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Compare the two dialog windows, created by the same code except in the first WindowSize has a value while I omit it in the second one. Note, that CreateDialog (and especially its default option WindowSize -> All) can lead to unexpected behaviour.

DynamicModule[{switch = 1},
  CreateDialog[
   DocumentNotebook@TextCell@Dynamic@Switch[switch, 1, "A", 2, "B"],
   WindowSize -> {200, 100}]];

DynamicModule[{switch = 1},
  CreateDialog[
   DocumentNotebook@TextCell@Dynamic@Switch[switch, 1, "A", 2, "B"]
   ]];

Mathematica graphics

While the value of the WindowSize option is recognized and used on the left, any explicit value prevents the evaluation of the dynamic content (be it a number, list of numbers, Automatic, Full, etc.). The same behavior is experience if Module is used instead of DynamicModule. Is it a bug? I need a workaround that works with a fullscreen window (i.e. WindowSize -> Full), any idea?

1. Update

Even more strange is the workaround that I've found by eliminating part of my code, expression-by-expression. I ended up with the following stripped piece:

DynamicModule[{a = 1, b, c, d, e, f, g, h, i, j, k},
  b = Plot3D[Join@{x, y}, {x, 0, 1}, {y, 0, 1}];
  CreateDialog[Dynamic@Switch[a, 1, "A"], WindowSize -> {200, 100}]
  ];

which correctly produces the dialog on the left, while (and this is the strangest bug I've ever experienced in Mathematica so far) when I comment out any part of this code it results in an unevaluated Switch in the dialog window (on the right)!

Mathematica graphics

Below are some examples, that obviously should not change the output, but they do, and are producing the above right dialog. I think this behaviour has something to do with the parsing of DynamicModule, but I am quite clueless...

DynamicModule[{a = 1, b(*,c,d,e,f,g,h,i,j,k*)},
  b = Plot3D[Join@{x, y}, {x, 0, 1}, {y, 0, 1}];
  CreateDialog[Dynamic@Switch[a, 1, "A"], WindowSize -> {200, 100}]
  ];

DynamicModule[{a = 1, b, c, d, e, f, g, h, i, j(*,k*)},
  b = Plot3D[Join@{x, y}, {x, 0, 1}, {y, 0, 1}];
  CreateDialog[Dynamic@Switch[a, 1, "A"], WindowSize -> {200, 100}]
  ];

DynamicModule[{a = 1, b, c, d, e, f, g, h, i, j, k},
  b = Plot3D[(*Join@*){x, y}, {x, 0, 1}, {y, 0, 1}];
  CreateDialog[Dynamic@Switch[a, 1, "A"], WindowSize -> {200, 100}]
  ];

DynamicModule[{a = 1, b, c, d, e, f, g, h, i, j, k},
  (*b =*)Plot3D[Join@{x, y}, {x, 0, 1}, {y, 0, 1}];
  CreateDialog[Dynamic@Switch[a, 1, "A"], WindowSize -> {200, 100}]
  ];

DynamicModule[{a = 1, b, c, d, e, f, g, h, i, j, k},
  (*b=Plot3D[Join@{x,y},{x,0,1},{y,0,1}];*)
  b = Plot3D[x, {x, 0, 1}, {y, 0, 1}];
  CreateDialog[Dynamic@Switch[a, 1, "A"], WindowSize -> {200, 100}]
  ];

Each of these were tried with a fresh kernel, without any user package loaded.

2. Update

The following example shows that the variable a displayed in the dialog has no initial value in spite of defining it two times (note however that the Initialization code is not evaluated at all, you can make sure about that by putting any Print in it):

DynamicModule[{a = None},
  Print[a];
  CreateDialog[{
    Dynamic@a,
    Dynamic@Switch[a, True, "A", False, "B", None, "C"],
    (*Checkbox@Dynamic@a*)
    }, WindowSize -> {200, 100}],
  Initialization :> (a = None)
  ];

None

Mathematica graphics

Thus a has a value (None) inside the DynamicModule but not inside the dialog. Uncommenting the commented line proves that the a displayed in the dialog is not the same as the a being locally defined in DynamicModule:

DynamicModule[{a = None},
  Print[a];
  CreateDialog[{
    Dynamic@a,
    Dynamic@Switch[a, True, "A", False, "B", None, "C"],
    Checkbox@Dynamic@a
    }, WindowSize -> {200, 100}],
  Initialization :> (a = None)
  ];

None

Mathematica graphics

that is: still printing None as the value of the DynamicModule-a, but displaying False as the dialog-a, which is the default value that Checkbox assignes to a variable without any value.

To conclude: a dialog does not necessarily inherit the variables of its enclosing (Dynamic)Module.

Printing Dynamic@a instead of simply a helps, as it forces the front-end to claim the dynamically displayed a of the wrapping module. Please correct me if I'm wrong.

