[Development] Use of Standard Library containers in Qt source code

Konstantin Tokarev annulen at yandex.ru
Fri Jul 1 21:52:24 CEST 2016

01.07.2016, 21:37, "Thiago Macieira" <thiago.macieira at intel.com>:
> Premises not under discussion:
>         Qt source code is product and meant to be read by our users
>         Qt source code must be clean and readable
> The above is not up for debate.
> For some time now, we've had a flurry of changes to Qt source code that uses
> the Standard Library's containers and algorithms, in the name of performance
> and often code size gains.
> I'm not disputing that there is a gain. But I am wondering about the trade-off
> we're making with regards to readability. For example, I was just reviewing
> this code:
>     if (d->currentReadChannel >= d->readHeaders.size()
>         || d->readHeaders[d->currentReadChannel].empty()) {
>         Q_ASSERT(d->buffer.isEmpty());
> The use of the Standard Library member "empty" is highly confusing at first
> sight because it does not follow the Qt naming guidelines. It's even more
> confusing because the next line has "isEmpty". When I read this code, I had to
> wonder if that "empty" was a verb in the imperative, meaning the author was
> trying to remove all elements from the container.
> I had to look up the definition of readHeaders in the review and note that it
> was a std::deque, not a Qt container.

STL was standardized 18 years ago, I think it should be enough to get used to empty().

> What do we do?
> Option 1:
> Not use Standard Library containers, just use the Qt containers as they exist.
> Option 2:
> Create new Qt containers to have the same complexity as Standard Library
> containers, but following the Qt naming conventions. Possibly with implicit
> sharing.
> Option 3:
> Create Qt API wrappers for those containers like std::deque, adding only a few
> inline functions to match the Qt-style API where the Standard Library API
> deviates. Examples are:
>         empty -> isEmpty
>         push_back -> append
>         front -> first
>         pop_front -> takeFirst
>         cbegin -> constBegin
>         cfind -> constFind
> --
> Thiago Macieira - thiago.macieira (AT) intel.com
>   Software Architect - Intel Open Source Technology Center
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