Strange Connected Dropdown with no Javascript

[Chandranshu24043817d2do]

I have a PDF with two dropdown and both are connected somehow.
If you select any value from first dropdown then based on that a list of values will be inserted into second 

dropdown to select from.
I have checked everying, there is no javascript in both dropdown and there is also no document level javascript in the pdf file.
Can anyone tell me how this is working ?

I am attaching the PDF, Please have a look
Thanks for your help

[try67 · Accepted solution]

Acrobat hides some scripts it considers to use "internal" code. This usually happens when they contain the string "AF" in them, but there might be other reasons, too.

[Thom Parker]

There 's a keystroke (i.e. commit) script .  For some reason it's not being shown.  Very Odd. The Dropdown also a field property that shouldn't have been set for a combobox.  But I don't think that has any affect. 

Whatever application built this PDF (and it's not Acrobat) did something screwy. 

[try67 · Accepted solution]

Acrobat hides some scripts it considers to use "internal" code. This usually happens when they contain the string "AF" in them, but there might be other reasons, too.

[Thom Parker]

It's a pretty straight forward case statement.  No AF or other obvious Acrobat internal function calls. 

It is indeed odd.

[try67 · Accepted solution]

It does contain "AF", actually, in these strings:

"Ventilation - HAF (Units: No)", "HU-Ventilation - HAF (Units: No)",

[try67]

Just to test it out I removed those two items from the code and re-applied it to the Keystroke event and it didn't disappear.

[Thom Parker]

Too funny, I saw those and discounted them since the "AF" is part of another word and in a quoted string. 

That's just sad.  I'm surprised scripts aren't disappearing in lots of forms. 

[try67]

The code is analyzed as a string, probably using a RegExp. And it appears to be case-sensitive, which is why it doesn't happen that often, only when "AF" appears in it. I agree it's very bad and near-sighted programming.

[Chandranshu24043817d2do]

Please tell me how to check these hidden code

[try67]

You can't do it from within Acrobat. I've attached it as a text file.

[Bernd Alheit]

At the internal you can following script:

[try67]

To solve this bug of Acrobat move the code to a function in a doc-level script and call it from there, instead of putting it directly under the field's action.