DynamicModule[{a = None},
  Print[Dynamic@a];
  CreateDialog[{
    Dynamic@a,
    Dynamic@Switch[a, True, "A", False, "B", None, "C"],
    Checkbox@Dynamic@a
    }, WindowSize -> {200, 130}],
  Initialization :> (a = None)
  ];

Mathematica graphics

**3. Update: **

The purpose of this construction is to design a gui where the displayed content switches according to user interaction. While there might be easier ways to do this, I am now inclined to solve the underlyings of this behavior. The following example uses three "screens" as different contents (first, second, third). Changes made to dynamic controls in one screen should affect other screens (hence the variable x).

DynamicModule[{a = 1, x = .5, first, second, third},
  first := Column@{"First", Row@{"x: ", Slider@Dynamic@x}, Button["Next", a = 2]};
  second := Column@{"Second", Row@{"x: ", Dynamic@x}, Button["Next", a = 3]};
  third := Column@{"Third", Button["Reset x", x = .5], Button["Next", a = 1]};
  CreateDialog[Dynamic@Switch[a,
     1, first,
     2, second,
     3, third
     ], WindowSize -> {300, 200}]];
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  • $\begingroup$ I don't think this has to do with the presence of the WindowSize option. I get the same behaviour in both windows. $\endgroup$ May 9, 2012 at 19:52
  • $\begingroup$ @SjoerdC.deVries the same correct or incorrect behaviour? Otherwise, you must be right, see my edit. $\endgroup$ May 9, 2012 at 20:01
  • $\begingroup$ The same incorrect (or, better, unintended) behavior. I think this is a scoping issue. $\endgroup$ May 9, 2012 at 20:03
  • $\begingroup$ I noticed that the same code executed from a FrontEnd window that has its own Context works as I described, whereas a standard window does what you reported. $\endgroup$ May 9, 2012 at 20:06
  • 1
    $\begingroup$ The wormhole section of tutorial/AdvancedDynamicFunctionality might be relevant here $\endgroup$ May 9, 2012 at 20:11

2 Answers 2

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The following works for me with Mathematica 8.0.4

DynamicModule[{switch = 1},
CreateDialog[
globalvar = DocumentNotebook@TextCell@Dynamic@Switch[switch, 1, "A", 2, "B"], 
WindowSize -> {200, 100}]];

However making the variable local to the DynamicModule does not work:

DynamicModule[{switch = 1, localvar},
CreateDialog[
localvar = DocumentNotebook@TextCell@Dynamic@Switch[switch, 1, "A", 2, "B"], 
WindowSize -> {200, 100}]];

It also fails if the variable is localized in a Module wrapping the whole thing:

Module[{localvar},
DynamicModule[{switch = 1},
CreateDialog[
localvar = DocumentNotebook@TextCell@Dynamic@Switch[switch, 1, "A", 2, "B"],
WindowSize -> {200, 100}]]];    
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1
  • $\begingroup$ Your first example (simply saving the dialog into a global variable) solves even my last problem of variables not referring to the same values (see latest edit in my post: module-a and dialog-a). Thanks! $\endgroup$ May 10, 2012 at 9:51
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Just replacing the DynamicModule in the right place may help...

CreateDialog[DynamicModule[{switch = 2}, 
  DocumentNotebook@TextCell@Switch[switch, 1, "A", 2, "B"]], 
  WindowSize -> {200, 100}];

or (see the comments below)

DynamicModule[{switch = True}, 
 CreateDialog[TextCell@{Dynamic@Switch[switch, True, "A", False, "B"],
 Checkbox@Dynamic@switch}, WindowSize -> {200, 100}]];
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4
  • $\begingroup$ And what if switch is not local to the dialog? $\endgroup$ May 10, 2012 at 7:59
  • $\begingroup$ switch = 2; CreateDialog[ DynamicModule[{}, DocumentNotebook@TextCell@Switch[switch, 1, "A", 2, "B"]], WindowSize -> {200, 100}]; also works. I think it's related to kernel-thread and gui-thread issue. the not running ones defined dynamic variables at kernel not at gui and there might be the problem. Just a guess. $\endgroup$
    – s.s.o
    May 10, 2012 at 8:33
  • $\begingroup$ While it displays correctly, but nothing tracks switch, so the content is not updated if switch changes, see example: switch = True; CreateDialog[DynamicModule[{}, TextCell@{Switch[switch, True, "A", False, "B"], Checkbox@Dynamic@switch}], WindowSize -> {200, 100}];. $\endgroup$ May 10, 2012 at 8:52
  • $\begingroup$ So a working example would be like this: DynamicModule[{switch = True}, CreateDialog[TextCell@{Dynamic@Switch[switch, True, "A", False, "B"], Checkbox@Dynamic@switch}, WindowSize -> {200, 100}]];. $\endgroup$ May 10, 2012 at 8:53

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