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playbackbox periodically jumps to the bottom of the title list

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dwilson at dslextreme

Nov 27, 2007, 9:44 PM

Post #1 of 4 (426 views)
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playbackbox periodically jumps to the bottom of the title list

When scrolling through recordings, the playbackbox sometimes jumps from where I am in the list down to the bottom of the list (or within 3 or 4 entries from the bottom). I set about debugging this behavior, and have traced it to invocation of the PlaybackBox::listChanged function.

As far as I understand it, this function is attached to the fillListTimer and invoked on a timeout condition.

What would cause this timer to expire and invoke the function, and what is the expected behavior when this happens (since I am pretty sure that jumping towards the bottom of the current title list isn't it)?

I will continue to try to unravel this and understand the problem, but any pointers or guidance that anyone could give is greatly appreciated!

I am running svn 14913, but have been seeing this behavior intermittently since moving from stable to svn.

Thanks,

Dan.

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dwilson at dslextreme

Nov 27, 2007, 11:35 PM

Post #2 of 4 (371 views)
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Re: playbackbox periodically jumps to the bottom of the title list [In reply to]

On 11/27/2007 at 9:44 PM Dan Wilson wrote:

> When scrolling through recordings, the playbackbox sometimes jumps from
> where I am in the list down to the bottom of the list (or within 3 or 4
> entries from the bottom). I set about debugging this behavior, and have
> traced it to invocation of the PlaybackBox::listChanged function.
>

This problem is caused by the presence of generic episodes with invalid identifying information in the program list. In early November, SchedulesDirect provided schedules for USA Network with a number of shows over a several day period that did not list episode-specific information. Most of these generic episodes have been stored in the recorded table with an original air date of 09/20/1999, but several of them have a <null> original air date. When the fillList function does it's reverse search for the current position in the list, the <null> original air date is seen by mythfrontend as 01/01/1900. Since this is a lower value than any other, it stops the search. (I had configured frontend to sort by original air date).

It is unclear to me what the best fix is for this. Null values need to be handled in some way, but what is the best way to deal with this?

I am going to delete all these generic episodes from the list and see if that clears up the problem with the list repositioning. I expect it will.

Thanks for any help,

Dan.

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dwilson at dslextreme

Nov 27, 2007, 11:51 PM

Post #3 of 4 (383 views)
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Re: playbackbox periodically jumps to the bottom of the title list [In reply to]

On 11/27/2007 at 11:35 PM Dan Wilson wrote:

>
> It is unclear to me what the best fix is for this. Null values need to
> be handled in some way, but what is the best way to deal with this?
>

I have corrected the null originalairdate values for all episodes that had them, and the problem has cleared up for those titles.

Knowing now what the problem is, I looked at the database and saw that all of the movies I have recorded also have null original air dates. If I go to one of the category lists, such as "War", and scroll through those movies, I see the same behavior - the cursor suddenly jumps to a different spot in the list.

The list sorting algorithm has a definite blind spot when it comes to null values in the original air date field if one is sorting by original air date. I would be happy to code and test a patch if someone with some experience with this piece of the code could provide me with some kind of guidance as to how it would be best to handle it. Should the null values simply be ignored and some other field be used for determining sort order for that record?

Dan.

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mtdean at thirdcontact

Nov 28, 2007, 5:00 PM

Post #4 of 4 (351 views)
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Re: playbackbox periodically jumps to the bottom of the title list [In reply to]

Sorry. Sent this 16 hours ago, but it didn't go through. Probably the
stupid hotel internet, but this time I'm tunneling through their
firewall to my mail server so it will go through.

On 11/28/2007 02:51 AM, Dan Wilson wrote:
>
> On 11/27/2007 at 11:35 PM Dan Wilson wrote:
>>
>> It is unclear to me what the best fix is for this. Null values
>> need to be handled in some way, but what is the best way to deal
>> with this?
>
> I have corrected the null originalairdate values for all episodes
> that had them, and the problem has cleared up for those titles.
>
> Knowing now what the problem is, I looked at the database and saw
> that all of the movies I have recorded also have null original air
> dates. If I go to one of the category lists, such as "War", and
> scroll through those movies, I see the same behavior - the cursor
> suddenly jumps to a different spot in the list.
>
> The list sorting algorithm has a definite blind spot when it comes to
> null values in the original air date field if one is sorting by
> original air date. I would be happy to code and test a patch if
> someone with some experience with this piece of the code could
> provide me with some kind of guidance as to how it would be best to
> handle it. Should the null values simply be ignored and some other
> field be used for determining sort order for that record?

What particular section of code are you referring to? It seems that
comp_originalAirDate() and comp_originalAirDate_rev() in
programs/mythfrontend/playbackbox.cpp properly use startts as a
secondary sort key and recstartts as a tertiary sort key.

Perhaps we just need to fix the hasAirDate determination (around
libs/libmythtv/programinfo.cpp +893 and +4592 and +4769 ) to include a
check for "0000-00-00" since that's the default value for the DB field
(which would also likely fix the "one of those warnings" mentioned at
http://svn.mythtv.org/trac/ticket/3478#comment:6 ). In other words,
TTBOMK, any time we have a NULL/empty/"0000-00-00" originalairdate,
hasAirDate should be false (where "should be" indicates the program is
designed such that it /must/ be--though it seems there's a bug that may
allow a NULL originalAirDate in certain situations).

It looks to me like the code was written assuming that "0000-00-00"
would parse to a valid date using QDate::fromString() and the check
for > QDate(1940, 1, 1) would set hasAirDate appropriately, but in my
experience (at least with QT 3.3.7--see
http://svn.mythtv.org/trac/ticket/3478#comment:3 ), a zero-valued date
passed to QDate::fromString() results in a NULL value. When testing the
patch I made for #3478, my initial tests indicated that "0000-00-00"
would parse correctly, but after more rigorous testing, I found that it
doesn't, so I completely understand how this case could have been missed
by the dev writing the hasAirDate determination code. :)

Mike

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