Add a Basic question Captcha

This is an update to the patch, fixing some bugs and adding regular expression checking for more advanced checks.

Hi, thank you for your work, I'll try to add it when I have more time to do this properly.

However, I am wondering about the name of the module.
"Question CAPTCHA" is not very descriptive because all CAPTCHAs ask a question :)

Some suggestions I could think of:
* "Generic question CAPTCHA"
* "Fixed question CAPTCHA"
* "Single question CAPTCHA" (which is not that good as a name, if you want to expand the functionality to a list of questions)
* "Plain question CAPTCHA"
* "Basic question CAPTCHA"
* "Ordinary question CAPTCHA"

English is not my mother tongue, so I'm not the best person to decide on this one, but I think I prefer "Ordinary question" and "Plain question".

* "Fixed question CAPTCHA"

Sounds best, it is vague enough to be flexible in terminology but states exactly what it does.

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There is a question I have about my programming on this CAPTCHA module.
When I added regular expression support, I was not certain how to do this through the main CAPTCHA project code.
My approach is a borderline hack, or so I suspect.

Instead of just returning the value the user submitted, I am exploiting the "preprocess" capability to do the regular expression check there.
I then return one of two strings "TRUE" and "FALSE".

The "generate" capability will read the "question_captcha_regex" variable and if the regex is being used, set the "$captcha['solution']" to be "TRUE".

Is this there a better or more correct approach?

Let me know if my wording is confusing.

The problem with "fixed" is that it conflicts a bit when you would allow multiple question/answers.

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About the prerocess stuff: I'm currently considering to drop that part from the API because it makes things more messy than it should. (#463002: Drop preprocess op of hook_captcha?)

Can you describe you use case in more depth, it is not very clear what you want to do with the regex'es. Do you want to do more advanced validation than a simple equality test?

The problem with the question captcha is that a question can have multiple answers or multiple forms of one answer.

Lets take slug. If there were somehow a question that begged snail to be the answer and then it could have multiple forms, then the regex might be:

((land[[:space:]]*|())snail|slug)
This regex accepts three main combinations:
- land snail
- snail
- slug

(and the [[:space:]]* allows for any amount of spaces or landsnail as a single word without spaces)

I could further extend this to handle the "scientific" names of the snail and the slug.

I can use the regex to pose multiple answers in a single text box.

My primary purpose is to allow for optionally making the answer more capable of handling tendencies of the user(s).

This is a yes to your question about needing more advanced validation capabilities.

Interesting example.

FYI: from http://drupal.org/node/463002#comment-1602102:

In this case, it would be easier if the validation itself could be done by that module, instead of only letting it preprocess the response before validation, without even knowing the original question or correct solution.

I'll try to come up with an example module that illustrates how this could be done more cleanly. I even think it's possible to do it in a way that is backwards compatible with the CAPTCHA API of 5.x-3.x and 6.x-1.x.
So nobody will be hurt :)

I created a feature request for custom CAPTCHA validation functions:
#473002: Provide a way to define custom CAPTCHA validation