touch-packages team mailing list archive

[Jussi Pakkanen <jussi.pakkanen@xxxxxxxxxxxxx>]

Qt's documentation says this:

To force asynchronous image loading, even for image sources that do not
have the asynchronous property set to true, you may pass the
QQuickImageProvider::ForceAsynchronousImageLoading flag to the image
provider constructor. This ensures that all image requests for the
provider are handled in a separate thread.

This is exactly what thumbnailer does (thumbnailgenerator.cpp:29). This
should make it fully asynchronous. All threading related to this is done
by Qt internals and they are not exposed to QQuickImageProviders. This
would indicate that the blocking happens somewhere inside Qt and thus is
not caused by thumbnailer.

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Touch seeded packages, which is subscribed to thumbnailer in Ubuntu.
https://bugs.launchpad.net/bugs/1410260

Title:
  Image provider blocking the UI thread

Status in thumbnailer package in Ubuntu:
  New

Bug description:
  Steps:
  * add some music to your device (phone or desktop is fine)
  * [on desktop] install unity8 and run "unity8-dash -mousetouch"
  * bottom-swipe to the Manage screen
  * select the "My Music" scope
  * scroll quickly

  Expected:
  * scope scrolls smoothly, even if there's no images

  Current:
  * scope scrolling blocked for seconds at a time

  This seems to be most visible the first time, when images are not
  cached on disk yet.

  AFAIK the impact of this is elevated by the fact that Qt serializes
  requests to image providers, so when it's blocked to download one
  image, it will not continue to the next image etc.

  ProblemType: Bug
  DistroRelease: Ubuntu 15.04
  Package: qtdeclarative5-ubuntu-thumbnailer0.1 1.3+15.04.20150106-0ubuntu1
  Uname: Linux 3.18.0-031800rc4-generic x86_64
  ApportVersion: 2.15.1-0ubuntu2
  Architecture: amd64
  CurrentDesktop: Unity
  Date: Tue Jan 13 14:26:35 2015
  SourcePackage: thumbnailer
  SystemImageInfo:
   current build number: 0
   device name: 
   channel: daily
   last update: Unknown
  UpgradeStatus: No upgrade log present (probably fresh install)

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