Sorry Bernd,

I mixed up the grips of a circle with those of an arc.

My favorite mechanical CAD package is AutoCAD release 2004, although
Inventor R10 (parametric 3D modeling) is winning ground here.

Anyway, in the AutoCAD universe the following grips exist.

Circle: grips on both center point and quadrants.

Dragging one of the quadrant grips alters the radius, the center
remains.

Dragging the center grip moves the whole circle.


Arc: both endpoints and a midpoint on the curve, no center point grip
here.

Dragging on of the endpoints alters both center point, midpoint grip and
the radius.

Dragging the midpoint grip alters the center point and radius, but
leaves the endpoints unchanged

However, with an arc you can select the center point with the "Object
Snap" set to center.

Although not implemented in AutoCAD a center point grip which moves the
entire arc would be an obvious action/event to expect.

I hope this clarifies the mess I put in my last e-mail.

Kind regards,

Bert Timmerman.

On Tue, 2008-07-15 at 12:50 +0200, Bernd Jendrissek wrote:
> On Mon, Jul 14, 2008 at 11:10 PM, Bert Timmerman
> <[EMAIL PROTECTED]> wrote:
> > FWIW, in my mechanical CAD universe I am used to the following
> > behaviour:
> >
> > 1) the complete arc (or circle) moves when the center grip
> > (GRIP_ARC_CENTER) is moved/dragged,
> 
> In gschem, that happens when you click-and-drag on the arc, somewhere
> other than on a grip.
> 
> > 2) the radius is being modified (smaller/larger) when the radius grip
> > (GRIP_ARC_RADIUS) is moved/dragged.
> 
> Where does your favourite mechanical CAD put the radius grip?
> 
> Some constraints cannot be satisfied.  An arc is uniquely defined by 3
> points: center, start, end; or, start, end, midpoint.  What is the
> user interface for a 3-parameter curve when you're presenting 4 grips?
> 
> 
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