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Re: DynamicModule values not saved correctly in "docked" cells?

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• Subject: [mg131577] Re: DynamicModule values not saved correctly in "docked" cells?
• From: Chris Osborn <chrisosb at gmail.com>
• Date: Sat, 7 Sep 2013 06:03:52 -0400 (EDT)
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Hi John,

Thanks very much for your very thorough answer; it is quite helpful.


Chris

On Thursday, September 5, 2013 5:06:39 AM UTC-7, John Fultz wrote:
> Yes, it is expected.  Docked cells are built from the expression on the 
> 
> rhs of the DockedCells option, and this option only changes when you 
> 
> explicitly set the option.  So, the in-memory docked cell may have 
> 
> updated values, but these values will not be written to disk or MathLink 
> 
> because doing so would require rewriting the rhs of the DockedCells 
> 
> option (which might be impossible to do with full fidelity).
> 
> 
> 
> One easy way to deal with this issue is to use TaggingRules at the 
> 
> notebook level as a sort of notebook-level DynamicModule variable.  
> 
> Here's an example function to replace your content[] function for docked 
> 
> cells:
> 
> 
> 
> dockedCellContent[] :=
> 
>  Button[Dynamic[
> 
>    CurrentValue[EvaluationNotebook[], {TaggingRules, "x"},
> 
>     RandomReal[]]],
> 
>   CurrentValue[EvaluationNotebook[], {TaggingRules, "x"}]++]
> 
> 
> 
> The technique is documented in the help system.  Look up the topic 
> 
> tutorial/StoringAndTrackingPaletteStates.  However, I'm adding one novel 
> 
> thing here which isn't documented there, which is the third argument of 
> 
> CurrentValue.  I could have initialized the CurrentValue[] by doing 
> 
> something like:
> 
> 
> 
> DynamicModule[{}, (* body *), =
> 
> Initialization:>If[CurrentValue[EvaluationNotebook[], {TaggingRules, 
> 
> "x"}]===Inherited,CurrentValue[EvaluationNotebook[], 
> 
> {TaggingRules, "x"}]=RandomReal[]]]
> 
> 
> 
> but this undocumented third argument does exactly that much more 
> 
> conveniently, and the format is unlikely to change (and probably will 
> 
> get documented in a future version).
> 
> 
> 
> John Fultz
> 
> jfultz at wolfram.com
> 
> User Interface Group
> 
> Wolfram Research, Inc.
> 
> 
> 
> 
> 
> 
> 
> On Sep 2, 2013, at 1:47 AM, Chris Osborn <chrisosb at gmail.com> wrote:
> 
> 
> 
> > It appears that for a DynamicModule expression in a "docked" cell, 
> 
> symbol assignments are not correctly saved when saving the associated 
> 
> notebook.
> 
> >
> 
> > In particular, when I save, close, and then reopen such a notebook, I 
> 
> find that the value assigned to each DynamicModule symbol is the initial 
> 
> value assigned to it, and not the value it had when the notebook was 
> 
> saved.
> 
> >
> 
> > Is this behavior expected?
> 
> >
> 
> >
> 
> > I have written some code, included below, to demonstrate this issue 
> 
> (tested on Mathematica 9.0.1.0). The code creates a new notebook with 
> 
> one docked cell and one non-docked cell. Both cells have DynamicModule 
> 
> expressions with a single variable in them, and have buttons that 
> 
> increment the value of their respective variables. To reproduce my 
> 
> issue:
> 
> >
> 
> > 1. Execute the code I give below
> 
> > 2. In that notebook that is created, click the button in each cell a 
> 
> few times, causing the values displayed in the buttons to increase by 1 
> 
> each time
> 
> > 3. Save the notebook and close it
> 
> > 4. Re-open the notebook
> 
> >
> 
> > The value in the non-docked cell will be as expected; the value in the 
> 
> docked cell will be the original value (before clicking the button.) 
> 
> Here is the code:
> 
> >
> 
> > ClearAll[content];
> 
> > content[] :=
> 
> >  DynamicModule[{x},
> 
> >   x = Random[];
> 
> >   Button[Dynamic[x], x++]
> 
> >   ];
> 
> >
> 
> > CreateDocument[
> 
> >  {content[]},
> 
> >  DockedCells -> Cell[BoxData@ToBoxes@content[], "DockedCell"]
> 
> >  ];
> 
> >
> 
> >
> 
> >
> 
> > Much thanks in advance for any suggestions!
> 
> >
> 
> >
> 
> > Thanks,
> 
> > Chris
> 
> >

• References:
  • DynamicModule values not saved correctly in "docked" cells?
    • From: Chris Osborn <chrisosb@gmail.com>