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Re: [Qt-interest] Model/View speed of Models with many many items and it

Subject: Re: [Qt-interest] Model/View speed of Models with many many items and item changes
From: Arnold Krille
Date: Sat, 13 Jun 2009 10:47:21 +0200

On Saturday 13 June 2009 01:09:04 RZ wrote:
> But the block signals effect was quite overwhelming and sufficient - so
> I stopped optimizing everything else ;-)

As far as I know this means all the update signals are then send afterwards. 
Which mean after changing 10.000 data points, instead of a continuous stream 
of 10.000 dataChanged(index) signals, you will get them all after the signals 
are unblocked again. But still these are 10.000 signals. Which means after you 
pushed new data into the model for 1 second, the gui will slowly adopt to this 
for the next second. This might work when you only change lots of data for a 
short period, it is the wrong behaviour when changing lots of data 
continuously for hours (I have evaluations that run for several days non-stop; 
and really before I optimized it, I had the gui update for several hours to 
adopt to all the signals).

And sadly Qt' doesn't allow combining of signals via a unified way, so you have 
to combine the dataChanged() signals somewhere in your code...

For these specialized high-troughput use-cases you simply _have_ to implement 
your own models. Which isn't hard unless you want the special stuff like 
drag'n'drop... (/me has yet to extend a custom model to do drag'n'drop.)

Have fun,

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