Backport QQuickAsyncImageProvider from upstream-dev

[Albert Astals Cid]

In Qt <= 5.5 there is exactly one thread that handles loading of images that come from custom image providers, this means that if a given image provider is very slow it will block the rest of image providers.

Qt 5.6 introduces QQuickAsyncImageProvider that is a job based API that allows the custom image providers to run threads on their side, this way they won't block other requests.

By backporting QQuickAsyncImageProvider we can solve https://bugs.launchpad.net/thumbnailer/+bug/1425043 by making the thumbnailer have a "slow" thread for thumbnails that it needs to do and a "fast" one for thumbnails that are already done as shown by the proof of concept implementation at https://code.launchpad.net/~aacid/thumbnailer/asyncprovider/+merge/253188

[Michał Sawicz (saviq)]

The relevant upstream change is https://codereview.qt-project.org/#/c/108540/.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Timo Jyrinki (timo-jyrinki)]

QtDeclarative part in the overlay PPA now.

---
qtdeclarative-opensource-src (5.4.1-1ubuntu7) vivid; urgency=medium

  * debian/patches/Add-QQuickAsyncImageProvider.patch:
    - Backport QQuickAsyncImageProvider (LP: #1439263) (LP: #1425043)
  * debian/patches/Always-remove-reply-from-replies-when-processing-can.patch:
    - Drop, replaced by the new patch.

 -- Timo Jyrinki <email address hidden> Tue, 28 Apr 2015 08:50:56 +0000
---

[Albert Astals Cid (aacid)]

Let's track the thumbnailer part in https://bugs.launchpad.net/thumbnailer/+bug/1425043