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I'm trying to create a demonstration in Mathematica where a checkbox will show an answer, but I only want the answer to be shown while the mouse button is pressed. There seems to be a "Momentary" option, but I can't figure out how it's used.

Checkbox[Momentary -> True]

seems to do what I want, but I need it in the Manipulate function.

Here's a simple example of what I'm trying to do:

Manipulate[
  ToString[x] <> " + " <> ToString[y] <> " = " <> If[a, ToString[x + y], ""], 
  {x, 1, 10, 1},
  {y, 1, 10, 1}, 
  {{a, False}, {True, False}, Momentary -> True}]

Doesn't work as I want. Replacing the last line with any of the following

 {{a, False}, {True, False}, CheckboxBoxOptions -> {Momentary -> True}}]

or

 Control[{{a, False}, {True, False}, Momentary -> True}]]

or

 Control[{{a, False}, {True, False}, CheckboxBoxOptions -> {Momentary -> True}}]]

doesn't do it either.

The documentation is very light in how Checkbox options are to be used.

Any ideas?

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    $\begingroup$ Where did you get that Option from? It does not seem to work standalone Checkbox[Dynamic@x, Momentary -> True]. $\endgroup$
    – Kuba
    Commented Nov 17, 2014 at 13:14
  • 3
    $\begingroup$ @Kuba It is an option of the underlying CheckboxBox and despite the red color it works for Checkbox[Momentary->True], without an argument or with argument True of False, but not if Dynamic is used as an argument. Therefore, my feeling is that this problem cannot be solved with a Checkbox alone and that you need an EventHandler or something like that, as in your solution. $\endgroup$
    – Fred Simons
    Commented Nov 17, 2014 at 13:55

1 Answer 1

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Here's a walkaround:

    Manipulate[
                x,
                Row @ List @ EventHandler[ Checkbox[Dynamic[x]], 
                                           {"MouseDown" :> (x = True), 
                                            "MouseUp" :> (x = False)}]
              ]
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