When studying, the learning count now indicates the number of
learning cards due within the learn ahead limit, instead of the total
number of learning steps required to complete that day.
Also fix the ineffective limit clauses in the learning counts.
To avoid all sorts of problems, we need to ensure cards scheduled with
the V2 scheduler are not studied in older clients. Unfortunately we
can't just bump the file's schema version, as the existing clients will
freely import files created with newer versions. This patch changes
that, so things should be a bit easier in the future.
In the mean time, we need a way to prevent older clients from importing
files created with the V2 scheduler. To do this, we switch to using a
'collection.anki21' file in the archive, and include a dummy collection
.anki2 file.
The code has been tested with both deck and collection packages, but
exporting deck packages w/ scheduling info will remain disabled until
the V2 scheduler has had more testing.
We can't preserve the original queues when in preview mode, as
otherwise the due counts report the remaining steps of cards in
the learning queue, instead of just 1.
Rather than the rather complicated approach of making the learning and
deck list code aware of the current mode we're in, preview mode moves
all cards to the review queue when the filtered deck is built - just as
cards are moved to the new queue in Anki 2.0.x. The reason for the
review queue is that users were frequently confused when cards appeared
as new - hopefully this is slightly less confusing.
- fetch reviews from all child decks at once, sorted by due order
- shuffle the gathered cards as we did previously
- review limits on child decks are ignored - only the current deck and
its parents control what the limit is
- to make the deck list consistent with actual counts, we can't sum the
child counts, as the sum in the parent limit>child limit case may not
reflect the actual number of cards that would be presented
the previous approach meant we weren't able to preserve the card state
exactly when cards were in learning, since we didn't record the step
position prior to cards being moved into the filtered deck.
it also meant the answer buttons needed to change depending on state - 4
for cards in learning/review, but 2 when the card is on the final step
or is a review.
instead, in preview mode cards always have 2 buttons: again will repeat
again after a delay, and good immediately removes the card and restores
it to its previous state.
to accomplish this, we use a separate queue #, as the learn count
always needs to have a 1:1 correspondence to the number of cards
- move fuzzing into _constrainedIvl() so it's applied prior to limits
like maxIvl
- don't fuzz early reviews, so cards get the same interval if a filtered
deck is rebuilt again
