[Development] Qt 5 file hierarchy

[Thiago Macieira]

On segunda-feira, 24 de setembro de 2012 10.20.12, Knoll Lars wrote:
> Hi Thiago,
> 
> On Sep 21, 2012, at 6:01 PM, Thiago Macieira <thiago.macieira at intel.com> 
wrote:
> > The Qt 5 file hierarchy upon installation should be:
> can you maybe come put up some motivations here and what you're trying to
> achieve? Just stating that this is how the file hierarchy is supposed to be
> is a bit weird. Is this a proposal for something?
> 
> In general, I agree that we should have a defined layout, but I am a bit
> confused about some your statements below, because they are very Linux
> specific in some places, and they change some fundamentals as names of
> binaries (from moc to moc5) that have to my knowledge not even been
> discussed yet.

The discussion is on the other thread on the why this is needed.

> So before going into details: Is this supposed to be a proposal for Linux or
> all platforms?

It's needed for Linux, but the path of least resistance is to do it on all 
platforms.

> > bin/		- executables run by the user
> > 
> > 		- unversioned applications, like assistant, linguist, qdbus,
> > 		
> > 		  qdbusviewer
> > 		
> > 		- versioned applications, like qmake[35], qdoc5, qmlviewer5,
> > 		
> > 		 maybe moc5, uic5, rcc5
> > 
> > doc/		- gone to share/qt5/doc
> > examples/ - gone to share/qt5/examples
> 
> All paths so far are Linux specific. I don't think they'd look that way on
> Mac or Windows.

Ok, fair enough. We do have configure options for those paths and every single 
packager is using them already.

> > include/	- versioned include dirs:
> > 	QtCore5 or QtCore-5 or QtCore.5 or Qt5Core/
> > 	[…]
> 
> Doesn't work. On Linux it has to be include/qt5/QtCore.

Yup, it was a mistake suggesting this.

> > 	qt5/ 		 - arch-specific support files:
> > 		bin/ or libexec/
> > 		
> > 		 - executables not run by the user, like syncqt, lrelease, lupdate
> > 		
> > 		imports/
> > 		
> > 		 - QtDeclarative imports
> > 		
> > 		qml2/
> > 		
> > 		 - QML2 (including QtQuick2) arch-specific imports
> 
> We already had a solution here (discussed that with Brisbane some months
> ago). QML2 is the default, so it goes into imports/. For QML1 we have a
> Quick1/ subfolder in imports.

That's not acceptable. The QtQuick1 & libQtDeclarative.so.5 hierarchy must be 
the default because that's what people are using now. QML2 plugins must be the 
ones in a different path.

Are you also implicitly agreeing to move imports into lib (which all distros 
already do anyway)?

> > Note on imports: the design is flawed. It was flawed in Qt 4 and it's
> > worse now on Qt 5. For Qt 4, the flaw was that it did not differentiate
> > QML imports that were arch-independent from the ones that required
> > plugins. With Qt 5, it becomes worse because Qt Quick 1 and 2 share the
> > same directory.
> 
> They don't share the same directory really. See above. I am unsure I really
> want to even start differentiating arch dependent vs independent stuff
> here. Let's just declare it all arch dependent and simplify our lives for
> now.

I think that goes against the purpose of QML. We've been suggesting to a lot 
of people that they can write QML-based applications and solutions without 
writing a single line of C++. I think we *want* to say that you can install 
platform-independent solutions.

I don't mind if the maintainers in QtQuick1 and QtQuick2 decide they want to 
declare QML to follow the same rules as native code. It's really their choice.

> > Instead, I recommend we immediately change QML2 to the system that Perl
> > uses: put the arch-specific files inside the lib hierarchy, for which
> > distributions have already solved the multiarch problem, but put
> > arch-independent files in the share hierarchy.
> 
> Yes, putting it in lib/ on linux sounds reasonable.

-importsdir is a nonstandard option. I recommend we move the imports dir into 
$prefix/lib/qt5 by default. On all platforms.

Also note my proposal missed the plugins dir. I make the same recommendation: 
move it into lib/qt5 by default.

-- 
Thiago Macieira - thiago.macieira (AT) intel.com
  Software Architect - Intel Open Source Technology Center
     Intel Sweden AB - Registration Number: 556189-6027
     Knarrarnäsgatan 15, 164 40 Kista, Stockholm, Sweden
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