Review Request: Analog clock painting performance

[Alain Boyer]

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http://reviewboard.vidsolbach.de/r/290/
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(Updated 2008-12-04 09:25:46.308156)


Review request for Plasma.


Summary
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This patch attempts to speed up the analog clock painting performance. Essentially, it caches the QRects of the theme elements and streamlines some of the painting code.

The speedup is explained below, however I think we can do even better. For example, we could draw the hour and minute hands and shadows to a pixmap and then use that when only the second hand needs an update. I'm not sure if this is the way to go? Comments or suggestions?


Diffs
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  /trunk/KDE/kdebase/workspace/plasma/applets/analog-clock/clock.h
  /trunk/KDE/kdebase/workspace/plasma/applets/analog-clock/clock.cpp

Diff: http://reviewboard.vidsolbach.de/r/290/diff


Testing
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Valgrind tells me that this patch introduces a 1.46 speedup to the drawHand() method. This contributes to a 1.40 speedup of paintInterface(). Not bad.

Another way of looking at it, paintInterface() used to spend 63% of its time actually painting (m_theme->paint()). Now, paintInterface() spends 98% of its time painting. Hence, painting is now the bottleneck.


Thanks,

Alain