MathGroup Archive 2012

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: Slow Locator in Manipulate

  • To: mathgroup at
  • Subject: [mg126613] Re: Slow Locator in Manipulate
  • From: "Kevin J. McCann" <kjm at>
  • Date: Fri, 25 May 2012 04:56:50 -0400 (EDT)
  • Delivered-to:
  • References: <>

I agree with most of your comments, especially the "underlying issues" 
and poor (nearly nonexistent?) documentation. It seems that the folks at 
Wolfram have been focused on providing new capabilities (very good) at 
the expense of documentation (very bad).

It is not clear to me why 2d sliders should be any better, although I 
agree that they are, since it would seem that the image must be redrawn 
each time for either case.

I guess we will have to wait for the documentation to catch up.


On 5/23/2012 8:01 AM, E. Martín-Serrano wrote:
> Kevin,
> I have reported similar problems in several occasions, with the Locator
> construct, even outside Manipulate but mostly inside Dynamic constructs. I
> guess, and now I insist, on that these problems would be connected to some
> underlying design issues in the construct.
> Other explanation could be that the documentation for Locator lacks
> information about non-explained restrictions on the way it should be used to
> avoid unexpected conflicts or behaviors. An  especial and evident case occur
> when dealing with Bezier curves, where if you drag a locator (a point in the
> control polygon) all  other locators conforming the control polygon  move as
> if they were being dragged  too.
> To summarize my experience with Locator: as soon as one goes beyond a toy (I
> mean, beyond something rather simple), Locator becomes almost useless and 2D
> sliders must be used instead.
> E. Martín-Serrano
> -----Mensaje original-----
> De: Kevin J. McCann [mailto:kjm at]
> Enviado el: miércoles, 23 de mayo de 2012 9:29
> Para: mathgroup at
> Asunto: Slow Locator in Manipulate
> The following is a simple example of the use of a Locator on a graphic:
> p1 = ContourPlot[
>      Sin[x y], {x, -3 \[Pi], 3 \[Pi]}, {y, -3 \[Pi], 3 \[Pi]},
>      ContourShading ->  False];
> Manipulate[
>    Show[p1, Graphics[{Red, AbsolutePointSize[5], Dynamic@Point[pt1]}],
>     PlotRange ->  {{-3 \[Pi], 3 \[Pi]}, {-3 \[Pi], 3 \[Pi]}}],
>    {{pt1, {0, 0}}, {-3 \[Pi], -3 \[Pi]}, {3 \[Pi], 3 \[Pi]}, Locator}
>    ]
> I find that the Locator moves slowly and in a jerky fashion; however, if I
> leave the underlying plot, i.e. p1, out of the Show, then it moves as I
> would expect. I had thought the use of Dynamic on the Point would keep
> Mathematica from constantly redrawing the graphic, but my guess is that the
> slowness indicates this is not the case.
> Anyone have an idea about how to make the locator move faster?
> Thanks,
> Kevin

  • Prev by Date: Re: On special polynomials decomposition
  • Next by Date: Re: Fourier DFT scaling problem
  • Previous by thread: Re: Slow Locator in Manipulate
  • Next by thread: Re: Slow Locator in Manipulate