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Re: Re: Re: How to find which variable caused the trigger in Manipulate[]

  • To: mathgroup at smc.vnet.net
  • Subject: [mg103919] Re: [mg103879] Re: [mg103821] Re: How to find which variable caused the trigger in Manipulate[]
  • From: John Fultz <jfultz at wolfram.com>
  • Date: Mon, 12 Oct 2009 06:39:02 -0400 (EDT)
  • Reply-to: jfultz at wolfram.com

I was quite explicit about this in my previous email...

>> * Use separate Dynamics, which display inside a Row[] as empty strings

I.e., the Row is scoping two empty strings and the Text[].  Replacing Row with 
Column makes empty space because empty strings take up a full line height in a 
Column.  The controls come from the surrounding Manipulate, and so nothing 
inside the Row is displaying as a column.

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


On Sun, 11 Oct 2009 14:30:22 -0500, DrMajorBob wrote:
> Why does that Row display as a column? (Even when I stretch the window
> over two monitors.)
>
> Replacing Row with Column gives the same result, except that there's a lot
> of excess space in the Text box... even when I specify 0 as the 3rd
> argument, as in
>
> Manipulate[
> Column[{Dynamic[
> Refresh[xFlag = True; yFlag = False; "", TrackedSymbols -> {x}]],
> Dynamic[Refresh[xFlag = False; yFlag = True; "",
> TrackedSymbols -> {y}]],
> Dynamic[Text[
> StringJoin["you moved the ", Which[xFlag, "x", yFlag, "y"],
> " slider"]]]}, Left, 0], {x, 0, 1}, {y, 0, 1}, {{xFlag, False},
> ControlType -> None}, {{yFlag, False}, ControlType -> None}]
>
> Why is that?
>
> Bobby
>
> On Sat, 10 Oct 2009 06:09:45 -0500, John Fultz <jfultz at wolfram.com> wrote:
>
>> This is a very simple version of what you asked for that doesn't solve
>> some of
>> the fundamental problems you'll probably come across, but it shows you
>> the
>> techniques to solving them.  Principally...
>>
>> * Contain all evaluation inside of scoped Dynamics to prevent the entire
>> Manipulate from refreshing.
>> * Add flag variables (and perhaps you'll want other variables, too) as
>> control
>> variables, but with ControlType->None so they don't appear.
>> * Use separate Dynamics, which display inside a Row[] as empty strings
>> (this is
>> important...remember that if a Dynamic doesn't display onscreen, then
>> there's
>> nothing available to update...see my previous posts on Dynamic if you're
>> at all
>> confused about this), to track the individual variables.
>> + These separate Dynamics each scope a single variable only.
>> + The scoped variable is determined by using Refresh with
>> TrackedSymbols
>>
>> One of the problems my version doesn't solve is sensibly setting a start
>> condition, so the evaluation assumes that the initial state has changed
>> the y
>> parameter (as a result of the initial creation of the flag-tracking
>> dynamics).
>> That's a problem I'll let you figure out.
>>
>>
>> Manipulate[Row[{
>> Dynamic[
>> Refresh[xFlag = True; yFlag = False; "", TrackedSymbols -> {x}]],
>> Dynamic[
>> Refresh[xFlag = False; yFlag = True; "", TrackedSymbols -> {y}]],
>> Dynamic[
>> Text[StringJoin["you moved the ", Which[xFlag, "x", yFlag, "y"],
>> " slider"]]]
>> }],
>> {x, 0, 1}, {y, 0, 1},
>> {{xFlag, False}, ControlType -> None},
>> {{yFlag, False}, ControlType -> None}]
>>
>>
>> Sincerely,
>> John Fultz
>> jfultz at wolfram.com
>> User Interface Group
>> Wolfram Research, Inc.
>>
>>
>> On Thu, 8 Oct 2009 07:49:43 -0400 (EDT), Nasser Abbasi wrote:
>>
>>>
>>> "Nasser Abbasi" <nma at 12000.org> wrote in message
>>> news:hafbgr$j4r$1 at smc.vnet.net...
>>>
>>>>> Again, I want something like this
>>>>>
>>>>> Manipulate[
>>>>> process[( pickTheCorrectControlVariableWhichChanged ],
>>>>> {a, 0, 1}, {b, 0, 1}, Initialization :>
>>>>>
>>>>> (process[arg_] := Module[{}, Plot[Sin[arg*x], {x, -Pi, Pi}]])
>>>>> ]
>>>>>
>>>
>>>> I made some progress and I think I have a solution.
>>>>
>>>> I save the old value of each control variable in a global variable,
>>>> then
>>>> in
>>>> the Manipulate expression, I check, using an If statement which
