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Frequent calls of DisplayConverter [message #1728173]

Thu, 31 March 2016 14:30

Carsten Tsara

Messages: 11
Registered: March 2016

Junior Member

Seems like NatTable repainting itself very frequently and on every cell painting DisplayConverter.canonicalToDisplayValue() is called. In my case computation of display value is expensive and I want calculate it only when data from DataProvider really changes. So why canonicalToDisplayValue() called so frequently and is there a way to call it when it really needed? Or should I provide some kind of caching of display values myself?
If I should do it myself, then how can I access DataProvider from DisplayConverter? I can't find straightforward way (I tried via ILayerCell using ContextualDisplayConverter)

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Re: Frequent calls of DisplayConverter [message #1728177 is a reply to message #1728173]

Thu, 31 March 2016 15:10

Dirk Fauth

Messages: 2902
Registered: July 2012

Senior Member

Quote:

So why canonicalToDisplayValue() called so frequently and is there a way to call it when it really needed?

Because it is needed for rendering the display value and we don't cache the display values internally. Therefore no, there is no way to only call it when it is "really" needed, because it is needed always.

Quote:

In my case computation of display value is expensive

That is your problem! You should not use expensive operations for computing the display value.

Quote:

Or should I provide some kind of caching of display values myself?

If you need that, yes.

Quote:

how can I access DataProvider from DisplayConverter?

You can't via NatTable API. You will need to create your implementation of a DisplayConverter that holds a reference to the IDataProvider. Not sure what you are trying to achieve if you need the IDataProvider in order to convert a cell, but I suppose you know what you are doing.

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