OCG response to other OCGs states

[claudinecombe]

Hi 👋

I am trying to set some interactions among different OCGs, something like a "radiobutton" but with variation: check ocg1 and ocg2 when ocg3 is checked in the ui
Maybe the add_layer() function might help? Actually I have not figured out how to use it and what is the purpose.

Thank you for your help !

[claudinecombe]

I can add more concrete examples:

The first 4 checkbox will control the other ones

- [X] Custom display only
- [ ] Standard display only
- [ ] All
- [ ] Select
----
- [ ] Standard ocg1
- [ ] Standard ocg2
- [ ] Standard ocg3
- [X] Custom ocg4

- [ ] Custom display only
- [X] Standard display only
- [ ] All
- [ ] Select
----
- [X] Standard ocg1
- [X] Standard ocg2
- [X] Standard ocg3
- [ ] Custom ocg4

- [ ] Custom display only
- [ ] Standard display only
- [X] All
- [ ] Select
----
- [X] Standard ocg1
- [X] Standard ocg2
- [X] Standard ocg3
- [X] Custom ocg4

- [ ] Custom display only
- [ ] Standard display only
- [ ] All
- [X] Select # all checkboxes below are unchecked and the user may check the desired ones
----
- [ ] Standard ocg1
- [ ] Standard ocg2
- [ ] Standard ocg3
- [ ] Custom ocg4

[JorjMcKie]

I think you should use OCMD objects (Optional Content Membership Dictionary). These objects are logical expressions about the ON / OFF values of multiple OCGs.
The good thing is, that they allow practically arbitrary conditions via their VE ("visibility expression") parameter, see here in the documentation. In the method description, there also is an example.
Other than that, an OCMD can be used like an OCG: it can be assigned to images, annotations, etc.
Compared to this, the radiobutton logic is a lot less flexible.

[claudinecombe]

Thank you Jorj for your reply !

I tried to use OCMDs and indeed it works very well, but they don't show up as checkboxes in the UI like OCGs, or maybe I missed something ?

[JorjMcKie]

Ah, I see your confusion now.
No, using the term "radiobutton group" in Optional Content context is something entirely different. Has nothing to do with radio buttons in Form Fields / Widgets.
The PDF specification only used the term to explain a roughly similar behavior: a radio button group is a list of OCG xrefs, of which no more than one OCG may be ON. Probably not the best idea.

[claudinecombe]

So there is no way to have such control with the checkboxes like in my examples above ?
The OCMDs would work but it won't reflect in the checkboxes status

[JorjMcKie]

So there is no way to have such control with the checkboxes like in my examples above ? The OCMDs would work but it won't reflect in the checkboxes status

This is correct - unfortunately. You can of course make your own checkboxes using page.add_widget() with appropriate logic in your script. You have to provide code that translates the checkbox widget value to the right ve syntax in doc.set_ocmd(ve=[...]) ... and vice versa.

[claudinecombe]

Thank you Jorj, I was not aware of the Widget class, I will definitely take a look ! 👍

[JorjMcKie]

Ah, ok. This class allows you to add form fields. Among the several types are checkboxes. For how to add a checkbox, have a look at this script.