>>>> current
>>>> value of the control variable is different from the old value. I
>>>> got it
>>>> to
>>>> work ok finally.
>>>>
>>>> Here is an example:
>>>>
>>>> olda = 999;
>>>> oldb = 999;
>>>>
>>>> Manipulate[
>>>> If[olda != a, {olda = a; Style[StringJoin["a=", ToString[a]]]},
>>>>
>>>> If[oldb != b, {oldb = b; Style[StringJoin["b=", ToString[b]]]},
>>>>
>>>> Text["this message should NOT show up!"]]], {a, 0, 1}, {b, 0, 1},
>>>>
>>>> LocalizeVariables -> True, TrackedSymbols -> {a, b}]
>>>>
>>>>
>>> It is me again, with the same problem.
>>>
>>> I found out that I can NOT use global variables in a demo, and I also
>>> can't
>>> wrap the whole Manipulate inside a module. Any one of the above method
>>> will
>>> have solved this problem, but rules are rules, so now I have to find
>>> another
>>> solution.  So I am stuck again.
>>>
>>> Before I recode everything again, which I would hate to do, I thought=
>> I'll
>>> ask one more time, may be some expert can have a solution. But this
>>> one=
>> is
>>> really hard.
>>>
>>> I'll explain again the problem to make sure we are all clear on it.
>>>
>>> I need to write a Manipulate where inside the Manipulate I need to
>>> detect
>>> which slider or in other words, which control variable was changed.
>>> i.e.
>>> which slider the user just changed to cause the Manipulate expression
>>> to
>>> be
>>> generated. (I need to do this so I can do different processing based
>>> on
>>> the
>>> slider that was selected)
>>>
>>> We all know that Manipulate generates a new version of its expression=
>> when
>>> one of the control variables changes value.  I need to know which
>>> control
>>> variable changed.
>>>
>>> There is the general layout
>>>
>>> Manipulate[
>>>
>>> (*   expression that uses control variables *)
>>>
>>> ,
>>>
>>> (* controls here which update the control variables values *)
>>> ]
>>>
>>> But there are restriction on the solution, since this will be for a
>>> demo.
>>> Again, there can NOT be global variables used, (i.e. no variables in
>>> the
>>> Manipulate initialization section, since these are global), and there
>>> can
>>> NOT be a module around Manipulate[], i.e. no  Module[{...},
>>> Manipulate[...]]
>>> allowed.
>>>
>>> Here is a small code to show the problem
>>>
>>> Manipulate[
>>> Text[StringJoin["you moved the ", "x or y", " slider"]],
>>> {x, 0, 1},
>>> {y, 0, 1}
>>> ]
>>>
>>> Could someone modify the above, so that the code above will tell which
>>> slider the user _just_ moved?
>>>
>>> It seems like an impossible problem for me to solve without the use of
>>> global variables or a module around Manipulate.
>>>
>>> Here is what I tried so far, and this fail:
>>>
>>> Manipulate[
>>> Which[
>>>
>>> x != oldx,
>>> {oldx = x; Text[StringJoin["you moved the ", "x ",  " slider"]]},
>>>
>>> y != oldy,
>>> {oldy = y; Text[StringJoin["you moved the ", "y ", " slider"]]},
>>>
>>> True, Text["why Ami here??"]
>>> ],
>>>
>>> {x, 0, 1},
>>> {y, 0, 1},
>>> {oldx, -999,  ControlType -> None},
>>> {oldy, -999,  ControlType -> None}
>>> ]
>>>
>>> The reason it fail is because oldx and oldy are updated to the same
>>> value
>>> of
>>> x and y whenever x or y changes before I get the chance to do the
>>> comparison. I.e. when the new version of the expression is generated,
>>> oldx=x
>>> and oldy=y each time.  This seems to consequences of Manipulate=
>> generating
>>> DynamicModule[] for the whole thing. You can see this by using the
>>> SnapShot
>>> option on the Manipulate output. This will generate the whole
>>> expression
>>> form. (Nice tool).
>>>
>>> If someone can make it so that the above will display the correct
>>> message
>>> each time, then I would declare that person to be the Mathematica Guru
>>> of
>>> the year.
>>>
>>> I think I have reached the limit of my current Mathematica
>>> understanding
>>> when it comes to internals of Manipulate and Dynamics to be to solve
>>> this
>>> one. But I'll keep on looking.
>>>
>>> Thank you,
>>> --Nasser





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