPolygon:
>
> If you have corners bigger than that, you end up righting a nice
> display method which draws four wedges/arcs for the separate corners
> and lines between them (or rectangles between them). It's fun (not so)
> to make sure you get the rounding right so the rounding lines up right.
>
> If you're willing to use CairoGraphics you can do:
>
> aGC newCairoContextWhile: [:cr | cr rectangle: myRect fillet:
> myCornerRadius; source: ColorValue whatever; stroke (or fill)]
>
> It'll draw a first class properly anti-aliased rounded rectangle, as a
> single path entity. The fact that you could fill/stroke it with a
> pattern or a gradient, or rotate/scale/skew/transform it arbitrarily
> is just icing. :) Did I mention that not only can you draw rounded
> rectangles with Cairo, but that you can use them as clip regions too?
>
> --
> Travis Griggs
> Objologist
> Light travels faster than sound. This is why some people appear bright
> until you hear them speak...
>
>
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