Qtractor graphics becomes very slow with many items

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Today I tried to write my first song in Qtractor today using MIDI and samples in the arrangement. At 145 BPM I used approximately 3 MIDI items and 15 audio items per bar. It played well on my fast desktop until I copy and pasted the song to 32 bars long, then it turns into a slideshow when I scroll the arrangement. During playback I only use 10% CPU, but when I try to scroll or zoom, one CPU core goes to 60% and stays there until scrolling finishes.

I think the problem may be the same as one of these.

http://labs.qt.nokia.com/2010/01/11/qt-graphics-and-performance-the-cos…

http://lists.trolltech.com/qt-interest/2001-08/thread00125-0.html

http://doc.qt.nokia.com/qq/qq06-flicker-free.html

may i look at a screenshot evidence, just to let me have an idea of how many clip item are in the scene?

otoh. do you sense any different behavior whether you switch qt_graphicssystem ? try launching qtractor with either of these:

qtractor -graphicssystem raster
qtractor -graphicssystem opengl

hth.
cheers

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