[LAD] [OT] need help from a Qt guru re: slow graphics

Rui Nuno Capela rncbc at rncbc.org
Sat May 26 14:25:57 UTC 2012

On 05/26/2012 02:35 PM, Dave Phillips wrote:
> Greetings:
> The problem: When I build Kdenlive for my Arch 64 system it compiles
> without problems and starts up okay. After that the sluggishness of its
> response is almost unbearable. For example, I've timed up to 10 seconds
> between a mouse click and the resulting action, e.g. right-click to Add
> Clip, and everything stalls badly when the program is calculating audio
> or video thumbnails. Response time gets better after running the program
> for a while, but getting it going is rather frustrating.
> I've already searched Google and asked about the problem on the Kdenlive
> forum and got no useful replies, hence my request here. Some of you use
> Arch systems, and some of you know Qt well enough that maybe you can
> advise me on this problem. (I'm hoping for a relatively simple solution,
> of course).
> Incidentally, the problem occurs with Arch's packaged Kdenlive and the
> binary I compile with the build script. I just upgraded both, the
> problem is still there. Other large Qt apps don't have the problem, e.g.
> QTractor. The problem is also absent with Kdenlive on my 32-bit machines.

jfyi, there have been at least one case of slowness re. qtractor:
   Qtractor graphics becomes very slow with many items

what about switching QT_GRAPHICSSYSTEM=raster (env var) or start with 
"-graphicssystem raster" command line option?

on my call and experience it (marginally) boosts rendering performance 
somehow, but it scores some artifact side-effects, specially on 
composite/opengl/eye-candy/sweetened WM's... as usual, ymmv ;)

rncbc aka Rui Nuno Capela
rncbc at rncbc.org

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