qt #include question

[marf]

I just have a general question.

When including QT libraries, is it better to

a)

#include <QDomDocument>
#include <QDomElement>
#include <QDomText>
...More Includes...

#include <QDomDocument>
#include <QDomElement>
#include <QDomText>
...More Includes...

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or

b)

#include <QtXml>

#include <QtXml>

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I'm just wondering, at what point should you just use the overall generic include of the whole QtXml library, rather than each specific class/object that you use?

Is there speed benefits to using one or the other?

[jpn]

See thread: Qt modules