Merge lp:~verzegnassi-stefano/ubuntu-docviewer-app/sgtileitem-keep-data into lp:ubuntu-docviewer-app

[Stefano Verzegnassi]

SGTileItem: keep QImage data so that QSG don't fail on repainting

Sometimes we get some blank tile when rendering a document.
This happens only when a document is loaded for the first time: the tile gets painted with the proper texture, then it becomes blank.

I don't know much how the Qt SceneGraph works behind the scenes, but it seems that it deletes the old node of a tile when an update() is requested.
Since m_data is null when that happens, SGTileItem does not repaint the node texture as expected.

[Jenkins Bot (ubuntu-core-apps-jenkins-bot)]

PASSED: Continuous integration, rev:279
https://core-apps-jenkins.ubuntu.com/job/run-ap-tests-ci/187/
Executed test runs:
    None: https://core-apps-jenkins.ubuntu.com/job/generic-update-mp/471/console

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review: Approve (continuous-integration)

[Jenkins Bot (ubuntu-core-apps-jenkins-bot)]

PASSED: Continuous integration, rev:279
https://core-apps-jenkins.ubuntu.com/job/run-ap-tests-ci/188/
Executed test runs:
    None: https://core-apps-jenkins.ubuntu.com/job/generic-update-mp/472/console

Click here to trigger a rebuild:
https://core-apps-jenkins.ubuntu.com/job/run-ap-tests-ci/188/rebuild

review: Approve (continuous-integration)

[Roman Shchekin (mrqtros)]

LGTM, only one question - should we also remove property? Sorry for dumb question, but I am away from source code :)

review: Approve

[Stefano Verzegnassi (verzegnassi-stefano)]

Do you mean the getter and setter for m_data?
I guess we should keep them, since we need to store the QImage returned by the RenderEngine as long as the tile is not deleted.

The Qt SceneGraph seems to repaint the node randomly several times when the tile is created and, if it does not find any QImage (because we delete it after the first paint), it just deletes the whole node, resulting in a portion of document not rendered on screen.

This is more a workaround, we probably could refine the code after the release.

[Stefano Verzegnassi (verzegnassi-stefano)]

Anyway, this was the last issue with paiting we found in these 7 months.
As this branch lands, we can say that the first part of the work on LOK plugin is completed! \o/

=== modified file 'src/plugin/libreofficetoolkit-qml-plugin/sgtileitem.cpp'
--- src/plugin/libreofficetoolkit-qml-plugin/sgtileitem.cpp	2016-01-21 00:29:15 +0000
+++ src/plugin/libreofficetoolkit-qml-plugin/sgtileitem.cpp	2016-01-26 14:02:47 +0000
@@ -32,9 +32,6 @@
         node->setOwnsTexture(true);
         node->setRect(m_area);
 
-        // We don't need anymore QImage's data
-        m_data = QImage();
-
 #ifdef DEBUG_SHOW_TILE_BORDER
         drawTileBorders(node);
 #endif