This is the standard trick of adding a redundant WHERE clause to a
subquery to help the database realise that it does not have to inspect
so many rows.
Here, we catch all the places where a student might be accessing their
own attempts, and make sure any automatic state transitions that
should happen, do happen, before the student sees the attempt.
The places where we need to check this are view.php, startattempt.php
and processattempt.php.
We do not really need to check attempt.php or summary.php, because if
the student is on one of those pages, the JavaScript timer will
auto-submit when time expires, taking them to processattempt.php,
which will do the acutal work.
We intentionally do not trigger state transition when a teacher is
looking at a student's quiz attemp. We will trigger state transitions
on cron, but that is still to do.
Also, the body of the process_... methods still needs to be written.
It is only necessary when there are (non-preview) attempts. However,
after making this change we have to ensure users cannot start attempts
when ->grade > 0 and ->sumgrades = 0.
Display ->grade on the order and paging tab of edit.php, so it is clear
what is going on when you are using that tab.
Finally, improve the error message a student gets if they try to start a
quiz with no questions.
This achieves a massive clean-up. It simplifies comples code in a number
of places. It allows some methods and functions to be moved to a more
appropriate home (for example cannot_review_message to the quiz class).
It moves more logic out of the renderer.
Overall feedback was being wiped because the quiz max grade was being set to zero when sumgrades was set to 0. The correct logic is to only set maxgrade to 0 if there are questions in the quiz and sumgrades is 0.
This avoids the problem that you cannot send messages in transactions.
It also means that the quiz submission will not be prevented, and the
message will still be sent eventually, if any part of the messaging
system is giving intermittent errors when the student wants to submit
their quiz.
1. We need this so that, for example, when previewing a question from
the quiz editing page, the preview uses the filter settings, theme and
language set for that quiz and course.
