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Re: Why are both locators moving?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg115258] Re: Why are both locators moving?
  • From: John Fultz <jfultz at wolfram.com>
  • Date: Wed, 5 Jan 2011 05:48:09 -0500 (EST)

Looks like a bug to me.  You can work around it, though, and even make the code
a bit less tortured in the process, by using LocatorPane[].

p1 == {0, 0}
p2 == {0, 1}
LocatorPane[Dynamic[{p1, p2}],
 Dynamic[a == p1;(*condition 1*)
  Show[Plot[Cos[b], {b, 1, 2}],(*condition 2*)
   Graphics[Line[{{0, 0}, {1, 1}}]],
   PlotRange -> {{-10, 10}, {-1, 1}}, Axes -> True, AspectRatio -> 1]]]
Dynamic[{p1, p2}]

Sincerely,

John Fultz
jfultz at wolfram.com
User Interface Group
Wolfram Research, Inc.


On Tue, 4 Jan 2011 18:49:50 -0500 (EST), Dims wrote:
> In the code below I expect that locators can be moved independently,
> but actually locator p1 causes locator p2 to move too if both
> conditions occure:
>
> 1) any "Plot" instruction presents within Show
> 2) a==p1; presents within Dynamic
>
> p1 == {0, 0}
> p2 == {0, 1}
> Dynamic[
> a == p1; (* condition 1 *)
> Show[
> Plot[Cos[b],{b,1,2}], (* condition 2 *)
> Graphics[Line[{{0, 0}, {1, 1}}]],
> Graphics[Locator[Dynamic[p1]]],
> Graphics[Locator[Dynamic[p2]]],
> PlotRange -> {{-10, 10}, {-1, 1}}, Axes -> True, AspectRatio -> 1
> ]
> ]
>
> My question is: why? Is it a bug or by-design behavior? Where is the
> value for p2 assigned?
>
> How to make both locators move independently along with plot?



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