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Cover Art Support

Report #4: July 13 - July 19

Last week: July 06 - July 12

First PR: Qt signal queue

As I explained in the last report, in order to sort out the issues around the pixmap update, we are now passing the pixmap values in the signal “pixmapFound(..)”. I did some tests and I cannot notice any loss of performance.

Another important change was to make the “pixmapFound” connection as Qt::DirectConnection. In this way it will process the signal immediately and not store copies in an event-queue.

First PR: id3Tag Crashes (SoundSource)

I faced up to some crashes due to metadata extraction. It occurs mainly when Mixxx is trying to read a lot of embedded_covers at the same time. I realized that Mixxx is getting the info directly from the tag and trying to convert to QString and it was also the cause of the crashes.

Although calling TStringToQString on a String::null should be safe since null is just a no-args-constructed String and not an actual NULL pointer[1], my solution was just check if the TString is not-null (before use it) and it seems to work fine now [2] (I did tons of tests and I did not get segfaults any more).

First PR: Bug when show/hide wcoverart

Test case:

  1. load Mixxx
  2. select a track (which has a cover)
  3. open wcoverwidget (wcoverart displays cover “A”)
  4. switch table view (eg. go to autodj)
  5. open wcoverwidget
  • Expected: displays default_cover
  • Actual: displays cover “A”

The widget must reset all members after a “switchToView()” [3]

Second PR: Fixes in the TrackInfo dialog

This week I also did many small improvements in the dlgtrackinfo layout and major changes in the actions of the popup menu (accessed clicking on the cover art).

- changing window title - using “Artist - Title” instead of “Title” - drawing all fields with fixed height (25px) - fixing bugs when the user resize the window - using cover placeholder as a qwidget instead of qgroupbox (causing weird behavior on Windows7) …

- changing the cover location to default_cover instead of use coverId=-1. It avoids Mixxx to keep searching for a cover (after unset).

- now it uses the searching algorithm. It will try to reload the cover as normally we do (firstly looking in the id3tag and then in the trackdir).

I also added an icon for each action of the popup menu [4]. The icons which I pushed are generics, it means that maybe they are not ideal yet (design). However, for future changes we just would have to overwrite the current files.

Second PR: Warning/Question Boxes

Considering that when the user choose “reload” the fields, all of them are overwritten without any kind of warning… So, we should do the same for cover_art reloading. It means that we are no longer using warning boxes [5].

Moreover, in cases when the current track has a cover and the reloading process return NULL, we do not unset the current cover any more.

Third PR: Corver Art Delegate

During this week I started to implement the coverartdelegate class, which is responsible for drawing the cover_art in the tableview.

This part corresponds to the “third pull request” [6] and it is already working for all features which should display cover arts (library, autodj, analyse, playlists and crates).

The idea is use paint() to request the pixmaps (from covercache). I changed the method requestPixmap(..) to return a valid pixmap when it is available in the pixmapcache (instead of just emit signals). So, paint() will be doing successive callings until it gets the requested pixmap.

Issues for the next week

Next week: July 20 - July 26

Adjust cover art size

Currently we are drawing the cover_art in the whole cell, so when the user resize the cover_art column he will see the cover deforming to fit in the cell.

I did some research and I saw that Traktor fixed the cover_art width (something about 70px) and it is not resized even if the column is smaller than the image. i think that we should use the same strategy for that.
However, it is important to think about how we would rescale (and cut) the covers because doing it in the paint event (for all pixmaps, all the time) seems to be a very bad idea, because rescale process might be slow and doing it in many pixmaps at the same time could bring performance issues…

Delaying cover loading

I also noticed that we can have some freezes when we scroll the tableview very fast (just when the covercache is “cold”). The solution for that would be using a “delay” as we did for the cover widget last week.

Copying covers

If the user changes the cover art and the new cover comes from a directory which is different from the track directory, Mixxx should copy it to the track dir, trying to use “cover.jpg” or “album.jpg”. If the dir already have any of these files, we must use “mixxx-cover.jpg” (just to do not overwrite the user files).

This is important because the user could choose an image from a removable disk or any another place which could not be available in a “near future”. So, it is much more safe let it together with the track. It is also good because the user could reuse the cover in other software (automatic)…

Switching Views

We must avoid showing the cover_art widget (left corner) for views which there is no cove_art support:

  • browse
  • recordings
  • history
  • rhythmbox
  • banshee
  • itunes


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cover_art_support_r4.1405882550.txt.gz · Last modified: 2014/07/20 14:55 by cardinot