Review Request: Fix GUI thread blocking caused by KFilePreviewGenerator when disabling preview

[Dawit Alemayehu]

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This is an automatically generated e-mail. To reply, visit:
http://git.reviewboard.kde.org/r/101512/
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(Updated June 5, 2011, 7:07 p.m.)


Review request for kdelibs and Peter Penz.


Summary (updated)
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The attached single line patch fixes KFilePreviewGenertor such that it does not completely block the GUI thread and hence lock up the application when you enable and disable preview in a directory that contains large number of files.

This fix still only solves the problem partially in that the app will no longer lock up for a very long period of time. Instead you get a few second lockup if you have an old machine like mine (Pentium D). It might not be noticable on much faster machines. However, such lock ups are to be expected because of how this class is designed to work. It is one of those few classes that can really benefit from being multi-threaded. Perhaps based on the ideas from http://labs.qt.nokia.com/2010/01/21/qt-graphics-and-performance-generating-content-in-threads/.


Diffs
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Diff: http://git.reviewboard.kde.org/r/101512/diff


Testing
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The following test was done to confirm the problem as well as to test the fix:

- In Dolphin or Konqueror, enable HTML file preview.
- Navigate to Qt's html documentation folder (/usr/share/doc/qt/html on my system). 
- Turn on preview if it is not already enabled.
- Scroll up and down to see the preview working.
- Disable preview and see what happens.


Thanks,

Dawit

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