Architecture Refactor Suggestion: App-irrelevent Format Filters

[Yue Liu]

2012/10/23 Inge Wallin <inge at lysator.liu.se>:
> On Sunday, October 21, 2012 18:11:18 Yue Liu wrote:
>> 2012/10/21 Boudewijn Rempt <boud at valdyas.org>:
>> > On Sunday 21 October 2012 Oct, Yue Liu wrote:
>> >> Hi,
>> >>
>> >> Currently filters are loaded based on application's native mime-type.
>> >> And now we have multiple applications with same native format, such as
>> >> Karbon and Flow, Words and Authors. Applications with same native
>> >> format should have same set of format filters, but format filter codes
>> >> are sorted under application categories.
>> >>
>> >> So I suggest change it from current structure
>> >>
>> >> filters/xxx_app/[im,ex]port/xxx_filter
>> >
>> > It's even messier in some places, where the odf2html filter is embedded
>> > in the epub filter.
>> >
>> >> to
>> >>
>> >> filters/xxx2xxx
>> >
>> > I wouldn't mind that change, but then, for Krita, we moved all the
>> > filters to the Krita folter anyway.
>> >
>> >> And tell distributions package filters as one component, not with
>> >> apps, to avoid conflicts between same-format apps. At least Arch and
>> >> Chakra is already doing it this way.
>> >
>> > Fedora also did/does that already, which meant lots of bug reports since
>> > people only installed the app, not the filter component and then
>> > complained that they couldn't even open a simple jpeg in Krita!
>> >
>> > There's a complication here with the Tables filters: some of them link
>> > directly to Tables and actually don't go though an ODS intermediate.
>> > Those probably should be moved to the tables folder itself.
>>
>> We can keep the dependency on App and involve new mime-types for those
>> filters. Just like Friedrich suggested before:
>> http://mail.kde.org/pipermail/calligra-devel/2012-May/005041.html
>>
>> For example, if karbon filter depends on KarbonPart, we can make a
>> mime-type calligra/karbon.document and use it in the filter, so Flow
>> won't load this filter since karon.document is not supported by Flow.
>>
>> And we can place the codes of this kind of app-dependent filters under
>> app/filters/xxx2xxx, and place those general filters under
>> filters/xxx2xxx, when packaging, app-dependent filters are packaged
>> with apps, general filters are packaged as a single package and every
>> app depends on it.
>>
>> >> Note: this is a problem for some Karbon filters, since they used
>> >> KarbonPart to access shapes for shape painting. We can modify
>> >> KoDocument::paintContent(painter, rect) to do that instead.
>> >
>> > Ah, so Karbon has the same problem already, too.
>> >
>> >
>> > --
>> > Boudewijn Rempt
>> > http://www.valdyas.org, http://www.krita.org,
>> > http://www.boudewijnrempt.nl
>> > _______________________________________________
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>> > calligra-devel at kde.org
>> > https://mail.kde.org/mailman/listinfo/calligra-devel
>>
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>
> Yue, it seems that your filter thread got a bit hijacked -- or at least
> expanded.  Sorry for that.
Expansion made discussion more valuable:)

>
> Is there anything we can do about this filter problem for Flow in the short
> term?  I guess that using the Karbon core is not bad in itself. Or should the
> Karbon core be extracted into a kind of vector document core in libs/ ? That
> way the Flow filter will not be dependent on another application but instead
> "just" of a library.
I prefer the latter idea. Already got some suggestion from Cyrille in
another thread.

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