Image provider blocking the UI thread

Bug #1410260 reported by Michał Sawicz
This bug affects 2 people
Affects Status Importance Assigned to Milestone
Fix Released
Albert Astals Cid
thumbnailer (Ubuntu)
Albert Astals Cid

Bug Description

* 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

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

* 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
 current build number: 0
 device name:
 channel: daily
 last update: Unknown
UpgradeStatus: No upgrade log present (probably fresh install)

Related branches

Revision history for this message
Michał Sawicz (saviq) wrote :
Revision history for this message
Jussi Pakkanen (jpakkane) wrote :

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.

Michał Sawicz (saviq)
Changed in thumbnailer (Ubuntu):
status: New → In Progress
importance: Undecided → Critical
importance: Critical → High
assignee: nobody → Albert Astals Cid (aacid)
Changed in thumbnailer:
status: New → In Progress
importance: Undecided → High
assignee: nobody → Albert Astals Cid (aacid)
Revision history for this message
Launchpad Janitor (janitor) wrote :

This bug was fixed in the package thumbnailer - 1.3+15.04.20150312-0ubuntu1

thumbnailer (1.3+15.04.20150312-0ubuntu1) vivid; urgency=medium

  [ Albert Astals Cid ]
  * Use own QDBusConnection (LP: #1410260)
 -- CI Train Bot <email address hidden> Thu, 12 Mar 2015 08:38:44 +0000

Changed in thumbnailer (Ubuntu):
status: In Progress → Fix Released
Changed in thumbnailer:
status: In Progress → Fix Released
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