check the checkboxes based on the export values when have same names

[satyajitnayk]

Describe your idea

• I have a checkbox.pdf with two check box groups.
• check boxes in each group have same name but different export values.
• How can I check checkbox based on their export value?

How could this be implemented?

• I am able to find the check box with the export value, but no idea how to check it using it's widget reference!!

      if (field instanceof PDFCheckBox) {
          const widgets = field.acroField.getWidgets();
          for (const widget of widgets) {
            const exportValue = widget
              .getOnValue()
              ?.['encodedName'].replace(/^\//, '');
            console.log(exportValue, ' ==> ', widget.getAppearanceState());
            if (exportValue == value) {
              // widget.setAppearances();
              // check the check box using widget => no functionality available  in pdf-lib as of now it seems
              break;
            }
          }
      }

• May be we need some method to check a checkbox using widget reference!

What problem are you trying to solve?

check the checkboxes based on the export values when all checkbox have same name.

Why does this matter to you?

• We have a product that helps customer to fill fillable pdfs.

• The requirement is customer wants to check checkbox 2 in first group & checkbox 1 in 2nd group. As all checkbox of first group have same names but different export values; same for 2nd group as well.

Would others find this helpful?

• It's useful when filling a fillable pdf having checkbox group with same names & different export values.
• Others will also find it useful.

Are you interested in implementing your proposal?

Yes

Why are you submitting a proposal?

shared in How could this be implemented?

Additional Notes

No response

[Sharcoux]

Sounds like a good addition. Do you think that you could open a PR? I don't think that we have the resources to develop this now.

[sam-goodwin]

I have the same problem - check boxes acting like radio groups because of export name.

Here's a nice sample PDF that exhibits the changes well:
RadioCheckBox_AcroForm.pdf

[sam-goodwin]

Sounds like a good addition. Do you think that you could open a PR? I don't think that we have the resources to develop this now.

@Sharcoux can you point out some key sections in the code that need to be changed?

[sam-goodwin]

This seems relevant.

pdf-lib/src/core/acroform/PDFAcroCheckBox.ts

Lines 22 to 27 in f57f239

	const onValue = this.getOnValue() ?? PDFName.of('Yes');
	if (value !== onValue && value !== PDFName.of('Off')) {
	throw new InvalidAcroFieldValueError();
	}
	this.dict.set(PDFName.of('V'), value);

[Sharcoux]

Or maybe src/api/form/PDFCheckBox.ts

I can't help much more, though. We just took over the maintenance of the repo and I only know a small subset of the code base.

[sam-goodwin]

I managed to set the value with the following hack:

Comment out the exception here: https://github.com/cantoo-scribe/pdf-lib/blob/master/src/core/acroform/PDFAcroCheckBox.ts#L24

if (value !== onValue && value !== PDFName_1.default.of('Off')) {
    // throw new errors_1.InvalidAcroFieldValueError();
}

Then, in my code:

if (field instanceof PDFCheckBox) {
  if (field.acroField.getWidgets().length > 1) {
    for (const widget of field.acroField.getWidgets()) {
      if (widget.getOnValue()!.decodeText() === value) {
        field.acroField.setValue(widget.getOnValue()!);
      }
    }
  }

This loops through until i find the widget with the onValue that matches the value i'm trying to set, in my case it's "Opt3".

I then call setValue on the acroField and pass the widget's onValue which is of type PDFName.

Moving forward, should we allow check to accept an optional PDFName value to set and update this exception to account for CheckBoxes with multiple widgets?

[sam-goodwin]

Here's my patch that is working for my use-case:

PDFAcroCheckBox.prototype.setValue = function (value: PDFName) {
  const onValue = this.getOnValue() ?? PDFName.of("Yes");
  const allowedValues = this.getWidgets().map((w) => w.getOnValue());
  if (
    value !== onValue &&
    !allowedValues.includes(value) &&
    value !== PDFName.of("Off")
  ) {
    throw new InvalidAcroFieldValueError();
  }

  this.dict.set(PDFName.of("V"), value);

  const widgets = this.getWidgets();
  for (let idx = 0, len = widgets.length; idx < len; idx++) {
    const widget = widgets[idx];
    const state = widget.getOnValue() === value ? value : PDFName.of("Off");
    widget.setAppearanceState(state);
  }
};

I don't know enough about the PDF spec to know if my allowedValues here is safe. What are the possible states getWidgets() can be in?

[sam-goodwin]

For consistency, I wonder if we should add a class specific for PDFCheckBoxRadioaGroup and align with the interface of PDFRadioGroup?

Or maybe this is a bug and it should just be a PDFRadioGroup instance? That would be a breaking change though.

[satyajitnayk]

Hey guys!! I found the working solution without any need for altering setValue. So we do not need any additional PR for this 🚀

   const value = "export value";
   if (field instanceof PDFCheckBox) {
        if (field.acroField.getWidgets().length > 1) {
          field.uncheck(); // to make sure any checkbox already checked is cleared
          for (const widget of field.acroField.getWidgets()) {
            const onValue = widget.getOnValue()!;
            if (onValue.decodeText() === value) {
              const state = onValue ?? PDFName.of('Off');
              widget.setAppearanceState(state);
            }
          }
        } else {
          if (value) {
            field.check();
          } else {
            field.uncheck();
          }
        }
    }

[sam-goodwin]

It's a nice workaround but I still think it's a gap in the abstraction. Might be worth keeping it open to discuss what it should look like from the high level api.

I am also unblocked, which is great, but this will likely affect anyone else stumbling into this problem.

[satyajitnayk]

I think it’s a working solution , but if you think it still needed, we can re open the issue.

[Sharcoux]

Anyway, there is this thread now, of someone is looking for the same thing

[giox069]

Hi, it took me days before finding @satyajitnayk hack. As proposed by @sam-goodwin, the correct place for this function is in the top level api, not in a closed issue.
There are still problem with this approach: if you flatten() the form after setting the checkbox, the checkbox disappear.

Another possible and maybe complete solution could be this never accepted PR on the original pdf-lib: Hopding#1685, but I never tested it.

I'm still investigating because I still need to set the value of a multivalue PDFCheckBox and then flatten() the form.