[Development] QFileSystemWatcher and Recursive Monitoring

[Konstantin Ritt]

> I would prefer that QFSW was simple and reliable and doesn't attempt to impose a heavy cost or internal complexity (which translates into bugs) for things that the underlying APIs do not really support
Same opinion here.
Since we could get a good solution for windows only, the
QRecursiveFileSystemWatcher class goes to be not really
cross-platform.
Where the amount of nested levels is relatively small, the
QFileSystemWatcher could be used for recursive watching manually
instead - in a cross-platform way.

P.S. I'm still interested in improving the QFSW windows backend by
using ReadDirectoryChanges WinAPI instead of thread pool of
waiters/listeners.

regards,
Konstantin


2012/7/20 Robert Knight <robertknight at gmail.com>:
>> With FSEvents you cannot emit signals such as fileChanged(), fileModified(),
>> pathCreated(), or pathDeleted() if all you're notified about is that
>> "something happened in this folder here",
>
> >From my experience building an app that 'watches' a folder and imports
> all files of a certain type
> added there, I would prefer that QFSW was simple and reliable and
> doesn't attempt
> to impose a heavy cost or internal complexity (which translates into
> bugs) for things
> that the underlying APIs do not really support - leaving it up to the
> app to decide how
> best to handle these limitations.
>
> As you say, applications which are watching (possibly large) directory
> trees will likely
> have their own database of content which they will compare any changes
> to.  The app
> can optimize this in domain-specfic ways, such as not recording any
> information about
> types of files it doesn't care about.
>
> Here is the FSEvents wrapper we use on Mac for example:
>
> https://gist.github.com/3149811
>
> If the underlying APIs for fine-grained notifications and broad file
> system watches are quite different (as is the case for Mac),
> I think it makes sense not to try and 'paper over' that in the Qt
> APIs, so providing different classes would be better.
>
>> Would be easiest to implement, we could even drop all the threading currently there now.
>
> There is a lot to be said for internal simplicity, especially where
> threading is concerned.
>
> Regards,
> Rob.
>
> On 20 July 2012 06:28, logic.cpp <logic.cpp at gmail.com> wrote:
>> #1
>> Clarification of original post:
>>
>> When I say "Making QFileSystemWatcher Recursive" I mean *adding* new functions
>> for recursive monitoring, such as "addPathRecursively()". I don't mean to
>> replace the current non-recursive functinality, which is very useful in its own
>> right (for "A" category use cases mentioned).
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