Bug 503152

I'm reporting 3 issues when filling out an embedded form in a PDF file.

To start, download this publicly available PDF to register to the French Social Security: https://www.ameli.fr/sites/default/files/Documents/Formulaire_s1106_demande_PUMA.pdf

Now open it with Okular and make sure to enable "Show Forms", either from the notification banner that appears at the top when opening the file, or via View -> Show Forms

Now for the issues:

1. the fields now have a black background. This isn't just a matter of aesthetics. Black completely obscures the background, and so when filling a date field, you may use an invalid format without noticing. An example: the date field on the 4th row ("Votre date de naissance") expects you to input ddmmyyyy (so, 8 chars), because separators are part of the template.
But if you didn't pay attention to this BEFORE enabling Show Forms, you won't have any way to know this, because the / are now covered by the black background. And now all you know is that you have to enter a date, and anything over the 8th char will be ignored. So you may try at first typing 01/01/2025, but your input will be truncated as you type at 01/01/20 (8 chars). As you see this, you may go for the short form ddmmyy, and type 010125, as you expect to get 01/01/25. Except that when you turn off "Show Forms", you notice that your input yielded an invalid value: 01|/0|1/25
For sure the template could do a better job here at documenting the expected format, but with a transparent background, this whole situation could be avoided, as the user would be able to peek at the form and notice the slightly larger separators between day and month, and month and year.
The ultimate solution to this would be a WYSIWYG field filling UI, so that the text you type has the same fixed width as the one you see when you are dong filling/editing.

2. checkboxes: click any checkbox while Show Forms is on, and you'll see the check mark. Quit Show Forms mode, and it's gone. It's actually recorded, but not displayed by Okular's UI. Proof: save the PDF and open it with any other app, and you'll see the check mark as expected.

3. the email field ("Votre courriel", on the right side of the 8th row) is impossible to fill with any reasonably sized email address. This might be an issue with the form itself. I tried to overcome it by using the Typewriter tool though (Alt + 5), but my email address still wouldn't fit on one line, and be truncated into two. I later realized that this was because I was just doing a simple click, which I think creates a (invisible!) fixed sized rectangle, which isn't enough to contain, on just one line, the text I'm typing. I had to click and drag to draw a larger rectangle to ultimately make it happen. This is poor UX, as the user only sees a precision pointer (the + thingy), but has no way to know how large of a rectangle they are drawing, and even that they're supposed to draw/drag in the first place!
This is also true for the Stamps features, BTW, and I suspect many other Okular tools. For these I think that the user should be guided visually. Maybe a hint to click and drag would be useful, and then while the drag is in progress, the rectangle being drawn should be visible. With the Stamp tool, it would be cool to show a real time preview of the Stamp as well - since I use that to insert a JPG of my signature, it would allow me to see if I'm drawing it in a way that keeps the right proportions, instead of finding out that my signature is all stretched after the fact.

Thanks!