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Re: Question on Dynamic with "DockedCell"

Hi Jason,

I have run into this as well when I wanted to create a menu in a
DockedCell that displayed the current set of files in a particular
directory.  One issue is that one has to trigger any Dynamic that is
in the cell, and for some cases one doesn't want something constantly
testing the cou=mputer's filesystem for changes.  I had played with
Refresh and things like that.

A solution that I came up with, that served my particular application
needs was to create a reason for a menu to update.

So, my menu was generated through a function likethe following.  Note
that it has an argument, but the parameter in the arrument is not used
in the funtion:

myMenu[z_] :=
  FileNameTake[#, -1] :> SystemOpen[#] & /@
   FileNames[{"*"}, {$UserDocumentsDirectory}]]

Note that if you create a cell with this menu in it it will not update
if you add or remove a file in $UserDocumentsDirector:

TextCell[Dynamic[myMenu[1]], "Text"] // CellPrint

The trick now is to introduce a new function which has as its only
purpose to change the value of a parameter: $MysteryParameter.  Make
sure that that parameter is Unprotected if it is in a Package.
$MysteryParameter will be used in the argument to myMenu to force it
to trigger the Dynamic. And this will be acomplished by having the
Cell that contains the menu have a CellEventAction.

$MysteryParameter = 1;

Toggle$MysteryParameter[] :=

   $MysteryParameter = 2,

   $MysteryParameter = 1,

   $MysteryParameter = 1];

And finally one intruduces a CellEventAction to the cell that causes
the value of $MysteryParameter to change and thereby causes the myMenu
in the Dynamic to update because its argument has changed.

TextCell[Dynamic[myMenu[$MysteryParameter]], "Text",
  CellEventActions -> {"MouseMoved" :> (Toggle$MysteryParameter
[])}] // \

Or, in a DockedCell

 DockedCells -> {
    TextCell[Dynamic[myMenu[$MysteryParameter]], "DockedCell",
     CellEventActions -> {"MouseMoved" :> (Toggle$MysteryParameter
     StripOnInput -> True]}

I hope this helps....


On Oct 20, 4:51 am, Jason Ledbetter <jasonbr... at> wrote:
> Folk,
> I'm attempting to create a dynamically-appearing set of choices/menus usi=
> ButtonBar in a notebook window but I've been unable to get the desired
> affect to date. I've cobbled together the following code which almost doe=
> what I'm looking for but I could use some pointers in getting the rest of
> the way.
> The goal here is for the "topMenu" items to appear when the notebook is
> first instantiated and for the "secondMenu" option to appear when a
> "topMenu" option is selected. As it stands now, I'm having to start with =
> "secondMenu" option pre-defined to a bogus value.
> If I were to abstract my goal some more, I'm trying to figure out how to
> dynamically add/remove RowBox items that include ButtonBars from the
> notebook based on options that are selected.
> I'm guessing that I somehow need to programmatically generate the content=
> of a Dynamically wrapped RowBox (e.g., Dynamic[RowBox[...]]) but I'm not
> quite sure how to go about that just yet.
> Any help is greatly appreciated...
> Here's what I have thus far:
> --snip--
> Module[
>   {topMenu, secondMenu},
>   topMenu = {"option1", "option2"};
>   secondMenu = {"No option selected"};
>   menuChoice[choice_] := Module[{},
>     Switch[choice,
>      "option1", secondMenu = {"one", "selected"},
>      "option2", secondMenu = {"two", "selected"}, _, Print[choice=
>      ]];
>   CreateWindow[DockedCells -> Cell[
>      RowBox[
>       {
>        ToBoxes[
>         ButtonBar[ToString[#] :> menuChoice[#] & /@ topMenu]
>         ],
>        ToBoxes[
>         Dynamic[
>          ButtonBar[ToString[#] :> menuChoice[#] & /@ secondMenu=
>          ]
>         ]
>        }
>       ],
>      "DockedCell"],
>    TextAlignment -> Center
>    ]
>   ];
> --snip--
> thanks,
> -jbl

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